Use CoreText's font metric

SwiftNeoVim/Grid.swift

@@ -157,6 +157,7 @@ class Grid: CustomStringConvertible {
   }
   
   private func clearRegion(region: Region) {
+    // FIXME: sometimes clearRegion gets called without first resizing the Grid. Should we handle this?
     guard self.hasData else {
       return
     }

SwiftNeoVim/NeoVimView.swift

@@ -48,7 +48,8 @@ public class NeoVimView: NSView {
     didSet {
       self.drawer.font = self.font
       self.cellSize = self.drawer.cellSize
-      self.lineSpace = self.drawer.lineSpace
+      self.descent = self.drawer.descent
+      self.leading = self.drawer.leading
       
       // FIXME: resize and redraw
     }
@@ -58,21 +59,23 @@ public class NeoVimView: NSView {
   private let drawer: TextDrawer
   
   private var cellSize = CGSize.zero
-  private var lineSpace = CGFloat(0)
+  private var descent = CGFloat(0)
+  private var leading = CGFloat(0)
 
   private let grid = Grid()
 
   init(frame rect: NSRect = CGRect.zero, xpc: NeoVimXpc) {
     self.xpc = xpc
     
-    self.font = NSFont(name: "Menlo", size: 13)!
+    self.font = NSFont(name: "Menlo", size: 16)!
     self.drawer = TextDrawer(font: font)
     
     super.init(frame: rect)
     
     self.wantsLayer = true
     self.cellSize = self.drawer.cellSize
-    self.lineSpace = self.drawer.lineSpace
+    self.descent = self.drawer.descent
+    self.leading = self.drawer.leading
   }
   
   override public func keyDown(theEvent: NSEvent) {
@@ -100,7 +103,7 @@ public class NeoVimView: NSView {
       self.drawBackground(positions: positions, background: rowFrag.attrs.background)
 
       let string = self.grid.cells[rowFrag.row][rowFrag.range].reduce("") { $0 + $1.string }
-      let glyphPositions = positions.map { CGPoint(x: $0.x, y: $0.y + self.lineSpace) }
+      let glyphPositions = positions.map { CGPoint(x: $0.x, y: $0.y + self.descent + self.leading) }
       self.drawer.drawString(string,
                              positions: UnsafeMutablePointer(glyphPositions), positionsCount: positions.count,
                              highlightAttrs: rowFrag.attrs,
@@ -120,23 +123,26 @@ public class NeoVimView: NSView {
   private func rowRunIntersecting(rects rects: [CGRect]) -> [RowRun] {
     return rects
       .map { rect -> Region in
+        // Get all Regions that intersects with the given rects. There can be overlaps between the Regions, but for the
+        // time being we ignore them; probably not necessary to optimize them away.
         let rowStart = Int(floor((self.frame.height - (rect.origin.y + rect.size.height)) / self.cellSize.height))
         let rowEnd = Int(ceil((self.frame.height - rect.origin.y) / self.cellSize.height)) - 1
         let columnStart = Int(floor(rect.origin.x / self.cellSize.width))
         let columnEnd = Int(ceil((rect.origin.x + rect.size.width) / self.cellSize.width)) - 1
+        
         return Region(top: rowStart, bottom: rowEnd, left: columnStart, right: columnEnd)
-      } // There can be overlaps between the Regions, but for the time being we ignore them.
+      }
       .map { region -> [RowRun] in
-        return (region.rowRange)
+        // Map Regions to RowRuns for drawing.
+        return region.rowRange
+          // Map each row in a Region to RowRuns
           .map { row -> [RowRun] in
-            let range = region.columnRange
+            let columns = region.columnRange
             let rowCells = self.grid.cells[row]
-            let startIndex = range.startIndex
+            let startIndex = columns.startIndex
             
-            var result = [
-              RowRun(row: row, range: startIndex...startIndex, attrs: rowCells[startIndex].attrs)
-            ]
-            range.forEach { idx in
+            var result = [ RowRun(row: row, range: startIndex...startIndex, attrs: rowCells[startIndex].attrs) ]
+            columns.forEach { idx in
               if rowCells[idx].attrs == result.last!.attrs {
                 let last = result.popLast()!
                 result.append(RowRun(row: row, range: last.range.startIndex...idx, attrs: last.attrs))
@@ -145,11 +151,11 @@ public class NeoVimView: NSView {
               }
             }
             
-            return result
-          } // -> [[RowRun]]
-          .flatMap { $0 } // -> [RowRun]
-      } // -> [[RowRun]]
-      .flatMap { $0 } // -> [RowRun]
+            return result // All RowRuns for a row in a Region.
+          }               // All RowRuns for all rows in a Region grouped by row.
+          .flatMap { $0 } // Flattened RowRuns for a Region.
+      }                   // All RowRuns for all Regions grouped by Region.
+      .flatMap { $0 }     // Flattened RowRuns for all Regions.
   }
 
   private func positionOnView(row: Int, column: Int) -> CGPoint {

SwiftNeoVim/TextDrawer.h

@@ -11,7 +11,8 @@
 @interface TextDrawer : NSObject
 
 @property (nonatomic, nonnull, retain) NSFont *font;
-@property (nonatomic, readonly) CGFloat lineSpace;
+@property (nonatomic, readonly) CGFloat leading;
+@property (nonatomic, readonly) CGFloat descent;
 @property (nonatomic, readonly) CGSize cellSize;
 
 - (instancetype _Nonnull)initWithFont:(NSFont *_Nonnull)font;

SwiftNeoVim/TextDrawer.m

@@ -19,8 +19,8 @@
   NSLayoutManager *_layoutManager;
 
   NSFont *_font;
-  CGFloat _fontDescent;
-  CGFloat _lineGap;
+  CGFloat _underlinePosition;
+  CGFloat _underlineThickness;
 
   NSMutableArray *_fontLookupCache;
   NSMutableDictionary *_fontTraitCache;
@@ -30,13 +30,23 @@
   [_font autorelease];
   _font = [font retain];
 
+  // cf. https://developer.apple.com/library/mac/documentation/TextFonts/Conceptual/CocoaTextArchitecture/FontHandling/FontHandling.html
+  CGFloat ascent = CTFontGetAscent((CTFontRef) _font);
+  CGFloat descent = CTFontGetDescent((CTFontRef) _font);
+  CGFloat leading = CTFontGetLeading((CTFontRef) _font);
+  CGFloat underlinePosition = CTFontGetUnderlinePosition((CTFontRef) _font);
+  CGFloat underlineThickness = CTFontGetUnderlineThickness((CTFontRef) _font);
+
   _cellSize = CGSizeMake(
       round([@"m" sizeWithAttributes:@{ NSFontAttributeName : _font }].width),
-      [_layoutManager defaultLineHeightForFont:_font] + _lineSpace
+      ceil(ascent + descent + leading)
   );
-  // https://developer.apple.com/library/mac/documentation/TextFonts/Conceptual/CocoaTextArchitecture/FontHandling/FontHandling.html
-  _lineGap = _cellSize.height - _font.ascender - _font.descender;
-  _fontDescent = CTFontGetDescent((CTFontRef) _font);
+
+  _leading = leading;
+  _descent = descent;
+  _underlinePosition = underlinePosition; // This seems to take the thickness into account
+  // TODO: Maybe we should use 0.5 or 1 as minimum thickness for Retina and non-Retina, respectively.
+  _underlineThickness = underlineThickness;
 }
 
 - (instancetype)initWithFont:(NSFont *_Nonnull)font {
@@ -49,7 +59,6 @@
   _fontLookupCache = [[NSMutableArray alloc] init];
   _fontTraitCache = [[NSMutableDictionary alloc] init];
 
-  _lineSpace = 4;
   self.font = font;
 
   return self;
@@ -79,11 +88,7 @@
   CGContextSaveGState(context);
 
   if (attrs.fontTrait & FontTraitUnderline) {
-    CGRect rect = {
-        {positions[0].x, positions[0].y - 1},
-        {positions[0].x + positions[positionsCount - 1].x + _cellSize.width, 1}
-    };
-    [self drawUnderline:rect color:attrs.special context:context];
+    [self drawUnderline:positions count:positionsCount color:attrs.special context:context];
   }
 
   [self drawString:string positions:positions
@@ -93,8 +98,16 @@
   CGContextRestoreGState(context);
 }
 
-- (void)drawUnderline:(CGRect)rect color:(unsigned int)color context:(CGContextRef _Nonnull)context {
+- (void)drawUnderline:(const CGPoint *_Nonnull)positions
+                count:(NSInteger)count
+                color:(unsigned int)color
+              context:(CGContextRef _Nonnull)context
+{
   CGContextSetRGBFillColor(context, RED(color), GREEN(color), BLUE(color), ALPHA(color));
+  CGRect rect = {
+      {positions[0].x, positions[0].y + _underlinePosition},
+      {positions[0].x + positions[count - 1].x + _cellSize.width, _underlineThickness}
+  };
   CGContextFillRect(context, rect);
 }
 
@@ -115,7 +128,7 @@
     unichars = unibuffer;
   }
 
-  CGGlyph *glyphs = malloc(unilength * sizeof(UniChar));
+  CGGlyph *glyphs = malloc(unilength * sizeof(CGGlyph));
   CTFontRef fontWithTraits = [self fontWithTrait:fontTrait];
 
   CGContextSetRGBFillColor(context, RED(foreground), GREEN(foreground), BLUE(foreground), 1.0);