Changeset 276739 in webkit

Timestamp:

Apr 28, 2021, 4:00:57 PM (5 years ago)

Author:

Cameron McCormack

Message:

Don't create custom scrollbars for fullscreen placeholders.
​https://bugs.webkit.org/show_bug.cgi?id=225141
Source/WebCore:

<rdar://64800098>

Reviewed by Darin Adler.

We can end up calling RenderScrollbar::createCustomScrollbar with
element = nullptr from RenderLayerScrollableArea::createScrollbar,
when the renderer is a RenderFullscreenPlaceholder.

We don't need to bother with scrollbars for the placeholder, so check to
make sure we have a valid element before creating custom scollbars.

Test: fullscreen/full-screen-crash-custom-scrollbars.html

• rendering/RenderLayerScrollableArea.cpp:

(WebCore::RenderLayerScrollableArea::createScrollbar):

LayoutTests:

Reviewed by Darin Adler.

• fullscreen/full-screen-crash-custom-scrollbars-expected.txt: Added.
• fullscreen/full-screen-crash-custom-scrollbars.html: Added.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/fullscreen/full-screen-crash-custom-scrollbars-expected.txt (added)
• LayoutTests/fullscreen/full-screen-crash-custom-scrollbars.html (added)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/rendering/RenderLayerScrollableArea.cpp (modified) (1 diff)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2021-04-28  Cameron McCormack  <heycam@apple.com>
+
+        Don't create custom scrollbars for fullscreen placeholders.
+        https://bugs.webkit.org/show_bug.cgi?id=225141
+
+        Reviewed by Darin Adler.
+
+        * fullscreen/full-screen-crash-custom-scrollbars-expected.txt: Added.
+        * fullscreen/full-screen-crash-custom-scrollbars.html: Added.
+
 2021-04-28  Chris Dumez  <cdumez@apple.com>
 

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2021-04-28  Cameron McCormack  <heycam@apple.com>
+
+        Don't create custom scrollbars for fullscreen placeholders.
+        https://bugs.webkit.org/show_bug.cgi?id=225141
+        <rdar://64800098>
+
+        Reviewed by Darin Adler.
+
+        We can end up calling RenderScrollbar::createCustomScrollbar with
+        `element = nullptr` from RenderLayerScrollableArea::createScrollbar,
+        when the renderer is a RenderFullscreenPlaceholder.
+
+        We don't need to bother with scrollbars for the placeholder, so check to
+        make sure we have a valid element before creating custom scollbars.
+
+        Test: fullscreen/full-screen-crash-custom-scrollbars.html
+
+        * rendering/RenderLayerScrollableArea.cpp:
+        (WebCore::RenderLayerScrollableArea::createScrollbar):
+
 2021-04-28  Chris Dumez  <cdumez@apple.com>
 

trunk/Source/WebCore/rendering/RenderLayerScrollableArea.cpp

@@ -819 +819 @@
     auto& actualRenderer = *rendererForScrollbar(renderer);
     bool hasCustomScrollbarStyle = is<RenderBox>(actualRenderer) && downcast<RenderBox>(actualRenderer).style().hasPseudoStyle(PseudoId::Scrollbar);
-    if (hasCustomScrollbarStyle)
-        widget = RenderScrollbar::createCustomScrollbar(*this, orientation, downcast<RenderBox>(actualRenderer).element());
+    auto element = downcast<RenderBox>(actualRenderer).element();
+    if (hasCustomScrollbarStyle && element)
+        widget = RenderScrollbar::createCustomScrollbar(*this, orientation, element);
     else {
         widget = Scrollbar::createNativeScrollbar(*this, orientation, ScrollbarControlSize::Regular);