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https://github.com/emilk/egui.git
synced 2026-06-26 14:49:06 -04:00
Make font hinting target configurable via FontTweak (#8262)
Fixes #8079, where font hinting only sharpens the vertical axis (vertical stems stay blurry), and none of the skrifa knobs were reachable — only switching to `Target::Mono` helped, but that wasn't exposed. This makes the hinting target configurable instead of hardcoding `Target::Smooth { symmetric_rendering: true, preserve_linear_metrics: true }`. ### API - New `epaint::text::HintingTarget` mirroring `skrifa::outline::Target`: - `Mono` - `Smooth(SmoothHinting)` where `SmoothHinting { light, symmetric_rendering, preserve_linear_metrics }` - New field `FontTweak::hinting_target: HintingTarget`. - Each variant/field is documented with what it does and the egui-specific caveats (e.g. `symmetric_rendering` only affects interpreter-hinted fonts; egui positions glyphs from shaper advances so `preserve_linear_metrics` mostly affects sharpness, not layout). ### Render - `font.rs` converts `HintingTarget` → `skrifa::outline::Target` and threads it into the per-glyph `reconfigure` call; the hinting instance is also reconfigured when the target changes. ### UI - The font-tweak settings panel gets a `hinting_target` row: Smooth/Mono radios, `light` / `symmetric_rendering` / `preserve_linear_metrics` checkboxes, and a `Reset` button — all with tooltips. ### Behavior - `HintingTarget::default()` matches egui's previous hardcoded target, so **rendering is unchanged** unless you opt in. To fix the horizontal blur from #8079, uncheck `preserve_linear_metrics` (or pick `Mono`). Whether to flip the *default* is left as a follow-up. 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Emil Ernerfeldt
GitHub
@@ -3,7 +3,7 @@
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use emath::Align;
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use epaint::{
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CornerRadius, FontColorTransferFunction, Shadow, Stroke, TextOptions,
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text::{FontTweak, FontVariationAxis},
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text::{FontTweak, FontVariationAxis, HintingTarget, SmoothHinting},
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};
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use std::{collections::BTreeMap, ops::RangeInclusive, sync::Arc};
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@@ -2902,6 +2902,7 @@ pub fn font_tweak_ui(ui: &mut Ui, tweak: &mut FontTweak, axes: &[FontVariationAx
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y_offset_factor,
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y_offset,
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hinting,
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hinting_target,
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coords,
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thin_space_width,
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tab_size,
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@@ -2929,6 +2930,59 @@ pub fn font_tweak_ui(ui: &mut Ui, tweak: &mut FontTweak, axes: &[FontVariationAx
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});
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ui.end_row();
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ui.label("hinting_target")
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.on_hover_text("How aggressively to snap glyph outlines to the pixel grid. Only matters when hinting is enabled.");
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ui.vertical(|ui| {
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ui.horizontal(|ui| {
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let is_mono = matches!(hinting_target, HintingTarget::Mono);
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if ui
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.radio(!is_mono, "Smooth")
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.on_hover_text("Hinting tuned for anti-aliased rendering. The normal choice.")
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.clicked()
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&& is_mono
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{
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*hinting_target = HintingTarget::default();
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}
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if ui
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.radio(is_mono, "Mono")
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.on_hover_text(
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"Strongest hinting (designed for 1-bit rendering). Sharpest, but \
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distorts glyph weight across sizes.",
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)
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.clicked()
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{
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*hinting_target = HintingTarget::Mono;
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}
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if ui
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.button("Reset")
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.on_hover_text("Reset the hinting target to its default.")
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.clicked()
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{
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*hinting_target = HintingTarget::default();
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}
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});
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if let HintingTarget::Smooth(SmoothHinting {
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light,
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symmetric_rendering,
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preserve_linear_metrics,
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}) = hinting_target
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{
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ui.checkbox(light, "light").on_hover_text(
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"Hint only vertically, preserving the font's horizontal proportions \
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(softer). Off also fits horizontally.",
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);
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ui.checkbox(symmetric_rendering, "symmetric_rendering").on_hover_text(
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"Render glyphs the same regardless of sub-pixel position (good for \
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caching/animation), but can blur stems. Only affects interpreter-hinted fonts.",
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);
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ui.checkbox(preserve_linear_metrics, "preserve_linear_metrics").on_hover_text(
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"Keep spacing independent of hinting. Off lets the hinter snap \
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horizontally for crisper vertical stems on low-dpi screens.",
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);
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}
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});
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ui.end_row();
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ui.label("subpixel_binning");
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ui.horizontal(|ui| {
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ui.radio_value(subpixel_binning, Some(true), "on");
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@@ -225,6 +225,7 @@ impl FontCell {
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glyph_id: GlyphId,
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bin: SubpixelBin,
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location: skrifa::instance::LocationRef<'_>,
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hinting_target: skrifa::outline::Target,
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) -> Option<GlyphAllocation> {
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debug_assert!(
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glyph_id != skrifa::GlyphId::NOTDEF,
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@@ -244,18 +245,10 @@ impl FontCell {
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let size = skrifa::instance::Size::new(metrics.scale);
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if hinting_instance.size() != size
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|| hinting_instance.location().coords() != location.coords()
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|| hinting_instance.target() != hinting_target
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{
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hinting_instance
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.reconfigure(
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&font_data.outline_glyphs,
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size,
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location,
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skrifa::outline::Target::Smooth {
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mode: skrifa::outline::SmoothMode::Normal,
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symmetric_rendering: true,
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preserve_linear_metrics: true,
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},
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)
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.reconfigure(&font_data.outline_glyphs, size, location, hinting_target)
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.ok()?;
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}
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let draw_settings = skrifa::outline::DrawSettings::hinted(hinting_instance, false);
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@@ -637,9 +630,17 @@ impl FontFace {
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let cache_key = GlyphCacheKey::new(glyph_id, metrics, bin);
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let hinting_target = self.tweak.hinting_target.into();
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let alloc = *self.glyph_alloc_cache.entry(cache_key).or_insert_with(|| {
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self.font
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.allocate_glyph_uncached(atlas, metrics, glyph_id, bin, (&metrics.location).into())
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.allocate_glyph_uncached(
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atlas,
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metrics,
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glyph_id,
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bin,
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(&metrics.location).into(),
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hinting_target,
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)
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.unwrap_or_default()
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});
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@@ -242,6 +242,11 @@ pub struct FontTweak {
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/// `None` means use the global setting in [`TextOptions::font_hinting`].
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pub hinting: Option<bool>,
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/// How to grid-fit the glyph outlines when hinting is enabled.
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///
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/// Has no effect when hinting is disabled (see [`Self::hinting`]).
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pub hinting_target: HintingTarget,
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/// Override the global sub-pixel binning setting for this specific font.
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///
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/// `None` means use the global setting in [`TextOptions::subpixel_binning`].
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@@ -271,6 +276,7 @@ impl Default for FontTweak {
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y_offset_factor: 0.0,
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y_offset: 0.0,
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hinting: None,
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hinting_target: HintingTarget::default(),
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subpixel_binning: None,
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coords: VariationCoords::default(),
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thin_space_width: 0.5,
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@@ -281,6 +287,111 @@ impl Default for FontTweak {
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// ----------------------------------------------------------------------------
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/// How to *hint* glyph outlines, i.e. how aggressively to nudge them onto the
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/// pixel grid before rasterizing. Mirrors [`skrifa::outline::Target`].
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///
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/// Hinting trades shape fidelity for sharpness: snapping stems to whole pixels
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/// makes text crisp at small sizes / low dpi, at the cost of slightly distorting
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/// the designer's outlines. At high dpi it matters little.
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///
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/// This only has an effect if the font is actually hinted — either it ships
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/// TrueType instructions, or it was auto-hinted (see [`FontTweak::hinting`]).
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///
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/// Used by [`FontTweak::hinting_target`].
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#[derive(Clone, Copy, Debug, PartialEq, Eq)]
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#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
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pub enum HintingTarget {
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/// Strongest hinting, designed for aliased 1-bit (black & white) rendering.
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///
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/// Snaps stems hard to the pixel grid for maximum sharpness. egui always
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/// renders anti-aliased, so in practice this looks much like [`Self::Smooth`]
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/// here; it mostly exists for completeness. Maps to `skrifa`'s `Target::Mono`.
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Mono,
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/// Hinting tuned for anti-aliased rendering. This is what you normally want,
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/// and what egui uses by default. Maps to `skrifa`'s `Target::Smooth`.
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Smooth(SmoothHinting),
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}
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impl Default for HintingTarget {
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fn default() -> Self {
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Self::Smooth(SmoothHinting::default())
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}
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}
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impl From<HintingTarget> for skrifa::outline::Target {
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fn from(hinting_target: HintingTarget) -> Self {
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use skrifa::outline::SmoothMode;
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match hinting_target {
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HintingTarget::Mono => Self::Mono,
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HintingTarget::Smooth(SmoothHinting {
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light,
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symmetric_rendering,
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preserve_linear_metrics,
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}) => Self::Smooth {
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mode: if light {
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SmoothMode::Light
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} else {
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SmoothMode::Normal
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},
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symmetric_rendering,
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preserve_linear_metrics,
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},
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}
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}
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}
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/// Tuning for [`HintingTarget::Smooth`], mirroring `skrifa`'s `Target::Smooth`.
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#[derive(Clone, Copy, Debug, PartialEq, Eq)]
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#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
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pub struct SmoothHinting {
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/// Hint only lightly: snap stems vertically but leave horizontal shapes
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/// alone (`FreeType`'s "light" mode). Preserves the font's proportions
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/// better, at the cost of a little horizontal sharpness.
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///
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/// `false` uses the "normal" mode, which also fits horizontally.
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/// Maps to `SmoothMode::Light` (`true`) vs `SmoothMode::Normal` (`false`).
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pub light: bool,
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/// Render a glyph the same way regardless of its sub-pixel position.
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///
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/// `true` makes glyphs position-independent (better for caching and
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/// animation), but a font's instructions may then widen stems and look
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/// slightly blurrier under an analytic rasterizer like egui's.
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///
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/// **Only affects fonts hinted via the TrueType interpreter** (i.e. fonts
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/// that ship their own instructions). It has no effect on the auto-hinter.
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/// Mirrors `Target::Smooth { symmetric_rendering }`.
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pub symmetric_rendering: bool,
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/// Keep advance widths independent of hinting (don't grid-fit horizontally
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/// in a way that changes spacing).
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///
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/// `true` keeps inter-glyph spacing identical to the unhinted font, so
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/// layout never depends on hinting — but it also prevents horizontal
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/// grid-fitting, leaving vertical stems softer on low-dpi screens.
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///
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/// `false` lets the (auto)hinter snap horizontally for crisper stems.
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/// egui positions glyphs from the shaper's advances, not the hinted
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/// outline, so this mainly affects sharpness here, not layout.
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/// Mirrors `Target::Smooth { preserve_linear_metrics }`.
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pub preserve_linear_metrics: bool,
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}
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impl Default for SmoothHinting {
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fn default() -> Self {
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// Matches the behavior egui had before the hinting target was configurable.
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// Note this means horizontal grid-fitting is opt-in (see `preserve_linear_metrics`).
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Self {
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light: false,
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symmetric_rendering: true,
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preserve_linear_metrics: true,
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}
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}
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}
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// ----------------------------------------------------------------------------
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pub type Blob = Arc<dyn AsRef<[u8]> + Send + Sync>;
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fn blob_from_font_data(data: &FontData) -> Blob {
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@@ -10,7 +10,8 @@ mod text_layout_types;
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pub use {
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fonts::{
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FontData, FontDefinitions, FontFamily, FontId, FontInsert, FontPriority, FontTweak,
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FontVariationAxis, Fonts, FontsImpl, FontsView, InsertFontFamily,
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FontVariationAxis, Fonts, FontsImpl, FontsView, HintingTarget, InsertFontFamily,
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SmoothHinting,
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},
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index::{ByteIndex, ByteRange, ByteRangeExt, CharIndex, CharRange, CharRangeExt},
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text_layout::*,
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