Bug 1696407: Don't use GDI font table loading for DWrite when win32k lockdown is enabled. r=jfkthame

Differential Revision: https://phabricator.services.mozilla.com/D107488

gfx/thebes/gfxDWriteFontList.cpp

@@ -18,6 +18,7 @@
 #include "mozilla/Sprintf.h"
 #include "mozilla/StaticPrefs_gfx.h"
 #include "mozilla/Telemetry.h"
+#include "mozilla/WindowsProcessMitigations.h"
 #include "mozilla/WindowsVersion.h"
 #include "nsDirectoryServiceUtils.h"
 #include "nsDirectoryServiceDefs.h"
@@ -968,6 +969,12 @@ gfxFontEntry* gfxDWriteFontList::MakePlatformFont(
   return entry.release();
 }
 
+bool gfxDWriteFontList::UseGDIFontTableAccess() const {
+  // Using GDI font table access for DWrite is controlled by a pref, but also we
+  // must be able to make win32k calls.
+  return mGDIFontTableAccess && !IsWin32kLockedDown();
+}
+
 static void GetPostScriptNameFromNameTable(IDWriteFontFace* aFace,
                                            nsCString& aName) {
   const auto kNAME =

gfx/thebes/gfxDWriteFontList.h

@@ -406,7 +406,7 @@ class gfxDWriteFontList final : public gfxPlatformFontList {
                                  uint32_t aLength) override;
 
   IDWriteGdiInterop* GetGDIInterop() { return mGDIInterop; }
-  bool UseGDIFontTableAccess() { return mGDIFontTableAccess; }
+  bool UseGDIFontTableAccess() const;
 
   bool FindAndAddFamilies(mozilla::StyleGenericFontFamily aGeneric,
                           const nsACString& aFamily,