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Add subpixel_binning to TextOptions and FontTweak (#8072)

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This lets you turn off subpixel horizontal binning of glyphs. The option
is a trade-off between even kerning and sharp text.

* Closes https://github.com/emilk/egui/issues/8034
This commit is contained in:
Emil Ernerfeldt
2026-04-07 10:38:37 +02:00
committed by GitHub
parent ab4bca65ea
commit 3abba21f2d
4 changed files with 51 additions and 21 deletions
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33
crates/egui/src/style.rs
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@@ -2344,11 +2344,13 @@ impl Visuals {
max_texture_side: _,
alpha_from_coverage,
font_hinting,
subpixel_binning,
} = text_options;
text_alpha_from_coverage_ui(ui, alpha_from_coverage);
ui.checkbox(font_hinting, "Enable font hinting");
ui.checkbox(font_hinting, "Font hinting (sharper text)");
ui.checkbox(subpixel_binning, "Sub-pixel binning (more even kerning)");
});
ui.collapsing("Text cursor", |ui| {
@@ -2913,10 +2915,11 @@ impl Widget for &mut FontTweak {
scale,
y_offset_factor,
y_offset,
hinting_override,
hinting,
coords,
thin_space_width,
tab_size,
subpixel_binning,
} = self;
ui.label("Scale");
@@ -2932,18 +2935,20 @@ impl Widget for &mut FontTweak {
ui.add(DragValue::new(y_offset).speed(-0.02));
ui.end_row();
ui.label("hinting_override");
ComboBox::from_id_salt("hinting_override")
.selected_text(match hinting_override {
None => "None",
Some(true) => "Enable",
Some(false) => "Disable",
})
.show_ui(ui, |ui| {
ui.selectable_value(hinting_override, None, "None");
ui.selectable_value(hinting_override, Some(true), "Enable");
ui.selectable_value(hinting_override, Some(false), "Disable");
});
ui.label("hinting");
ui.horizontal(|ui| {
ui.radio_value(hinting, Some(true), "on");
ui.radio_value(hinting, Some(false), "off");
ui.radio_value(hinting, None, "default");
});
ui.end_row();
ui.label("subpixel_binning");
ui.horizontal(|ui| {
ui.radio_value(subpixel_binning, Some(true), "on");
ui.radio_value(subpixel_binning, Some(false), "off");
ui.radio_value(subpixel_binning, None, "default");
});
ui.end_row();
ui.label("coords");

12
crates/epaint/src/text/font.rs
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@@ -316,6 +316,7 @@ pub struct FontFace {
name: String,
font: FontCell,
tweak: FontTweak,
subpixel_binning: bool,
/// Cached `harfrust` shaper data (parsed GSUB/GPOS tables).
/// `ShaperData` is `Copy` — lives outside the `self_cell`.
@@ -352,7 +353,7 @@ impl FontFace {
skrifa::instance::LocationRef::default(),
);
let hinting_enabled = tweak.hinting_override.unwrap_or(options.font_hinting);
let hinting_enabled = tweak.hinting.unwrap_or(options.font_hinting);
let hinting_instance = hinting_enabled
.then(|| {
// It doesn't really matter what we put here for options. Since the size is `unscaled()`, we will
@@ -379,10 +380,13 @@ impl FontFace {
let shaper_data = harfrust::ShaperData::new(&font.borrow_dependent().skrifa);
let subpixel_binning = tweak.subpixel_binning.unwrap_or(options.subpixel_binning);
Ok(Self {
name,
font,
tweak,
subpixel_binning,
shaper_data,
glyph_info_cache: Default::default(),
glyph_alloc_cache: Default::default(),
@@ -551,12 +555,12 @@ impl FontFace {
return (GlyphAllocation::default(), h_pos.round() as i32);
}
let (h_pos_round, bin) = if is_cjk {
let (h_pos_round, bin) = if self.subpixel_binning && !is_cjk {
SubpixelBin::new(h_pos)
} else {
// CJK scripts contain a lot of characters and could hog the glyph atlas
// if we stored 4 subpixel offsets per glyph.
(h_pos.round() as i32, SubpixelBin::Zero)
} else {
SubpixelBin::new(h_pos)
};
let cache_key = GlyphCacheKey::new(glyph_id, metrics, bin);

12
crates/epaint/src/text/fonts.rs
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@@ -188,8 +188,13 @@ pub struct FontTweak {
/// Override the global font hinting setting for this specific font.
///
/// `None` means use the global setting.
pub hinting_override: Option<bool>,
/// `None` means use the global setting in [`TextOptions::font_hinting`].
pub hinting: Option<bool>,
/// Override the global sub-pixel binning setting for this specific font.
///
/// `None` means use the global setting in [`TextOptions::subpixel_binning`].
pub subpixel_binning: Option<bool>,
/// Override the font's default variation coordinates.
pub coords: VariationCoords,
@@ -214,7 +219,8 @@ impl Default for FontTweak {
scale: 1.0,
y_offset_factor: 0.0,
y_offset: 0.0,
hinting_override: None,
hinting: None,
subpixel_binning: None,
coords: VariationCoords::default(),
thin_space_width: 0.5,
tab_size: 4.0,

15
crates/epaint/src/text/mod.rs
View File

@@ -34,6 +34,20 @@ pub struct TextOptions {
///
/// Default is `true`.
pub font_hinting: bool,
/// Enable sub-pixel binning for glyphs.
///
/// Sub-pixel binning renders each glyph at up to four fractional horizontal offsets,
/// giving more even kerning at the cost of more atlas space.
///
/// It also lead to text looking more blurry.
///
/// This is always disabled for CJK characters (which have too many unique glyphs).
///
/// Can be overridden per font with [`FontTweak::subpixel_binning`].
///
/// Default: `true`.
pub subpixel_binning: bool,
}
impl Default for TextOptions {
@@ -42,6 +56,7 @@ impl Default for TextOptions {
max_texture_side: 2048, // Small but portable
alpha_from_coverage: crate::AlphaFromCoverage::default(),
font_hinting: true,
subpixel_binning: true,
}
}
}