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LibPDF: Tweak vertical position of truetype fonts again

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See #22821 for a previous attempt. This attempt should settle
things once and for all.

The opentype render path adjusts by `-font_ascender * -y_scale` in
Glyf::Glyph::append_simple_path(), so that's what we need to undo
to draw at the font's baseline.

(OpenType::Font::metrics() returns ascender scaled by y_scale already,
so no need to have the scale here where we undo the shift.)

Previously, we called `baseline()` which just returns the font's
font size, which is pretty meaningless:

https://tonsky.me/blog/font-size/
https://simoncozens.github.io/fonts-and-layout/opentype.html#vertical-metrics-hhea-and-os2

Also, conceptually it makes sense to translate up by the ascender
to get from the upper edge of the glyph to the baseline.
This commit is contained in:
Nico Weber 2024-01-31 21:08:01 -05:00 • committed by Jelle Raaijmakers
parent d930ea1242
commit 384c6cf0f9
2 changed files with 4 additions and 4 deletions
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4
Userland/Libraries/LibPDF/Fonts/TrueTypeFont.cpp
View file

@ -52,8 +52,8 @@ PDFErrorOr<void> TrueTypeFont::draw_glyph(Gfx::Painter& painter, Gfx::FloatPoint
{ {
auto style = renderer.state().paint_style; auto style = renderer.state().paint_style;
// Account for the reversed font baseline // Undo shift in Glyf::Glyph::append_simple_path() via OpenType::Font::rasterize_glyph().
auto position = point.translated(0, -m_font->pixel_metrics().descent - m_font->baseline()); auto position = point.translated(0, -m_font->pixel_metrics().ascent);
if (style.has<Color>()) { if (style.has<Color>()) {
painter.draw_glyph(position, char_code, *m_font, style.get<Color>()); painter.draw_glyph(position, char_code, *m_font, style.get<Color>());

4
Userland/Libraries/LibPDF/Fonts/Type1Font.cpp
View file

@ -70,8 +70,8 @@ PDFErrorOr<void> Type1Font::draw_glyph(Gfx::Painter& painter, Gfx::FloatPoint po
auto style = renderer.state().paint_style; auto style = renderer.state().paint_style;
if (!m_font_program) { if (!m_font_program) {
// Account for the reversed font baseline // Undo shift in Glyf::Glyph::append_simple_path() via OpenType::Font::rasterize_glyph().
auto position = point.translated(0, -m_font->pixel_metrics().descent - m_font->baseline()); auto position = point.translated(0, -m_font->pixel_metrics().ascent);
// FIXME: Bounding box and sample point look to be pretty wrong // FIXME: Bounding box and sample point look to be pretty wrong
if (style.has<Color>()) { if (style.has<Color>()) {
painter.draw_glyph(position, char_code, *m_font, style.get<Color>()); painter.draw_glyph(position, char_code, *m_font, style.get<Color>());