Bug 1728050 - Move opacity flattening to be part of WR DL serialization. r=miko

Differential Revision: https://phabricator.services.mozilla.com/D124005

Author: mattwoodrow

gfx/layers/wr/DisplayItemCache.cpp

@@ -180,6 +180,12 @@ Maybe<uint16_t> DisplayItemCache::CanReuseItem(
     return Nothing();
   }
 
+  if (mSuppressed) {
+    slot.mOccupied = false;
+    slotIndex = Nothing();
+    return Nothing();
+  }
+
   if (!(aSpaceAndClip == slot.mSpaceAndClip)) {
     // Spatial id and clip id can change between display lists, if items that
     // generate them change their order.

gfx/layers/wr/DisplayItemCache.h

@@ -100,9 +100,9 @@ class DisplayItemCache final {
   /**
    * Suppress display item caching. This doesn't clear any existing cached
    * items or change the underlying capacity, it just makes IsEnabled() return
-   * false. It is not meant to be flipped in the middle of a display list build,
-   * but rather set before the display list build starts to suppress use of the
-   * cache for that display list build.
+   * false.
+   * It will also make CanReuseItem return false for the duration of the
+   * suppression.
    */
   bool SetSuppressed(bool aSuppressed) {
     if (aSuppressed == mSuppressed) {

gfx/layers/wr/WebRenderCommandBuilder.cpp

@@ -2484,14 +2484,16 @@ Maybe<wr::ImageMask> WebRenderCommandBuilder::BuildWrMaskImage(
 
   nsPoint maskOffset = aMaskItem->ToReferenceFrame() - bounds.TopLeft();
 
+  bool shouldHandleOpacity = aBuilder.GetInheritedOpacity() != 1.0f;
+
   nsRect dirtyRect;
   // If this mask item is being painted for the first time, some members of
   // WebRenderMaskData are still default initialized. This is intentional.
   if (aMaskItem->IsInvalid(dirtyRect) ||
       !itemRect.IsEqualInterior(maskData->mItemRect) ||
       !(aMaskItem->Frame()->StyleSVGReset()->mMask == maskData->mMaskStyle) ||
       maskOffset != maskData->mMaskOffset || !sameScale ||
-      aMaskItem->ShouldHandleOpacity() != maskData->mShouldHandleOpacity) {
+      shouldHandleOpacity != maskData->mShouldHandleOpacity) {
     IntSize size = itemRect.Size().ToUnknownSize();
 
     if (!Factory::AllowedSurfaceSize(size)) {
@@ -2535,8 +2537,8 @@ Maybe<wr::ImageMask> WebRenderCommandBuilder::BuildWrMaskImage(
                            .PreScale(scale.width, scale.height));
 
     bool maskPainted = false;
-    bool maskIsComplete =
-        aMaskItem->PaintMask(aDisplayListBuilder, context, &maskPainted);
+    bool maskIsComplete = aMaskItem->PaintMask(
+        aDisplayListBuilder, context, shouldHandleOpacity, &maskPainted);
     if (!maskPainted) {
       return Nothing();
     }
@@ -2587,7 +2589,7 @@ Maybe<wr::ImageMask> WebRenderCommandBuilder::BuildWrMaskImage(
       maskData->mMaskOffset = maskOffset;
       maskData->mScale = scale;
       maskData->mMaskStyle = aMaskItem->Frame()->StyleSVGReset()->mMask;
-      maskData->mShouldHandleOpacity = aMaskItem->ShouldHandleOpacity();
+      maskData->mShouldHandleOpacity = shouldHandleOpacity;
     }
   }
 

gfx/webrender_bindings/WebRenderAPI.h

@@ -684,6 +684,17 @@ class DisplayListBuilder final {
     mClipChainLeaf = aClipRect;
   }
 
+  // Used for opacity flattening. When we flatten away an opacity item,
+  // we push the opacity value onto the builder.
+  // Descendant items should pull the inherited opacity during
+  // their CreateWebRenderCommands implementation. This can only happen if all
+  // descendant items reported supporting this functionality, via
+  // nsDisplayItem::CanApplyOpacity.
+  float GetInheritedOpacity() { return mInheritedOpacity; }
+  void SetInheritedOpacity(float aOpacity) { mInheritedOpacity = aOpacity; }
+
+  layers::DisplayItemCache* GetDisplayItemCache() { return mDisplayItemCache; }
+
   // A chain of RAII objects, each holding a (ASR, ViewID, SideBits) tuple of
   // data. The topmost object is pointed to by the mActiveFixedPosTracker
   // pointer in the wr::DisplayListBuilder.
@@ -750,6 +761,7 @@ class DisplayListBuilder final {
 
   layers::DisplayItemCache* mDisplayItemCache;
   Maybe<uint16_t> mCurrentCacheSlot;
+  float mInheritedOpacity = 1.0f;
 
   friend class WebRenderAPI;
   friend class SpaceAndClipChainHelper;