Bug 1722258 - Split out fallible composite-only path of PresShell::Paint. r=miko

Differential Revision: https://phabricator.services.mozilla.com/D120919

dom/base/nsDOMWindowUtils.cpp

@@ -409,9 +409,8 @@ nsDOMWindowUtils::UpdateLayerTree() {
     RefPtr<nsViewManager> vm = presShell->GetViewManager();
     if (nsView* view = vm->GetRootView()) {
       nsAutoScriptBlocker scriptBlocker;
-      presShell->Paint(
-          view, view->GetBounds(),
-          PaintFlags::PaintLayers | PaintFlags::PaintSyncDecodeImages);
+      presShell->Paint(view, view->GetBounds(),
+                       PaintFlags::PaintSyncDecodeImages);
       presShell->GetWindowRenderer()->WaitOnTransactionProcessed();
     }
   }

dom/ipc/BrowserChild.cpp

@@ -2732,7 +2732,7 @@ mozilla::ipc::IPCResult BrowserChild::RecvRenderLayers(
   } else {
     RefPtr<nsViewManager> vm = presShell->GetViewManager();
     if (nsView* view = vm->GetRootView()) {
-      presShell->Paint(view, view->GetBounds(), PaintFlags::PaintLayers);
+      presShell->Paint(view, view->GetBounds(), PaintFlags::None);
     }
   }
   presShell->SuppressDisplayport(false);

layout/base/PresShell.cpp

@@ -6239,6 +6239,36 @@ class nsAutoNotifyDidPaint {
   PaintFlags mFlags;
 };
 
+bool PresShell::Composite(nsView* aViewToPaint) {
+  nsCString url;
+  nsIURI* uri = mDocument->GetDocumentURI();
+  Document* contentRoot = GetPrimaryContentDocument();
+  if (contentRoot) {
+    uri = contentRoot->GetDocumentURI();
+  }
+  url = uri ? uri->GetSpecOrDefault() : "N/A"_ns;
+  AUTO_PROFILER_LABEL_DYNAMIC_NSCSTRING("PresShell::Composite", GRAPHICS, url);
+
+  nsIFrame* frame = aViewToPaint->GetFrame();
+  WindowRenderer* renderer = aViewToPaint->GetWidget()->GetWindowRenderer();
+  NS_ASSERTION(renderer, "Must be in paint event");
+
+  if (!renderer->BeginTransaction(url)) {
+    // If we can't begin a transaction and paint, then there's not
+    // much the caller can do.
+    return true;
+  }
+
+  if (frame) {
+    if (renderer->EndEmptyTransaction()) {
+      GetPresContext()->NotifyDidPaintForSubtree();
+      return true;
+    }
+    NS_WARNING("Must complete empty transaction when compositing!");
+  }
+  return false;
+}
+
 void PresShell::Paint(nsView* aViewToPaint, const nsRegion& aDirtyRegion,
                       PaintFlags aFlags) {
   nsCString url;
@@ -6317,20 +6347,6 @@ void PresShell::Paint(nsView* aViewToPaint, const nsRegion& aDirtyRegion,
   }
 
   if (frame) {
-    // Try to do an empty transaction, if the frame tree does not
-    // need to be updated. Do not try to do an empty transaction on
-    // a non-retained layer manager (like the BasicLayerManager that
-    // draws the window title bar on Mac), because a) it won't work
-    // and b) below we don't want to clear NS_FRAME_UPDATE_LAYER_TREE,
-    // that will cause us to forget to update the real layer manager!
-
-    if (!(aFlags & PaintFlags::PaintLayers)) {
-      if (renderer->EndEmptyTransaction()) {
-        return;
-      }
-      NS_WARNING("Must complete empty transaction when compositing!");
-    }
-
     if (!(aFlags & PaintFlags::PaintSyncDecodeImages) &&
         !frame->HasAnyStateBits(NS_FRAME_UPDATE_LAYER_TREE) &&
         !mNextPaintCompressed) {

layout/base/PresShell.h

@@ -1268,6 +1268,8 @@ class PresShell final : public nsStubDocumentObserver,
   void Paint(nsView* aViewToPaint, const nsRegion& aDirtyRegion,
              PaintFlags aFlags);
 
+  bool Composite(nsView* aViewToPaint);
+
   /**
    * Notify that we're going to call Paint with PaintFlags::PaintLayers
    * on the pres shell for a widget (which might not be this one, since

layout/base/PresShellForwards.h

@@ -188,10 +188,6 @@ MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(AddCanvasBackgroundColorFlags)
 
 enum class PaintFlags {
   None = 0,
-  /* Update the layer tree and paint PaintedLayers. If this is not specified,
-   * we may still have to do it if the layer tree lost PaintedLayer contents
-   * we need for compositing. */
-  PaintLayers = 1 << 0,
   /* Composite layers to the window. */
   PaintComposite = 1 << 1,
   /* Sync-decode images. */

view/nsViewManager.cpp

@@ -333,7 +333,12 @@ void nsViewManager::Refresh(nsView* aView,
       if (!renderer->NeedsWidgetInvalidation()) {
         renderer->FlushRendering();
       } else {
-        presShell->Paint(aView, damageRegion, PaintFlags::PaintComposite);
+        // Try to just Composite the current WindowRenderer contents. If
+        // that fails then we need tor repaint, and request that it gets
+        // composited as well.
+        if (!presShell->Composite(aView)) {
+          presShell->Paint(aView, damageRegion, PaintFlags::PaintComposite);
+        }
       }
 #ifdef MOZ_DUMP_PAINTING
       if (nsLayoutUtils::InvalidationDebuggingIsEnabled()) {
@@ -456,7 +461,7 @@ void nsViewManager::ProcessPendingUpdatesPaint(nsIWidget* aWidget) {
       }
 #endif
 
-      presShell->Paint(view, nsRegion(), PaintFlags::PaintLayers);
+      presShell->Paint(view, nsRegion(), PaintFlags::None);
       view->SetForcedRepaint(false);
 
 #ifdef MOZ_DUMP_PAINTING