Highlight cursors differently when they lie on an end of line

When on an end of line, certain behaviours can be surprising, for
example delete will join the following line (which makes sense, and
is consistent, but hard to predict if we do not know the cursor is
on and end of line).

As Kakoune is moving more and more towards treating end of lines
as any other character, making it clear when the cursor lies on
them seems like a good way to reduce surprise.

colors/default.kak

@@ -31,6 +31,8 @@ face PrimarySelection white,blue
 face SecondarySelection black,blue
 face PrimaryCursor black,white
 face SecondaryCursor black,white
+face PrimaryCursorEol black,cyan
+face SecondaryCursorEol black,cyan
 face LineNumbers default,default
 face LineNumberCursor default,default+r
 face MenuForeground white,blue

doc/pages/faces.asciidoc

@@ -57,6 +57,12 @@ areas of the user interface:
 *SecondaryCursor*::
     cursor of the secondary selection
 
+*PrimaryCursorEol*::
+    cursor of the primary selection when it lies on and end of line character
+
+*SecondaryCursorEol*::
+    cursor of the secondary selection when it lies on and end of line character
+
 *LineNumbers*::
     face used by the number_lines highlighter
 

src/face_registry.cc

@@ -133,6 +133,8 @@ FaceRegistry::FaceRegistry()
         { "SecondarySelection", {Face{ Color::Black, Color::Blue }} },
         { "PrimaryCursor", {Face{ Color::Black, Color::White }} },
         { "SecondaryCursor", {Face{ Color::Black, Color::White }} },
+        { "PrimaryCursorEol", {Face{ Color::Black, Color::Cyan }} },
+        { "SecondaryCursorEol", {Face{ Color::Black, Color::Cyan }} },
         { "LineNumbers", {Face{ Color::Default, Color::Default }} },
         { "LineNumberCursor", {Face{ Color::Default, Color::Default, Attribute::Reverse }} },
         { "LineNumbersWrapped", {Face{ Color::Default, Color::Default, Attribute::Italic }} },

src/highlighters.cc

@@ -1163,10 +1163,11 @@ HighlighterAndId create_matching_char_highlighter(HighlighterParameters params)
 void highlight_selections(HighlightContext context, DisplayBuffer& display_buffer, BufferRange)
 {
     const auto& buffer = context.context.buffer();
-    const Face primary_face = get_face("PrimarySelection");
-    const Face secondary_face = get_face("SecondarySelection");
-    const Face primary_cursor_face = get_face("PrimaryCursor");
-    const Face secondary_cursor_face = get_face("SecondaryCursor");
+    const Face faces[6] = {
+            get_face("PrimarySelection"), get_face("SecondarySelection"),
+            get_face("PrimaryCursor"),    get_face("SecondaryCursor"),
+            get_face("PrimaryCursorEol"), get_face("SecondaryCursorEol"),
+    };
 
     const auto& selections = context.context.selections();
     for (size_t i = 0; i < selections.size(); ++i)
@@ -1178,14 +1179,16 @@ void highlight_selections(HighlightContext context, DisplayBuffer& display_buffe
 
         const bool primary = (i == selections.main_index());
         highlight_range(display_buffer, begin, end, false,
-                        apply_face(primary ? primary_face : secondary_face));
+                        apply_face(faces[primary ? 0 : 1]));
     }
     for (size_t i = 0; i < selections.size(); ++i)
     {
         auto& sel = selections[i];
+        const BufferCoord coord = sel.cursor();
         const bool primary = (i == selections.main_index());
-        highlight_range(display_buffer, sel.cursor(), buffer.char_next(sel.cursor()), false,
-                        apply_face(primary ? primary_cursor_face : secondary_cursor_face));
+        const bool eol = buffer[coord.line].length() - 1 == coord.column;
+        highlight_range(display_buffer, coord, buffer.char_next(coord), false,
+                        apply_face(faces[2 + (eol ? 2 : 0) + (primary ? 0 : 1)]));
     }
 }
 

test/regression/1435-misplaced-cursor-with-show_matching-hl/display

@@ -1,4 +1,4 @@
-{ "jsonrpc": "2.0", "method": "draw", "params": [[[{ "face": { "fg": "default", "bg": "default", "attributes": [] }, "contents": "·" }, { "face": { "fg": "black", "bg": "white", "attributes": [] }, "contents": "¬" }], [{ "face": { "fg": "default", "bg": "default", "attributes": [] }, "contents": "¬" }]], { "fg": "default", "bg": "default", "attributes": [] }, { "fg": "blue", "bg": "default", "attributes": [] }] }
+{ "jsonrpc": "2.0", "method": "draw", "params": [[[{ "face": { "fg": "default", "bg": "default", "attributes": [] }, "contents": "·" }, { "face": { "fg": "black", "bg": "cyan", "attributes": [] }, "contents": "¬" }], [{ "face": { "fg": "default", "bg": "default", "attributes": [] }, "contents": "¬" }]], { "fg": "default", "bg": "default", "attributes": [] }, { "fg": "blue", "bg": "default", "attributes": [] }] }
 { "jsonrpc": "2.0", "method": "menu_hide", "params": [] }
 { "jsonrpc": "2.0", "method": "info_hide", "params": [] }
 { "jsonrpc": "2.0", "method": "draw_status", "params": [[], [{ "face": { "fg": "default", "bg": "default", "attributes": [] }, "contents": "out 1:2 " }, { "face": { "fg": "black", "bg": "yellow", "attributes": [] }, "contents": "[+]" }, { "face": { "fg": "default", "bg": "default", "attributes": [] }, "contents": " " }, { "face": { "fg": "yellow", "bg": "default", "attributes": [] }, "contents": "insert" }, { "face": { "fg": "cyan", "bg": "default", "attributes": [] }, "contents": " " }, { "face": { "fg": "blue", "bg": "default", "attributes": [] }, "contents": "1 sels (1)" }, { "face": { "fg": "default", "bg": "default", "attributes": [] }, "contents": " - unnamed0@[kak-tests]" }], { "fg": "cyan", "bg": "default", "attributes": [] }] }