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gfx: Derive line-through metrics for fonts on MacOS #31756

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merged 1 commit into from
Mar 19, 2024
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gfx: Derive line-through metrics for fonts on MacOS #31756

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17 changes: 13 additions & 4 deletions components/gfx/platform/macos/font.rs
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Expand Up @@ -278,6 +278,9 @@ impl FontHandleMethods for FontHandle {
}

fn metrics(&self) -> FontMetrics {
// TODO(mrobinson): Gecko first tries to get metrics from the SFNT tables via
// HarfBuzz and only afterward falls back to platform APIs. We should do something
// similar here. This will likely address issue #201 mentioned below.
let bounding_rect: CGRect = self.ctfont.bounding_box();
let ascent = self.ctfont.ascent();
let descent = self.ctfont.descent();
Expand All @@ -294,18 +297,24 @@ impl FontHandleMethods for FontHandle {
.map(Au::from_f64_px)
.unwrap_or(max_advance);

let underline_size = au_from_pt(self.ctfont.underline_thickness());
let x_height = au_from_pt(self.ctfont.x_height() * scale);

let metrics = FontMetrics {
underline_size: au_from_pt(self.ctfont.underline_thickness()),
underline_size,
// TODO(Issue #201): underline metrics are not reliable. Have to pull out of font table
// directly.
//
// see also: https://bugs.webkit.org/show_bug.cgi?id=16768
// see also: https://bugreports.qt-project.org/browse/QTBUG-13364
underline_offset: au_from_pt(self.ctfont.underline_position()),
strikeout_size: Au(0), // FIXME(Issue #942)
strikeout_offset: Au(0), // FIXME(Issue #942)
// There is no way to get these from CoreText or CoreGraphics APIs, so
// derive them from the other font metrics. These should eventually be
// found in the font tables directly when #201 is fixed.
strikeout_size: underline_size,
strikeout_offset: x_height.scale_by(0.5) + underline_size.scale_by(0.5),
leading: au_from_pt(leading),
x_height: au_from_pt(self.ctfont.x_height() * scale),
x_height,
em_size,
ascent: au_from_pt(ascent * scale),
descent: au_from_pt(descent * scale),
Expand Down
1 change: 0 additions & 1 deletion components/layout_2020/display_list/mod.rs
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Expand Up @@ -410,7 +410,6 @@ impl Fragment {
{
let mut rect = rect;
rect.origin.y += Length::from(font_metrics.ascent - font_metrics.strikeout_offset);
// XXX(ferjm) This does not work on MacOS #942
rect.size.height = Length::new(font_metrics.strikeout_size.to_nearest_pixel(dppx));
self.build_display_list_for_text_decoration(fragment, builder, &rect, &color);
}
Expand Down