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fix(gui): calculate cell size from full block glyph bounding box

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This commit is contained in:
CJ van den Berg 2026-03-31 22:34:20 +02:00
parent 50d9773956
commit fab38872ee
Signed by: neurocyte
GPG key ID: 8EB1E1BB660E3FB9
1 changed files with 19 additions and 4 deletions
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23
src/gui/rasterizer/truetype.zig
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@ -49,14 +49,29 @@ pub fn loadFont(self: *Self, name: []const u8, size_px: u16) !Font {
const scale = tt.scaleForPixelHeight(@floatFromInt(size_px));
const vm = tt.verticalMetrics();
const ascent_px: i32 = @intFromFloat(@round(@as(f32, @floatFromInt(vm.ascent)) * scale));
const descent_px: i32 = @intFromFloat(@round(@as(f32, @floatFromInt(vm.descent)) * scale));
const cell_h: u16 = @intCast(@max(ascent_px - descent_px, 1));
// Use the full block glyph (U+2588) to derive exact cell dimensions.
// Its rasterized bbox defines exactly how many pixels tall a full-height
// character is, and where the baseline sits within the cell. Using font
// metrics (vm.ascent/vm.descent) produces a cell_h that may differ from
// the glyph because the font bbox can diverge from nominal metrics.
const full_block_glyph = tt.codepointGlyphIndex('█');
const block_bbox = tt.glyphBitmapBox(full_block_glyph, scale, scale);
const has_block = full_block_glyph != .notdef and block_bbox.y1 > block_bbox.y0;
const ascent_px: i32 = if (has_block)
-@as(i32, block_bbox.y0)
else
@as(i32, @intFromFloat(@ceil(@as(f32, @floatFromInt(vm.ascent)) * scale)));
const cell_h: u16 = @as(u16, if (has_block)
@intCast(@max(block_bbox.y1 - block_bbox.y0, 1))
else blk: {
const d: i32 = @intFromFloat(@floor(@as(f32, @floatFromInt(vm.descent)) * scale));
break :blk @intCast(@max(ascent_px - d, 1));
}) -| 1;
const m_glyph = tt.codepointGlyphIndex('M');
const m_hmetrics = tt.glyphHMetrics(m_glyph);
const cell_w_f: f32 = @as(f32, @floatFromInt(m_hmetrics.advance_width)) * scale;
const cell_w: u16 = @intFromFloat(@ceil(cell_w_f));
const cell_w: u16 = @as(u16, @intFromFloat(@ceil(cell_w_f))) -| 1;
try self.font_data.append(self.allocator, data);