Add font variations API

.typos.toml

@@ -9,6 +9,7 @@ isse = "isse" # part of @IsseW username
 tye = "tye" # part of @tye-exe username
 ro = "ro" # read-only, also part of the username @Phen-Ro
 typ = "typ" # Often used because `type` is a keyword in Rust
+wdth = "wdth" # The `wdth` tag is used in variable fonts
 
 # I mistype these so often
 tesalator = "tessellator"

Cargo.lock

@@ -1567,6 +1567,7 @@ dependencies = [
  "ecolor",
  "emath",
  "epaint_default_fonts",
+ "font-types",
  "log",
  "mimalloc",
  "nohash-hasher",
@@ -1577,6 +1578,7 @@ dependencies = [
  "serde",
  "similar-asserts",
  "skrifa",
+ "smallvec",
  "vello_cpu",
 ]
 
@@ -1741,6 +1743,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b1e4d2d0cf79d38430cc9dc9aadec84774bff2e1ba30ae2bf6c16cfce9385a23"
 dependencies = [
  "bytemuck",
+ "serde",
 ]
 
 [[package]]
@@ -4136,6 +4139,9 @@ name = "smallvec"
 version = "1.15.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "67b1b7a3b5fe4f1376887184045fcf45c69e92af734b7aaddc05fb777b6fbd03"
+dependencies = [
+ "serde",
+]
 
 [[package]]
 name = "smithay-client-toolkit"

Cargo.toml

@@ -90,6 +90,7 @@ document-features = "0.2.11"
 ehttp = { version = "0.6.0", default-features = false }
 enum-map = "2.7.3"
 env_logger = { version = "0.11.8", default-features = false }
+font-types = { version = "0.11.0", default-features = false, features = ["std"] }
 glow = "0.16.0"
 glutin = { version = "0.32.3", default-features = false }
 glutin-winit = { version = "0.5.0", default-features = false }

crates/egui/src/context.rs

@@ -3262,7 +3262,7 @@ impl Context {
 
         for (name, data) in &mut font_definitions.font_data {
             ui.collapsing(name, |ui| {
-                let mut tweak = data.tweak;
+                let mut tweak = data.tweak.clone();
                 if tweak.ui(ui).changed() {
                     Arc::make_mut(data).tweak = tweak;
                     changed = true;

crates/egui/src/style.rs

@@ -1,7 +1,11 @@
 //! egui theme (spacing, colors, etc).
 
 use emath::Align;
-use epaint::{AlphaFromCoverage, CornerRadius, Shadow, Stroke, TextOptions, text::FontTweak};
+use epaint::{
+    AlphaFromCoverage, CornerRadius, Shadow, Stroke, TextOptions,
+    mutex::Mutex,
+    text::{FontTweak, Tag},
+};
 use std::{collections::BTreeMap, ops::RangeInclusive, sync::Arc};
 
 use crate::{
@@ -2837,7 +2841,7 @@ impl Widget for &mut crate::Frame {
 
 impl Widget for &mut FontTweak {
     fn ui(self, ui: &mut Ui) -> Response {
-        let original: FontTweak = *self;
+        let original: FontTweak = self.clone();
 
         let mut response = Grid::new("font_tweak")
             .num_columns(2)
@@ -2847,6 +2851,7 @@ impl Widget for &mut FontTweak {
                     y_offset_factor,
                     y_offset,
                     hinting_override,
+                    coords,
                 } = self;
 
                 ui.label("Scale");
@@ -2874,6 +2879,50 @@ impl Widget for &mut FontTweak {
                         ui.selectable_value(hinting_override, Some(true), "Enable");
                         ui.selectable_value(hinting_override, Some(false), "Disable");
                     });
+                ui.end_row();
+
+                ui.label("coords");
+                ui.end_row();
+                let mut to_remove = None;
+                for (i, (tag, value)) in coords.as_mut().iter_mut().enumerate() {
+                    let tag_text = ui.ctx().data_mut(|data| {
+                        let tag = *tag;
+                        Arc::clone(data.get_temp_mut_or_insert_with(ui.id().with(i), move || {
+                            Arc::new(Mutex::new(tag.to_string()))
+                        }))
+                    });
+
+                    let tag_text = &mut *tag_text.lock();
+                    let response = ui.text_edit_singleline(tag_text);
+                    if response.changed()
+                        && let Ok(new_tag) = Tag::new_checked(tag_text.as_bytes())
+                    {
+                        *tag = new_tag;
+                    }
+                    // Reset stale text when not actively editing
+                    // (e.g. after an item was removed and indices shifted)
+                    if !response.has_focus()
+                        && Tag::new_checked(tag_text.as_bytes()).ok() != Some(*tag)
+                    {
+                        *tag_text = tag.to_string();
+                    }
+
+                    ui.add(DragValue::new(value));
+                    if ui.small_button("🗑").clicked() {
+                        to_remove = Some(i);
+                    }
+                    ui.end_row();
+                }
+                if let Some(i) = to_remove {
+                    coords.remove(i);
+                }
+                if ui.button("Add coord").clicked() {
+                    coords.push(b"wght", 0.0);
+                }
+                if ui.button("Clear coords").clicked() {
+                    coords.clear();
+                }
+                ui.end_row();
 
                 if ui.button("Reset").clicked() {
                     *self = Default::default();

crates/egui/src/widget_text.rs

@@ -1,5 +1,5 @@
 use emath::GuiRounding as _;
-use epaint::text::TextFormat;
+use epaint::text::{IntoTag, TextFormat, VariationCoords};
 use std::fmt::Formatter;
 use std::{borrow::Cow, sync::Arc};
 
@@ -34,6 +34,7 @@ pub struct RichText {
     background_color: Color32,
     expand_bg: f32,
     text_color: Option<Color32>,
+    coords: VariationCoords,
     code: bool,
     strong: bool,
     weak: bool,
@@ -55,6 +56,7 @@ impl Default for RichText {
             background_color: Default::default(),
             expand_bg: 1.0,
             text_color: Default::default(),
+            coords: Default::default(),
             code: Default::default(),
             strong: Default::default(),
             weak: Default::default(),
@@ -196,6 +198,23 @@ impl RichText {
         self
     }
 
+    /// Add a variation coordinate.
+    #[inline]
+    pub fn variation(mut self, tag: impl IntoTag, coord: f32) -> Self {
+        self.coords.push(tag, coord);
+        self
+    }
+
+    /// Override the variation coordinates completely.
+    #[inline]
+    pub fn variations<T: IntoTag>(
+        mut self,
+        variations: impl IntoIterator<Item = (T, f32)>,
+    ) -> Self {
+        self.coords = VariationCoords::new(variations);
+        self
+    }
+
     /// Override the [`TextStyle`].
     #[inline]
     pub fn text_style(mut self, text_style: TextStyle) -> Self {
@@ -391,6 +410,7 @@ impl RichText {
             background_color,
             expand_bg,
             text_color: _, // already used by `get_text_color`
+            coords,
             code,
             strong: _, // already used by `get_text_color`
             weak: _,   // already used by `get_text_color`
@@ -449,6 +469,7 @@ impl RichText {
                 line_height,
                 color: text_color,
                 background: background_color,
+                coords,
                 italics,
                 underline,
                 strikethrough,

crates/epaint/Cargo.toml

@@ -48,7 +48,7 @@ mint = ["emath/mint"]
 rayon = ["dep:rayon"]
 
 ## Allow serialization using [`serde`](https://docs.rs/serde).
-serde = ["dep:serde", "ahash/serde", "emath/serde", "ecolor/serde"]
+serde = ["dep:serde", "ahash/serde", "emath/serde", "ecolor/serde", "font-types/serde", "smallvec/serde"]
 
 ## Change Vertex layout to be compatible with unity
 unity = []
@@ -62,12 +62,14 @@ emath.workspace = true
 ecolor.workspace = true
 
 ahash.workspace = true
+font-types.workspace = true
 log.workspace = true
 nohash-hasher.workspace = true
 parking_lot.workspace = true # Using parking_lot over std::sync::Mutex gives 50% speedups in some real-world scenarios.
 profiling.workspace = true
 self_cell.workspace = true
 skrifa.workspace = true
+smallvec.workspace = true
 vello_cpu.workspace = true
 
 #! ### Optional dependencies