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LibGfx: Add ability to request glyphs at subpixel offsets to fonts

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This adds the option to pass a subpixel offset when fetching a glyph
from a font, this offset is currently snapped to thirds of a pixel
(i.e. 0, 0.33, 0.66). This is then used when rasterizing the glyph,
which is then cached like usual.

Note that when using subpixel offsets you're trading a bit of space
for accuracy. With the current third of a pixel offsets you can end
up with up to 9 bitmaps per glyph.
This commit is contained in:
MacDue 2023-01-02 20:10:00 +01:00 • committed by Andreas Kling
parent a1726b1ba5
commit ada48a1daf
14 changed files with 121 additions and 21 deletions
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22
Userland/Libraries/LibGfx/Font/ScaledFont.cpp
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@ -38,25 +38,37 @@ ALWAYS_INLINE float ScaledFont::unicode_view_width(T const& view) const
return longest_width;
}
RefPtr<Gfx::Bitmap> ScaledFont::rasterize_glyph(u32 glyph_id) const
RefPtr<Gfx::Bitmap> ScaledFont::rasterize_glyph(u32 glyph_id, GlyphSubpixelOffset subpixel_offset) const
{
auto glyph_iterator = m_cached_glyph_bitmaps.find(glyph_id);
GlyphIndexWithSubpixelOffset index { glyph_id, subpixel_offset };
auto glyph_iterator = m_cached_glyph_bitmaps.find(index);
if (glyph_iterator != m_cached_glyph_bitmaps.end())
return glyph_iterator->value;
auto glyph_bitmap = m_font->rasterize_glyph(glyph_id, m_x_scale, m_y_scale);
m_cached_glyph_bitmaps.set(glyph_id, glyph_bitmap);
auto glyph_bitmap = m_font->rasterize_glyph(glyph_id, m_x_scale, m_y_scale, subpixel_offset);
m_cached_glyph_bitmaps.set(index, glyph_bitmap);
return glyph_bitmap;
}
Gfx::Glyph ScaledFont::glyph(u32 code_point) const
{
return glyph(code_point, GlyphSubpixelOffset { 0, 0 });
}
Gfx::Glyph ScaledFont::glyph(u32 code_point, GlyphSubpixelOffset subpixel_offset) const
{
auto id = glyph_id_for_code_point(code_point);
auto bitmap = rasterize_glyph(id);
auto bitmap = rasterize_glyph(id, subpixel_offset);
auto metrics = glyph_metrics(id);
return Gfx::Glyph(bitmap, metrics.left_side_bearing, metrics.advance_width, metrics.ascender);
}
float ScaledFont::glyph_left_bearing(u32 code_point) const
{
auto id = glyph_id_for_code_point(code_point);
return glyph_metrics(id).left_side_bearing;
}
float ScaledFont::glyph_width(u32 code_point) const
{
auto id = glyph_id_for_code_point(code_point);