Bug 1923289 - Don't report popups as transparent in uncomposited screens. r=stransky

This makes us choose the right rounding mode in nsView::CalcWidgetBounds
in order to prevent seams.

Remove composited screen special case which is no longer relevant now
that the X11 shape mask code is gone.

Differential Revision: https://phabricator.services.mozilla.com/D224918

Author: emilio

view/nsView.cpp

@@ -400,7 +400,7 @@ void nsView::NotifyEffectiveVisibilityChanged(bool aEffectivelyVisible) {
 
   SetForcedRepaint(true);
 
-  if (nullptr != mWindow) {
+  if (mWindow) {
     ResetWidgetBounds(false, false);
   }
 

widget/gtk/nsWindow.cpp

@@ -758,13 +758,9 @@ bool nsWindow::WidgetTypeSupportsAcceleration() {
   if (IsSmallPopup()) {
     return false;
   }
-  // Workaround for Bug 1479135
-  // We draw transparent popups on non-compositing screens by SW as we don't
-  // implement X shape masks in WebRender.
   if (mWindowType == WindowType::Popup) {
-    return HasRemoteContent() && mCompositedScreen;
+    return HasRemoteContent();
   }
-
   return true;
 }
 
@@ -5911,7 +5907,7 @@ nsresult nsWindow::Create(nsIWidget* aParent, const LayoutDeviceIntRect& aRect,
   ConstrainSize(&mBounds.width, &mBounds.height);
   mLastSizeRequest = mBounds.Size();
 
-  bool popupNeedsAlphaVisual =
+  const bool popupNeedsAlphaVisual =
       mWindowType == WindowType::Popup && aInitData &&
       aInitData->mTransparencyMode == TransparencyMode::Transparent;
 
@@ -6009,6 +6005,9 @@ nsresult nsWindow::Create(nsIWidget* aParent, const LayoutDeviceIntRect& aRect,
         gtk_widget_set_visual(mShell, visual);
         mHasAlphaVisual = true;
       }
+    } else {
+      // We can't really provide transparency...
+      mIsTransparent = false;
     }
   }
 
@@ -6830,11 +6829,16 @@ void nsWindow::SetTransparencyMode(TransparencyMode aMode) {
     // Ignore the request so as to workaround that.
     // mIsTransparent is set in Create() if transparency may be required.
     if (isTransparent) {
-      NS_WARNING("Transparent mode not supported on non-popup windows.");
+      NS_WARNING(
+          "Non-initial transparent mode not supported on non-popup windows.");
     }
     return;
   }
 
+  if (!mCompositedScreen) {
+    return;
+  }
+
   mIsTransparent = isTransparent;
 
   if (!mHasAlphaVisual) {