Bug 1707744 - Avoid far gradient endpoints causing large gradient segments. r=gfx-reviewers,lsalzman

Large segment bounds trip an assertion when casting coordinates to integers. Clipping early also reduces the amount of cached pixels.

Differential Revision: https://phabricator.services.mozilla.com/D113819

gfx/wr/webrender/src/prim_store/gradient/linear.rs

@@ -118,8 +118,8 @@ pub fn optimize_linear_gradient(
     end: &mut LayoutPoint,
     extend_mode: ExtendMode,
     stops: &mut [GradientStopKey],
-    // Callback called for each fast-path segment (rect, clip, start end, stops).
-    callback: &mut dyn FnMut(&LayoutRect, &LayoutRect, LayoutPoint, LayoutPoint, &[GradientStopKey])
+    // Callback called for each fast-path segment (rect, start end, stops).
+    callback: &mut dyn FnMut(&LayoutRect, LayoutPoint, LayoutPoint, &[GradientStopKey])
 ) -> bool {
     let offset = apply_gradient_local_clip(
         prim_rect,
@@ -264,13 +264,25 @@ pub fn optimize_linear_gradient(
         let mut start = point2(0.0, 0.0);
         let mut end = point2(segment_length, 0.0);
 
-        adjust_rect(&mut segment_rect);
         adjust_point(&mut start);
         adjust_point(&mut end);
+        adjust_rect(&mut segment_rect);
+
+        let origin_before_clip = segment_rect.origin;
+        segment_rect = match segment_rect.intersection(&clip_rect) {
+            Some(rect) => rect,
+            None => {
+                continue;
+            }
+        };
+        let offset = segment_rect.origin - origin_before_clip;
+
+        // Account for the clipping since start and end are relative to the origin.
+        start -= offset;
+        end -= offset;
 
         callback(
             &segment_rect,
-            &clip_rect,
             start,
             end,
             &[

gfx/wr/webrender/src/scene_building.rs

@@ -1244,8 +1244,8 @@ impl<'a> SceneBuilder<'a> {
                     &mut end,
                     info.gradient.extend_mode,
                     &mut stops,
-                    &mut |rect, clip, start, end, stops| {
-                        let layout = LayoutPrimitiveInfo { rect: *rect, clip_rect: *clip, flags };
+                    &mut |rect, start, end, stops| {
+                        let layout = LayoutPrimitiveInfo { rect: *rect, clip_rect: *rect, flags };
                         if let Some(prim_key_kind) = self.create_linear_gradient_prim(
                             &layout,
                             start,

gfx/wr/wrench/reftests/gradient/linear-far-endpoints.yaml

@@ -0,0 +1,10 @@
+# Axis-aligned linear gradient with very far endpoints. It goes through the gradient
+# decomposition path which should not choke on overflow or casting failure.
+---
+root:
+  items:
+    - type: gradient
+      bounds: 50 50 500 500
+      start: -19958788096 0
+      end: 19958788096 0
+      stops: [0.0, red, 1.0, blue]

gfx/wr/wrench/reftests/gradient/reftest.list

@@ -115,3 +115,6 @@ fuzzy-range(<=1,1) == gradient_cache_hardstop_clip.yaml gradient_cache_hardstop_
 fuzzy(2,23000) == linear-large.yaml linear-large-ref.yaml
 == conic-large.yaml conic-large-ref.yaml
 fuzzy(1,7000) == radial-large.yaml radial-large-ref.png
+
+# crash tests
+== linear-far-endpoints.yaml linear-far-endpoints.yaml