Part of #394: Highlight Alternate Glyphs paints pink behind OpenType substitutions.

crates/render/src/lib.rs

@@ -123,6 +123,10 @@ pub struct RenderOptions {
     pub mask_view: Option<NodeId>,
     /// Screen view: highlight substituted fonts and glyphs as Document Setup asks.
     pub highlight_substitutions: bool,
+    /// Screen view: Preferences › Type › Highlight Alternate Glyphs. Pink behind glyphs OpenType
+    /// features substituted (ligatures, contextual forms), not Document Setup's missing-glyph
+    /// highlights.
+    pub highlight_alternate_glyphs: bool,
     /// Edge smoothing (raster export option).
     pub anti_alias: AntiAlias,
     /// Screen view: placed documents draw from cached bitmaps made in the background (see
@@ -227,6 +231,7 @@ impl Default for RenderOptions {
             guide: ([0x4a, 0xd8, 0xff], false),
             mask_view: None,
             highlight_substitutions: false,
+            highlight_alternate_glyphs: false,
             anti_alias: AntiAlias::Art,
             progressive_placed: false,
             trace_views: false,
@@ -1789,8 +1794,11 @@ impl Renderer {
         }
         if f.opts.highlight_substitutions {
             let setup = &f.doc.setup;
-            for (on, path) in [(setup.highlight_substituted_fonts, &g.substituted_fonts), (setup.highlight_substituted_glyphs, &g.substituted_glyphs)]
-            {
+            for (on, path) in [
+                (setup.highlight_substituted_fonts, &g.substituted_fonts),
+                (setup.highlight_substituted_glyphs, &g.substituted_glyphs),
+                (f.opts.highlight_alternate_glyphs, &g.alternate_glyphs),
+            ] {
                 if on && !path.elements().is_empty() {
                     ctx.set_transform(xf);
                     ctx.set_fill_rule(peniko::Fill::NonZero);
@@ -2218,6 +2226,9 @@ struct TextGeom {
     /// font lacks (drawn from a fallback font): Document Setup's substitution highlights.
     substituted_fonts: BezPath,
     substituted_glyphs: BezPath,
+    /// Boxes of glyphs OpenType features substituted (ligatures, contextual forms): Preferences ›
+    /// Highlight Alternate Glyphs.
+    alternate_glyphs: BezPath,
     /// Inline graphics placed by the layout.
     inlines: Vec<vectorcraft_text::InlineGlyph>,
 }
@@ -2243,12 +2254,18 @@ impl TextGeom {
     /// Approximate heap bytes, for the cache's budget.
     fn bytes(&self) -> usize {
         size_of::<Self>()
-            + [&self.all, &self.substituted_fonts, &self.substituted_glyphs].into_iter().map(lru::path_bytes).sum::<usize>()
+            + [&self.all, &self.substituted_fonts, &self.substituted_glyphs, &self.alternate_glyphs].into_iter().map(lru::path_bytes).sum::<usize>()
             + self.spans.len() * size_of::<(usize, usize, usize)>()
             + self.inlines.len() * size_of::<vectorcraft_text::InlineGlyph>()
     }
 }
 
+/// OpenType-substituted form: a ligature (several source characters → one glyph) or a glyph whose
+/// id is not the face's cmap mapping for its first character (contextual / stylistic alternate).
+pub(crate) fn is_opentype_alternate(nominal_gid: u32, shaped_gid: u32, cluster_chars: usize) -> bool {
+    shaped_gid != 0 && (cluster_chars > 1 || shaped_gid != nominal_gid)
+}
+
 fn text_geom(t: &TextObject) -> TextGeom {
     text_geom_snapped(t, None)
 }
@@ -2288,30 +2305,39 @@ fn text_geom_snapped(t: &TextObject, snap: Option<Affine>) -> TextGeom {
             None => (true, None),
         })
         .collect();
-    let (mut substituted_fonts, mut substituted_glyphs) = (BezPath::new(), BezPath::new());
+    let (mut substituted_fonts, mut substituted_glyphs, mut alternate_glyphs) = (BezPath::new(), BezPath::new(), BezPath::new());
+    let plain = t.plain_text();
     for g in &layout.glyphs {
         push(&mut all, g.run, &g.outline);
         let Some(&(missing, face)) = faces.get(g.run) else { continue };
-        let target = if missing {
-            &mut substituted_fonts
-        } else if face.is_some_and(|f| f != g.font_id) {
-            &mut substituted_glyphs
-        } else {
-            continue;
-        };
         let Some(line) = layout.lines.get(g.line) else { continue };
         let mut cell = Rect::new(g.origin.x, g.origin.y - line.ascent, g.origin.x + g.advance, g.origin.y + line.descent).to_path(0.1);
         cell.apply_affine(Affine::rotate_about(g.angle, g.origin));
-        target.extend(cell.iter());
+        if missing {
+            substituted_fonts.extend(cell.iter());
+            continue;
+        }
+        if face.is_some_and(|f| f != g.font_id) {
+            substituted_glyphs.extend(cell.iter());
+            continue;
+        }
+        // Same face: OpenType may have swapped the glyph (liga, calt, …).
+        let Some(cluster) = plain.get(g.byte..g.byte.saturating_add(g.len)) else { continue };
+        let cluster_chars = cluster.chars().count();
+        let Some(first) = cluster.chars().next() else { continue };
+        let nominal = db.face_by_id(g.font_id).map(|f| f.glyph_for(first)).unwrap_or(0);
+        if is_opentype_alternate(nominal, g.gid, cluster_chars) {
+            alternate_glyphs.extend(cell.iter());
+        }
     }
     // Underline and strikethrough bars, painted as their run's type is (#847).
     for (run, bar) in vectorcraft_text::decorations(&layout, db, t) {
         push(&mut all, run, &bar);
     }
-    TextGeom { all, spans, bounds: layout.bounds, substituted_fonts, substituted_glyphs, inlines: layout.inlines }
+    TextGeom { all, spans, bounds: layout.bounds, substituted_fonts, substituted_glyphs, alternate_glyphs, inlines: layout.inlines }
 }
 
-/// Document Setup's highlight behind substituted fonts and glyphs (screen only).
+/// Document Setup's and Preferences › Highlight Alternate Glyphs pink (screen only).
 const SUBSTITUTED: peniko::Color = peniko::Color::from_rgba8(255, 120, 190, 110);
 /// The pixel size of `region` rendered at `scale` pixels per point (at least 1×1).
 pub fn region_pixels(region: Rect, scale: f64) -> (u32, u32) {
@@ -2367,6 +2393,8 @@ mod tests;
 #[cfg(test)]
 mod tests_adjust;
 #[cfg(test)]
+mod tests_alternate;
+#[cfg(test)]
 mod tests_blend;
 #[cfg(test)]
 mod tests_charstroke;

crates/render/src/tests_alternate.rs

@@ -0,0 +1,37 @@
+//! Preferences › Type › Highlight Alternate Glyphs (#394): OpenType substitutions get a pink
+//! cell behind them on screen when the preference is on.
+
+use super::*;
+
+#[test]
+fn is_opentype_alternate_marks_ligatures_and_forms() {
+    assert!(is_opentype_alternate(100, 100, 2), "ligature cluster");
+    assert!(is_opentype_alternate(50, 99, 1), "contextual / stylistic form");
+    assert!(!is_opentype_alternate(50, 50, 1), "nominal cmap glyph");
+    assert!(!is_opentype_alternate(50, 0, 2), "missing glyph");
+}
+
+#[test]
+fn highlight_alternate_glyphs_paints_pink_behind_a_ligature() {
+    use vectorcraft_doc::text::{CharStyle, TextObject};
+    use vectorcraft_doc::{Node, NodeKind};
+    use vectorcraft_geom::Point;
+
+    // Source Serif 4 ships with standard ligatures for "fi".
+    let mut d = Document::new(200.0, 100.0);
+    let style = CharStyle { size: 48.0, font_family: "Source Serif 4".into(), ..Default::default() };
+    let mut n = Node::new(NodeId(0), NodeKind::Text(Box::new(TextObject::point(Point::new(20.0, 70.0), "fi", style))));
+    n.id = d.alloc_id();
+    let l = d.layers[0].id;
+    d.insert(Some(l), 0, n).unwrap();
+
+    let off = RenderOptions { background: Some([255, 255, 255, 255]), highlight_substitutions: true, highlight_alternate_glyphs: false, ..Default::default() };
+    let on = RenderOptions { highlight_alternate_glyphs: true, ..off.clone() };
+    let mut r = Renderer::new();
+    let without = r.render(&d, 200, 100, Affine::IDENTITY, &off);
+    let with = r.render(&d, 200, 100, Affine::IDENTITY, &on);
+    assert_ne!(without.pixels, with.pixels, "the preference changes the frame");
+    // Pink SUBSTITUTED = (255, 120, 190) at alpha 110, blended over white / ink.
+    let pinkish = with.pixels.chunks(4).filter(|p| p[0] > 200 && p[1] < 180 && p[2] > 150 && p[2] < 230).count();
+    assert!(pinkish > 10, "pink highlight cells behind the ligature ({pinkish} pixels)");
+}

crates/ui-egui/src/canvas.rs

@@ -302,6 +302,7 @@ pub fn show(app: &mut VectorcraftApp, ui: &mut Ui) {
         hidden: vec![],
         rot: v.rotation,
         anti_alias: app.session.prefs.anti_aliased_artwork,
+        highlight_alternate_glyphs: app.session.prefs.highlight_alternate_glyphs,
         placed: vectorcraft_render::placed_document::generation(),
         pixel,
         smooth_images,
@@ -354,6 +355,8 @@ pub fn show(app: &mut VectorcraftApp, ui: &mut Ui) {
             guide: key.guide,
             mask_view,
             highlight_substitutions: true,
+            // Type › Highlight Alternate Glyphs (#394): pink behind OpenType substitutions.
+            highlight_alternate_glyphs: app.session.prefs.highlight_alternate_glyphs,
             // General › Anti-aliased Artwork: off, edges are hard on screen (raster effects and
             // pattern tiles stay smooth), as in Illustrator.
             anti_alias: if app.session.prefs.anti_aliased_artwork { vectorcraft_render::AntiAlias::Art } else { vectorcraft_render::AntiAlias::None },

crates/ui-egui/src/lib.rs

@@ -332,6 +332,8 @@ pub struct CacheKey {
     pub rot: f64,
     /// General › Anti-aliased Artwork.
     pub anti_alias: bool,
+    /// Type › Highlight Alternate Glyphs (#394).
+    pub highlight_alternate_glyphs: bool,
     /// [`vectorcraft_render::placed_document::generation`]: placed documents' bitmaps made since.
     pub placed: u64,
     /// View › Pixel Preview: the document pixels rendered (x0, y0, x1, y1), one per point, shown

docs/gaps.md

@@ -193,8 +193,8 @@ from G14 and the budget run of G15: **~170–270 h** one agent, ~50–80 h wall
 
 ## G12 Preferences and panels that don't act yet
 
+- **Missing:** ~14 Preferences options stored but not acted on (#394: Open
 - **Done:** quick Image Trace presets reveal Threshold and Advanced controls (Paths, Corners, Noise); Properties can reopen them. Other context-specific Properties gaps remain.
-
 - **Missing:** ~15 Preferences options stored but not acted on (#394: Highlight Alternate Glyphs, Open
   Documents As Tabs, Real-time Drawing, hyphenation language, devices…), Properties panel per
   context, context menus beyond the canvas, Layers panel row menus and Collect for Export, SVG Interactivity.

docs/mcp.md

@@ -1974,9 +1974,11 @@ their own Anti-aliasing option),
 `scrubNumericFields` (on: a horizontal drag on a numeric field's label steps the field, one undo step per drag; the
 control channel's `ui.drag` scrubs), `showHomeScreen` (on by default: the Home screen while no document is open;
 off, an empty window, and the Home button or `app.home` still shows the screen), `autoCollapseIconPanels` (off by
-default: on, a click away from a panel popped out of the icon column puts it away) and `displayPrintSize` (off by
+default: on, a click away from a panel popped out of the icon column puts it away), `displayPrintSize` (off by
 default: View › Actual Size / `view.actualSize` is one document point per screen point; on, one document inch fills
-96 screen points, an inch at the system's reference density whatever the display scaling). `blackOnScreen`
+96 screen points, an inch at the system's reference density whatever the display scaling). `highlightAlternateGlyphs` (on by default: the canvas paints a pink cell behind glyphs OpenType features
+substituted — ligatures, contextual forms — on screen; Document Setup's Highlight Substituted Fonts / Glyphs stay
+separate). `blackOnScreen`
 (Appearance of Black › On Screen, `accurate` by default) sets how the canvas shows pure CMYK black, black ink alone
 at 100%: `accurate` shows it through the CMYK profile, a dark grey, and `rich` shows it as RGB black. Rich blacks,
 black tints and images show the same either way, and exports are unchanged. `blackOutput` (Appearance of Black ›

docs/type-parity.md

@@ -25,7 +25,7 @@ against Illustrator's public documentation; **estimated** unless noted.
 | Character and Paragraph panels, styles with overrides | done | Character-style Auto-leading resets, partial definitions, local leading overrides, override markers, Undo/Redo and native serialization have regression coverage; differing paragraph alignments leave the shared alignment buttons unselected (headless regressions, full integration CI and visual review pass); mixed-value display for other paragraph fields remains missing |
 | Character size and horizontal scale after object/group scaling | done | #1034: fields and setters compensate the stored affine; point size follows the transformed em-height axis, not the glyph ink bounds. Range edits, keyboard increments, leading and baseline shift use document points; rotation, reflection and shear remain editable. |
 | Preserve font sizes while scaling a group | missing | Separate enhancement; scaling still scales text with the other artwork. |
-| OpenType panel, Glyphs panel, alternates | done | Highlight Alternate Glyphs preference unused (#394); stylistic sets ss01–ss20, stylistic and titling alternates, proportional and lining figures, superscript and subscript are character-style features (`text.setStyle {features}`, #1607) |
+| OpenType panel, Glyphs panel, alternates | done | Highlight Alternate Glyphs preference (#394) paints pink behind OpenType substitutions on screen; stylistic sets ss01–ss20, stylistic and titling alternates, proportional and lining figures, superscript and subscript are character-style features (`text.setStyle {features}`, #1607) |
 | Font menu: samples, live preview, filters, favourites; font matching by any name; Find Font | done | #339; script filter: Japanese, Latin, Thai; the font scan on Linux also reads the folders fontconfig's configuration lists, such as TeX fonts under `/usr/share/texmf/fonts` (#1548, fixes #1529; not verified on Linux) |
 | Missing glyphs set in an installed font made for their script (Thai, Lao, Khmer, Myanmar first; then any font that has them) | done | Thai: Leelawadee UI, Tahoma, Thonburi, Sukhumvit Set, Noto Sans Thai, TLWG |
 | Full font-name matching (OpenType name ID 4) | done | #1258: loaded/cataloged faces and Missing Fonts searches; localized names and variable default faces; Windows font-service QA pending |