font: add cursor-height metric, and adjust- config for it. (#3062)

Subsumes #2580 (which has multiple conflicts with main due to recent
changes to metrics); I figured it'd be easier to just implement it this
way.

#2580 claimed to solve #2487 but I don't think it really does- ideally
we can think of a good way to configure each individual cursor type, but
I don't wanna just do something ad hoc and add a bunch of config keys
blindly so I limited the scope of this.

src/config/Config.zig

@@ -241,16 +241,15 @@ const c = @cImport({
 /// `-100%`) can cause the terminal to be unusable. Use with caution and reason.
 ///
 /// Some values are clamped to minimum or maximum values. This can make it
-/// appear that certain values are ignored. For example, the underline position
-/// is clamped to the height of a cell. If you set the underline position so
-/// high that it extends beyond the bottom of the cell size, it will be clamped
-/// to the bottom of the cell.
+/// appear that certain values are ignored. For example, many `*-thickness`
+/// adjustments cannot go below 1px.
 ///
 /// `adjust-cell-height` has some additional behaviors to describe:
 ///
 ///   * The font will be centered vertically in the cell.
 ///
-///   * The cursor will remain the same size as the font.
+///   * The cursor will remain the same size as the font, but may be
+///     adjusted separately with `adjust-cursor-height`.
 ///
 ///   * Powerline glyphs will be adjusted along with the cell height so
 ///     that things like status lines continue to look aligned.
@@ -276,6 +275,9 @@ const c = @cImport({
 @"adjust-overline-thickness": ?MetricModifier = null,
 /// Thickness in pixels of the bar cursor and outlined rect cursor.
 @"adjust-cursor-thickness": ?MetricModifier = null,
+/// Height in pixels of the cursor. Currently applies to all cursor types:
+/// bar, rect, and outlined rect.
+@"adjust-cursor-height": ?MetricModifier = null,
 /// Thickness in pixels of box drawing characters.
 @"adjust-box-thickness": ?MetricModifier = null,
 

src/font/SharedGridSet.zig

@@ -430,6 +430,7 @@ pub const DerivedConfig = struct {
     @"adjust-overline-position": ?Metrics.Modifier,
     @"adjust-overline-thickness": ?Metrics.Modifier,
     @"adjust-cursor-thickness": ?Metrics.Modifier,
+    @"adjust-cursor-height": ?Metrics.Modifier,
     @"adjust-box-thickness": ?Metrics.Modifier,
     @"freetype-load-flags": font.face.FreetypeLoadFlags,
 
@@ -468,6 +469,7 @@ pub const DerivedConfig = struct {
             .@"adjust-overline-position" = config.@"adjust-overline-position",
             .@"adjust-overline-thickness" = config.@"adjust-overline-thickness",
             .@"adjust-cursor-thickness" = config.@"adjust-cursor-thickness",
+            .@"adjust-cursor-height" = config.@"adjust-cursor-height",
             .@"adjust-box-thickness" = config.@"adjust-box-thickness",
             .@"freetype-load-flags" = if (font.face.FreetypeLoadFlags != void) config.@"freetype-load-flags" else {},
 
@@ -613,6 +615,7 @@ pub const Key = struct {
             if (config.@"adjust-overline-position") |m| try set.put(alloc, .overline_position, m);
             if (config.@"adjust-overline-thickness") |m| try set.put(alloc, .overline_thickness, m);
             if (config.@"adjust-cursor-thickness") |m| try set.put(alloc, .cursor_thickness, m);
+            if (config.@"adjust-cursor-height") |m| try set.put(alloc, .cursor_height, m);
             if (config.@"adjust-box-thickness") |m| try set.put(alloc, .box_thickness, m);
             break :set set;
         };

src/font/face/Metrics.zig

@@ -32,10 +32,12 @@ box_thickness: u32,
 /// because it is not determined by fonts but rather by user configuration.
 cursor_thickness: u32 = 1,
 
-/// Original cell width and height. These are used to render the cursor
-/// in the original cell size after modification.
+/// The height in pixels of the cursor sprite.
+cursor_height: u32,
+
+/// Original cell width in pixels. This is used to keep
+/// glyphs centered if the cell width is adjusted wider.
 original_cell_width: ?u32 = null,
-original_cell_height: ?u32 = null,
 
 /// Minimum acceptable values for some fields to prevent modifiers
 /// from being able to, for example, cause 0-thickness underlines.
@@ -47,6 +49,7 @@ const Minimums = struct {
     const overline_thickness = 1;
     const box_thickness = 1;
     const cursor_thickness = 1;
+    const cursor_height = 1;
 };
 
 const CalcOpts = struct {
@@ -167,6 +170,7 @@ pub fn calc(opts: CalcOpts) Metrics {
         .overline_position = 0,
         .overline_thickness = @intFromFloat(underline_thickness),
         .box_thickness = @intFromFloat(underline_thickness),
+        .cursor_height = @intFromFloat(cell_height),
     };
 
     // Ensure all metrics are within their allowable range.
@@ -192,10 +196,9 @@ pub fn apply(self: *Metrics, mods: ModifierSet) void {
                 const new = @max(entry.value_ptr.apply(original), 1);
                 if (new == original) continue;
 
-                // Preserve the original cell width and height if not set.
+                // Preserve the original cell width if not set.
                 if (self.original_cell_width == null) {
                     self.original_cell_width = self.cell_width;
-                    self.original_cell_height = self.cell_height;
                 }
 
                 // Set the new value
@@ -410,6 +413,7 @@ fn init() Metrics {
         .overline_position = 0,
         .overline_thickness = 0,
         .box_thickness = 0,
+        .cursor_height = 0,
     };
 }
 
@@ -440,12 +444,14 @@ test "Metrics: adjust cell height smaller" {
     m.underline_position = 55;
     m.strikethrough_position = 30;
     m.cell_height = 100;
+    m.cursor_height = 100;
     m.apply(set);
     try testing.expectEqual(@as(u32, 50), m.cell_height);
     try testing.expectEqual(@as(u32, 25), m.cell_baseline);
     try testing.expectEqual(@as(u32, 30), m.underline_position);
     try testing.expectEqual(@as(u32, 5), m.strikethrough_position);
-    try testing.expectEqual(@as(u32, 100), m.original_cell_height.?);
+    // Cursor height is separate from cell height and does not follow it.
+    try testing.expectEqual(@as(u32, 100), m.cursor_height);
 }
 
 test "Metrics: adjust cell height larger" {
@@ -461,12 +467,14 @@ test "Metrics: adjust cell height larger" {
     m.underline_position = 55;
     m.strikethrough_position = 30;
     m.cell_height = 100;
+    m.cursor_height = 100;
     m.apply(set);
     try testing.expectEqual(@as(u32, 200), m.cell_height);
     try testing.expectEqual(@as(u32, 100), m.cell_baseline);
     try testing.expectEqual(@as(u32, 105), m.underline_position);
     try testing.expectEqual(@as(u32, 80), m.strikethrough_position);
-    try testing.expectEqual(@as(u32, 100), m.original_cell_height.?);
+    // Cursor height is separate from cell height and does not follow it.
+    try testing.expectEqual(@as(u32, 100), m.cursor_height);
 }
 
 test "Modifier: parse absolute" {

src/font/face/coretext.zig

@@ -1045,6 +1045,7 @@ test "coretext: metrics" {
         .overline_position = 0,
         .overline_thickness = 1,
         .box_thickness = 1,
+        .cursor_height = 17,
     }, ct_font.metrics);
 
     // Resize should change metrics
@@ -1060,5 +1061,6 @@ test "coretext: metrics" {
         .overline_position = 0,
         .overline_thickness = 2,
         .box_thickness = 2,
+        .cursor_height = 34,
     }, ct_font.metrics);
 }

src/font/face/freetype.zig

@@ -906,6 +906,7 @@ test "color emoji" {
                 .overline_position = 0,
                 .overline_thickness = 0,
                 .box_thickness = 0,
+                .cursor_height = 0,
             },
         });
         try testing.expectEqual(@as(u32, 24), glyph.height);
@@ -952,6 +953,7 @@ test "metrics" {
         .overline_position = 0,
         .overline_thickness = 1,
         .box_thickness = 1,
+        .cursor_height = 17,
     }, ft_font.metrics);
 
     // Resize should change metrics
@@ -967,6 +969,7 @@ test "metrics" {
         .overline_position = 0,
         .overline_thickness = 2,
         .box_thickness = 2,
+        .cursor_height = 34,
     }, ft_font.metrics);
 }
 

src/font/sprite/Face.zig

@@ -126,29 +126,20 @@ pub fn renderGlyph(
         },
 
         .cursor => cursor: {
-            // Cursors should be drawn with the original cell height if
-            // it has been adjusted larger, so they don't get stretched.
-            const height, const dy = adjust: {
-                const h = metrics.cell_height;
-                if (metrics.original_cell_height) |original| {
-                    if (h > original) {
-                        break :adjust .{ original, (h - original) / 2 };
-                    }
-                }
-                break :adjust .{ h, 0 };
-            };
-
             var g = try cursor.renderGlyph(
                 alloc,
                 atlas,
                 @enumFromInt(cp),
                 width,
-                height,
+                metrics.cursor_height,
                 metrics.cursor_thickness,
             );
 
-            // Keep the cursor centered in the cell if it's shorter.
-            g.offset_y += @intCast(dy);
+            // Cursors are drawn at their specified height
+            // and are centered vertically within the cell.
+            const cursor_height: i32 = @intCast(metrics.cursor_height);
+            const cell_height: i32 = @intCast(metrics.cell_height);
+            g.offset_y += @divTrunc(cell_height - cursor_height, 2);
 
             break :cursor g;
         },