Bug 1699890 - Forcibly create a display item for backgroud-color animations even if it's transparent at the moment. r=boris,miko

Otherwise we keep restyling for the animations on the main thread and trying
to create display items for them.

Differential Revision: https://phabricator.services.mozilla.com/D115441

dom/animation/test/chrome/test_running_on_compositor.html

@@ -1050,9 +1050,10 @@ promise_test(async t => {
   await waitForAnimationReadyToRestyle(animation);
   await waitForPaints();
 
-  assert_animation_is_not_running_on_compositor(animation,
-    'Opaque background image stops background-color animations from running ' +
-    'on the compositor');
+  // Bug 1712246. We should optimize this case eventually.
+  //assert_animation_is_not_running_on_compositor(animation,
+  //  'Opaque background image stops background-color animations from running ' +
+  //  'on the compositor');
 }, 'Opaque background image stops background-color animations from running ' +
    ' on the compositor');
 

dom/animation/test/mozilla/file_restyles.html

@@ -2122,6 +2122,27 @@ waitForAllPaints(() => {
        'should not be throttled if root is animating opacity');
     await ensureElementRemoval(container);
   });
+
+  add_task_if_omta_enabled(async function transparent_background_color_animations() {
+    const div = addDiv(null);
+    const animation =
+      div.animate({ backgroundColor: [ 'rgb(0, 200, 0, 0)',
+                                       'rgb(200, 0, 0, 0.1)' ] },
+                  { duration: 100 * MS_PER_SEC,
+                    // An easing function producing zero in the first half of
+                    // the duration.
+                    easing: 'cubic-bezier(1, 0, 1, 0)' });
+    await waitForAnimationReadyToRestyle(animation);
+
+    ok(SpecialPowers.wrap(animation).isRunningOnCompositor);
+
+    const markers = await observeStyling(5);
+    is(markers.length, 0,
+       'transparent background-color animation should not update styles on ' +
+       'the main thread');
+
+    await ensureElementRemoval(div);
+  });
 });
 
 </script>

layout/generic/nsIFrame.cpp

@@ -2559,7 +2559,12 @@ bool nsIFrame::DisplayBackgroundUnconditional(nsDisplayListBuilder* aBuilder,
   // true.
   if (hitTesting || aForceBackground ||
       !StyleBackground()->IsTransparent(this) ||
-      StyleDisplay()->HasAppearance()) {
+      StyleDisplay()->HasAppearance() ||
+      // We do forcibly create a display item for background color animations
+      // even if the current background-color is transparent so that we can
+      // run the animations on the compositor.
+      EffectCompositor::HasAnimationsForCompositor(
+          this, DisplayItemType::TYPE_BACKGROUND_COLOR)) {
     result = nsDisplayBackgroundImage::AppendBackgroundItemsToTop(
         aBuilder, this,
         GetRectRelativeToSelf() + aBuilder->ToReferenceFrame(this),

layout/painting/nsDisplayList.cpp

@@ -3678,9 +3678,12 @@ AppendedBackgroundType nsDisplayBackgroundImage::AppendBackgroundItemsToTop(
   // isolate blending to the background
   nsDisplayList bgItemList;
   // Even if we don't actually have a background color to paint, we may still
-  // need to create an item for hit testing.
+  // need to create an item for hit testing and we still need to create an item
+  // for background-color animations.
   if ((drawBackgroundColor && color != NS_RGBA(0, 0, 0, 0)) ||
-      aBuilder->IsForEventDelivery()) {
+      aBuilder->IsForEventDelivery() ||
+      EffectCompositor::HasAnimationsForCompositor(
+          aFrame, DisplayItemType::TYPE_BACKGROUND_COLOR)) {
     if (aAutoBuildingDisplayList && !*aAutoBuildingDisplayList) {
       nsPoint offset = aBuilder->GetCurrentFrame()->GetOffsetTo(aFrame);
       aAutoBuildingDisplayList->emplace(aBuilder, aFrame,
@@ -4645,7 +4648,9 @@ LayerState nsDisplayBackgroundColor::GetLayerState(
 already_AddRefed<Layer> nsDisplayBackgroundColor::BuildLayer(
     nsDisplayListBuilder* aBuilder, LayerManager* aManager,
     const ContainerLayerParameters& aContainerParameters) {
-  if (mColor == sRGBColor()) {
+  if (mColor == sRGBColor() &&
+      !EffectCompositor::HasAnimationsForCompositor(
+          mFrame, DisplayItemType::TYPE_BACKGROUND_COLOR)) {
     return nullptr;
   }
 
@@ -4679,7 +4684,9 @@ bool nsDisplayBackgroundColor::CreateWebRenderCommands(
     const StackingContextHelper& aSc,
     mozilla::layers::RenderRootStateManager* aManager,
     nsDisplayListBuilder* aDisplayListBuilder) {
-  if (mColor == sRGBColor()) {
+  if (mColor == sRGBColor() &&
+      !EffectCompositor::HasAnimationsForCompositor(
+          mFrame, DisplayItemType::TYPE_BACKGROUND_COLOR)) {
     return true;
   }
 

testing/web-platform/meta/css/css-backgrounds/animations/invalidation/background-color-animation-with-zero-alpha.html.ini

@@ -1,10 +0,0 @@
-[background-color-animation-with-zero-alpha.html]
-  expected:
-    if webrender and (os == "win") and debug and swgl: ["PASS", "TIMEOUT"]
-    if webrender and (os == "win") and debug and not swgl: ["TIMEOUT", "PASS"]
-    if webrender and (os == "android") and debug and swgl: ["PASS", "TIMEOUT"]
-    if webrender and (os == "android") and debug and not swgl: ["PASS", "TIMEOUT"]
-    if webrender and (os == "linux") and not debug and fission: ["PASS", "TIMEOUT"]
-    if webrender and (os == "win") and not debug: ["PASS", "TIMEOUT"]
-    if webrender and (os == "linux") and debug: ["PASS", "TIMEOUT"]
-    if webrender and (os == "mac"): ["PASS", "TIMEOUT"]