font: allow fractional pixel sizes

src/font/face.zig

@@ -51,9 +51,9 @@ pub const DesiredSize = struct {
     ydpi: u16 = default_dpi,
 
     // Converts points to pixels
-    pub fn pixels(self: DesiredSize) u16 {
+    pub fn pixels(self: DesiredSize) f32 {
         // 1 point = 1/72 inch
-        return @intFromFloat(@round((self.points * @as(f32, @floatFromInt(self.ydpi))) / 72));
+        return (self.points * @as(f32, @floatFromInt(self.ydpi))) / 72;
     }
 };
 

src/font/face/coretext.zig

@@ -78,7 +78,7 @@ pub const Face = struct {
         // but we need to scale the points by the DPI and to do that we use our
         // function called "pixels".
         const ct_font = try base.copyWithAttributes(
-            @floatFromInt(opts.size.pixels()),
+            opts.size.pixels(),
             null,
             null,
         );
@@ -94,7 +94,8 @@ pub const Face = struct {
 
         var hb_font = if (comptime harfbuzz_shaper) font: {
             var hb_font = try harfbuzz.coretext.createFont(ct_font);
-            hb_font.setScale(opts.size.pixels(), opts.size.pixels());
+            const pixels: opentype.sfnt.F26Dot6 = .from(opts.size.pixels());
+            hb_font.setScale(@bitCast(pixels), @bitCast(pixels));
             break :font hb_font;
         } else {};
         errdefer if (comptime harfbuzz_shaper) hb_font.destroy();

src/font/face/freetype.zig

@@ -217,7 +217,7 @@ pub const Face = struct {
         if (face.isScalable()) {
             const size_26dot6: i32 = @intFromFloat(@round(size.points * 64));
             try face.setCharSize(0, size_26dot6, size.xdpi, size.ydpi);
-        } else try selectSizeNearest(face, size.pixels());
+        } else try selectSizeNearest(face, @intFromFloat(@round(size.pixels())));
     }
 
     /// Selects the fixed size in the loaded face that is closest to the

src/font/shaper/harfbuzz.zig

@@ -158,16 +158,11 @@ pub const Shaper = struct {
                 .glyph_index = info_v.codepoint,
             });
 
-            if (font.options.backend.hasFreetype()) {
+            // Under both FreeType and CoreText the harfbuzz scale is
-                // Freetype returns 26.6 fixed point values, so we need to
+            // in 26.6 fixed point units, so we round to the nearest
-                // divide by 64 to get the actual value. I can't find any
+            // whole value here.
-                // HB API to stop this.
+            cell_offset.x += (pos_v.x_advance + 0b100_000) >> 6;
-                cell_offset.x += pos_v.x_advance >> 6;
+            cell_offset.y += (pos_v.y_advance + 0b100_000) >> 6;
-                cell_offset.y += pos_v.y_advance >> 6;
-            } else {
-                cell_offset.x += pos_v.x_advance;
-                cell_offset.y += pos_v.y_advance;
-            }
 
             // const i = self.cell_buf.items.len - 1;
             // log.warn("i={} info={} pos={} cell={}", .{ i, info_v, pos_v, self.cell_buf.items[i] });