Fix caching display lists with opacity bindings that are values.

Most of the time when property bindings are used, they are bound
to a specific key that can be animation. However, they can also
be set to a fixed value.

It was previously possible for a property binding with a fixed
value to not be included in a cached picture dependency. This
meant a stale tile could be used in cases where a new display
list arrives with the same property binding IDs but different
values, where everything else is the same.

This patch includes fixed value property bindings in the tile
descriptor's opacity binding dependencies.

This is a fix for https://bugzilla.mozilla.org/show_bug.cgi?id=1518050

webrender/src/picture.rs

@@ -100,6 +100,22 @@ pub struct OpacityBindingInfo {
     changed: bool,
 }
 
+/// Information stored in a tile descriptor for an opacity binding.
+#[derive(Debug, PartialEq, Clone)]
+pub enum OpacityBinding {
+    Value(f32),
+    Binding(PropertyBindingId),
+}
+
+impl From<PropertyBinding<f32>> for OpacityBinding {
+    fn from(binding: PropertyBinding<f32>) -> OpacityBinding {
+        match binding {
+            PropertyBinding::Binding(key, _) => OpacityBinding::Binding(key.id),
+            PropertyBinding::Value(value) => OpacityBinding::Value(value),
+        }
+    }
+}
+
 /// A stable ID for a given tile, to help debugging.
 #[derive(Debug, Copy, Clone)]
 struct TileId(usize);
@@ -195,7 +211,7 @@ pub struct TileDescriptor {
 
     /// The set of opacity bindings that this tile depends on.
     // TODO(gw): Ugh, get rid of all opacity binding support!
-    opacity_bindings: ComparableVec<PropertyBindingId>,
+    opacity_bindings: ComparableVec<OpacityBinding>,
 
     /// List of the required valid rectangles for each primitive.
     needed_rects: Vec<WorldRect>,
@@ -605,14 +621,16 @@ impl TileCache {
             }
 
             // Invalidate the tile if any opacity bindings changed.
-            for id in tile.descriptor.opacity_bindings.items() {
-                let changed = match self.opacity_bindings.get(id) {
-                    Some(info) => info.changed,
-                    None => true,
-                };
-                if changed {
-                    tile.is_valid = false;
-                    break;
+            for binding in tile.descriptor.opacity_bindings.items() {
+                if let OpacityBinding::Binding(id) = binding {
+                    let changed = match self.opacity_bindings.get(id) {
+                        Some(info) => info.changed,
+                        None => true,
+                    };
+                    if changed {
+                        tile.is_valid = false;
+                        break;
+                    }
                 }
             }
 
@@ -700,7 +718,7 @@ impl TileCache {
         let (p0, p1) = self.get_tile_coords_for_rect(&world_rect);
 
         // Build the list of resources that this primitive has dependencies on.
-        let mut opacity_bindings: SmallVec<[PropertyBindingId; 4]> = SmallVec::new();
+        let mut opacity_bindings: SmallVec<[OpacityBinding; 4]> = SmallVec::new();
         let mut clip_chain_uids: SmallVec<[ItemUid; 8]> = SmallVec::new();
         let mut clip_vertices: SmallVec<[LayoutPoint; 8]> = SmallVec::new();
         let mut image_keys: SmallVec<[ImageKey; 8]> = SmallVec::new();
@@ -729,9 +747,7 @@ impl TileCache {
                 // Pictures can depend on animated opacity bindings.
                 let pic = &pictures[pic_index.0];
                 if let Some(PictureCompositeMode::Filter(FilterOp::Opacity(binding, _))) = pic.requested_composite_mode {
-                    if let PropertyBinding::Binding(key, _) = binding {
-                        opacity_bindings.push(key.id);
-                    }
+                    opacity_bindings.push(binding.into());
                 }
 
                 false
@@ -740,9 +756,7 @@ impl TileCache {
                 if opacity_binding_index != OpacityBindingIndex::INVALID {
                     let opacity_binding = &opacity_binding_store[opacity_binding_index];
                     for binding in &opacity_binding.bindings {
-                        if let PropertyBinding::Binding(key, _) = binding {
-                            opacity_bindings.push(key.id);
-                        }
+                        opacity_bindings.push(OpacityBinding::from(*binding));
                     }
                 }
 
@@ -756,9 +770,7 @@ impl TileCache {
                 if opacity_binding_index != OpacityBindingIndex::INVALID {
                     let opacity_binding = &opacity_binding_store[opacity_binding_index];
                     for binding in &opacity_binding.bindings {
-                        if let PropertyBinding::Binding(key, _) = binding {
-                            opacity_bindings.push(key.id);
-                        }
+                        opacity_bindings.push(OpacityBinding::from(*binding));
                     }
                 }