Bug 1559518 - Use LayoutDevicePixel for BrowserChild visible rect and composition size. r=kats

App units of a remote browser element in the parent process are
different from app units inside the remote content in the child
process. We should apply the appropriate conversions by exposing
the relevant data as LayoutDevicePixel.

Differential Revision: https://phabricator.services.mozilla.com/D35334

--HG--
extra : moz-landing-system : lando

dom/ipc/BrowserChild.cpp

@@ -3332,14 +3332,16 @@ ScreenIntSize BrowserChild::GetInnerSize() {
       innerSize, PixelCastJustification::LayoutDeviceIsScreenForTabDims);
 };
 
-nsRect BrowserChild::GetVisibleRect() {
+LayoutDeviceIntRect BrowserChild::GetVisibleRect() {
+  CSSRect visibleRect;
   if (mIsTopLevel) {
     // We are conservative about visible rects for top-level browsers to avoid
     // artifacts when resizing
-    return nsRect(nsPoint(), CSSPixel::ToAppUnits(mUnscaledInnerSize));
+    visibleRect = CSSRect(CSSPoint(), mUnscaledInnerSize);
   } else {
-    return mEffectsInfo.mVisibleRect;
+    visibleRect = CSSPixel::FromAppUnits(mEffectsInfo.mVisibleRect);
   }
+  return RoundedToInt(visibleRect * mPuppetWidget->GetDefaultScale());
 }
 
 ScreenIntRect BrowserChild::GetOuterRect() {

dom/ipc/BrowserChild.h

@@ -549,7 +549,7 @@ class BrowserChild final : public nsMessageManagerScriptExecutor,
 
   ScreenIntSize GetInnerSize();
 
-  nsRect GetVisibleRect();
+  LayoutDeviceIntRect GetVisibleRect();
 
   // Call RecvShow(nsIntSize(0, 0)) and block future calls to RecvShow().
   void DoFakeShow(const ShowInfo& aShowInfo);

layout/base/nsLayoutUtils.cpp

@@ -3792,8 +3792,11 @@ nsresult nsLayoutUtils::PaintFrame(gfxContext* aRenderingContext,
 
   // If we are in a remote browser, then apply clipping from ancestor browsers
   if (BrowserChild* browserChild = BrowserChild::GetFrom(presShell)) {
+    LayoutDeviceIntRect unscaledVisibleRect = browserChild->GetVisibleRect();
+    CSSRect visibleRect =
+        unscaledVisibleRect / presContext->CSSToDevPixelScale();
     rootVisualOverflow.IntersectRect(rootVisualOverflow,
-                                     browserChild->GetVisibleRect());
+                                     CSSPixel::ToAppUnits(visibleRect));
   }
 
   nsIFrame* rootScrollFrame = presShell->GetRootScrollFrame();

widget/PuppetWidget.cpp

@@ -1158,6 +1158,13 @@ LayoutDeviceIntRect PuppetWidget::GetScreenBounds() {
   return LayoutDeviceIntRect(WidgetToScreenOffset(), mBounds.Size());
 }
 
+LayoutDeviceIntSize PuppetWidget::GetCompositionSize() {
+  if (!mBrowserChild) {
+    return nsBaseWidget::GetCompositionSize();
+  }
+  return mBrowserChild->GetVisibleRect().Size();
+}
+
 uint32_t PuppetWidget::GetMaxTouchPoints() const {
   uint32_t maxTouchPoints = 0;
   if (mBrowserChild) {

widget/PuppetWidget.h

@@ -242,6 +242,8 @@ class PuppetWidget : public nsBaseWidget,
 
   virtual LayoutDeviceIntRect GetScreenBounds() override;
 
+  virtual LayoutDeviceIntSize GetCompositionSize() override;
+
   virtual MOZ_MUST_USE nsresult StartPluginIME(
       const mozilla::WidgetKeyboardEvent& aKeyboardEvent, int32_t aPanelX,
       int32_t aPanelY, nsString& aCommitted) override;