Bug 1765331 - Account for dest rect correctly in nsDisplayRemote painting. r=tnikkel

The in-process code does this here:

  https://searchfox.org/mozilla-central/rev/4b3039b48c3cb67774270ebcc2a7d8624d888092/layout/generic/nsSubDocumentFrame.cpp#729-742

This doesn't do much for regular iframes because they have no meaningful
intrinsic ratio, but this will matter for bug 1595491.

Differential Revision: https://phabricator.services.mozilla.com/D144000

layout/generic/nsSubDocumentFrame.cpp

@@ -267,6 +267,17 @@ mozilla::PresShell* nsSubDocumentFrame::GetSubdocumentPresShellForPainting(
   return presShell;
 }
 
+nsRect nsSubDocumentFrame::GetDestRect() {
+  nsRect rect = GetContent()->IsHTMLElement(nsGkAtoms::frame)
+                    ? GetRectRelativeToSelf()
+                    : GetContentRectRelativeToSelf();
+
+  // Adjust subdocument size, according to 'object-fit' and the subdocument's
+  // intrinsic size and ratio.
+  return nsLayoutUtils::ComputeObjectDestRect(
+      rect, GetIntrinsicSize(), GetIntrinsicRatio(), StylePosition());
+}
+
 ScreenIntSize nsSubDocumentFrame::GetSubdocumentSize() {
   if (HasAnyStateBits(NS_FRAME_FIRST_REFLOW)) {
     if (RefPtr<nsFrameLoader> frameloader = FrameLoader()) {
@@ -285,24 +296,10 @@ ScreenIntSize nsSubDocumentFrame::GetSubdocumentSize() {
     return ScreenIntSize(10, 10);
   }
 
-  nsSize docSizeAppUnits;
-  nsPresContext* presContext = PresContext();
-  if (GetContent()->IsHTMLElement(nsGkAtoms::frame)) {
-    docSizeAppUnits = GetSize();
-  } else {
-    docSizeAppUnits = GetContentRect().Size();
-  }
-
-  // Adjust subdocument size, according to 'object-fit' and the subdocument's
-  // intrinsic size and ratio.
-  docSizeAppUnits = nsLayoutUtils::ComputeObjectDestRect(
-                        nsRect(nsPoint(), docSizeAppUnits), GetIntrinsicSize(),
-                        GetIntrinsicRatio(), StylePosition())
-                        .Size();
-
-  return ScreenIntSize(
-      presContext->AppUnitsToDevPixels(docSizeAppUnits.width),
-      presContext->AppUnitsToDevPixels(docSizeAppUnits.height));
+  nsSize docSizeAppUnits = GetDestRect().Size();
+  nsPresContext* pc = PresContext();
+  return ScreenIntSize(pc->AppUnitsToDevPixels(docSizeAppUnits.width),
+                       pc->AppUnitsToDevPixels(docSizeAppUnits.height));
 }
 
 static void WrapBackgroundColorInOwnLayer(nsDisplayListBuilder* aBuilder,
@@ -1269,24 +1266,6 @@ void nsSubDocumentFrame::SubdocumentIntrinsicSizeOrRatioChanged() {
   }
 }
 
-/**
- * Gets the layer-pixel offset of aContainerFrame's content rect top-left
- * from the nearest display item reference frame (which we assume will be
- * inducing a ContainerLayer).
- */
-static nsPoint GetContentRectLayerOffset(nsIFrame* aContainerFrame,
-                                         nsDisplayListBuilder* aBuilder) {
-  // Offset to the content rect in case we have borders or padding
-  // Note that aContainerFrame could be a reference frame itself, so
-  // we need to be careful here to ensure that we call ToReferenceFrame
-  // on aContainerFrame and not its parent.
-  nsPoint frameOffset =
-      aBuilder->ToReferenceFrame(aContainerFrame) +
-      aContainerFrame->GetContentRectRelativeToSelf().TopLeft();
-
-  return frameOffset;
-}
-
 // Return true iff |aManager| is a "temporary layer manager".  They're
 // used for small software rendering tasks, like drawWindow.  That's
 // currently implemented by a BasicLayerManager without a backing
@@ -1308,14 +1287,6 @@ nsDisplayRemote::nsDisplayRemote(nsDisplayListBuilder* aBuilder,
   mPaintData = aFrame->GetRemotePaintData();
 }
 
-LayerIntSize GetFrameSize(const nsIFrame* aFrame) {
-  LayoutDeviceSize size = LayoutDeviceRect::FromAppUnits(
-      aFrame->GetContentRectRelativeToSelf().Size(),
-      aFrame->PresContext()->AppUnitsPerDevPixel());
-
-  return LayerIntSize::Round(size.width, size.height);
-}
-
 namespace mozilla {
 
 void nsDisplayRemote::Paint(nsDisplayListBuilder* aBuilder, gfxContext* aCtx) {
@@ -1366,6 +1337,9 @@ bool nsDisplayRemote::CreateWebRenderCommands(
 
   nsPresContext* pc = mFrame->PresContext();
   nsFrameLoader* fl = GetFrameLoader();
+
+  auto* subDocFrame = static_cast<nsSubDocumentFrame*>(mFrame);
+  nsRect destRect = subDocFrame->GetDestRect();
   if (RefPtr<RemoteBrowser> remoteBrowser = fl->GetRemoteBrowser()) {
     if (pc->GetPrintSettings()) {
       // HACK(emilio): Usually we update sizing/positioning from
@@ -1376,15 +1350,14 @@ bool nsDisplayRemote::CreateWebRenderCommands(
       //
       // UpdatePositionAndSize() can cause havoc for non-remote frames but
       // luckily we don't care about those, so this is fine.
-      fl->UpdatePositionAndSize(static_cast<nsSubDocumentFrame*>(mFrame));
+      fl->UpdatePositionAndSize(subDocFrame);
     }
 
     // Adjust mItemVisibleRect, which is relative to the reference frame, to be
     // relative to this frame
     nsRect visibleRect = GetBuildingRect() - ToReferenceFrame();
-    nsRect contentRect = Frame()->GetContentRectRelativeToSelf();
-    visibleRect.IntersectRect(visibleRect, contentRect);
-    visibleRect -= contentRect.TopLeft();
+    visibleRect.IntersectRect(visibleRect, destRect);
+    visibleRect -= destRect.TopLeft();
 
     // Generate an effects update notifying the browser it is visible
     gfx::Size scale = aSc.GetInheritedScale();
@@ -1411,13 +1384,11 @@ bool nsDisplayRemote::CreateWebRenderCommands(
   }
 
   nscoord auPerDevPixel = pc->AppUnitsPerDevPixel();
-  nsPoint layerOffset = GetContentRectLayerOffset(mFrame, aDisplayListBuilder);
+  nsPoint layerOffset = aDisplayListBuilder->ToReferenceFrame(mFrame) + destRect.TopLeft();
   mOffset = LayoutDevicePoint::FromAppUnits(layerOffset, auPerDevPixel);
 
-  nsRect contentRect = mFrame->GetContentRectRelativeToSelf();
-  contentRect.MoveTo(0, 0);
-  LayoutDeviceRect rect =
-      LayoutDeviceRect::FromAppUnits(contentRect, auPerDevPixel);
+  destRect.MoveTo(0, 0);
+  auto rect = LayoutDeviceRect::FromAppUnits(destRect, auPerDevPixel);
   rect += mOffset;
 
   aBuilder.PushIFrame(mozilla::wr::ToLayoutRect(rect), !BackfaceIsHidden(),
@@ -1449,10 +1420,11 @@ bool nsDisplayRemote::UpdateScrollData(
       aLayerData->SetResolution(resolution);
     }
 
+    auto size = static_cast<nsSubDocumentFrame*>(mFrame)->GetSubdocumentSize();
     Matrix4x4 m = Matrix4x4::Translation(mOffset.x, mOffset.y, 0.0);
     aLayerData->SetTransform(m);
     aLayerData->SetEventRegionsOverride(mEventRegionsOverride);
-    aLayerData->SetRemoteDocumentSize(GetFrameSize(mFrame));
+    aLayerData->SetRemoteDocumentSize(LayerIntSize(size.width, size.height));
   }
   return true;
 }

layout/generic/nsSubDocumentFrame.h

@@ -109,6 +109,7 @@ class nsSubDocumentFrame final : public nsAtomicContainerFrame,
   nsIFrame* GetSubdocumentRootFrame();
   enum { IGNORE_PAINT_SUPPRESSION = 0x1 };
   mozilla::PresShell* GetSubdocumentPresShellForPainting(uint32_t aFlags);
+  nsRect GetDestRect();
   mozilla::ScreenIntSize GetSubdocumentSize();
 
   // nsIReflowCallback