Merge branch 'issue/339-md-preview' into develop

2024-12-25 14:52:19 +03:00 · 2017-01-08 16:07:36 +01:00 · 2017-01-08 16:07:36 +01:00 · aba4fbec2f
commit aba4fbec2f
parent c620fec2d0 ec0f84b656
46 changed files with 2380 additions and 172 deletions
--- a/2
+++ b/2
@ -3,3 +3,5 @@ github "PureLayout/PureLayout" == 3.0.2
 github "eonil/FileSystemEvents" "master"
 github "sparkle-project/Sparkle" == 1.15.1
 github "qvacua/CocoaFontAwesome" "master"
+github "qvacua/CocoaMarkdown" "master"
+github "sindresorhus/github-markdown-css" == 2.4.1
--- a/Cartfile.resolved
+++ b/Cartfile.resolved
@ -1,6 +1,8 @@
 github "qvacua/CocoaFontAwesome" "71865fc2c0275ebc5c8601edc23290e85aca9979"
+github "qvacua/CocoaMarkdown" "5d1c1e3dd74486dfc358c9cc3ddd7e993842113d"
 github "eonil/FileSystemEvents" "aa5c6af1fd35939f9aca3b9eba3b672bfa549b3a"
 github "Quick/Nimble" "v5.1.0"
 github "PureLayout/PureLayout" "v3.0.2"
 github "ReactiveX/RxSwift" "3.1.0"
 github "sparkle-project/Sparkle" "1.15.1"
+github "sindresorhus/github-markdown-css" "v2.4.1"
--- a/NeoVimServer/NeoVimMsgIds.h
+++ b/NeoVimServer/NeoVimMsgIds.h
@ -36,8 +36,7 @@ typedef NS_ENUM(NSUInteger, NeoVimServerMsgId) {
    NeoVimServerMsgIdStop,

    NeoVimServerMsgIdDirtyStatusChanged,
-    NeoVimServerMsgIdCwdChanged,
-    NeoVimServerMsgIdBufferEvent,
+    NeoVimServerMsgIdAutoCommandEvent,

 #ifdef DEBUG
    NeoVimServerDebug1,
@ -53,6 +52,7 @@ typedef NS_ENUM(NSUInteger, NeoVimAgentMsgId) {
    NeoVimAgentMsgIdDelete,
    NeoVimAgentMsgIdResize,
    NeoVimAgentMsgIdSelectWindow,
+    NeoVimAgentMsgIdCursorGoto,
    NeoVimAgentMsgIdQuit,

    NeoVimAgentMsgIdGetDirtyDocs,
--- a/NeoVimServer/NeoVimServer.m
+++ b/NeoVimServer/NeoVimServer.m
@ -99,6 +99,8 @@ static CFDataRef local_server_callback(CFMessagePortRef local, SInt32 msgid, CFD

      case NeoVimAgentMsgIdDelete: return null_data_async(data, neovim_delete);

+      case NeoVimAgentMsgIdCursorGoto: return null_data_async(data, neovim_cursor_goto);
+
      default: return NULL;

    }
--- a/NeoVimServer/server_globals.h
+++ b/NeoVimServer/server_globals.h
@ -27,3 +27,5 @@ extern void neovim_vim_command(void **argv);
 extern void neovim_vim_input(void **argv);
 extern void neovim_vim_input_marked_text(void **argv);
 extern void neovim_delete(void **argv);
+
+extern void neovim_cursor_goto(void **argv);
--- a/NeoVimServer/server_ui.m
+++ b/NeoVimServer/server_ui.m
@ -24,12 +24,10 @@
 #import <nvim/api/vim.h>
 #import <nvim/ui.h>
 #import <nvim/ui_bridge.h>
-#import <nvim/main.h>
-#import <nvim/ex_docmd.h>
 #import <nvim/ex_getln.h>
 #import <nvim/fileio.h>
 #import <nvim/undo.h>
-#import <nvim/eval.h>
+#import <nvim/api/window.h>


 #define pun_type(t, x) (*((t *) (&(x))))
@ -100,20 +98,6 @@ static bool has_dirty_docs() {
  return false;
 }

-static void send_dirty_status() {
-  bool new_dirty_status = has_dirty_docs();
-  DLOG("dirty status: %d vs. %d", _dirty, new_dirty_status);
-  if (_dirty == new_dirty_status) {
-    return;
-  }
-
-  _dirty = new_dirty_status;
-  DLOG("sending dirty status: %d", _dirty);
-  NSData *data = [[NSData alloc] initWithBytes:&_dirty length:sizeof(bool)];
-  [_neovim_server sendMessageWithId:NeoVimServerMsgIdDirtyStatusChanged data:data];
-  [data release];
-}
-
 static void insert_marked_text(NSString *markedText) {
  _marked_text = [markedText retain]; // release when the final text is input in -vimInput

@ -183,6 +167,20 @@ static void server_ui_main(UIBridgeData *bridge, UI *ui) {
  xfree(ui);
 }

+static void send_dirty_status() {
+  bool new_dirty_status = has_dirty_docs();
+  DLOG("dirty status: %d vs. %d", _dirty, new_dirty_status);
+  if (_dirty == new_dirty_status) {
+    return;
+  }
+
+  _dirty = new_dirty_status;
+  DLOG("sending dirty status: %d", _dirty);
+  NSData *data = [[NSData alloc] initWithBytes:&_dirty length:sizeof(bool)];
+  [_neovim_server sendMessageWithId:NeoVimServerMsgIdDirtyStatusChanged data:data];
+  [data release];
+}
+
 #pragma mark NeoVim's UI callbacks

 static void server_ui_resize(UI *ui __unused, int width, int height) {
@ -204,9 +202,15 @@ static void server_ui_cursor_goto(UI *ui __unused, int row, int col) {
  _put_row = row;
  _put_column = col;

-  int values[] = {row, col, screen_cursor_row(), screen_cursor_column()};
-  DLOG("%d:%d - %d:%d", values[0], values[1], values[2], values[3]);
-  NSData *data = [[NSData alloc] initWithBytes:values length:(4 * sizeof(int))];
+  int values[] = {
+    row, col,
+    screen_cursor_row(), screen_cursor_column(),
+    (int) curwin->w_cursor.lnum, curwin->w_cursor.col + 1
+  };
+
+  DLOG("%d:%d - %d:%d - %d:%d", values[0], values[1], values[2], values[3], values[4], values[5]);
+
+  NSData *data = [[NSData alloc] initWithBytes:values length:(6 * sizeof(int))];
  [_neovim_server sendMessageWithId:NeoVimServerMsgIdSetPosition data:data];
  [data release];
 }
@ -442,31 +446,39 @@ void custom_ui_start(void) {
 void custom_ui_autocmds_groups(
    event_T event, char_u *fname, char_u *fname_io, int group, bool force, buf_T *buf, exarg_T *eap
 ) {
+  // We don't need these events in the UI (yet) and they slow down scrolling: Enable them, if necessary, only after
+  // optimizing the scrolling.
+  if (event == EVENT_CURSORMOVED || event == EVENT_CURSORMOVEDI) {
+    return;
+  }
+
  @autoreleasepool {
    DLOG("got event %d for file %s in group %d.", event, fname, group);

-    switch (event) {
-      // Dirty status: Did we get them all?
-      case EVENT_TEXTCHANGED:
-      case EVENT_TEXTCHANGEDI:
-      case EVENT_BUFWRITEPOST:
-      case EVENT_BUFLEAVE:
+    if (event == EVENT_TEXTCHANGED
+      || event == EVENT_TEXTCHANGEDI
+      || event == EVENT_BUFWRITEPOST
+      || event == EVENT_BUFLEAVE)
+    {
      send_dirty_status();
-        return;
-
-      // For buffer list changes
-      case EVENT_BUFWINENTER:
-      case EVENT_BUFWINLEAVE:
-        [_neovim_server sendMessageWithId:NeoVimServerMsgIdBufferEvent];
-        break;
-
-      case EVENT_CWDCHANGED:
-        [_neovim_server sendMessageWithId:NeoVimServerMsgIdCwdChanged];
-        break;
-
-      default:
-        break;
    }
+
+    NSUInteger eventCode = event;
+
+    NSMutableData *data;
+    if (buf == NULL) {
+      data = [[NSMutableData alloc] initWithBytes:&eventCode length:sizeof(NSUInteger)];
+    } else {
+      NSInteger bufHandle = buf->handle;
+
+      data = [[NSMutableData alloc] initWithCapacity:(sizeof(NSUInteger) + sizeof(NSInteger))];
+      [data appendBytes:&eventCode length:sizeof(NSUInteger)];
+      [data appendBytes:&bufHandle length:sizeof(NSInteger)];
+    }
+
+    [_neovim_server sendMessageWithId:NeoVimServerMsgIdAutoCommandEvent data:data];
+
+    [data release];
  }
 }

@ -650,18 +662,8 @@ void neovim_vim_command_output(void **argv) {
    NSString *input = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

    Error err = ERROR_INIT;
-
-    // We don't know why nvim_command_output does not work when the optimization level is set to -Os.
-    // If set to -O0, nvim_command_output works fine... -_-
-    // String commandOutput = nvim_command_output((String) {
-    //     .data = (char *) input.cstr,
-    //     .size = [input lengthOfBytesUsingEncoding:NSUTF8StringEncoding]
-    // }, &err);
-    do_cmdline_cmd("redir => v:command_output");
-    nvim_command(vim_string_from(input), &err);
-    do_cmdline_cmd("redir END");
-
-    char_u *output = get_vim_var_str(VV_COMMAND_OUTPUT);
+    String commandOutput = nvim_command_output(vim_string_from(input), &err);
+    char_u *output = (char_u *) commandOutput.data;

    // FIXME: handle err.set == true
    NSString *result = nil;
@ -773,7 +775,9 @@ void neovim_vim_command(void **argv) {
    Error err = ERROR_INIT;
    nvim_command(vim_string_from(input), &err);

-    // FIXME: handle err.set == true
+    if (err.set) {
+      WLOG("ERROR while executing command %s: %s", input.cstr, err.msg);
+    }

    [input release];

@ -867,3 +871,36 @@ void neovim_delete(void **argv) {
    return nil;
  });
 }
+
+void neovim_cursor_goto(void **argv) {
+  work_async(argv, ^NSData *(NSData *data) {
+    const int *values = data.bytes;
+
+    Array position = ARRAY_DICT_INIT;
+
+    position.size = 2;
+    position.capacity = 2;
+    position.items = xmalloc(2 * sizeof(Object));
+
+    Object row = OBJECT_INIT;
+    row.type = kObjectTypeInteger;
+    row.data.integer = values[0];
+
+    Object col = OBJECT_INIT;
+    col.type = kObjectTypeInteger;
+    col.data.integer = values[1];
+
+    position.items[0] = row;
+    position.items[1] = col;
+
+    Error err = ERROR_INIT;
+
+    nvim_win_set_cursor(nvim_get_current_win(), position, &err);
+    // The above call seems to be not enough...
+    nvim_input((String) { .data="<ESC>", .size=5 });
+
+    xfree(position.items);
+
+    return nil;
+  });
+}
--- a/SwiftNeoVim/NeoVimAgent.h
+++ b/SwiftNeoVim/NeoVimAgent.h
@ -21,6 +21,9 @@ NS_ASSUME_NONNULL_BEGIN
@property (nonatomic, weak) id <NeoVimUiBridgeProtocol> bridge;

 - (instancetype)initWithUuid:(NSString *)uuid;
+
+- (void)debug;
+
 - (void)quit;

 - (bool)runLocalServerAndNeoVim;
@ -32,6 +35,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)deleteCharacters:(NSInteger)count;

 - (void)resizeToWidth:(int)width height:(int)height;
+- (void)cursorGoToRow:(int)row column:(int)column;

 - (bool)hasDirtyDocs;
 - (NSString *)escapedFileName:(NSString *)fileName;
--- a/SwiftNeoVim/NeoVimAgent.m
+++ b/SwiftNeoVim/NeoVimAgent.m
@ -23,6 +23,7 @@ static type *data_to_ ## type ## _array(NSData *data, NSUInteger count) { \
 }

 data_to_array(int)
+data_to_array(NSUInteger)
 data_to_array(bool)
 data_to_array(CellAttributes)

@ -83,7 +84,7 @@ static CFDataRef local_server_callback(CFMessagePortRef local, SInt32 msgid, CFD
  NSCondition *_neoVimReadyCondition;
  bool _isInitErrorPresent;

-  uint32_t _neoVimIsQuitting;
+  volatile uint32_t _neoVimIsQuitting;
 }

 - (instancetype)initWithUuid:(NSString *)uuid {
@ -107,6 +108,12 @@ static CFDataRef local_server_callback(CFMessagePortRef local, SInt32 msgid, CFD
  return _neoVimIsQuitting == 1;
 }

+- (void)debug {
+#ifdef DEBUG
+  [self sendMessageWithId:NeoVimAgentDebug1 data:nil expectsReply:NO];
+#endif
+}
+
 // We cannot use -dealloc for this since -dealloc is not called until the run loop in the thread stops.
 - (void)quit {
  OSAtomicOr32Barrier(1, &_neoVimIsQuitting);
@ -231,11 +238,17 @@ static CFDataRef local_server_callback(CFMessagePortRef local, SInt32 msgid, CFD
  [self sendMessageWithId:NeoVimAgentMsgIdResize data:data expectsReply:NO];
 }

+- (void)cursorGoToRow:(int)row column:(int)column {
+  int values[] = { row, column };
+  NSData *data = [[NSData alloc] initWithBytes:values length:(2 * sizeof(int))];
+  [self sendMessageWithId:NeoVimAgentMsgIdCursorGoto data:data expectsReply:NO];
+}
+
 - (bool)hasDirtyDocs {
  NSData *response = [self sendMessageWithId:NeoVimAgentMsgIdGetDirtyDocs data:nil expectsReply:YES];
  if (response == nil) {
    log4Warn("The response for the msg %lu was nil.", NeoVimAgentMsgIdGetDirtyDocs);
-    return YES;
+    return NO;
  }

  NSNumber *value = [NSKeyedUnarchiver unarchiveObjectWithData:response];
@ -439,9 +452,10 @@ static CFDataRef local_server_callback(CFMessagePortRef local, SInt32 msgid, CFD
      return;

    case NeoVimServerMsgIdSetPosition: {
-      int *values = data_to_int_array(data, 4);
+      int *values = data_to_int_array(data, 6);
      [_bridge gotoPosition:(Position) { .row = values[0], .column = values[1] }
-               screenCursor:(Position) { .row = values[2], .column = values[3] }];
+               screenCursor:(Position) { .row = values[2], .column = values[3] }
+            currentPosition:(Position) { .row = values[4], .column = values[5] }];
      return;
    }

@ -566,13 +580,18 @@ static CFDataRef local_server_callback(CFMessagePortRef local, SInt32 msgid, CFD
      return;
    }

-    case NeoVimServerMsgIdCwdChanged:
-      [_bridge cwdChanged];
-      return;
-
-    case NeoVimServerMsgIdBufferEvent:
-      [_bridge bufferListChanged];
+    case NeoVimServerMsgIdAutoCommandEvent: {
+      if (data.length == sizeof(NSUInteger) + sizeof(NSInteger)) {
+        NSUInteger *values = (NSUInteger *) data.bytes;
+        NeoVimAutoCommandEvent event = (NeoVimAutoCommandEvent) values[0];
+        NSInteger bufferHandle = ((NSInteger *)(values + 1))[0];
+        [_bridge autoCommandEvent:event bufferHandle:bufferHandle];
+      } else {
+        NSUInteger *values = data_to_NSUInteger_array(data, 1);
+        [_bridge autoCommandEvent:(NeoVimAutoCommandEvent) values[0] bufferHandle:-1];
+      }
      return;
+    }

    default:
      return;
--- a/SwiftNeoVim/NeoVimAutoCommandEvent.generated.h
+++ b/SwiftNeoVim/NeoVimAutoCommandEvent.generated.h
@ -0,0 +1,97 @@
+@import Foundation;
+typedef NS_ENUM(NSUInteger, NeoVimAutoCommandEvent) {
+  NeoVimAutoCommandEventBUFADD = 0,
+  NeoVimAutoCommandEventBUFDELETE = 1,
+  NeoVimAutoCommandEventBUFENTER = 2,
+  NeoVimAutoCommandEventBUFFILEPOST = 3,
+  NeoVimAutoCommandEventBUFFILEPRE = 4,
+  NeoVimAutoCommandEventBUFHIDDEN = 5,
+  NeoVimAutoCommandEventBUFLEAVE = 6,
+  NeoVimAutoCommandEventBUFNEW = 7,
+  NeoVimAutoCommandEventBUFNEWFILE = 8,
+  NeoVimAutoCommandEventBUFREADCMD = 9,
+  NeoVimAutoCommandEventBUFREADPOST = 10,
+  NeoVimAutoCommandEventBUFREADPRE = 11,
+  NeoVimAutoCommandEventBUFUNLOAD = 12,
+  NeoVimAutoCommandEventBUFWINENTER = 13,
+  NeoVimAutoCommandEventBUFWINLEAVE = 14,
+  NeoVimAutoCommandEventBUFWIPEOUT = 15,
+  NeoVimAutoCommandEventBUFWRITECMD = 16,
+  NeoVimAutoCommandEventBUFWRITEPOST = 17,
+  NeoVimAutoCommandEventBUFWRITEPRE = 18,
+  NeoVimAutoCommandEventCMDUNDEFINED = 19,
+  NeoVimAutoCommandEventCMDWINENTER = 20,
+  NeoVimAutoCommandEventCMDWINLEAVE = 21,
+  NeoVimAutoCommandEventCOLORSCHEME = 22,
+  NeoVimAutoCommandEventCOMPLETEDONE = 23,
+  NeoVimAutoCommandEventCURSORHOLD = 24,
+  NeoVimAutoCommandEventCURSORHOLDI = 25,
+  NeoVimAutoCommandEventCURSORMOVED = 26,
+  NeoVimAutoCommandEventCURSORMOVEDI = 27,
+  NeoVimAutoCommandEventCWDCHANGED = 28,
+  NeoVimAutoCommandEventENCODINGCHANGED = 29,
+  NeoVimAutoCommandEventFILEAPPENDCMD = 30,
+  NeoVimAutoCommandEventFILEAPPENDPOST = 31,
+  NeoVimAutoCommandEventFILEAPPENDPRE = 32,
+  NeoVimAutoCommandEventFILECHANGEDRO = 33,
+  NeoVimAutoCommandEventFILECHANGEDSHELL = 34,
+  NeoVimAutoCommandEventFILECHANGEDSHELLPOST = 35,
+  NeoVimAutoCommandEventFILEREADCMD = 36,
+  NeoVimAutoCommandEventFILEREADPOST = 37,
+  NeoVimAutoCommandEventFILEREADPRE = 38,
+  NeoVimAutoCommandEventFILETYPE = 39,
+  NeoVimAutoCommandEventFILEWRITECMD = 40,
+  NeoVimAutoCommandEventFILEWRITEPOST = 41,
+  NeoVimAutoCommandEventFILEWRITEPRE = 42,
+  NeoVimAutoCommandEventFILTERREADPOST = 43,
+  NeoVimAutoCommandEventFILTERREADPRE = 44,
+  NeoVimAutoCommandEventFILTERWRITEPOST = 45,
+  NeoVimAutoCommandEventFILTERWRITEPRE = 46,
+  NeoVimAutoCommandEventFOCUSGAINED = 47,
+  NeoVimAutoCommandEventFOCUSLOST = 48,
+  NeoVimAutoCommandEventFUNCUNDEFINED = 49,
+  NeoVimAutoCommandEventGUIENTER = 50,
+  NeoVimAutoCommandEventGUIFAILED = 51,
+  NeoVimAutoCommandEventINSERTCHANGE = 52,
+  NeoVimAutoCommandEventINSERTCHARPRE = 53,
+  NeoVimAutoCommandEventINSERTENTER = 54,
+  NeoVimAutoCommandEventINSERTLEAVE = 55,
+  NeoVimAutoCommandEventJOBACTIVITY = 56,
+  NeoVimAutoCommandEventMENUPOPUP = 57,
+  NeoVimAutoCommandEventOPTIONSET = 58,
+  NeoVimAutoCommandEventQUICKFIXCMDPOST = 59,
+  NeoVimAutoCommandEventQUICKFIXCMDPRE = 60,
+  NeoVimAutoCommandEventQUITPRE = 61,
+  NeoVimAutoCommandEventREMOTEREPLY = 62,
+  NeoVimAutoCommandEventSESSIONLOADPOST = 63,
+  NeoVimAutoCommandEventSHELLCMDPOST = 64,
+  NeoVimAutoCommandEventSHELLFILTERPOST = 65,
+  NeoVimAutoCommandEventSOURCECMD = 66,
+  NeoVimAutoCommandEventSOURCEPRE = 67,
+  NeoVimAutoCommandEventSPELLFILEMISSING = 68,
+  NeoVimAutoCommandEventSTDINREADPOST = 69,
+  NeoVimAutoCommandEventSTDINREADPRE = 70,
+  NeoVimAutoCommandEventSWAPEXISTS = 71,
+  NeoVimAutoCommandEventSYNTAX = 72,
+  NeoVimAutoCommandEventTABCLOSED = 73,
+  NeoVimAutoCommandEventTABENTER = 74,
+  NeoVimAutoCommandEventTABLEAVE = 75,
+  NeoVimAutoCommandEventTABNEW = 76,
+  NeoVimAutoCommandEventTABNEWENTERED = 77,
+  NeoVimAutoCommandEventTERMCHANGED = 78,
+  NeoVimAutoCommandEventTERMCLOSE = 79,
+  NeoVimAutoCommandEventTERMOPEN = 80,
+  NeoVimAutoCommandEventTERMRESPONSE = 81,
+  NeoVimAutoCommandEventTEXTCHANGED = 82,
+  NeoVimAutoCommandEventTEXTCHANGEDI = 83,
+  NeoVimAutoCommandEventTEXTYANKPOST = 84,
+  NeoVimAutoCommandEventUSER = 85,
+  NeoVimAutoCommandEventVIMENTER = 86,
+  NeoVimAutoCommandEventVIMLEAVE = 87,
+  NeoVimAutoCommandEventVIMLEAVEPRE = 88,
+  NeoVimAutoCommandEventVIMRESIZED = 89,
+  NeoVimAutoCommandEventWINENTER = 90,
+  NeoVimAutoCommandEventWINLEAVE = 91
+};
+
+#define NumberOfAutoCommandEvents 92
--- a/SwiftNeoVim/NeoVimUiBridgeProtocol.h
+++ b/SwiftNeoVim/NeoVimUiBridgeProtocol.h
@ -5,6 +5,8 @@

@import Foundation;

+#import "NeoVimAutoCommandEvent.generated.h"
+

 // Keep in sync with the constants in vim.h
 typedef NS_ENUM(NSUInteger, Mode) {
@ -67,7 +69,7 @@ NS_ASSUME_NONNULL_BEGIN
 * 2. NeoVim wants to put the cursor at (row, column).
 * In case of 1. NeoVim will put in subsequent call. In case of 2. NeoVim seems to flush twice in a row.
 */
- (void)gotoPosition:(Position)position screenCursor:(Position)screenCursor;
+- (void)gotoPosition:(Position)position screenCursor:(Position)screenCursor currentPosition:(Position)currentPosition;

 - (void)updateMenu;
 - (void)busyStart;
@ -115,8 +117,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)setTitle:(NSString *)title;
 - (void)setIcon:(NSString *)icon;
 - (void)setDirtyStatus:(bool)dirty;
- (void)cwdChanged;
- (void)bufferListChanged;
+- (void)autoCommandEvent:(NeoVimAutoCommandEvent)event bufferHandle:(NSInteger)bufferHandle;

 /**
 * NeoVim has been stopped.
--- a/SwiftNeoVim/NeoVimView.swift
+++ b/SwiftNeoVim/NeoVimView.swift
@ -107,6 +107,8 @@ public class NeoVimView: NSView, NeoVimUiBridgeProtocol, NSUserInterfaceValidati
    return true
  }

+  public fileprivate(set) var currentPosition = Position(row: 1, column: 1)
+
  fileprivate static let emojis: [UInt32] = [
    0x1F600...0x1F64F,
    0x1F910...0x1F918,
@ -208,10 +210,7 @@ public class NeoVimView: NSView, NeoVimUiBridgeProtocol, NSUserInterfaceValidati

  @IBAction public func debug1(_ sender: AnyObject?) {
    NSLog("DEBUG 1 - Start")
-    Swift.print("!!!!!!!!!!!!!!!!! \(self.agent.boolOption("paste"))")
-    self.agent.setBoolOption("paste", to: true)
-    self.agent.vimInput(self.vimPlainString("foo\nbar"))
-    self.agent.setBoolOption("paste", to: false)
+    self.agent.cursorGo(toRow: 10, column: 5)
    NSLog("DEBUG 1 - End")
  }

@ -336,10 +335,16 @@ extension NeoVimView {
    self.exec(command: "qa!")
  }

-  fileprivate func open(_ url: URL, cmd: String) {
-    let path = url.path
-    let escapedFileName = self.agent.escapedFileName(path)
-    self.exec(command: "\(cmd) \(escapedFileName)")
+  public func vimOutput(of command: String) -> String {
+    return self.agent.vimCommandOutput(command) ?? ""
+  }
+
+  public func vimExCommand(_ command: String) {
+    self.agent.vimCommand(command)
+  }
+
+  public func cursorGo(to position: Position) {
+    self.agent.cursorGo(toRow: Int32(position.row), column: Int32(position.column))
  }

  /**
@ -358,6 +363,12 @@ extension NeoVimView {
      self.agent.vimInput("<Esc>:\(cmd)<CR>")
    }
  }
+
+  fileprivate func open(_ url: URL, cmd: String) {
+    let path = url.path
+    let escapedFileName = self.agent.escapedFileName(path)
+    self.exec(command: "\(cmd) \(escapedFileName)")
+  }
 }

 // MARK: - Resizing
@ -1246,8 +1257,9 @@ extension NeoVimView {
    }
  }

-  public func gotoPosition(_ position: Position, screenCursor: Position) {
+  public func gotoPosition(_ position: Position, screenCursor: Position, currentPosition: Position) {
    DispatchUtils.gui {
+      self.currentPosition = currentPosition
 //      NSLog("\(#function): \(position), \(screenCursor)")

      let curScreenCursor = self.grid.screenCursor
@ -1276,6 +1288,9 @@ extension NeoVimView {
      self.grid.goto(position)
      self.grid.moveCursor(screenCursor)
    }
+    DispatchUtils.gui {
+      self.delegate?.cursor(to: currentPosition)
+    }
  }

  public func updateMenu() {
@ -1310,6 +1325,9 @@ extension NeoVimView {
    DispatchUtils.gui {
      self.grid.scroll(Int(count))
      self.setNeedsDisplay(region: self.grid.region)
+      // Do not send msgs to agent -> neovim in the delegate method. It causes spinning when you're opening a file with
+      // existing swap file.
+      self.delegate?.scroll()
    }
  }

@ -1429,15 +1447,25 @@ extension NeoVimView {
    }
  }

-  public func cwdChanged() {
+  public func autoCommandEvent(_ event: NeoVimAutoCommandEvent, bufferHandle: Int) {
    DispatchUtils.gui {
-      self.delegate?.cwdChanged()
-    }
+//    NSLog("\(event.rawValue) with buffer \(bufferHandle)")
+
+      if event == .BUFWINENTER || event == .BUFWINLEAVE {
+        self.bufferListChanged()
      }

-  public func bufferListChanged() {
-    DispatchUtils.gui {
-      self.delegate?.bufferListChanged()
+      if event == .TABENTER {
+        self.tabChanged()
+      }
+
+      if event == .CWDCHANGED {
+        self.cwdChanged()
+      }
+
+      if event == .BUFREADPOST || event == .BUFWRITEPOST {
+        self.currentBufferChanged(bufferHandle)
+      }
    }
  }

@ -1454,6 +1482,30 @@ extension NeoVimView {
    }
  }

+  fileprivate func currentBufferChanged(_ handle: Int) {
+    guard let currentBuffer = self.currentBuffer() else {
+      return
+    }
+
+    guard currentBuffer.handle == handle else {
+      return
+    }
+
+    self.delegate?.currentBufferChanged(currentBuffer)
+  }
+
+  fileprivate func tabChanged() {
+    self.delegate?.tabChanged()
+  }
+
+  fileprivate func cwdChanged() {
+    self.delegate?.cwdChanged()
+  }
+
+  fileprivate func bufferListChanged() {
+    self.delegate?.bufferListChanged()
+  }
+
  fileprivate func updateCursorWhenPutting(currentPosition curPos: Position, screenCursor: Position) {
    if self.mode == .Cmdline {
      // When the cursor is in the command line, then we need this...
--- a/SwiftNeoVim/NeoVimViewDelegate.swift
+++ b/SwiftNeoVim/NeoVimViewDelegate.swift
@ -13,6 +13,11 @@ public protocol NeoVimViewDelegate: class {
  func set(dirtyStatus: Bool)
  func cwdChanged()
  func bufferListChanged()
+  func tabChanged()
+  func currentBufferChanged(_ currentBuffer: NeoVimBuffer)

  func ipcBecameInvalid(reason: String)
+
+  func scroll()
+  func cursor(to: Position)
 }
--- a/SwiftNeoVim/SwiftNeoVim.h
+++ b/SwiftNeoVim/SwiftNeoVim.h
@ -19,3 +19,4 @@ FOUNDATION_EXPORT const unsigned char SwiftNeoVimVersionString[];
 #import <SwiftNeoVim/NeoVimBuffer.h>
 #import <SwiftNeoVim/NeoVimTab.h>
 #import <SwiftNeoVim/NeoVimWindow.h>
+#import <SwiftNeoVim/NeoVimAutoCommandEvent.generated.h>
--- a/VimR.xcodeproj/project.pbxproj
+++ b/VimR.xcodeproj/project.pbxproj
@ -13,6 +13,7 @@
 		1929B1E05C116514C1D3A384 /* CocoaCategories.m in Sources */ = {isa = PBXBuildFile; fileRef = 1929B5C3F2F1CA4113DABFFD /* CocoaCategories.m */; };
 		1929B3CEE0C1A1850E9CCE2F /* BasicTypes.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929B2FBE11048569391E092 /* BasicTypes.swift */; };
 		1929B3F5743967125F357C9F /* Matcher.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929BEEB33113B0E33C3830F /* Matcher.swift */; };
+		1929B4145AA81F006BAF3B5C /* PreviewService.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929BB8BCA48637156F92945 /* PreviewService.swift */; };
 		1929B462CD4935AFF6D69457 /* FileItem.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929B7CB4863F80230C32D3C /* FileItem.swift */; };
 		1929B53876E6952D378C2B30 /* ScoredFileItem.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929BDF9EBAF1D9D44399045 /* ScoredFileItem.swift */; };
 		1929B6388EAF16C190B82955 /* FileItemIgnorePattern.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929B69499B2569793350CEC /* FileItemIgnorePattern.swift */; };
@ -22,15 +23,23 @@
 		1929B7A2F2B423AA9740FD45 /* FileUtilsTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929B5D977261F1EBFA9E8F1 /* FileUtilsTest.swift */; };
 		1929B93DBAD09835E428F610 /* PrefPane.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929BB251F74BEFC82CEEF84 /* PrefPane.swift */; };
 		1929BA120290D6A2A61A4468 /* ArrayCommonsTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929B477E1E62433BC48E10B /* ArrayCommonsTest.swift */; };
+		1929BA3BB94B77E9AE051FE5 /* PreviewComponent.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929B8DA5AA33536F0082200 /* PreviewComponent.swift */; };
 		1929BCF444CE7F1D14D421DE /* FileItemTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929B4778E20696E3AAFB69B /* FileItemTest.swift */; };
 		1929BD3F9E609BFADB27584B /* Scorer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929B9D510177918080BE39B /* Scorer.swift */; };
 		1929BD4CA2204E061A86A140 /* MatcherTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929BC19C1BC19246AFF1621 /* MatcherTests.swift */; };
+		1929BD52275A6570C666A7BA /* PreviewRenderer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929B1EC32D8A26958FB39B1 /* PreviewRenderer.swift */; };
 		1929BEB90DCDAF7A2B68C886 /* ColorUtils.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929BA6128BFDD54CA92F46E /* ColorUtils.swift */; };
 		1929BEFEABA0448306CDB6D4 /* FileItemIgnorePatternTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = 1929BBC84557C8351EC6183E /* FileItemIgnorePatternTest.swift */; };
 		1929BF81A40B4154D3EA33CE /* server_ui.m in Sources */ = {isa = PBXBuildFile; fileRef = 1929B93013228985F509C8F6 /* server_ui.m */; settings = {COMPILER_FLAGS = "-fno-objc-arc"; }; };
 		4B029F1A1D45E349004EE0D3 /* PrefWindow.xib in Resources */ = {isa = PBXBuildFile; fileRef = 4B029F1C1D45E349004EE0D3 /* PrefWindow.xib */; };
 		4B0677371D99D9C3001A2588 /* FileBrowserComponent.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4B0677361D99D9C3001A2588 /* FileBrowserComponent.swift */; };
 		4B0BCC941D70320C00D3CE65 /* Logger.h in Headers */ = {isa = PBXBuildFile; fileRef = 4B0BCC931D70320C00D3CE65 /* Logger.h */; settings = {ATTRIBUTES = (Private, ); }; };
+		4B183E0E1E06E2940079E8A8 /* CocoaMarkdown.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 4B183E0D1E06E2940079E8A8 /* CocoaMarkdown.framework */; };
+		4B183E101E06E29C0079E8A8 /* CocoaMarkdown.framework in Embed Frameworks */ = {isa = PBXBuildFile; fileRef = 4B183E0D1E06E2940079E8A8 /* CocoaMarkdown.framework */; settings = {ATTRIBUTES = (CodeSignOnCopy, RemoveHeadersOnCopy, ); }; };
+		4B183E1B1E08748B0079E8A8 /* NeoVimAutoCommandEvent.generated.h in Headers */ = {isa = PBXBuildFile; fileRef = 4B183E1A1E08748B0079E8A8 /* NeoVimAutoCommandEvent.generated.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		4B183E1E1E09931E0079E8A8 /* MarkdownRenderer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4B183E1D1E09931E0079E8A8 /* MarkdownRenderer.swift */; };
+		4B19BEFC1E110183007E823C /* markdown in Resources */ = {isa = PBXBuildFile; fileRef = 4B19BEFA1E110183007E823C /* markdown */; };
+		4B19BEFD1E110183007E823C /* preview in Resources */ = {isa = PBXBuildFile; fileRef = 4B19BEFB1E110183007E823C /* preview */; };
 		4B22F7F01D7C029400929B0E /* ScorerTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4B22F7EF1D7C029400929B0E /* ScorerTest.swift */; };
 		4B22F7F21D7C6B9000929B0E /* ImageAndTextTableCell.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4B22F7F11D7C6B9000929B0E /* ImageAndTextTableCell.swift */; };
 		4B238BE11D3BF24200CBDD98 /* Application.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4B238BE01D3BF24200CBDD98 /* Application.swift */; };
@ -192,6 +201,7 @@
 				4BDD056B1DB0CACB00D1B405 /* Sparkle.framework in Embed Frameworks */,
 				4BDF50121D760B7200D8FBC3 /* EonilFileSystemEvents.framework in Embed Frameworks */,
 				4B91FFF61DEB772B00447068 /* CocoaFontAwesome.framework in Embed Frameworks */,
+				4B183E101E06E29C0079E8A8 /* CocoaMarkdown.framework in Embed Frameworks */,
 				4B2A2BFF1D0351810074CE9A /* SwiftNeoVim.framework in Embed Frameworks */,
 				4B2A2BEF1D02261F0074CE9A /* RxSwift.framework in Embed Frameworks */,
 				4B401B161D0454E900D99EDC /* PureLayout.framework in Embed Frameworks */,
@ -269,6 +279,7 @@
 		1929B0EEBE4A765934AF8335 /* DataWrapper.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = DataWrapper.h; sourceTree = "<group>"; };
 		1929B15B7EDC9B0F40E5E95C /* Logging.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = Logging.h; sourceTree = "<group>"; };
 		1929B1A51F076E088EF4CCA4 /* server_globals.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = server_globals.h; sourceTree = "<group>"; };
+		1929B1EC32D8A26958FB39B1 /* PreviewRenderer.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = PreviewRenderer.swift; sourceTree = "<group>"; };
 		1929B2FBE11048569391E092 /* BasicTypes.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = BasicTypes.swift; sourceTree = "<group>"; };
 		1929B39DA7AC4A9B62D7CD39 /* Component.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Component.swift; sourceTree = "<group>"; };
 		1929B3A98687DF171307AAC8 /* FileItemService.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FileItemService.swift; sourceTree = "<group>"; };
@ -278,6 +289,7 @@
 		1929B5D977261F1EBFA9E8F1 /* FileUtilsTest.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FileUtilsTest.swift; sourceTree = "<group>"; };
 		1929B69499B2569793350CEC /* FileItemIgnorePattern.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FileItemIgnorePattern.swift; sourceTree = "<group>"; };
 		1929B7CB4863F80230C32D3C /* FileItem.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FileItem.swift; sourceTree = "<group>"; };
+		1929B8DA5AA33536F0082200 /* PreviewComponent.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = PreviewComponent.swift; sourceTree = "<group>"; };
 		1929B93013228985F509C8F6 /* server_ui.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = server_ui.m; sourceTree = "<group>"; };
 		1929B9AF20D7BD6E5C975128 /* FoundationCommons.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FoundationCommons.swift; sourceTree = "<group>"; };
 		1929B9D510177918080BE39B /* Scorer.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Scorer.swift; sourceTree = "<group>"; };
@ -285,6 +297,7 @@
 		1929BA8AC40B901B20F20B71 /* FileUtils.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FileUtils.swift; sourceTree = "<group>"; };
 		1929BB251F74BEFC82CEEF84 /* PrefPane.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = PrefPane.swift; sourceTree = "<group>"; };
 		1929BB6CFF4CC0B5E8B00C62 /* DataWrapper.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = DataWrapper.m; sourceTree = "<group>"; };
+		1929BB8BCA48637156F92945 /* PreviewService.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = PreviewService.swift; sourceTree = "<group>"; };
 		1929BBC84557C8351EC6183E /* FileItemIgnorePatternTest.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FileItemIgnorePatternTest.swift; sourceTree = "<group>"; };
 		1929BC19C1BC19246AFF1621 /* MatcherTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MatcherTests.swift; sourceTree = "<group>"; };
 		1929BDF9EBAF1D9D44399045 /* ScoredFileItem.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ScoredFileItem.swift; sourceTree = "<group>"; };
@ -294,6 +307,11 @@
 		4B029F1B1D45E349004EE0D3 /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.xib; name = Base; path = Base.lproj/PrefWindow.xib; sourceTree = "<group>"; };
 		4B0677361D99D9C3001A2588 /* FileBrowserComponent.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = FileBrowserComponent.swift; sourceTree = "<group>"; };
 		4B0BCC931D70320C00D3CE65 /* Logger.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = Logger.h; path = VimR/Logger.h; sourceTree = SOURCE_ROOT; };
+		4B183E0D1E06E2940079E8A8 /* CocoaMarkdown.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = CocoaMarkdown.framework; path = Carthage/Build/Mac/CocoaMarkdown.framework; sourceTree = SOURCE_ROOT; };
+		4B183E1A1E08748B0079E8A8 /* NeoVimAutoCommandEvent.generated.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = NeoVimAutoCommandEvent.generated.h; sourceTree = "<group>"; };
+		4B183E1D1E09931E0079E8A8 /* MarkdownRenderer.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MarkdownRenderer.swift; sourceTree = "<group>"; };
+		4B19BEFA1E110183007E823C /* markdown */ = {isa = PBXFileReference; lastKnownFileType = folder; path = markdown; sourceTree = "<group>"; };
+		4B19BEFB1E110183007E823C /* preview */ = {isa = PBXFileReference; lastKnownFileType = folder; path = preview; sourceTree = "<group>"; };
 		4B1BB3521D16C5E500CA4FEF /* InputTestView.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = InputTestView.swift; sourceTree = "<group>"; };
 		4B22F7EF1D7C029400929B0E /* ScorerTest.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ScorerTest.swift; sourceTree = "<group>"; };
 		4B22F7F11D7C6B9000929B0E /* ImageAndTextTableCell.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = ImageAndTextTableCell.swift; sourceTree = "<group>"; };
@ -456,6 +474,7 @@
 				4B2A2BFE1D0351810074CE9A /* SwiftNeoVim.framework in Frameworks */,
 				4BDD056A1DB0CAB700D1B405 /* Sparkle.framework in Frameworks */,
 				4B337FBB1DEB76F20020ADD2 /* CocoaFontAwesome.framework in Frameworks */,
+				4B183E0E1E06E2940079E8A8 /* CocoaMarkdown.framework in Frameworks */,
 				4B2A2BEE1D02261F0074CE9A /* RxSwift.framework in Frameworks */,
 				4B401B141D0454DC00D99EDC /* PureLayout.framework in Frameworks */,
 				4BDF50081D7607BF00D8FBC3 /* EonilFileSystemEvents.framework in Frameworks */,
@ -482,6 +501,16 @@
 			path = resources;
 			sourceTree = "<group>";
 		};
+		1929BA610ADEA2BA4424FBE5 /* Preview */ = {
+			isa = PBXGroup;
+			children = (
+				4B183E1C1E0992FD0079E8A8 /* Preview Renderers */,
+				1929B8DA5AA33536F0082200 /* PreviewComponent.swift */,
+				1929BB8BCA48637156F92945 /* PreviewService.swift */,
+			);
+			name = Preview;
+			sourceTree = "<group>";
+		};
 		1929BFC86BF38D341F2DDCBD /* NeoVim Objects */ = {
 			isa = PBXGroup;
 			children = (
@ -504,6 +533,15 @@
 			name = "File Browser";
 			sourceTree = "<group>";
 		};
+		4B183E1C1E0992FD0079E8A8 /* Preview Renderers */ = {
+			isa = PBXGroup;
+			children = (
+				4B183E1D1E09931E0079E8A8 /* MarkdownRenderer.swift */,
+				1929B1EC32D8A26958FB39B1 /* PreviewRenderer.swift */,
+			);
+			name = "Preview Renderers";
+			sourceTree = "<group>";
+		};
 		4B1AC1AF1D7F395300898F0B /* Open Quickly */ = {
 			isa = PBXGroup;
 			children = (
@ -534,6 +572,7 @@
 		4B2A2BE61D0225840074CE9A /* Frameworks */ = {
 			isa = PBXGroup;
 			children = (
+				4B183E0D1E06E2940079E8A8 /* CocoaMarkdown.framework */,
 				4B337FBA1DEB76F20020ADD2 /* CocoaFontAwesome.framework */,
 				4BDD05691DB0CAB700D1B405 /* Sparkle.framework */,
 				4BDF50071D7607BF00D8FBC3 /* EonilFileSystemEvents.framework */,
@ -607,6 +646,7 @@
 				4B705BA01DDF7639005F844B /* ToolPrefData.swift */,
 				4B0677351D99D9A2001A2588 /* File Browser */,
 				4B705C0D1DE2167A005F844B /* BufferListComponent.swift */,
+				1929BA610ADEA2BA4424FBE5 /* Preview */,
 			);
 			name = Tools;
 			sourceTree = "<group>";
@ -655,6 +695,8 @@
 		4B97E2CF1D33F92200FC0660 /* resources */ = {
 			isa = PBXGroup;
 			children = (
+				4B19BEFA1E110183007E823C /* markdown */,
+				4B19BEFB1E110183007E823C /* preview */,
 				4BEBA50C1CFF374B00673FDF /* MainMenu.xib */,
 				4B97E2CE1D33F53D00FC0660 /* MainWindow.xib */,
 				4B029F1C1D45E349004EE0D3 /* PrefWindow.xib */,
@ -789,6 +831,7 @@
 				4B401B191D046E0600D99EDC /* NeoVimViewDelegate.swift */,
 				4B570DC01D303CAF006EDC21 /* NeoVimAgent.h */,
 				4B570DC11D303CAF006EDC21 /* NeoVimAgent.m */,
+				4B183E1A1E08748B0079E8A8 /* NeoVimAutoCommandEvent.generated.h */,
 				4B2A2C061D0352CB0074CE9A /* NeoVimUiBridgeProtocol.h */,
 			);
 			name = NeoVimView;
@ -820,6 +863,7 @@
 				4BDD05881DBBC50000D1B405 /* NeoVimTab.h in Headers */,
 				4BDCFAEA1D31486E00F62670 /* NeoVimMsgIds.h in Headers */,
 				4B2A2BFA1D0351810074CE9A /* SwiftNeoVim.h in Headers */,
+				4B183E1B1E08748B0079E8A8 /* NeoVimAutoCommandEvent.generated.h in Headers */,
 				4B0BCC941D70320C00D3CE65 /* Logger.h in Headers */,
 				4BDF64241D08CAB000D47E1D /* MMCoreTextView.h in Headers */,
 			);
@ -832,6 +876,7 @@
 			isa = PBXNativeTarget;
 			buildConfigurationList = 4B2A2C021D0351810074CE9A /* Build configuration list for PBXNativeTarget "SwiftNeoVim" */;
 			buildPhases = (
+				4B183E191E08746B0079E8A8 /* ShellScript */,
 				4B2A2BF21D0351810074CE9A /* Sources */,
 				4B2A2BF31D0351810074CE9A /* Frameworks */,
 				4B2A2BF41D0351810074CE9A /* Headers */,
@ -925,6 +970,7 @@
 			isa = PBXNativeTarget;
 			buildConfigurationList = 4BEBA51D1CFF374B00673FDF /* Build configuration list for PBXNativeTarget "VimR" */;
 			buildPhases = (
+				4B19BEFF1E110208007E823C /* ShellScript */,
 				4BEBA5011CFF374B00673FDF /* Sources */,
 				4BEBA5021CFF374B00673FDF /* Frameworks */,
 				4BEBA5031CFF374B00673FDF /* Resources */,
@ -966,7 +1012,7 @@
 			isa = PBXProject;
 			attributes = {
 				LastSwiftUpdateCheck = 0810;
-				LastUpgradeCheck = 0810;
+				LastUpgradeCheck = 0820;
 				ORGANIZATIONNAME = "Tae Won Ha";
 				TargetAttributes = {
 					4B2A2BF61D0351810074CE9A = {
@ -1070,7 +1116,9 @@
 				4BB409E51DD68CCC005F39A2 /* FileBrowserMenu.xib in Resources */,
 				4BEBA50E1CFF374B00673FDF /* MainMenu.xib in Resources */,
 				4B97E2CC1D33F53D00FC0660 /* MainWindow.xib in Resources */,
+				4B19BEFC1E110183007E823C /* markdown in Resources */,
 				4B029F1A1D45E349004EE0D3 /* PrefWindow.xib in Resources */,
+				4B19BEFD1E110183007E823C /* preview in Resources */,
 				4B3AC8941DB031C600AC5823 /* sparkle_pub.pem in Resources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
@ -1086,6 +1134,32 @@
 /* End PBXResourcesBuildPhase section */

 /* Begin PBXShellScriptBuildPhase section */
+		4B183E191E08746B0079E8A8 /* ShellScript */ = {
+			isa = PBXShellScriptBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputPaths = (
+			);
+			outputPaths = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = "if [ \"${CONFIGURATION}\" = \"Debug\" ]; then\n    if [ -f \"SwiftNeoVim/NeoVimAutoCommandEvent.generated.h\" ]; then\n        exit 0\n    fi\nfi\n\nsed 's/^typedef enum auto_event/typedef NS_ENUM(NSUInteger, NeoVimAutoCommandEvent)/' <./neovim/build/include/auevents_enum.generated.h | sed 's/ event_T//' | sed 's/EVENT_/NeoVimAutoCommandEvent/' | sed 's/NUM_EVENTS/NumberOfAutoCommandEvents/' | sed -e '1s/^/@import Foundation;\\'$'\\n/' > SwiftNeoVim/NeoVimAutoCommandEvent.generated.h\n";
+		};
+		4B19BEFF1E110208007E823C /* ShellScript */ = {
+			isa = PBXShellScriptBuildPhase;
+			buildActionMask = 2147483647;
+			files = (
+			);
+			inputPaths = (
+			);
+			outputPaths = (
+			);
+			runOnlyForDeploymentPostprocessing = 0;
+			shellPath = /bin/sh;
+			shellScript = "cp ${SRCROOT}/Carthage/Checkouts/github-markdown-css/github-markdown.css ${SRCROOT}/VimR/markdown/";
+		};
 		4BBA71F11D319E0900E16612 /* ShellScript */ = {
 			isa = PBXShellScriptBuildPhase;
 			buildActionMask = 2147483647;
@ -1213,9 +1287,13 @@
 				1929BD3F9E609BFADB27584B /* Scorer.swift in Sources */,
 				4B6B0A781DA2A1A500212D6D /* FileOutlineView.swift in Sources */,
 				4BB409EE1DDA77E9005F39A2 /* ProxyWorkspaceBar.swift in Sources */,
+				4B183E1E1E09931E0079E8A8 /* MarkdownRenderer.swift in Sources */,
 				4BAD84E81D7CA8FC00A79CC3 /* OpenQuicklyFilterOperation.swift in Sources */,
 				1929B0E0C3BC59F52713D5A2 /* FoundationCommons.swift in Sources */,
 				1929B3CEE0C1A1850E9CCE2F /* BasicTypes.swift in Sources */,
+				1929BA3BB94B77E9AE051FE5 /* PreviewComponent.swift in Sources */,
+				1929B4145AA81F006BAF3B5C /* PreviewService.swift in Sources */,
+				1929BD52275A6570C666A7BA /* PreviewRenderer.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
--- a/VimR.xcodeproj/xcshareddata/xcschemes/NeoVimServer.xcscheme
+++ b/VimR.xcodeproj/xcshareddata/xcschemes/NeoVimServer.xcscheme
@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0810"
+   LastUpgradeVersion = "0820"
   version = "1.3">
   <BuildAction
      parallelizeBuildables = "YES"
--- a/VimR.xcodeproj/xcshareddata/xcschemes/SwiftNeoVim.xcscheme
+++ b/VimR.xcodeproj/xcshareddata/xcschemes/SwiftNeoVim.xcscheme
@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0810"
+   LastUpgradeVersion = "0820"
   version = "1.3">
   <BuildAction
      parallelizeBuildables = "YES"
--- a/VimR.xcodeproj/xcshareddata/xcschemes/VimR-Workspace-Demo.xcscheme
+++ b/VimR.xcodeproj/xcshareddata/xcschemes/VimR-Workspace-Demo.xcscheme
@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0810"
+   LastUpgradeVersion = "0820"
   version = "1.3">
   <BuildAction
      parallelizeBuildables = "YES"
--- a/VimR.xcodeproj/xcshareddata/xcschemes/VimR.xcscheme
+++ b/VimR.xcodeproj/xcshareddata/xcschemes/VimR.xcscheme
@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "0810"
+   LastUpgradeVersion = "0820"
   version = "1.3">
   <BuildAction
      parallelizeBuildables = "YES"
--- a/VimR/AdvancedPrefPane.swift
+++ b/VimR/AdvancedPrefPane.swift
@ -80,9 +80,9 @@ class AdvancedPrefPane: PrefPane {
                           action: #selector(AdvancedPrefPane.useInteractiveZshAction(_:)))

    let useInteractiveZshInfo = self.infoTextField(
-      text: "If your login shell is zsh, when checked, the '-i' option will be used to launch zsh.\n"
-        + "Checking this option may break VimR if your .zshrc contains complex stuff.\n"
-        + "It may be a good idea to put the PATH-settings in .zshenv and let this unchecked.\n"
+      markdown: "If your login shell is `zsh`, when checked, the `-i` option will be used to launch `zsh`.  \n"
+                + "Checking this option may break VimR if your `.zshrc` contains complex stuff.  \n"
+                + "It may be a good idea to put the `PATH`-settings in `.zshenv` and let this unchecked.  \n"
                + "Use with caution."
    )

@ -92,7 +92,7 @@ class AdvancedPrefPane: PrefPane {
                           action: #selector(AdvancedPrefPane.useSnapshotUpdateChannelAction(_:)))

    let useSnapshotUpdateInfo = self.infoTextField(
-      text: "If you are adventurous, check this.\n"
+      markdown: "If you are adventurous, check this.  \n"
                + "You'll be test driving the newest snapshot builds of VimR in no time!"
    )

--- a/VimR/AppKitCommons.swift
+++ b/VimR/AppKitCommons.swift
@ -4,6 +4,7 @@
 */

 import Cocoa
+import CocoaMarkdown

 extension NSImage {

@ -33,6 +34,19 @@ extension NSButton {
  }
 }

+extension NSMenuItem {
+
+  var boolState: Bool {
+    get {
+      return self.state == NSOnState ? true : false
+    }
+
+    set {
+      self.state = newValue ? NSOnState : NSOffState
+    }
+  }
+}
+
 extension NSAttributedString {

  func draw(at point: CGPoint, angle: CGFloat) {
@ -75,6 +89,32 @@ extension NSAttributedString {
  var wholeRange: NSRange {
    return NSRange(location: 0, length: self.length)
  }
+
+  static func infoLabel(markdown: String) -> NSAttributedString {
+    let size = NSFont.smallSystemFontSize()
+    let document = CMDocument(data: markdown.data(using: .utf8), options: .normalize)
+
+    let attrs = CMTextAttributes()
+    attrs?.textAttributes = [
+      NSFontAttributeName: NSFont.systemFont(ofSize: size),
+      NSForegroundColorAttributeName: NSColor.gray,
+    ]
+    attrs?.inlineCodeAttributes = [
+      NSFontAttributeName: NSFont.userFixedPitchFont(ofSize: size)!,
+      NSForegroundColorAttributeName: NSColor.gray,
+    ]
+
+    let renderer = CMAttributedStringRenderer(document: document, attributes: attrs)
+    renderer?.register(CMHTMLStrikethroughTransformer())
+    renderer?.register(CMHTMLSuperscriptTransformer())
+    renderer?.register(CMHTMLUnderlineTransformer())
+
+    guard let result = renderer?.render() else {
+      preconditionFailure("Wrong markdown: \(markdown)")
+    }
+
+    return result
+  }
 }

 extension NSView {
--- a/VimR/BufferListComponent.swift
+++ b/VimR/BufferListComponent.swift
@ -12,7 +12,7 @@ enum BufferListAction {
  case open(buffer: NeoVimBuffer)
 }

-class BufferListComponent: ViewComponent, NSTableViewDataSource, NSTableViewDelegate {
+class BufferListComponent: StandardViewComponent, NSTableViewDataSource, NSTableViewDelegate {

  fileprivate var buffers: [NeoVimBuffer] = []
  fileprivate let bufferList = NSTableView.standardTableView()
--- a/VimR/Component.swift
+++ b/VimR/Component.swift
@ -12,6 +12,11 @@ protocol Flow: class {
  var sink: Observable<Any> { get }
 }

+protocol ViewComponent: Flow {
+
+  var view: NSView { get }
+}
+
 class PublishingFlow: Flow {

  var sink: Observable<Any> {
@ -62,7 +67,7 @@ class EmbeddableComponent: Flow {

  fileprivate let subject = PublishSubject<Any>()
  fileprivate let source: Observable<Any>
-  fileprivate let disposeBag = DisposeBag()
+  let disposeBag = DisposeBag()

  init(source: Observable<Any>) {
    self.source = source
@ -116,10 +121,11 @@ class StandardComponent: NSObject, Flow {
  }
 }

-class ViewComponent: NSView, Flow {
+
+class StandardViewComponent: NSView, ViewComponent {

  var view: NSView {
-    preconditionFailure("Please override")
+    return self
  }

  var sink: Observable<Any> {
--- a/VimR/FileBrowserComponent.swift
+++ b/VimR/FileBrowserComponent.swift
@ -46,7 +46,7 @@ struct FileBrowserData: StandardPrefData {
  }
 }

-class FileBrowserComponent: ViewComponent, ToolDataHolder {
+class FileBrowserComponent: StandardViewComponent, ToolDataHolder {

  fileprivate let fileView: FileOutlineView
  fileprivate let fileItemService: FileItemService
@ -99,21 +99,14 @@ class FileBrowserComponent: ViewComponent, ToolDataHolder {
    }

    fileprivate func addViews() {
-      let goToParentIcon = NSImage.fontAwesomeIcon(name: .levelUp,
-                                                   textColor: InnerToolBar.iconColor,
-                                                   dimension: InnerToolBar.iconDimension)
-
      let goToParent = self.goToParentButton
+      InnerToolBar.configureToStandardIconButton(button: goToParent, iconName: .levelUp)
      goToParent.toolTip = "Set parent as working directory"
-      InnerToolBar.configureToStandardIconButton(button: goToParent, image: goToParentIcon)
      goToParent.action = #selector(FileBrowserComponent.goToParentAction)

-      let scrollToSourceIcon = NSImage.fontAwesomeIcon(name: .bullseye,
-                                                       textColor: InnerToolBar.iconColor,
-                                                       dimension: InnerToolBar.iconDimension)
      let scrollToSource = self.scrollToSourceButton
+      InnerToolBar.configureToStandardIconButton(button: scrollToSource, iconName: .bullseye)
      scrollToSource.toolTip = "Navigate to the current buffer"
-      InnerToolBar.configureToStandardIconButton(button: scrollToSource, image: scrollToSourceIcon)
      scrollToSource.action = #selector(FileBrowserComponent.scrollToSourceAction)

      self.addSubview(goToParent)
@ -145,7 +138,7 @@ class FileBrowserComponent: ViewComponent, ToolDataHolder {
    let showHiddenMenuItem = NSMenuItem(title: "Show Hidden Files",
                                        action: #selector(FileBrowserComponent.showHiddenAction),
                                        keyEquivalent: "")
-    showHiddenMenuItem.state = initialData.isShowHidden ? NSOnState : NSOffState
+    showHiddenMenuItem.boolState = initialData.isShowHidden
    self.menuItems = [
      showHiddenMenuItem,
    ]
--- a/VimR/GeneralPrefPane.swift
+++ b/VimR/GeneralPrefPane.swift
@ -111,8 +111,13 @@ class GeneralPrefPane: PrefPane, NSTextFieldDelegate {
    { [unowned self] _ in
      self.ignorePatternsAction()
    }
-    let ignoreInfo = self.infoTextField(text: "")
-    ignoreInfo.attributedStringValue = self.ignoreInfoText()
+    let ignoreInfo =
+      self.infoTextField(markdown:
+                         "Comma-separated list of ignore patterns  \n"
+                         + "Matching files will be ignored in \"Open Quickly\" and the file browser.  \n"
+                         + "Example: `*/.git, */node_modules`  \n"
+                         + "For detailed information see [VimR Wiki](https://github.com/qvacua/vimr/wiki)."
+      )

    let cliToolTitle = self.titleTextField(title: "CLI Tool:")
    let cliToolButton = NSButton(forAutoLayout: ())
@ -123,7 +128,7 @@ class GeneralPrefPane: PrefPane, NSTextFieldDelegate {
    cliToolButton.target = self
    cliToolButton.action = #selector(GeneralPrefPane.copyCliTool(_:))
    let cliToolInfo = self.infoTextField(
-      text: "Put the executable 'vimr' in your $PATH and execute 'vimr -h' for help."
+      markdown: "Put the executable `vimr` in your `$PATH` and execute `vimr -h` for help."
    )

    self.addSubview(paneTitle)
@ -203,24 +208,12 @@ class GeneralPrefPane: PrefPane, NSTextFieldDelegate {
  }

  fileprivate func ignoreInfoText() -> NSAttributedString {
-    let font = NSFont.systemFont(ofSize: NSFont.smallSystemFontSize())
-    let attrs = [
-      NSFontAttributeName: font,
-      NSForegroundColorAttributeName: NSColor.gray
-    ]
+    let markdown = "Comma-separated list of ignore patterns\n\n"
+                   + "Matching files will be ignored in \"Open Quickly\" and the file browser.\n\n"
+                   + "Example: `*/.git, */node_modules`\n\n"
+                   + "For detailed information see [VimR Wiki](https://github.com/qvacua/vimr/wiki)."

-    let wikiUrl = URL(string: "https://github.com/qvacua/vimr/wiki")!
-    let linkStr = NSAttributedString.link(withUrl: wikiUrl, text: "VimR Wiki", font: font)
-    let str = "Comma-separated list of ignore patterns\n"
-        + "Matching files will be ignored in \"Open Quickly\" and the file browser.\n"
-        + "Example: */.git, */node_modules\n"
-        + "For detailed information see "
-    
-    let ignoreInfoStr = NSMutableAttributedString(string:str, attributes:attrs)
-    ignoreInfoStr.append(linkStr)
-    ignoreInfoStr.append(NSAttributedString(string: ".", attributes: attrs))
-
-    return ignoreInfoStr
+    return NSAttributedString.infoLabel(markdown: markdown)
  }

  fileprivate func updateViews(newData: GeneralPrefData) {
--- a/VimR/MainWindowComponent.swift
+++ b/VimR/MainWindowComponent.swift
@ -15,6 +15,9 @@ enum MainWindowAction {
  case changeBufferList(mainWindow: MainWindowComponent, buffers: [NeoVimBuffer])
  case changeFileBrowserSelection(mainWindow: MainWindowComponent, url: URL)
  case close(mainWindow: MainWindowComponent, mainWindowPrefData: MainWindowPrefData)
+
+  case toggleTool(tool: WorkspaceTool)
+  case currentBufferChanged(mainWindow: MainWindowComponent, buffer: NeoVimBuffer)
 }

 struct MainWindowPrefData: StandardPrefData {
@ -28,6 +31,7 @@ struct MainWindowPrefData: StandardPrefData {
                                            toolPrefDatas: [
                                                ToolPrefData.defaults[.fileBrowser]!,
                                                ToolPrefData.defaults[.bufferList]!,
+                                                ToolPrefData.defaults[.preview]!,
                                            ])

  var isAllToolsVisible: Bool
@ -50,11 +54,10 @@ struct MainWindowPrefData: StandardPrefData {
    }

    // Add default tool pref data for missing identifiers.
-    let toolDatas = toolDataDicts.map { ToolPrefData(dict: $0) }.flatMap { $0 }
+    let toolDatas = toolDataDicts.flatMap { ToolPrefData(dict: $0) }
    let missingToolDatas = Set(ToolIdentifier.all)
        .subtracting(toolDatas.map { $0.identifier })
-        .map { ToolPrefData.defaults[$0] }
-        .flatMap { $0 }
+        .flatMap { ToolPrefData.defaults[$0] }

    self.init(isAllToolsVisible: isAllToolsVisible,
              isToolButtonsVisible: isToolButtonsVisible,
@ -70,7 +73,7 @@ struct MainWindowPrefData: StandardPrefData {
  }

  func toolPrefData(for identifier: ToolIdentifier) -> ToolPrefData {
-    guard let data = self.toolPrefDatas.filter({ $0.identifier == identifier }).first else {
+    guard let data = self.toolPrefDatas.first(where: { $0.identifier == identifier }) else {
      preconditionFailure("[ERROR] No tool for \(identifier) found!")
    }

@ -85,6 +88,12 @@ class MainWindowComponent: WindowComponent,
                           WorkspaceDelegate
 {

+  enum ScrollAction {
+
+    case scroll(to: Position)
+    case cursor(to: Position)
+  }
+
  fileprivate static let nibName = "MainWindow"

  fileprivate var defaultEditorFont: NSFont
@ -98,6 +107,8 @@ class MainWindowComponent: WindowComponent,
  fileprivate let neoVimView: NeoVimView
  fileprivate var tools = [ToolIdentifier: WorkspaceToolComponent]()

+  fileprivate let scrollFlow: EmbeddableComponent
+
  // MARK: - API
  var uuid: String {
    return self.neoVimView.uuid
@ -141,6 +152,8 @@ class MainWindowComponent: WindowComponent,
    self.defaultEditorFont = initialData.appearance.editorFont
    self.fileItemService = fileItemService

+    self.scrollFlow = EmbeddableComponent(source: Observable.empty())
+
    super.init(source: source, nibName: MainWindowComponent.nibName)

    self.window.delegate = self
@ -171,6 +184,7 @@ class MainWindowComponent: WindowComponent,
    // By default the tool buttons are shown and only the file browser tool is shown.
    let fileBrowserToolData = mainWindowData.toolPrefData(for: .fileBrowser)
    let bufferListToolData = mainWindowData.toolPrefData(for: .bufferList)
+    let previewToolData = mainWindowData.toolPrefData(for: .preview)

    let fileBrowserData = fileBrowserToolData.toolData as? FileBrowserData ?? FileBrowserData.default

@ -196,11 +210,25 @@ class MainWindowComponent: WindowComponent,
    let bufferListTool = WorkspaceToolComponent(toolIdentifier: .bufferList, config: bufferListConfig)
    self.tools[.bufferList] = bufferListTool

+    let previewData = previewToolData.toolData as? PreviewComponent.PrefData ?? PreviewComponent.PrefData.default
+    let preview = PreviewComponent(source: self.sink,
+                                   scrollSource: self.scrollFlow.sink,
+                                   initialData: previewData)
+    let previewConfig = WorkspaceTool.Config(title: "Preview",
+                                             view: preview,
+                                             minimumDimension: 200,
+                                             withInnerToolbar: true)
+    let previewTool = WorkspaceToolComponent(toolIdentifier: .preview, config: previewConfig)
+    preview.workspaceTool = previewTool
+    self.tools[.preview] = previewTool
+
    self.workspace.append(tool: fileBrowserTool, location: fileBrowserToolData.location)
    self.workspace.append(tool: bufferListTool, location: bufferListToolData.location)
+    self.workspace.append(tool: previewTool, location: previewToolData.location)

    fileBrowserTool.dimension = fileBrowserToolData.dimension
    bufferListTool.dimension = bufferListToolData.dimension
+    previewTool.dimension = previewToolData.dimension

    if !mainWindowData.isAllToolsVisible {
      self.toggleAllTools(self)
@ -217,6 +245,10 @@ class MainWindowComponent: WindowComponent,
    if bufferListToolData.isVisible {
      bufferListTool.toggle()
    }
+
+    if previewToolData.isVisible {
+      previewTool.toggle()
+    }
  }

  func open(urls: [URL]) {
@ -276,8 +308,16 @@ class MainWindowComponent: WindowComponent,
        case let BufferListAction.open(buffer: buffer):
          self.neoVimView.select(buffer: buffer)

+        case let PreviewComponent.Action.reverseSearch(to: position):
+          self.neoVimView.cursorGo(to: position)
+          return
+
+        case let PreviewComponent.Action.scroll(to: position):
+          NSLog("preview scrolled to \(position)")
+          return
+
        default:
-          NSLog("WARN unrecognized action: \(action)")
+          NSLog("Not handled action: \(action)")
          return
        }

@ -321,6 +361,10 @@ extension MainWindowComponent {
  func resizeDidEnd(workspace: Workspace) {
    self.neoVimView.exitResizeMode()
  }
+
+  func toggled(tool: WorkspaceTool) {
+    self.publish(event: MainWindowAction.toggleTool(tool: tool))
+  }
 }

 // MARK: - File Menu Item Actions
@ -426,18 +470,18 @@ extension MainWindowComponent {
    let fileBrowserTool = self.tools[.fileBrowser]!

    if fileBrowserTool.isSelected {
-      if fileBrowserTool.viewComponent.isFirstResponder {
+      if fileBrowserTool.viewComponent.view.isFirstResponder {
        fileBrowserTool.toggle()
        self.focusNeoVimView(self)
      } else {
-        fileBrowserTool.viewComponent.beFirstResponder()
+        fileBrowserTool.viewComponent.view.beFirstResponder()
      }

      return
    }

    fileBrowserTool.toggle()
-    fileBrowserTool.viewComponent.beFirstResponder()
+    fileBrowserTool.viewComponent.view.beFirstResponder()
  }

  @IBAction func focusNeoVimView(_ sender: Any?) {
@ -500,6 +544,18 @@ extension MainWindowComponent {
    self.publish(event: MainWindowAction.changeBufferList(mainWindow: self, buffers: buffers))
  }

+  func currentBufferChanged(_ currentBuffer: NeoVimBuffer) {
+    self.publish(event: MainWindowAction.currentBufferChanged(mainWindow: self, buffer: currentBuffer))
+  }
+
+  func tabChanged() {
+    guard let currentBuffer = self.neoVimView.currentBuffer() else {
+      return
+    }
+
+    self.publish(event: MainWindowAction.currentBufferChanged(mainWindow: self, buffer: currentBuffer))
+  }
+
  func ipcBecameInvalid(reason: String) {
    let alert = NSAlert()
    alert.addButton(withTitle: "Close")
@ -511,6 +567,14 @@ extension MainWindowComponent {
      self?.windowController.close()
    }
  }
+
+  func scroll() {
+    self.scrollFlow.publish(event: ScrollAction.scroll(to: self.neoVimView.currentPosition))
+  }
+
+  func cursor(to position: Position) {
+    self.scrollFlow.publish(event: ScrollAction.cursor(to: self.neoVimView.currentPosition))
+  }
 }

 // MARK: - NSWindowDelegate
@ -549,7 +613,14 @@ extension MainWindowComponent {
                                      isVisible: bufferList.isSelected,
                                      dimension: bufferList.dimension)

-    return [ fileBrowserData, bufferListData ]
+    let preview = self.tools[.preview]!
+    let previewData = ToolPrefData(identifier: .preview,
+                                   location: preview.location,
+                                   isVisible: preview.isSelected,
+                                   dimension: preview.dimension,
+                                   toolData: preview.toolData)
+
+    return [ fileBrowserData, bufferListData, previewData ]
  }

  func windowShouldClose(_ sender: Any) -> Bool {
--- a/VimR/MainWindowManager.swift
+++ b/VimR/MainWindowManager.swift
@ -49,7 +49,7 @@ class MainWindowManager: StandardFlow {
        case let .close(mainWindow, mainWindowPrefData):
          self.close(mainWindow, prefData: mainWindowPrefData)

-        case .changeCwd, .changeBufferList, .changeFileBrowserSelection:
+        default:
          break;
        }
      })
--- a/VimR/MarkdownRenderer.swift
+++ b/VimR/MarkdownRenderer.swift
@ -0,0 +1,402 @@
+/**
+ * Tae Won Ha - http://taewon.de - @hataewon
+ * See LICENSE
+ */
+
+import Cocoa
+import RxSwift
+import PureLayout
+import CocoaMarkdown
+import WebKit
+
+fileprivate class WebviewMessageHandler: NSObject, WKScriptMessageHandler {
+
+  enum Action {
+
+    case scroll(lineBegin: Int, columnBegin: Int, lineEnd: Int, columnEnd: Int)
+  }
+
+  fileprivate let flow: EmbeddableComponent
+
+  override init() {
+    flow = EmbeddableComponent(source: Observable.empty())
+    super.init()
+  }
+
+  func userContentController(_: WKUserContentController, didReceive message: WKScriptMessage) {
+    guard let msgBody = message.body as? [String: Int] else {
+      return
+    }
+
+    guard let lineBegin = msgBody["lineBegin"],
+          let columnBegin = msgBody["columnBegin"],
+          let lineEnd = msgBody["lineEnd"],
+          let columnEnd = msgBody["columnEnd"]
+      else {
+      return
+    }
+
+    flow.publish(event: Action.scroll(lineBegin: lineBegin, columnBegin: columnBegin,
+                                      lineEnd: lineEnd, columnEnd: columnEnd))
+  }
+}
+
+class MarkdownRenderer: NSObject, Flow, PreviewRenderer {
+
+  static let identifier = "com.qvacua.vimr.tool.preview.markdown"
+  static func prefData(from dict: [String: Any]) -> StandardPrefData? {
+    return PrefData(dict: dict)
+  }
+
+  struct PrefData: StandardPrefData {
+
+    fileprivate static let identifier = "identifier"
+    fileprivate static let isForwardSearchAutomatically = "is-forward-search-automatically"
+    fileprivate static let isReverseSearchAutomatically = "is-reverse-search-automatically"
+    fileprivate static let isRefreshOnWrite = "is-refresh-on-write"
+
+    static let `default` = PrefData(isForwardSearchAutomatically: false,
+                                    isReverseSearchAutomatically: false,
+                                    isRefreshOnWrite: true)
+
+    var isForwardSearchAutomatically: Bool
+    var isReverseSearchAutomatically: Bool
+    var isRefreshOnWrite: Bool
+
+    init(isForwardSearchAutomatically: Bool, isReverseSearchAutomatically: Bool, isRefreshOnWrite: Bool) {
+      self.isForwardSearchAutomatically = isForwardSearchAutomatically
+      self.isReverseSearchAutomatically = isReverseSearchAutomatically
+      self.isRefreshOnWrite = isRefreshOnWrite
+    }
+
+    init?(dict: [String: Any]) {
+      guard PrefUtils.string(from: dict, for: PrefData.identifier) == MarkdownRenderer.identifier else {
+        return nil
+      }
+
+      guard let isForward = PrefUtils.bool(from: dict, for: PrefData.isForwardSearchAutomatically) else {
+        return nil
+      }
+
+      guard let isReverse = PrefUtils.bool(from: dict, for: PrefData.isReverseSearchAutomatically) else {
+        return nil
+      }
+
+      guard let isRefreshOnWrite = PrefUtils.bool(from: dict, for: PrefData.isRefreshOnWrite) else {
+        return nil
+      }
+
+      self.init(isForwardSearchAutomatically: isForward,
+                isReverseSearchAutomatically: isReverse,
+                isRefreshOnWrite: isRefreshOnWrite)
+    }
+
+    func dict() -> [String: Any] {
+      return [
+        PrefData.identifier: MarkdownRenderer.identifier,
+        PrefData.isForwardSearchAutomatically: self.isForwardSearchAutomatically,
+        PrefData.isReverseSearchAutomatically: self.isReverseSearchAutomatically,
+        PrefData.isRefreshOnWrite: self.isRefreshOnWrite,
+      ]
+    }
+  }
+
+  fileprivate let flow: EmbeddableComponent
+  fileprivate let scrollFlow: EmbeddableComponent
+
+  fileprivate let scheduler = ConcurrentDispatchQueueScheduler(qos: .userInitiated)
+  fileprivate let baseUrl = Bundle.main.resourceURL!.appendingPathComponent("markdown")
+  fileprivate let extensions = Set(["md", "markdown", ])
+  fileprivate let template: String
+
+  fileprivate let userContentController = WKUserContentController()
+  fileprivate let webviewMessageHandler = WebviewMessageHandler()
+
+  fileprivate var isForwardSearchAutomatically = false
+  fileprivate var isReverseSearchAutomatically = false
+  fileprivate var isRefreshOnWrite = true
+
+  fileprivate let automaticForwardMenuItem = NSMenuItem(title: "Automatic Forward Search",
+                                                        action: nil,
+                                                        keyEquivalent: "")
+  fileprivate let automaticReverseMenuItem = NSMenuItem(title: "Automatic Reverse Search",
+                                                        action: nil,
+                                                        keyEquivalent: "")
+  fileprivate let refreshOnWriteMenuItem = NSMenuItem(title: "Refresh on Write", action: nil, keyEquivalent: "")
+
+  fileprivate let webview: WKWebView
+
+  fileprivate var ignoreNextForwardSearch = false;
+
+  fileprivate var currentEditorPosition = Position(row: 1, column: 1)
+  fileprivate var currentUrl: URL?
+  fileprivate var currentPreviewPosition = Position(row: 1, column: 1)
+
+  let identifier: String = MarkdownRenderer.identifier
+  var prefData: StandardPrefData? {
+    return PrefData(isForwardSearchAutomatically: self.isForwardSearchAutomatically,
+                    isReverseSearchAutomatically: self.isReverseSearchAutomatically,
+                    isRefreshOnWrite: self.isRefreshOnWrite)
+  }
+
+  var sink: Observable<Any> {
+    return self.flow.sink
+  }
+
+  var scrollSink: Observable<Any> {
+    return self.scrollFlow.sink
+  }
+
+  let toolbar: NSView? = NSView(forAutoLayout: ())
+  let menuItems: [NSMenuItem]?
+
+  init(source: Observable<Any>, scrollSource: Observable<Any>, initialData: PrefData) {
+    guard let templateUrl = Bundle.main.url(forResource: "template",
+                                            withExtension: "html",
+                                            subdirectory: "markdown")
+      else {
+      preconditionFailure("ERROR Cannot load markdown template")
+    }
+
+    guard let template = try? String(contentsOf: templateUrl) else {
+      preconditionFailure("ERROR Cannot load markdown template")
+    }
+
+    self.template = template
+
+    self.flow = EmbeddableComponent(source: source)
+    self.scrollFlow = EmbeddableComponent(source: scrollSource)
+
+    let configuration = WKWebViewConfiguration()
+    configuration.userContentController = self.userContentController
+    self.webview = WKWebView(frame: .zero, configuration: configuration)
+    self.webview.configureForAutoLayout()
+
+    self.isForwardSearchAutomatically = initialData.isForwardSearchAutomatically
+    self.isReverseSearchAutomatically = initialData.isReverseSearchAutomatically
+    self.isRefreshOnWrite = initialData.isRefreshOnWrite
+
+    let refreshMenuItem = NSMenuItem(title: "Refresh Now", action: nil, keyEquivalent: "")
+    let forwardSearchMenuItem = NSMenuItem(title: "Forward Search", action: nil, keyEquivalent: "")
+    let reverseSearchMenuItem = NSMenuItem(title: "Reverse Search", action: nil, keyEquivalent: "")
+
+    let automaticForward = self.automaticForwardMenuItem
+    let automaticReverse = self.automaticReverseMenuItem
+    let refreshOnWrite = self.refreshOnWriteMenuItem
+
+    automaticForward.boolState = self.isForwardSearchAutomatically
+    automaticReverse.boolState = self.isReverseSearchAutomatically
+    refreshOnWrite.boolState = self.isRefreshOnWrite
+
+    self.menuItems = [
+      refreshMenuItem,
+      forwardSearchMenuItem,
+      reverseSearchMenuItem,
+      NSMenuItem.separator(),
+      automaticForward,
+      automaticReverse,
+      NSMenuItem.separator(),
+      refreshOnWrite,
+    ]
+
+    super.init()
+
+    self.initCustomUiElements()
+
+    refreshMenuItem.target = self
+    refreshMenuItem.action = #selector(MarkdownRenderer.refreshNowAction)
+    forwardSearchMenuItem.target = self
+    forwardSearchMenuItem.action = #selector(MarkdownRenderer.forwardSearchAction)
+    reverseSearchMenuItem.target = self
+    reverseSearchMenuItem.action = #selector(MarkdownRenderer.reverseSearchAction)
+    automaticForward.target = self
+    automaticForward.action = #selector(MarkdownRenderer.automaticForwardSearchAction)
+    automaticReverse.target = self
+    automaticReverse.action = #selector(MarkdownRenderer.automaticReverseSearchAction)
+    refreshOnWrite.target = self
+    refreshOnWrite.action = #selector(MarkdownRenderer.refreshOnWriteAction)
+
+    self.flow.set(subscription: self.subscription)
+    self.scrollFlow.set(subscription: self.scrollSubscription)
+
+    self.addReactions()
+    self.userContentController.add(webviewMessageHandler, name: "com_vimr_preview_markdown")
+  }
+
+  func canRender(fileExtension: String) -> Bool {
+    return extensions.contains(fileExtension)
+  }
+
+  fileprivate func subscription(source: Observable<Any>) -> Disposable {
+    return source
+      .observeOn(self.scheduler)
+      .mapOmittingNil { (action) -> URL? in
+
+        switch action {
+        case let PreviewComponent.Action.automaticRefresh(url):
+          guard self.isRefreshOnWrite else {
+            return nil
+          }
+
+          return url
+
+        default:
+          return nil
+
+        }
+      }
+      .subscribe(onNext: { [unowned self] url in
+        self.currentUrl = url
+
+        guard self.canRender(fileExtension: url.pathExtension) else {
+          return
+        }
+
+        self.render(from: url)
+      })
+  }
+
+  fileprivate func initCustomUiElements() {
+    let refresh = NSButton(forAutoLayout: ())
+    InnerToolBar.configureToStandardIconButton(button: refresh, iconName: .refresh)
+    refresh.toolTip = "Refresh Now"
+    refresh.target = self
+    refresh.action = #selector(MarkdownRenderer.refreshNowAction)
+
+    let forward = NSButton(forAutoLayout: ())
+    InnerToolBar.configureToStandardIconButton(button: forward, iconName: .chevronCircleRight)
+    forward.toolTip = "Forward Search"
+    forward.target = self
+    forward.action = #selector(MarkdownRenderer.forwardSearchAction)
+
+    let reverse = NSButton(forAutoLayout: ())
+    InnerToolBar.configureToStandardIconButton(button: reverse, iconName: .chevronCircleLeft)
+    reverse.toolTip = "Reverse Search"
+    reverse.target = self
+    reverse.action = #selector(MarkdownRenderer.reverseSearchAction)
+
+    self.toolbar?.addSubview(forward)
+    self.toolbar?.addSubview(reverse)
+    self.toolbar?.addSubview(refresh)
+
+    forward.autoPinEdge(toSuperviewEdge: .top)
+    forward.autoPinEdge(toSuperviewEdge: .right)
+
+    reverse.autoPinEdge(toSuperviewEdge: .top)
+    reverse.autoPinEdge(.right, to: .left, of: forward)
+
+    refresh.autoPinEdge(toSuperviewEdge: .top)
+    refresh.autoPinEdge(.right, to: .left, of: reverse)
+  }
+
+  fileprivate func scrollSubscription(source: Observable<Any>) -> Disposable {
+    return source
+      .throttle(0.75, latest: true, scheduler: MainScheduler.instance)
+      .filter { $0 is MainWindowComponent.ScrollAction }
+      .map { $0 as! MainWindowComponent.ScrollAction }
+      .subscribe(onNext: { [unowned self] action in
+        switch action {
+        case let .scroll(to: position), let .cursor(to: position):
+          self.currentEditorPosition = position
+        }
+
+        guard self.isForwardSearchAutomatically && self.ignoreNextForwardSearch == false else {
+          self.ignoreNextForwardSearch = false
+          return
+        }
+
+        self.forwardSearch(position: self.currentEditorPosition)
+      })
+  }
+
+  fileprivate func addReactions() {
+    self.webviewMessageHandler.flow.sink
+      .throttle(0.75, latest: true, scheduler: MainScheduler.instance)
+      .filter { $0 is WebviewMessageHandler.Action }
+      .map { $0 as! WebviewMessageHandler.Action }
+      .subscribe(onNext: { [weak self] action in
+        switch action {
+        case let .scroll(lineBegin, columnBegin, _, _):
+          self?.currentPreviewPosition = Position(row: lineBegin, column: columnBegin)
+
+          guard self?.isReverseSearchAutomatically == true else {
+            return
+          }
+
+          if self?.isForwardSearchAutomatically == true {
+            self?.ignoreNextForwardSearch = true
+          }
+
+          self?.flow.publish(
+            event: PreviewRendererAction.reverseSearch(to: Position(row: lineBegin, column: columnBegin))
+          )
+        }
+      })
+      .addDisposableTo(self.flow.disposeBag)
+  }
+
+  fileprivate func filledTemplate(body: String, title: String) -> String {
+    return self.template
+      .replacingOccurrences(of: "{{ title }}", with: title)
+      .replacingOccurrences(of: "{{ body }}", with: body)
+  }
+
+  fileprivate func render(from url: URL) {
+    let doc = CMDocument(contentsOfFile: url.path, options: .sourcepos)
+    let renderer = CMHTMLRenderer(document: doc)
+
+    guard let body = renderer?.render() else {
+      self.flow.publish(event: PreviewRendererAction.error)
+      return
+    }
+
+    let html = filledTemplate(body: body, title: url.lastPathComponent)
+    self.webview.loadHTMLString(html, baseURL: self.baseUrl)
+
+    try? html.write(toFile: "/tmp/markdown-preview.html", atomically: false, encoding: .utf8)
+    self.flow.publish(event: PreviewRendererAction.view(renderer: self, view: self.webview))
+  }
+}
+
+// MARK: - Actions
+extension MarkdownRenderer {
+
+  fileprivate func forwardSearch(position: Position) {
+    self.webview.evaluateJavaScript("scrollToPosition(\(position.row), \(position.column));")
+  }
+
+  func refreshNowAction(_: Any?) {
+    guard let url = self.currentUrl else {
+      return
+    }
+
+    guard self.canRender(fileExtension: url.pathExtension) else {
+      return
+    }
+
+    self.render(from: url)
+  }
+
+  func forwardSearchAction(_: Any?) {
+    self.forwardSearch(position: self.currentEditorPosition)
+  }
+
+  func reverseSearchAction(_: Any?) {
+    self.flow.publish(event: PreviewRendererAction.reverseSearch(to: self.currentPreviewPosition))
+  }
+
+  func automaticForwardSearchAction(_: Any?) {
+    self.isForwardSearchAutomatically = !self.isForwardSearchAutomatically
+    self.automaticForwardMenuItem.boolState = self.isForwardSearchAutomatically
+  }
+
+  func automaticReverseSearchAction(_: Any?) {
+    self.isReverseSearchAutomatically = !self.isReverseSearchAutomatically
+    self.automaticReverseMenuItem.boolState = self.isReverseSearchAutomatically
+  }
+
+  func refreshOnWriteAction(_: Any?) {
+    self.isRefreshOnWrite = !self.isRefreshOnWrite
+    self.refreshOnWriteMenuItem.boolState = self.isRefreshOnWrite
+  }
+}
--- a/VimR/PrefPane.swift
+++ b/VimR/PrefPane.swift
@ -6,7 +6,7 @@
 import Cocoa
 import RxSwift

-class PrefPane: ViewComponent {
+class PrefPane: StandardViewComponent {
  
  // Return true to place this to the upper left corner when the scroll view is bigger than this view.
  override var isFlipped: Bool {
@ -44,19 +44,18 @@ extension PrefPane {
    return field
  }

-  func infoTextField(text: String) -> NSTextField {
+  func infoTextField(markdown: String) -> NSTextField {
    let field = NSTextField(forAutoLayout: ())
-    field.font = NSFont.systemFont(ofSize: NSFont.smallSystemFontSize())
-    field.textColor = NSColor.gray
    field.backgroundColor = NSColor.clear
    field.isEditable = false
    field.isBordered = false
+    field.usesSingleLineMode = false

    // both are needed, otherwise hyperlink won't accept mousedown
    field.isSelectable = true
    field.allowsEditingTextAttributes = true

-    field.stringValue = text
+    field.attributedStringValue = NSAttributedString.infoLabel(markdown: markdown)

    return field
  }
--- a/VimR/PrefUtils.swift
+++ b/VimR/PrefUtils.swift
@ -71,6 +71,10 @@ class PrefUtils {
    return (dict[key] as? NSNumber)?.boolValue ?? defaultValue
  }

+  static func string(from dict: [String: Any], for key: String) -> String? {
+    return dict[key] as? String
+  }
+
  static func saneFont(_ fontName: String, fontSize: CGFloat) -> NSFont {
    var editorFont = NSFont(name: fontName, size: fontSize) ?? NeoVimView.defaultFont
    if !editorFont.isFixedPitch {
--- a/VimR/PreviewComponent.swift
+++ b/VimR/PreviewComponent.swift
@ -0,0 +1,279 @@
+/**
+ * Tae Won Ha - http://taewon.de - @hataewon
+ * See LICENSE
+ */
+
+import Cocoa
+import RxSwift
+import PureLayout
+import WebKit
+
+class PreviewComponent: NSView, ViewComponent, ToolDataHolder {
+
+  enum Action {
+
+    case automaticRefresh(url: URL)
+    case reverseSearch(to: Position)
+    case scroll(to: Position)
+  }
+
+  struct PrefData: StandardPrefData {
+
+    fileprivate static let rendererDatas = "renderer-datas"
+
+    fileprivate static let rendererPrefDataFns = [
+      MarkdownRenderer.identifier: MarkdownRenderer.prefData,
+    ]
+
+    fileprivate static let rendererDefaultPrefDatas = [
+      MarkdownRenderer.identifier: MarkdownRenderer.PrefData.default,
+    ]
+
+    static let `default` = PrefData(rendererDatas: PrefData.rendererDefaultPrefDatas)
+
+    var rendererDatas: [String: StandardPrefData]
+
+    init(rendererDatas: [String: StandardPrefData]) {
+      self.rendererDatas = rendererDatas
+    }
+
+    init?(dict: [String: Any]) {
+      guard let rendererDataDict = dict[PrefData.rendererDatas] as? [String: [String: Any]] else {
+        return nil
+      }
+
+      let storedRendererDatas: [(String, StandardPrefData)] = rendererDataDict.flatMap { (identifier, dict) in
+        guard let prefDataFn = PrefData.rendererPrefDataFns[identifier] else {
+          return nil
+        }
+
+        guard let prefData = prefDataFn(dict) else {
+          return nil
+        }
+
+        return (identifier, prefData)
+      }
+
+      let missingRendererDatas: [(String, StandardPrefData)] = Set(PrefData.rendererDefaultPrefDatas.keys)
+        .subtracting(storedRendererDatas.map { $0.0 })
+        .flatMap { identifier in
+          guard let data = PrefData.rendererDefaultPrefDatas[identifier] else {
+            return nil
+          }
+
+          return (identifier, data)
+        }
+
+      self.init(rendererDatas: toDict([storedRendererDatas, missingRendererDatas].flatMap { $0 }))
+    }
+
+    func dict() -> [String: Any] {
+      return [
+        PrefData.rendererDatas: self.rendererDatas.mapToDict { (key, value) in (key, value.dict()) }
+      ]
+    }
+  }
+
+  fileprivate let scheduler = ConcurrentDispatchQueueScheduler(qos: .userInitiated)
+  fileprivate let flow: EmbeddableComponent
+
+  fileprivate var currentUrl: URL?
+
+  fileprivate let renderers: [PreviewRenderer]
+  fileprivate var currentRenderer: PreviewRenderer? {
+    didSet {
+      guard oldValue !== currentRenderer else {
+        return
+      }
+
+      if let toolbar = self.currentRenderer?.toolbar {
+        self.workspaceTool?.customInnerToolbar = toolbar
+      }
+      if let menuItems = self.currentRenderer?.menuItems {
+        self.workspaceTool?.customInnerMenuItems = menuItems
+      }
+    }
+  }
+  fileprivate let markdownRenderer: MarkdownRenderer
+
+  fileprivate let baseUrl: URL
+  fileprivate let webview = WKWebView(frame: .zero, configuration: WKWebViewConfiguration())
+  fileprivate let previewService = PreviewService()
+
+  fileprivate var isOpen = false
+  fileprivate var currentView: NSView {
+    willSet {
+      self.currentView.removeFromSuperview()
+    }
+
+    didSet {
+      self.addSubview(self.currentView)
+      self.currentView.autoPinEdgesToSuperviewEdges()
+    }
+  }
+
+  required init?(coder: NSCoder) {
+    fatalError("init(coder:) has not been implemented")
+  }
+
+  weak var workspaceTool: WorkspaceTool?
+
+  var toolData: StandardPrefData {
+    let rendererDatas = self.renderers.flatMap { (renderer) -> (String, StandardPrefData)? in
+      guard let data = renderer.prefData else {
+        return nil
+      }
+      return (renderer.identifier, data)
+    }
+
+    return PrefData(rendererDatas: toDict(rendererDatas))
+  }
+
+  var sink: Observable<Any> {
+    return self.flow.sink
+  }
+
+  var view: NSView {
+    return self
+  }
+
+  init(source: Observable<Any>, scrollSource: Observable<Any>, initialData: PrefData) {
+    self.flow = EmbeddableComponent(source: source)
+
+    self.baseUrl = self.previewService.baseUrl()
+    let markdownData = initialData.rendererDatas[MarkdownRenderer.identifier] as? MarkdownRenderer.PrefData ??
+                       MarkdownRenderer.PrefData.default
+    self.markdownRenderer = MarkdownRenderer(source: self.flow.sink,
+                                             scrollSource: scrollSource,
+                                             initialData: markdownData)
+
+    self.renderers = [
+      self.markdownRenderer,
+    ]
+
+    self.webview.configureForAutoLayout()
+    self.currentView = self.webview
+
+    super.init(frame: .zero)
+    self.configureForAutoLayout()
+
+    self.flow.set(subscription: self.subscription)
+
+    self.webview.loadHTMLString(self.previewService.emptyHtml(), baseURL: self.baseUrl)
+
+    self.addViews()
+    self.addReactions()
+  }
+
+  fileprivate func addViews() {
+    self.addSubview(self.currentView)
+    self.currentView.autoPinEdgesToSuperviewEdges()
+  }
+
+  fileprivate func subscription(source: Observable<Any>) -> Disposable {
+    return source
+      .filter { $0 is MainWindowAction }
+      .map { $0 as! MainWindowAction }
+      .subscribe(onNext: { [unowned self] action in
+        switch action {
+
+        case let .currentBufferChanged(_, currentBuffer):
+          self.currentUrl = currentBuffer.url
+
+          guard let url = currentBuffer.url else {
+            self.currentRenderer = nil
+            self.currentView = self.webview
+            self.webview.loadHTMLString(self.previewService.saveFirstHtml(), baseURL: self.baseUrl)
+            return
+          }
+
+          guard self.isOpen else {
+            return
+          }
+
+          self.currentRenderer = self.renderers.first { $0.canRender(fileExtension: url.pathExtension) }
+          if self.currentRenderer == nil {
+            self.currentView = self.webview
+            self.webview.loadHTMLString(self.previewService.emptyHtml(), baseURL: self.baseUrl)
+          }
+
+          self.flow.publish(event: PreviewComponent.Action.automaticRefresh(url: url))
+
+        case let .toggleTool(tool):
+          guard tool.view == self else {
+            return
+          }
+          self.isOpen = tool.isSelected
+
+          guard let url = self.currentUrl else {
+            self.currentRenderer = nil
+            self.currentView = self.webview
+            self.webview.loadHTMLString(self.previewService.saveFirstHtml(), baseURL: self.baseUrl)
+            return
+          }
+
+          self.currentRenderer = self.renderers.first { $0.canRender(fileExtension: url.pathExtension) }
+          if self.currentRenderer != nil {
+            self.flow.publish(event: PreviewComponent.Action.automaticRefresh(url: url))
+          }
+
+        default:
+          return
+
+        }
+      })
+  }
+
+  fileprivate func addReactions() {
+    self.markdownRenderer.scrollSink
+      .throttle(1, latest: true, scheduler: self.scheduler)
+      .filter { $0 is PreviewRendererAction }
+      .map { $0 as! PreviewRendererAction }
+      .subscribe(onNext: { action in
+        guard self.isOpen else {
+          return
+        }
+
+        switch action {
+
+        case let .scroll(to: position):
+          self.flow.publish(event: Action.scroll(to: position))
+
+        default:
+          return
+
+        }
+      })
+      .addDisposableTo(self.flow.disposeBag)
+
+    self.markdownRenderer.sink
+      .filter { $0 is PreviewRendererAction }
+      .map { $0 as! PreviewRendererAction }
+      .observeOn(MainScheduler.instance)
+      .subscribe(onNext: { [unowned self] action in
+        guard self.isOpen else {
+          return
+        }
+
+        switch action {
+
+        case let .reverseSearch(to: position):
+          self.flow.publish(event: Action.reverseSearch(to: position))
+
+        case let .htmlString(_, html, baseUrl):
+          self.webview.loadHTMLString(html, baseURL: baseUrl)
+
+        case let .view(_, view):
+          self.currentView = view
+
+        case .error:
+          self.webview.loadHTMLString(self.previewService.errorHtml(), baseURL: self.baseUrl)
+
+        default:
+          return
+
+        }
+      })
+      .addDisposableTo(self.flow.disposeBag)
+  }
+}
--- a/VimR/PreviewRenderer.swift
+++ b/VimR/PreviewRenderer.swift
@ -0,0 +1,33 @@
+/**
+ * Tae Won Ha - http://taewon.de - @hataewon
+ * See LICENSE
+ */
+
+import Cocoa
+import RxSwift
+
+protocol PreviewRenderer: class {
+
+  static var identifier: String { get }
+  static func prefData(from: [String: Any]) -> StandardPrefData?
+
+  var identifier: String { get }
+  var prefData: StandardPrefData? { get }
+  var scrollSink: Observable<Any> { get }
+
+  var toolbar: NSView? { get }
+  var menuItems: [NSMenuItem]? { get }
+
+  func canRender(fileExtension: String) -> Bool
+}
+
+enum PreviewRendererAction {
+
+  case htmlString(renderer: PreviewRenderer, html: String, baseUrl: URL)
+  case view(renderer: PreviewRenderer, view: NSView)
+
+  case reverseSearch(to: Position)
+  case scroll(to: Position)
+
+  case error(renderer: PreviewRenderer)
+}
--- a/VimR/PreviewService.swift
+++ b/VimR/PreviewService.swift
@ -0,0 +1,62 @@
+/**
+ * Tae Won Ha - http://taewon.de - @hataewon
+ * See LICENSE
+ */
+
+import Foundation
+
+class PreviewService {
+
+  fileprivate let empty: String
+  fileprivate let error: String
+  fileprivate let saveFirst: String
+
+  init() {
+    guard let emptyUrl = Bundle.main.url(forResource: "empty", withExtension: "html", subdirectory: "preview") else {
+      preconditionFailure("No empty.html!")
+    }
+
+    guard let errorUrl = Bundle.main.url(forResource: "error", withExtension: "html", subdirectory: "preview") else {
+      preconditionFailure("No error.html!")
+    }
+
+    guard let saveFirstUrl = Bundle.main.url(forResource: "save-first",
+                                             withExtension: "html",
+                                             subdirectory: "preview")
+      else {
+      preconditionFailure("No save-first.html!")
+    }
+
+    guard let emptyHtml = try? String(contentsOf: emptyUrl) else {
+      preconditionFailure("Error getting empty.html!")
+    }
+
+    guard let errorHtml = try? String(contentsOf: errorUrl) else {
+      preconditionFailure("Error getting error.html!")
+    }
+
+    guard let saveFirstHtml = try? String(contentsOf: saveFirstUrl) else {
+      preconditionFailure("Error getting save-first.html!")
+    }
+
+    self.empty = emptyHtml
+    self.error = errorHtml
+    self.saveFirst = saveFirstHtml
+  }
+
+  func baseUrl() -> URL {
+    return Bundle.main.resourceURL!.appendingPathComponent("preview")
+  }
+
+  func emptyHtml() -> String {
+    return self.empty
+  }
+
+  func errorHtml() -> String {
+    return self.error
+  }
+
+  func saveFirstHtml() -> String {
+    return self.saveFirst
+  }
+}
--- a/VimR/RxSwiftCommons.swift
+++ b/VimR/RxSwiftCommons.swift
@ -16,3 +16,13 @@ extension Array {
      .flatMap { $0 }
  }
 }
+
+extension ObservableType {
+
+  func mapOmittingNil<R>(_ transform: @escaping (Self.E) throws -> R?) -> RxSwift.Observable<R> {
+    return self
+      .map(transform)
+      .filter { $0 != nil }
+      .map { $0! }
+  }
+}
--- a/VimR/SwiftCommons.swift
+++ b/VimR/SwiftCommons.swift
@ -56,6 +56,29 @@ extension Array {
  }
 }

+func toDict<K: Hashable, V, S: Sequence>(_ sequence: S) -> Dictionary<K, V> where S.Iterator.Element == (K, V) {
+  var result = Dictionary<K, V>(minimumCapacity: sequence.underestimatedCount)
+
+  for (key, value) in sequence {
+    result[key] = value
+  }
+
+  return result
+}
+
+extension Dictionary {
+
+  func mapToDict<T>(_ transform: ((key: Key, value: Value)) throws -> (Key, T)) rethrows -> Dictionary<Key, T> {
+    let array = try self.map(transform)
+    return toDict(array)
+  }
+
+  func flatMapToDict<T>(_ transform: ((key: Key, value: Value)) throws -> (Key, T)?) rethrows -> Dictionary<Key, T> {
+    let array = try self.flatMap(transform)
+    return toDict(array)
+  }
+}
+
 extension Array where Element: Equatable {

  /**
@ -66,7 +89,7 @@ extension Array where Element: Equatable {
   */
  func substituting(elements: [Element]) -> [Element] {
    let elementsInArray = elements.filter { self.contains($0) }
-    let indices = elementsInArray.map { self.index(of: $0) }.flatMap { $0 }
+    let indices = elementsInArray.flatMap { self.index(of: $0) }

    var result = self
    indices.enumerated().forEach { result[$0.1] = elementsInArray[$0.0] }
--- a/VimR/ToolPrefData.swift
+++ b/VimR/ToolPrefData.swift
@ -9,8 +9,9 @@ enum ToolIdentifier: String {

  case fileBrowser = "com.qvacua.vimr.tool.file-browser"
  case bufferList = "com.qvacua.vimr.tool.buffer-list"
+  case preview = "com.qvacua.vimr.tool.preview"

-  static let all = [ fileBrowser, bufferList ]
+  static let all = [ fileBrowser, bufferList, preview ]
 }

 protocol ToolDataHolder: class {
@ -37,6 +38,11 @@ struct ToolPrefData: StandardPrefData {
                              isVisible: false,
                              dimension: 200,
                              toolData: EmptyPrefData.default),
+    .preview: ToolPrefData(identifier: .preview,
+                           location: .right,
+                           isVisible: false,
+                           dimension: 300,
+                           toolData: PreviewComponent.PrefData.default),
  ]

  var identifier: ToolIdentifier
@ -88,6 +94,8 @@ struct ToolPrefData: StandardPrefData {
    switch identifier {
    case .fileBrowser:
      toolData = FileBrowserData(dict: toolDataDict) ?? FileBrowserData.default
+    case .preview:
+      toolData = PreviewComponent.PrefData(dict: toolDataDict) ?? PreviewComponent.PrefData.default
    default:
      toolData = EmptyPrefData.default
    }
--- a/VimR/Workspace/InnterToolBar.swift
+++ b/VimR/Workspace/InnterToolBar.swift
@ -40,9 +40,13 @@ class InnerToolBar: NSView, NSUserInterfaceValidations {
  static let iconDimension = CGFloat(19)
  static let iconColor = NSColor.darkGray

-  static func configureToStandardIconButton(button: NSButton, image: NSImage?) {
+  static func configureToStandardIconButton(button: NSButton, iconName: CocoaFontAwesome.FontAwesome) {
+    let icon = NSImage.fontAwesomeIcon(name: iconName,
+                                       textColor: InnerToolBar.iconColor,
+                                       dimension: InnerToolBar.iconDimension)
+
    button.imagePosition = .imageOnly
-    button.image = image
+    button.image = icon
    button.isBordered = false

    // The following disables the square appearing when pushed.
@ -50,8 +54,18 @@ class InnerToolBar: NSView, NSUserInterfaceValidations {
    cell?.highlightsBy = .contentsCellMask
  }

-  let customMenuItems: [NSMenuItem]
-  var customToolbar: NSView?
+  var customMenuItems: [NSMenuItem]? {
+    didSet {
+      self.removeCustomUiElements()
+      self.addViews()
+    }
+  }
+  var customToolbar: NSView? {
+    didSet {
+      self.removeCustomUiElements()
+      self.addViews()
+    }
+  }

  weak var tool: WorkspaceTool? {
    didSet {
@ -99,6 +113,11 @@ class InnerToolBar: NSView, NSUserInterfaceValidations {
    }
  }

+  fileprivate func removeCustomUiElements() {
+    [self.titleField, self.customToolbar, self.closeButton, self.cogButton].forEach { $0?.removeFromSuperview() }
+    self.cogButton.menu = nil
+  }
+
  fileprivate func addViews() {
    let title = self.titleField
    let close = self.closeButton
@ -110,18 +129,13 @@ class InnerToolBar: NSView, NSUserInterfaceValidations {
    title.isSelectable = false
    title.controlSize = .small

-    let closeIcon = NSImage.fontAwesomeIcon(code: "fa-times-circle",
-                                            textColor: InnerToolBar.iconColor,
-                                            dimension: InnerToolBar.iconDimension)
-    InnerToolBar.configureToStandardIconButton(button: close, image: closeIcon)
-
+    InnerToolBar.configureToStandardIconButton(button: close, iconName: .timesCircle)
    close.target = self
    close.action = #selector(InnerToolBar.closeAction)

    let cogIcon = NSImage.fontAwesomeIcon(name: .cog,
                                          textColor: InnerToolBar.iconColor,
                                          dimension: InnerToolBar.iconDimension)
-
    cog.configureForAutoLayout()
    cog.imagePosition = .imageOnly
    cog.pullsDown = true
@ -167,8 +181,8 @@ class InnerToolBar: NSView, NSUserInterfaceValidations {

    cogMenu.addItem(cogMenuItem)

-    if self.customMenuItems.isEmpty == false {
-      self.customMenuItems.forEach(cogMenu.addItem)
+    if self.customMenuItems?.isEmpty == false {
+      self.customMenuItems?.forEach(cogMenu.addItem)
      cogMenu.addItem(NSMenuItem.separator())
    }

--- a/VimR/Workspace/Workspace.swift
+++ b/VimR/Workspace/Workspace.swift
@ -20,6 +20,8 @@ protocol WorkspaceDelegate: class {

  func resizeWillStart(workspace: Workspace)
  func resizeDidEnd(workspace: Workspace)
+
+  func toggled(tool: WorkspaceTool)
 }

 class Workspace: NSView, WorkspaceBarDelegate {
@ -136,7 +138,6 @@ extension Workspace {
    self.isDragOngoing = false
    self.draggedOnBarLocation = nil
    self.proxyBar.removeFromSuperview()
-    self.proxyBar.removeAllConstraints()
  }

  override func performDragOperation(_ sender: NSDraggingInfo) -> Bool {
@ -196,6 +197,10 @@ extension Workspace {
  func resizeDidEnd(workspaceBar: WorkspaceBar) {
    self.delegate?.resizeDidEnd(workspace: self)
  }
+
+  func toggle(tool: WorkspaceTool) {
+    self.delegate?.toggled(tool: tool)
+  }
 }

 // MARK: - Layout
--- a/VimR/Workspace/WorkspaceBar.swift
+++ b/VimR/Workspace/WorkspaceBar.swift
@ -10,6 +10,8 @@ protocol WorkspaceBarDelegate: class {

  func resizeWillStart(workspaceBar: WorkspaceBar)
  func resizeDidEnd(workspaceBar: WorkspaceBar)
+
+  func toggle(tool: WorkspaceTool)
 }

 /**
@ -113,7 +115,6 @@ class WorkspaceBar: NSView, WorkspaceToolDelegate {

  func relayout() {
    self.removeConstraints(self.layoutConstraints)
-    self.proxyBar.removeAllConstraints()
    self.removeAllSubviews()

    if self.isEmpty() {
@ -835,5 +836,6 @@ extension WorkspaceBar {
    self.relayout()

    self.delegate?.resizeDidEnd(workspaceBar: self)
+    self.delegate?.toggle(tool: tool)
  }
 }
--- a/VimR/Workspace/WorkspaceTool.swift
+++ b/VimR/Workspace/WorkspaceTool.swift
@ -13,6 +13,8 @@ protocol WorkspaceToolDelegate: class {

 class WorkspaceTool: NSView {

+  fileprivate var innerToolbar: InnerToolBar?
+
  required init?(coder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
  }
@ -55,11 +57,30 @@ class WorkspaceTool: NSView {
    return self.bar?.workspace
  }

-  var innerToolbar: InnerToolBar?
-
  let minimumDimension: CGFloat
  var dimension: CGFloat

+  var customInnerToolbar: NSView? {
+    get {
+      return self.innerToolbar?.customToolbar
+    }
+
+    set {
+      DispatchUtils.gui {
+        self.innerToolbar?.customToolbar = newValue
+      }
+    }
+  }
+  var customInnerMenuItems: [NSMenuItem]? {
+    get {
+      return self.innerToolbar?.customMenuItems
+    }
+
+    set {
+      self.innerToolbar?.customMenuItems = newValue
+    }
+  }
+
  struct Config {

    let title: String
@ -76,8 +97,7 @@ class WorkspaceTool: NSView {
         minimumDimension: CGFloat = 50,
         withInnerToolbar: Bool = true,
         customToolbar: NSView? = nil,
-         customMenuItems: [NSMenuItem] = [])
-    {
+         customMenuItems: [NSMenuItem] = []) {
      self.title = title
      self.view = view
      self.minimumDimension = minimumDimension
@ -110,8 +130,8 @@ class WorkspaceTool: NSView {
  }

  func toggle() {
-    self.delegate?.toggle(self)
    self.isSelected = !self.isSelected
+    self.delegate?.toggle(self)
  }

  fileprivate func addViews() {
--- a/VimR/markdown/github-markdown.css
+++ b/VimR/markdown/github-markdown.css
@ -0,0 +1,681 @@
+@font-face {
+  font-family: octicons-link;
+  src: url(data:font/woff;charset=utf-8;base64,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) format('woff');
+}
+
+.markdown-body {
+  -ms-text-size-adjust: 100%;
+  -webkit-text-size-adjust: 100%;
+  line-height: 1.5;
+  color: #333;
+  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
+  font-size: 16px;
+  line-height: 1.5;
+  word-wrap: break-word;
+}
+
+.markdown-body .pl-c {
+  color: #969896;
+}
+
+.markdown-body .pl-c1,
+.markdown-body .pl-s .pl-v {
+  color: #0086b3;
+}
+
+.markdown-body .pl-e,
+.markdown-body .pl-en {
+  color: #795da3;
+}
+
+.markdown-body .pl-smi,
+.markdown-body .pl-s .pl-s1 {
+  color: #333;
+}
+
+.markdown-body .pl-ent {
+  color: #63a35c;
+}
+
+.markdown-body .pl-k {
+  color: #a71d5d;
+}
+
+.markdown-body .pl-s,
+.markdown-body .pl-pds,
+.markdown-body .pl-s .pl-pse .pl-s1,
+.markdown-body .pl-sr,
+.markdown-body .pl-sr .pl-cce,
+.markdown-body .pl-sr .pl-sre,
+.markdown-body .pl-sr .pl-sra {
+  color: #183691;
+}
+
+.markdown-body .pl-v {
+  color: #ed6a43;
+}
+
+.markdown-body .pl-id {
+  color: #b52a1d;
+}
+
+.markdown-body .pl-ii {
+  color: #f8f8f8;
+  background-color: #b52a1d;
+}
+
+.markdown-body .pl-sr .pl-cce {
+  font-weight: bold;
+  color: #63a35c;
+}
+
+.markdown-body .pl-ml {
+  color: #693a17;
+}
+
+.markdown-body .pl-mh,
+.markdown-body .pl-mh .pl-en,
+.markdown-body .pl-ms {
+  font-weight: bold;
+  color: #1d3e81;
+}
+
+.markdown-body .pl-mq {
+  color: #008080;
+}
+
+.markdown-body .pl-mi {
+  font-style: italic;
+  color: #333;
+}
+
+.markdown-body .pl-mb {
+  font-weight: bold;
+  color: #333;
+}
+
+.markdown-body .pl-md {
+  color: #bd2c00;
+  background-color: #ffecec;
+}
+
+.markdown-body .pl-mi1 {
+  color: #55a532;
+  background-color: #eaffea;
+}
+
+.markdown-body .pl-mdr {
+  font-weight: bold;
+  color: #795da3;
+}
+
+.markdown-body .pl-mo {
+  color: #1d3e81;
+}
+
+.markdown-body .octicon {
+  display: inline-block;
+  vertical-align: text-top;
+  fill: currentColor;
+}
+
+.markdown-body a {
+  background-color: transparent;
+  -webkit-text-decoration-skip: objects;
+}
+
+.markdown-body a:active,
+.markdown-body a:hover {
+  outline-width: 0;
+}
+
+.markdown-body strong {
+  font-weight: inherit;
+}
+
+.markdown-body strong {
+  font-weight: bolder;
+}
+
+.markdown-body h1 {
+  font-size: 2em;
+  margin: 0.67em 0;
+}
+
+.markdown-body img {
+  border-style: none;
+}
+
+.markdown-body svg:not(:root) {
+  overflow: hidden;
+}
+
+.markdown-body code,
+.markdown-body kbd,
+.markdown-body pre {
+  font-family: monospace, monospace;
+  font-size: 1em;
+}
+
+.markdown-body hr {
+  box-sizing: content-box;
+  height: 0;
+  overflow: visible;
+}
+
+.markdown-body input {
+  font: inherit;
+  margin: 0;
+}
+
+.markdown-body input {
+  overflow: visible;
+}
+
+.markdown-body [type="checkbox"] {
+  box-sizing: border-box;
+  padding: 0;
+}
+
+.markdown-body * {
+  box-sizing: border-box;
+}
+
+.markdown-body input {
+  font-family: inherit;
+  font-size: inherit;
+  line-height: inherit;
+}
+
+.markdown-body a {
+  color: #4078c0;
+  text-decoration: none;
+}
+
+.markdown-body a:hover,
+.markdown-body a:active {
+  text-decoration: underline;
+}
+
+.markdown-body strong {
+  font-weight: 600;
+}
+
+.markdown-body hr {
+  height: 0;
+  margin: 15px 0;
+  overflow: hidden;
+  background: transparent;
+  border: 0;
+  border-bottom: 1px solid #ddd;
+}
+
+.markdown-body hr::before {
+  display: table;
+  content: "";
+}
+
+.markdown-body hr::after {
+  display: table;
+  clear: both;
+  content: "";
+}
+
+.markdown-body table {
+  border-spacing: 0;
+  border-collapse: collapse;
+}
+
+.markdown-body td,
+.markdown-body th {
+  padding: 0;
+}
+
+.markdown-body h1,
+.markdown-body h2,
+.markdown-body h3,
+.markdown-body h4,
+.markdown-body h5,
+.markdown-body h6 {
+  margin-top: 0;
+  margin-bottom: 0;
+}
+
+.markdown-body h1 {
+  font-size: 32px;
+  font-weight: 600;
+}
+
+.markdown-body h2 {
+  font-size: 24px;
+  font-weight: 600;
+}
+
+.markdown-body h3 {
+  font-size: 20px;
+  font-weight: 600;
+}
+
+.markdown-body h4 {
+  font-size: 16px;
+  font-weight: 600;
+}
+
+.markdown-body h5 {
+  font-size: 14px;
+  font-weight: 600;
+}
+
+.markdown-body h6 {
+  font-size: 12px;
+  font-weight: 600;
+}
+
+.markdown-body p {
+  margin-top: 0;
+  margin-bottom: 10px;
+}
+
+.markdown-body blockquote {
+  margin: 0;
+}
+
+.markdown-body ul,
+.markdown-body ol {
+  padding-left: 0;
+  margin-top: 0;
+  margin-bottom: 0;
+}
+
+.markdown-body ol ol,
+.markdown-body ul ol {
+  list-style-type: lower-roman;
+}
+
+.markdown-body ul ul ol,
+.markdown-body ul ol ol,
+.markdown-body ol ul ol,
+.markdown-body ol ol ol {
+  list-style-type: lower-alpha;
+}
+
+.markdown-body dd {
+  margin-left: 0;
+}
+
+.markdown-body code {
+  font-family: Consolas, "Liberation Mono", Menlo, Courier, monospace;
+  font-size: 12px;
+}
+
+.markdown-body pre {
+  margin-top: 0;
+  margin-bottom: 0;
+  font: 12px Consolas, "Liberation Mono", Menlo, Courier, monospace;
+}
+
+.markdown-body .octicon {
+  vertical-align: text-bottom;
+}
+
+.markdown-body input {
+  -webkit-font-feature-settings: "liga" 0;
+  font-feature-settings: "liga" 0;
+}
+
+.markdown-body::before {
+  display: table;
+  content: "";
+}
+
+.markdown-body::after {
+  display: table;
+  clear: both;
+  content: "";
+}
+
+.markdown-body>*:first-child {
+  margin-top: 0 !important;
+}
+
+.markdown-body>*:last-child {
+  margin-bottom: 0 !important;
+}
+
+.markdown-body a:not([href]) {
+  color: inherit;
+  text-decoration: none;
+}
+
+.markdown-body .anchor {
+  float: left;
+  padding-right: 4px;
+  margin-left: -20px;
+  line-height: 1;
+}
+
+.markdown-body .anchor:focus {
+  outline: none;
+}
+
+.markdown-body p,
+.markdown-body blockquote,
+.markdown-body ul,
+.markdown-body ol,
+.markdown-body dl,
+.markdown-body table,
+.markdown-body pre {
+  margin-top: 0;
+  margin-bottom: 16px;
+}
+
+.markdown-body hr {
+  height: 0.25em;
+  padding: 0;
+  margin: 24px 0;
+  background-color: #e7e7e7;
+  border: 0;
+}
+
+.markdown-body blockquote {
+  padding: 0 1em;
+  color: #777;
+  border-left: 0.25em solid #ddd;
+}
+
+.markdown-body blockquote>:first-child {
+  margin-top: 0;
+}
+
+.markdown-body blockquote>:last-child {
+  margin-bottom: 0;
+}
+
+.markdown-body kbd {
+  display: inline-block;
+  padding: 3px 5px;
+  font-size: 11px;
+  line-height: 10px;
+  color: #555;
+  vertical-align: middle;
+  background-color: #fcfcfc;
+  border: solid 1px #ccc;
+  border-bottom-color: #bbb;
+  border-radius: 3px;
+  box-shadow: inset 0 -1px 0 #bbb;
+}
+
+.markdown-body h1,
+.markdown-body h2,
+.markdown-body h3,
+.markdown-body h4,
+.markdown-body h5,
+.markdown-body h6 {
+  margin-top: 24px;
+  margin-bottom: 16px;
+  font-weight: 600;
+  line-height: 1.25;
+}
+
+.markdown-body h1 .octicon-link,
+.markdown-body h2 .octicon-link,
+.markdown-body h3 .octicon-link,
+.markdown-body h4 .octicon-link,
+.markdown-body h5 .octicon-link,
+.markdown-body h6 .octicon-link {
+  color: #000;
+  vertical-align: middle;
+  visibility: hidden;
+}
+
+.markdown-body h1:hover .anchor,
+.markdown-body h2:hover .anchor,
+.markdown-body h3:hover .anchor,
+.markdown-body h4:hover .anchor,
+.markdown-body h5:hover .anchor,
+.markdown-body h6:hover .anchor {
+  text-decoration: none;
+}
+
+.markdown-body h1:hover .anchor .octicon-link,
+.markdown-body h2:hover .anchor .octicon-link,
+.markdown-body h3:hover .anchor .octicon-link,
+.markdown-body h4:hover .anchor .octicon-link,
+.markdown-body h5:hover .anchor .octicon-link,
+.markdown-body h6:hover .anchor .octicon-link {
+  visibility: visible;
+}
+
+.markdown-body h1 {
+  padding-bottom: 0.3em;
+  font-size: 2em;
+  border-bottom: 1px solid #eee;
+}
+
+.markdown-body h2 {
+  padding-bottom: 0.3em;
+  font-size: 1.5em;
+  border-bottom: 1px solid #eee;
+}
+
+.markdown-body h3 {
+  font-size: 1.25em;
+}
+
+.markdown-body h4 {
+  font-size: 1em;
+}
+
+.markdown-body h5 {
+  font-size: 0.875em;
+}
+
+.markdown-body h6 {
+  font-size: 0.85em;
+  color: #777;
+}
+
+.markdown-body ul,
+.markdown-body ol {
+  padding-left: 2em;
+}
+
+.markdown-body ul ul,
+.markdown-body ul ol,
+.markdown-body ol ol,
+.markdown-body ol ul {
+  margin-top: 0;
+  margin-bottom: 0;
+}
+
+.markdown-body li>p {
+  margin-top: 16px;
+}
+
+.markdown-body li+li {
+  margin-top: 0.25em;
+}
+
+.markdown-body dl {
+  padding: 0;
+}
+
+.markdown-body dl dt {
+  padding: 0;
+  margin-top: 16px;
+  font-size: 1em;
+  font-style: italic;
+  font-weight: bold;
+}
+
+.markdown-body dl dd {
+  padding: 0 16px;
+  margin-bottom: 16px;
+}
+
+.markdown-body table {
+  display: block;
+  width: 100%;
+  overflow: auto;
+}
+
+.markdown-body table th {
+  font-weight: bold;
+}
+
+.markdown-body table th,
+.markdown-body table td {
+  padding: 6px 13px;
+  border: 1px solid #ddd;
+}
+
+.markdown-body table tr {
+  background-color: #fff;
+  border-top: 1px solid #ccc;
+}
+
+.markdown-body table tr:nth-child(2n) {
+  background-color: #f8f8f8;
+}
+
+.markdown-body img {
+  max-width: 100%;
+  box-sizing: content-box;
+  background-color: #fff;
+}
+
+.markdown-body code {
+  padding: 0;
+  padding-top: 0.2em;
+  padding-bottom: 0.2em;
+  margin: 0;
+  font-size: 85%;
+  background-color: rgba(0,0,0,0.04);
+  border-radius: 3px;
+}
+
+.markdown-body code::before,
+.markdown-body code::after {
+  letter-spacing: -0.2em;
+  content: "\00a0";
+}
+
+.markdown-body pre {
+  word-wrap: normal;
+}
+
+.markdown-body pre>code {
+  padding: 0;
+  margin: 0;
+  font-size: 100%;
+  word-break: normal;
+  white-space: pre;
+  background: transparent;
+  border: 0;
+}
+
+.markdown-body .highlight {
+  margin-bottom: 16px;
+}
+
+.markdown-body .highlight pre {
+  margin-bottom: 0;
+  word-break: normal;
+}
+
+.markdown-body .highlight pre,
+.markdown-body pre {
+  padding: 16px;
+  overflow: auto;
+  font-size: 85%;
+  line-height: 1.45;
+  background-color: #f7f7f7;
+  border-radius: 3px;
+}
+
+.markdown-body pre code {
+  display: inline;
+  max-width: auto;
+  padding: 0;
+  margin: 0;
+  overflow: visible;
+  line-height: inherit;
+  word-wrap: normal;
+  background-color: transparent;
+  border: 0;
+}
+
+.markdown-body pre code::before,
+.markdown-body pre code::after {
+  content: normal;
+}
+
+.markdown-body .pl-0 {
+  padding-left: 0 !important;
+}
+
+.markdown-body .pl-1 {
+  padding-left: 3px !important;
+}
+
+.markdown-body .pl-2 {
+  padding-left: 6px !important;
+}
+
+.markdown-body .pl-3 {
+  padding-left: 12px !important;
+}
+
+.markdown-body .pl-4 {
+  padding-left: 24px !important;
+}
+
+.markdown-body .pl-5 {
+  padding-left: 36px !important;
+}
+
+.markdown-body .pl-6 {
+  padding-left: 48px !important;
+}
+
+.markdown-body .full-commit .btn-outline:not(:disabled):hover {
+  color: #4078c0;
+  border: 1px solid #4078c0;
+}
+
+.markdown-body kbd {
+  display: inline-block;
+  padding: 3px 5px;
+  font: 11px Consolas, "Liberation Mono", Menlo, Courier, monospace;
+  line-height: 10px;
+  color: #555;
+  vertical-align: middle;
+  background-color: #fcfcfc;
+  border: solid 1px #ccc;
+  border-bottom-color: #bbb;
+  border-radius: 3px;
+  box-shadow: inset 0 -1px 0 #bbb;
+}
+
+.markdown-body :checked+.radio-label {
+  position: relative;
+  z-index: 1;
+  border-color: #4078c0;
+}
+
+.markdown-body .task-list-item {
+  list-style-type: none;
+}
+
+.markdown-body .task-list-item+.task-list-item {
+  margin-top: 3px;
+}
+
+.markdown-body .task-list-item input {
+  margin: 0 0.2em 0.25em -1.6em;
+  vertical-align: middle;
+}
+
+.markdown-body hr {
+  border-bottom-color: #eee;
+}
--- a/VimR/markdown/template.html
+++ b/VimR/markdown/template.html
@ -0,0 +1,154 @@
+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <link rel="stylesheet" href="github-markdown.css">
+  <script>
+    // Scrolling
+    const sourceposRegex = /(\d+):(\d+)-(\d+):(\d+)/;
+
+    let suppressNextScrollEvent = false;
+
+    function isTopLeftInsideViewport(el) {
+      const rect = el.getBoundingClientRect();
+      return rect.top >= 0 && rect.left >= 0;
+    }
+
+    function isElementVisibleInViewport(el) {
+      const rect = el.getBoundingClientRect();
+
+      return (
+        ((rect.top >= 0 && window.innerHeight - rect.top >= 0) || (rect.top < 0 && rect.bottom > 0)) &&
+        ((rect.left >= 0 && window.innerWidth - rect.left >= 0) || (rect.left < 0 && rect.right > 0))
+      );
+    }
+
+    function positionOfMarkdownElement(element) {
+      const regexResult = element.dataset.sourcepos.match(sourceposRegex);
+
+      if (regexResult.length != 5) {
+        return null;
+      }
+
+      return {
+        lineBegin: parseInt(regexResult[1], 10),
+        columnBegin: parseInt(regexResult[2], 10),
+        lineEnd: parseInt(regexResult[3], 10),
+        columnEnd: parseInt(regexResult[4], 10)
+      };
+    }
+
+    function toArray(nodeList) {
+      return Array.prototype.slice.call(nodeList)
+    }
+
+    function currentTopMarkdownElement() {
+      const mdElements = toArray(document.querySelectorAll("[data-sourcepos]"));
+      return mdElements.find(isTopLeftInsideViewport) || mdElements.find(isElementVisibleInViewport);
+    }
+
+    let lastMarkdownPosition = {
+      lineBegin: 1,
+      columnBegin: 1,
+      lineEnd: 1,
+      columnEnd: 1
+    };
+
+    function scrollCallback() {
+      const candidate = currentTopMarkdownElement();
+
+      if (!candidate) {
+        return;
+      }
+
+      const result = positionOfMarkdownElement(candidate);
+      if (result.lineBegin == lastMarkdownPosition.lineBegin
+        && result.columnBegin == lastMarkdownPosition.columnBegin
+        && result.lineEnd == lastMarkdownPosition.lineEnd
+        && result.columnEnd == lastMarkdownPosition.columnEnd)
+      {
+        return;
+      }
+
+      lastMarkdownPosition = result;
+//      console.log(`webview scrolled to ${result.lineBegin}:${result.columnBegin}`);
+      window.webkit.messageHandlers.com_vimr_preview_markdown.postMessage(result);
+    }
+
+    let lastKnownScrollPos = 0;
+    let ticking = false;
+
+    window.addEventListener('scroll', () => {
+      lastKnownScrollPos = window.scrollY;
+      if (!ticking) {
+        window.requestAnimationFrame(() => {
+          if (lastKnownScrollPos >= 0 && !suppressNextScrollEvent) {
+            scrollCallback();
+          }
+
+          suppressNextScrollEvent = false;
+          ticking = false;
+        });
+      }
+      ticking = true;
+    });
+
+    // Forward search
+    function scrollToPosition(row, column) {
+      const entries = toArray(document.querySelectorAll("[data-sourcepos]"))
+        .map(element => {
+          const position = positionOfMarkdownElement(element);
+          return {
+            element: element,
+            position: position,
+            rowDistance: Math.abs(row - position.lineBegin),
+            columnDistance: Math.abs(column - position.columnBegin)
+          };
+        });
+
+      const minRowDistance = entries.reduce((result, entry) => {
+        return Math.min(result, entry.rowDistance)
+      }, Number.MAX_SAFE_INTEGER);
+
+      const entriesWithMinRowDistance = entries.filter(entry => entry.rowDistance == minRowDistance);
+
+      const minColumnDistance = entriesWithMinRowDistance.reduce((result, entry) => {
+        return Math.min(result, entry.columnDistance)
+      }, Number.MAX_SAFE_INTEGER);
+
+      const candidateEntry = entriesWithMinRowDistance.find(entry => entry.columnDistance == minColumnDistance);
+      if (!candidateEntry) {
+        return;
+      }
+
+      const element = candidateEntry.element;
+      if (isElementVisibleInViewport(element)) {
+        return;
+      }
+
+      let {x, y}  = scrollPosition(element);
+      suppressNextScrollEvent = true;
+      window.scrollTo(x, y);
+//      console.log(`scrolled webview to ${x}:${y}`);
+    }
+
+    function scrollPosition(element) {
+      let {x, y} = { x: 0, y: 0 };
+
+      let curEl = element;
+      while (curEl) {
+        x += curEl.offsetLeft;
+        y += curEl.offsetTop;
+
+        curEl = curEl.offsetParent;
+      }
+
+      return { x: x, y: y };
+    }
+  </script>
+  <title>{{ title }}</title>
+</head>
+<body class="markdown-body">
+{{ body }}
+</body>
+</html>
--- a/VimR/preview/base.css
+++ b/VimR/preview/base.css
@ -0,0 +1,62 @@
+/* http://meyerweb.com/eric/tools/css/reset/
+   v2.0 | 20110126
+   License: none (public domain)
+*/
+
+html, body, div, span, applet, object, iframe,
+h1, h2, h3, h4, h5, h6, p, blockquote, pre,
+a, abbr, acronym, address, big, cite, code,
+del, dfn, em, img, ins, kbd, q, s, samp,
+small, strike, strong, sub, sup, tt, var,
+b, u, i, center,
+dl, dt, dd, ol, ul, li,
+fieldset, form, label, legend,
+table, caption, tbody, tfoot, thead, tr, th, td,
+article, aside, canvas, details, embed,
+figure, figcaption, footer, header, hgroup,
+menu, nav, output, ruby, section, summary,
+time, mark, audio, video {
+  margin: 0;
+  padding: 0;
+  border: 0;
+  vertical-align: baseline;
+}
+/* HTML5 display-role reset for older browsers */
+article, aside, details, figcaption, figure,
+footer, header, hgroup, menu, nav, section {
+  display: block;
+}
+body {
+  line-height: 1;
+}
+ol, ul {
+  list-style: none;
+}
+blockquote, q {
+  quotes: none;
+}
+blockquote:before, blockquote:after,
+q:before, q:after {
+  content: none;
+}
+table {
+  border-collapse: collapse;
+  border-spacing: 0;
+}
+
+body {
+  font-family: -apple-system, sans-serif;
+}
+
+#message {
+  text-align: center;
+  position: absolute;
+  top: 50%;
+  left: 50%;
+  transform: translate(-50%, -50%);
+}
+
+.info-text {
+  font-size: small;
+  color: gray;
+}
--- a/VimR/preview/empty.html
+++ b/VimR/preview/empty.html
@ -0,0 +1,15 @@
+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <link rel="stylesheet" href="../github-markdown.css">
+  <link rel="stylesheet" href="base.css">
+  <title>Empty</title>
+</head>
+<body>
+  <div id="message">
+    <h1>😶</h1>
+    <span class="info-text">no preview...</span>
+</div>
+</body>
+</html>
--- a/VimR/preview/error.html
+++ b/VimR/preview/error.html
@ -0,0 +1,15 @@
+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <link rel="stylesheet" href="../github-markdown.css">
+  <link rel="stylesheet" href="base.css">
+  <title>Error</title>
+</head>
+<body>
+  <div id="message">
+    <h1>😱</h1>
+    <span class="info-text">There was an error...</span>
+</div>
+</body>
+</html>
--- a/VimR/preview/save-first.html
+++ b/VimR/preview/save-first.html
@ -0,0 +1,15 @@
+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <link rel="stylesheet" href="../github-markdown.css">
+  <link rel="stylesheet" href="base.css">
+  <title>Error</title>
+</head>
+<body>
+<div id="message">
+  <h1>😶</h1>
+  <span class="info-text">Save first for preview</span>
+</div>
+</body>
+</html>