firefox/mozilla-1577024.patch

diff -up firefox-69.0/widget/gtk/nsWaylandDisplay.cpp.mozilla-1577024 firefox-69.0/widget/gtk/nsWaylandDisplay.cpp
--- firefox-69.0/widget/gtk/nsWaylandDisplay.cpp.mozilla-1577024	2019-09-17 21:09:15.817764591 +0200
+++ firefox-69.0/widget/gtk/nsWaylandDisplay.cpp	2019-09-17 21:09:15.822764568 +0200
@@ -13,10 +13,15 @@ namespace widget {
 #define GBMLIB_NAME "libgbm.so.1"
 #define DRMLIB_NAME "libdrm.so.2"
 
+#define DMABUF_PREF "widget.wayland_dmabuf_backend.enabled"
+// See WindowSurfaceWayland::RenderingCacheMode for details.
+#define CACHE_MODE_PREF "widget.wayland_cache_mode"
+
 bool nsWaylandDisplay::mIsDMABufEnabled = false;
 // -1 mean the pref was not loaded yet
 int nsWaylandDisplay::mIsDMABufPrefState = -1;
 bool nsWaylandDisplay::mIsDMABufConfigured = false;
+int nsWaylandDisplay::mRenderingCacheModePref = -1;
 
 wl_display* WaylandDisplayGetWLDisplay(GdkDisplay* aGdkDisplay) {
   if (!aGdkDisplay) {
@@ -373,14 +378,15 @@ nsWaylandDisplay::nsWaylandDisplay(wl_di
   wl_registry_add_listener(mRegistry, &registry_listener, this);
 
   if (NS_IsMainThread()) {
-    // We can't load the preference from compositor/render thread,
-    // only from main one. So we can't call it directly from
-    // nsWaylandDisplay::IsDMABufEnabled() as it can be called from various
-    // threads.
+    // We can't load the preference from compositor/render thread
+    // so load all Wayland prefs here.
     if (mIsDMABufPrefState == -1) {
-      mIsDMABufPrefState =
-          Preferences::GetBool("widget.wayland_dmabuf_backend.enabled", false);
+      mIsDMABufPrefState = Preferences::GetBool(DMABUF_PREF, false);
+    }
+    if (mRenderingCacheModePref == -1) {
+      mRenderingCacheModePref = Preferences::GetInt(CACHE_MODE_PREF, 0);
     }
+
     // Use default event queue in main thread operated by Gtk+.
     mEventQueue = nullptr;
     wl_display_roundtrip(mDisplay);
diff -up firefox-69.0/widget/gtk/nsWaylandDisplay.h.mozilla-1577024 firefox-69.0/widget/gtk/nsWaylandDisplay.h
--- firefox-69.0/widget/gtk/nsWaylandDisplay.h.mozilla-1577024	2019-09-17 21:09:15.818764586 +0200
+++ firefox-69.0/widget/gtk/nsWaylandDisplay.h	2019-09-17 21:09:15.822764568 +0200
@@ -83,6 +83,9 @@ class nsWaylandDisplay {
                          uint32_t mModifierLo);
   static bool IsDMABufEnabled();
 
+  // See WindowSurfaceWayland::CacheMode for details.
+  int GetRenderingCacheModePref() { return mRenderingCacheModePref; };
+
  private:
   bool ConfigureGbm();
 
@@ -108,6 +111,7 @@ class nsWaylandDisplay {
   static bool mIsDMABufEnabled;
   static int mIsDMABufPrefState;
   static bool mIsDMABufConfigured;
+  static int mRenderingCacheModePref;
 };
 
 void WaylandDispatchDisplays();
diff -up firefox-69.0/widget/gtk/WindowSurfaceWayland.cpp.mozilla-1577024 firefox-69.0/widget/gtk/WindowSurfaceWayland.cpp
--- firefox-69.0/widget/gtk/WindowSurfaceWayland.cpp.mozilla-1577024	2019-09-17 21:09:15.820764577 +0200
+++ firefox-69.0/widget/gtk/WindowSurfaceWayland.cpp	2019-09-18 08:34:50.568111279 +0200
@@ -192,7 +192,7 @@ It owns wl_buffer object, owns WaylandDM
 (which provides the DMA Buffer) and ties them together.
 
 WindowBackBufferDMABuf backend is used only when WaylandDMABufSurface is
-available and gfx.wayland_dmabuf_backend.enabled preference is set.
+available and widget.wayland_dmabuf_backend.enabled preference is set.
 
 */
 
@@ -519,9 +519,11 @@ WindowSurfaceWayland::WindowSurfaceWayla
       mBufferNeedsClear(false),
       mIsMainThread(NS_IsMainThread()),
       mNeedScaleFactorUpdate(true) {
-  for (int i = 0; i < BACK_BUFFER_NUM; i++) mBackupBuffer[i] = nullptr;
-  mRenderingCacheMode = CACHE_ALL;
-
+  for (int i = 0; i < BACK_BUFFER_NUM; i++) {
+      mBackupBuffer[i] = nullptr;
+  }
+  mRenderingCacheMode = static_cast<RenderingCacheMode>(
+      mWaylandDisplay->GetRenderingCacheModePref());
 }
 
 WindowSurfaceWayland::~WindowSurfaceWayland() {
diff -up firefox-69.0/widget/gtk/WindowSurfaceWayland.h.mozilla-1577024 firefox-69.0/widget/gtk/WindowSurfaceWayland.h