tor-browser

commit 0295e6c095d8354ab6004eead9e54ac2187c0016
parent 032216be296baeda24895cf5dcc63dfd2c2fcbd6
Author: Emilio Cobos Álvarez <emilio@crisal.io>
Date:   Mon, 20 Oct 2025 20:59:49 +0000

Bug 1994908 - Use nearest pres shell widget in ComputeBackstopColor if there's no frame. r=layout-reviewers,dshin

The problem is that we're painting an about:blank document which hasn't
been laid out yet (there's no root frame).

In that case, we used to get a widget from the view tree, but now we
don't.

Introduce PresShell::GetNearestWidget(), and use it to get the closest
widget if there's no root frame so that we don't paint an opaque
backdrop incorrectly.

Differential Revision: https://phabricator.services.mozilla.com/D269293

Diffstat:
M
layout/base/PresShell.cpp
 | 
24
++++++++++++++++++++----
M
layout/base/PresShell.h
 | 
4
++++

2 files changed, 24 insertions(+), 4 deletions(-)
diff --git a/layout/base/PresShell.cpp b/layout/base/PresShell.cpp
@@ -126,6 +126,7 @@
 #include "mozilla/gfx/Types.h"
 #include "mozilla/glean/GfxMetrics.h"
 #include "mozilla/glean/LayoutMetrics.h"
+#include "mozilla/glue/Debug.h"
 #include "mozilla/layers/APZPublicUtils.h"
 #include "mozilla/layers/CompositorBridgeChild.h"
 #include "mozilla/layers/FocusTarget.h"
@@ -5610,7 +5611,8 @@ PresShell::CanvasBackground PresShell::ComputeCanvasBackground() const {
 }
 
 nscolor PresShell::ComputeBackstopColor(nsIFrame* aDisplayRoot) {
-  nsIWidget* widget = aDisplayRoot ? aDisplayRoot->GetNearestWidget() : nullptr;
+  nsIWidget* widget =
+      aDisplayRoot ? aDisplayRoot->GetNearestWidget() : GetNearestWidget();
   if (widget &&
       (widget->GetTransparencyMode() != widget::TransparencyMode::Opaque ||
        widget->WidgetPaintsBackground())) {
@@ -5630,9 +5632,7 @@ struct PaintParams {
 
 WindowRenderer* PresShell::GetWindowRenderer() {
   NS_ASSERTION(mViewManager, "Should have view manager");
-
-  nsView* rootView = mViewManager->GetRootView();
-  if (rootView) {
+  if (nsView* rootView = mViewManager->GetRootView()) {
     if (nsIWidget* widget = rootView->GetWidget()) {
       return widget->GetWindowRenderer();
     }
@@ -5640,6 +5640,22 @@ WindowRenderer* PresShell::GetWindowRenderer() {
   return nullptr;
 }
 
+nsIWidget* PresShell::GetNearestWidget() const {
+  if (mViewManager) {
+    if (auto* root = mViewManager->GetRootView()) {
+      if (nsIWidget* widget = root->GetWidget()) {
+        return widget;
+      }
+    }
+  }
+  if (auto* el = mDocument->GetEmbedderElement()) {
+    if (auto* f = el->GetPrimaryFrame()) {
+      return f->GetNearestWidget();
+    }
+  }
+  return GetRootWidget();
+}
+
 bool PresShell::AsyncPanZoomEnabled() {
   NS_ASSERTION(mViewManager, "Should have view manager");
   nsView* rootView = mViewManager->GetRootView();
diff --git a/layout/base/PresShell.h b/layout/base/PresShell.h
@@ -456,6 +456,10 @@ class PresShell final : public nsStubDocumentObserver,
   // Return the closest root widget (widget owned by a root frame).
   nsIWidget* GetRootWidget() const;
 
+  // Return the closest widget (including popups, if our document is inside a
+  // popup).
+  nsIWidget* GetNearestWidget() const;
+
   /**
    * Get root scroll container frame from the frame constructor.
    */