From 1190eb1c6a485c5ab20817b28849a0aef2d3980c Mon Sep 17 00:00:00 2001
From: wuggy <ownedbywuigi@gmail.com>
Date: Thu, 17 Sep 2026 23:27:05 -0700
Subject: [PATCH] WebRender preference (gfx.webrender.enable, false by default)

---
 gfx/layers/composite/ColorLayerComposite.cpp | 3 ++-
 gfx/thebes/gfxPrefs.h                        | 2 ++
 modules/libpref/init/all.js                  | 3 +++
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/gfx/layers/composite/ColorLayerComposite.cpp b/gfx/layers/composite/ColorLayerComposite.cpp
index 03058b6b60..7f19357ea8 100644
--- a/gfx/layers/composite/ColorLayerComposite.cpp
+++ b/gfx/layers/composite/ColorLayerComposite.cpp
@@ -14,6 +14,7 @@
 #include "mozilla/layers/CompositorTypes.h"  // for DiagnosticFlags::COLOR
 #include "mozilla/layers/Effects.h"     // for Effect, EffectChain, etc
 #include "mozilla/mozalloc.h"           // for operator delete, etc
+#include "gfxPrefs.h"                   // for gfxPrefs::WebRenderEnabled
 
 namespace mozilla {
 namespace layers {
@@ -34,7 +35,7 @@ ColorLayerComposite::RenderLayer(const IntRect& aClipRect)
     // Masked or 3D layers continue through the established effect path until
     // equivalent WebRender primitives are available for those cases.
     CompositorOGL* compositorOGL = mCompositor->AsCompositorOGL();
-    if (compositorOGL &&
+    if (gfxPrefs::WebRenderEnabled() && compositorOGL &&
         !effectChain.mSecondaryEffects[EffectTypes::MASK] &&
         GetEffectiveMixBlendMode() == CompositionOp::OP_OVER &&
         transform.Is2D() && !clipRect.IsEmpty()) {
diff --git a/gfx/thebes/gfxPrefs.h b/gfx/thebes/gfxPrefs.h
index adab38e25b..121b132a1d 100644
--- a/gfx/thebes/gfxPrefs.h
+++ b/gfx/thebes/gfxPrefs.h
@@ -409,6 +409,8 @@ private:
 
   DECL_GFX_PREF(Once, "gfx.use-iosurface-textures",            UseIOSurfaceTextures, bool, false);
 
+  DECL_GFX_PREF(Live, "gfx.webrender.enabled",                WebRenderEnabled, bool, false);
+
   // These times should be in milliseconds
   DECL_GFX_PREF(Once, "gfx.touch.resample.delay-threshold",    TouchResampleVsyncDelayThreshold, int32_t, 20);
   DECL_GFX_PREF(Once, "gfx.touch.resample.max-predict",        TouchResampleMaxPredict, int32_t, 8);
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 2bcf534e75..71f9ed86da 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -727,6 +727,9 @@ pref("layout.scroll.root-frame-containers", false);
 pref("gfx.layerscope.enabled", false);
 pref("gfx.layerscope.port", 23456);
 
+// Enable the incremental C WebRender path for supported compositor primitives.
+pref("gfx.webrender.enabled", false);
+
 // Log severe performance warnings to the error console and profiles.
 // This should be use to quickly find which slow paths are used by test cases.
 pref("gfx.perf-warnings.enabled", false);