This is a hack to clear the issue described here:

https://bugs.webkit.org/show_bug.cgi?id=265460

See also Bug 248823, Bug 209118 Comment 8, and Bug 154147 Comment 3.

The problem is that the compositor is forcing accelerated compositing
ON when accelerated compositing is disabled or not supported; this
results in a crash.

Note that effective 295482@main, this situation can also be triggered from
WebCore::Document::setActiveViewTransition; the patch address this as well.

While this patch is surely not the correct fix, it both clears the
crash and causes the content to be rendered as expected.


--- webkitgtk-2.49.90/Source/WebCore/rendering/RenderLayerCompositor.cpp.~1~	2025-08-08 10:17:55.540470800 +0000
+++ webkitgtk-2.49.90/Source/WebCore/rendering/RenderLayerCompositor.cpp	2025-09-14 17:29:30.798727222 +0000
@@ -612,6 +612,11 @@
 
 void RenderLayerCompositor::enableCompositingMode(bool enable /* = true */)
 {
+    if (enable && !m_hasAcceleratedCompositing) {
+        LOG(Compositing, "RenderLayerCompositor::enableCompositingMode: Accelerated compositing unavailable; disabling");
+        enable = false;
+    }
+
     if (enable != m_compositing) {
         m_compositing = enable;
         
@@ -1507,6 +1512,10 @@
     }
 
     ASSERT(willBeComposited == needsToBeComposited(layer, queryData));
+    if (willBeComposited && !m_hasAcceleratedCompositing) {
+        LOG(Compositing, "RenderLayerCompositor::computeCompositingRequirements: Accelerated compositing unavailable; using BackingRequired::No");
+        willBeComposited = false;
+    }
 
     // Create or destroy backing here. However, we can't update geometry because layers above us may become composited
     // during post-order traversal (e.g. for clipping).