Render: bound bevel edge work, shape-gradient flattening and colour-glyph fills

crates/render/src/bevel.rs

@@ -125,7 +125,9 @@ pub fn draw(ctx: &mut RenderContext, bevel: &Bevel, fill: Option<Rgba>, path: &B
     let longest = bounds.width().max(bounds.height()) * k;
     let s = (MAX_SIDE / longest).min(1.0) * k;
     let (pw, ph) = (((bounds.width() * s).ceil() as u32).clamp(1, 2048), ((bounds.height() * s).ceil() as u32).clamp(1, 2048));
-    let polys = crate::pathgrad::polygons(path);
+    // Each pixel tests every edge, so a dense outline is simplified to the raster's edge budget.
+    let pixel = (bounds.width() / f64::from(pw)).min(bounds.height() / f64::from(ph));
+    let polys = crate::pathgrad::simplify(crate::pathgrad::polygons(path), pixel, crate::pathgrad::edge_budget(pw, ph));
     if polys.is_empty() {
         return;
     }

crates/render/src/colr.rs

@@ -11,6 +11,8 @@ use vello_cpu::{RenderContext, peniko};
 
 /// Nesting depth of clips and layers past which a glyph opens no more (hostile fonts).
 const MAX_DEPTH: usize = 64;
+/// Fills and gradient stops one colour glyph may paint; the rest of a hostile glyph is skipped.
+const MAX_WORK: usize = 100_000;
 
 /// Paint `gid` of `face` as a colour glyph, its origin mapped by `at` (y down, points) at `scale`
 /// points per font unit. `fg` is the text colour (palette index 0xFFFF) and `alpha` fades it all.
@@ -26,7 +28,7 @@ pub fn paint(ctx: &mut RenderContext, face: &FontFace, gid: u32, at: Affine, sca
         .unwrap_or_default();
     // Font units are y up; the slide is y down.
     let base = at * Affine::scale(scale) * Affine::scale_non_uniform(1.0, -1.0);
-    let mut p = Painter { ctx, face, base, stack: vec![Affine::IDENTITY], palette, fg, opened: Vec::new() };
+    let mut p = Painter { ctx, face, base, stack: vec![Affine::IDENTITY], palette, fg, opened: Vec::new(), work: 0 };
     p.ctx.push_layer(None, None, Some(alpha.clamp(0.0, 1.0) as f32), None, None);
     let ok = glyph.paint(face.location(), &mut p).is_ok();
     // A malformed glyph may leave layers open: close them all.
@@ -50,6 +52,8 @@ struct Painter<'a> {
     /// Clips and composite groups pushed by the glyph, innermost last: true when a layer was
     /// opened on the context for it (false past `MAX_DEPTH`, so its pop is skipped too).
     opened: Vec<bool>,
+    /// Fills plus gradient stops painted so far, against [`MAX_WORK`].
+    work: usize,
 }
 
 fn affine(t: &Transform) -> Affine {
@@ -174,6 +178,16 @@ impl ColorPainter for Painter<'_> {
     }
 
     fn fill(&mut self, brush: Brush<'_>) {
+        let stops = match &brush {
+            Brush::Solid { .. } => 0,
+            Brush::LinearGradient { color_stops, .. } | Brush::RadialGradient { color_stops, .. } | Brush::SweepGradient { color_stops, .. } => {
+                color_stops.len()
+            }
+        };
+        self.work = self.work.saturating_add(1 + stops);
+        if self.work > MAX_WORK {
+            return;
+        }
         match brush {
             Brush::Solid { palette_index, alpha } => {
                 let c = self.color(palette_index, alpha);

crates/render/src/pathgrad.rs

@@ -25,6 +25,16 @@ const MAX_EDGE_WORK: u64 = 64_000_000;
 /// Fewest edges a simplified polygon keeps, so a coarse outline still has a shape.
 const MIN_POLY_EDGES: usize = 8;
 
+/// Most points `polygons` keeps from one path; a path flattening past this (a huge finite curve) is
+/// not drawn rather than held in memory first.
+const MAX_POINTS: usize = 2_000_000;
+
+/// The edge budget for a `pw` x `ph` raster where each pixel tests every edge.
+pub(crate) fn edge_budget(pw: u32, ph: u32) -> usize {
+    let pixels = u64::from(pw).saturating_mul(u64::from(ph)).max(1);
+    usize::try_from(MAX_EDGE_WORK / pixels).unwrap_or(usize::MAX).max(MIN_POLY_EDGES)
+}
+
 /// Colour position (0 at the focus, 1 at the edge) of `p` for path `kind` in `bounds` with the
 /// focus rect `focus` (fractions inset from left, top, right, bottom), `outline` being the
 /// shape's flattened polygon(s) for `shape`.
@@ -114,21 +124,31 @@ fn shape_position(outline: &[Vec<Point>], c: Point, p: Point) -> f64 {
 pub fn polygons(path: &BezPath) -> Vec<Vec<Point>> {
     let mut out: Vec<Vec<Point>> = Vec::new();
     let mut cur: Vec<Point> = Vec::new();
-    kurbo::flatten(path.iter(), 0.25, |el| match el {
-        PathEl::MoveTo(p) => {
-            if cur.len() > 1 {
-                out.push(std::mem::take(&mut cur));
-            }
-            cur = vec![p];
+    let mut total = 0usize;
+    kurbo::flatten(path.iter(), 0.25, |el| {
+        total += 1;
+        if total > MAX_POINTS {
+            return;
         }
-        PathEl::LineTo(p) => cur.push(p),
-        PathEl::ClosePath => {
-            if let Some(f) = cur.first().copied() {
-                cur.push(f);
+        match el {
+            PathEl::MoveTo(p) => {
+                if cur.len() > 1 {
+                    out.push(std::mem::take(&mut cur));
+                }
+                cur = vec![p];
             }
+            PathEl::LineTo(p) => cur.push(p),
+            PathEl::ClosePath => {
+                if let Some(f) = cur.first().copied() {
+                    cur.push(f);
+                }
+            }
+            _ => {}
         }
-        _ => {}
     });
+    if total > MAX_POINTS {
+        return Vec::new();
+    }
     if cur.len() > 1 {
         out.push(cur);
     }
@@ -146,7 +166,7 @@ pub fn polygons(path: &BezPath) -> Vec<Vec<Point>> {
 /// `outline` cut down to at most about `max_edges` edges in total: first by dropping points
 /// closer than `tol` to the last kept one (detail finer than a raster pixel), then, if still too
 /// many, by keeping every k-th point. Each polygon stays closed. Returns it unchanged when it fits.
-fn simplify(outline: Vec<Vec<Point>>, tol: f64, max_edges: usize) -> Vec<Vec<Point>> {
+pub(crate) fn simplify(outline: Vec<Vec<Point>>, tol: f64, max_edges: usize) -> Vec<Vec<Point>> {
     let edges = |o: &[Vec<Point>]| o.iter().map(|p| p.len().saturating_sub(1)).sum::<usize>();
     if edges(&outline) <= max_edges {
         return outline;
@@ -233,8 +253,7 @@ pub fn fill(ctx: &mut RenderContext, kind: &str, focus: [f64; 4], stops: &[(f64,
     let s = (MAX_SIDE / longest).min(1.0) * k;
     let (pw, ph) = (((bounds.width() * s).ceil() as u32).clamp(1, 4096), ((bounds.height() * s).ceil() as u32).clamp(1, 4096));
     let outline = if kind == "shape" {
-        let pixels = u64::from(pw).saturating_mul(u64::from(ph)).max(1);
-        let max_edges = usize::try_from(MAX_EDGE_WORK / pixels).unwrap_or(usize::MAX).max(MIN_POLY_EDGES);
+        let max_edges = edge_budget(pw, ph);
         let pixel = (bounds.width() / f64::from(pw)).min(bounds.height() / f64::from(ph));
         simplify(polygons(path), pixel, max_edges)
     } else {

crates/ui-egui/src/panels/thumbs.rs

@@ -112,21 +112,6 @@ pub fn show(app: &mut SlideApp, ui: &mut Ui) {
     }
 }
 
-/// Slide index -> the first section starting there, built once instead of searched per slide.
-fn section_starts(doc: &deckcraft_model::Presentation) -> std::collections::HashMap<usize, usize> {
-    let mut index_of = std::collections::HashMap::new();
-    for (i, s) in doc.slides.iter().enumerate() {
-        index_of.entry(s.id).or_insert(i);
-    }
-    let mut starts = std::collections::HashMap::new();
-    for (si, s) in doc.sections.iter().enumerate() {
-        if let Some(&i) = s.slides.first().and_then(|id| index_of.get(id)) {
-            starts.entry(i).or_insert(si);
-        }
-    }
-    starts
-}
-
 /// Render the scrollable thumbnail list, scrolling the current slide into view when it changes.
 fn list(app: &mut SlideApp, ui: &mut Ui) {
     let t = Tokens::get(ui.ctx());
@@ -150,10 +135,11 @@ fn list(app: &mut SlideApp, ui: &mut Ui) {
     let ppp = ui.ctx().pixels_per_point();
     let mut budget = 3u32;
     let mut rects = vec![];
-    let section_starts = section_starts(&doc);
+    let section_starts: Vec<(usize, usize)> =
+        doc.sections.iter().enumerate().filter_map(|(si, s)| s.slides.first().and_then(|id| doc.slide_index(*id)).map(|i| (i, si))).collect();
     let mut need_more = false;
     for i in 0..doc.slides.len() {
-        if let Some(si) = section_starts.get(&i)
+        if let Some((_, si)) = section_starts.iter().find(|(start, _)| *start == i)
             && let Some(sec) = doc.sections.get(*si)
         {
             ui.add_space(4.0);
@@ -448,26 +434,6 @@ mod tests {
         h
     }
 
-    #[test]
-    fn section_starts_map_each_first_slide_to_its_first_section() {
-        let mut s = Session::with_new();
-        for _ in 0..3 {
-            s.execute("slide.new", &json!({})).unwrap();
-        }
-        let mut doc = (*s.active().unwrap().doc).clone();
-        let ids: Vec<_> = doc.slides.iter().map(|sl| sl.id).collect();
-        doc.sections = vec![
-            deckcraft_model::Section { name: "a".into(), slides: vec![ids[0], ids[1]] },
-            deckcraft_model::Section { name: "dup".into(), slides: vec![ids[0]] },
-            deckcraft_model::Section { name: "c".into(), slides: vec![ids[2]] },
-            deckcraft_model::Section { name: "empty".into(), slides: vec![] },
-        ];
-        let starts = section_starts(&doc);
-        assert_eq!(starts.get(&0), Some(&0), "the first section starting at a slide wins");
-        assert_eq!(starts.get(&2), Some(&2));
-        assert_eq!(starts.len(), 2);
-    }
-
     /// Vertical scroll offset of the thumbnail pane, as recorded each frame by `show`.
     fn thumbs_scroll(h: &Harness<'_, SlideApp>) -> f32 {
         h.state().ui.thumbs_scroll