Bug 1334761 - Update ClearType usage at startup, and flush caches and reflow everything if it changes during the session. r=bas

gfx/thebes/gfxDWriteFonts.cpp

@@ -44,7 +44,7 @@ GetCairoAntialiasOption(gfxFont::AntialiasOption anAntialiasOption)
 #define FE_FONTSMOOTHINGCLEARTYPE 2
 #endif
 
-bool gfxDWriteFont::mUseClearType = true;
+bool gfxDWriteFont::sUseClearType = true;
 
 // This function is expensive so we only want to call it when we have to.
 static bool
@@ -114,8 +114,15 @@ gfxDWriteFont::~gfxDWriteFont()
 void
 gfxDWriteFont::UpdateClearTypeUsage()
 {
-  Factory::UpdateSystemTextQuality();
-  mUseClearType = UsingClearType();
+    Factory::UpdateSystemTextQuality();
+    // Check if ClearType status has changed; if so, toggle our flag,
+    // flush cached stuff that depended on the old setting, and force
+    // reflow everywhere to ensure we are using correct glyph metrics.
+    if (sUseClearType != UsingClearType()) {
+        sUseClearType = !sUseClearType;
+        gfxPlatform::FlushFontAndWordCaches();
+        gfxPlatform::ForceGlobalReflow();
+    }
 }
 
 UniquePtr<gfxFont>
@@ -175,7 +182,7 @@ gfxDWriteFont::ComputeMetrics(AntialiasOption anAAOption)
 
     // Note that GetMeasuringMode depends on mAdjustedSize
     if ((anAAOption == gfxFont::kAntialiasDefault &&
-         mUseClearType &&
+         sUseClearType &&
          GetMeasuringMode() == DWRITE_MEASURING_MODE_NATURAL) ||
         anAAOption == gfxFont::kAntialiasSubpixel)
     {
@@ -688,7 +695,7 @@ gfxDWriteFont::GetScaledFont(mozilla::gfx::DrawTarget *aTarget)
         bool forceGDI = GetForceGDIClassic();
 
         IDWriteRenderingParams* params = gfxWindowsPlatform::GetPlatform()->GetRenderingParams(
-            mUseClearType ?
+            sUseClearType ?
                 (forceGDI ?
                     gfxWindowsPlatform::TEXT_RENDERING_GDI_CLASSIC :
                     gfxWindowsPlatform::TEXT_RENDERING_NORMAL) :

gfx/thebes/gfxDWriteFonts.h

@@ -105,7 +105,8 @@ protected:
     bool mNeedsBold;
     bool mUseSubpixelPositions;
     bool mAllowManualShowGlyphs;
-    static bool mUseClearType;
+
+    static bool sUseClearType;
 };
 
 #endif

gfx/thebes/gfxPlatform.cpp

@@ -2167,6 +2167,15 @@ gfxPlatform::FlushFontAndWordCaches()
     gfxPlatform::PurgeSkiaFontCache();
 }
 
+/* static */ void
+gfxPlatform::ForceGlobalReflow()
+{
+    // modify a preference that will trigger reflow everywhere
+    static const char kPrefName[] = "font.internaluseonly.changed";
+    bool fontInternalChange = Preferences::GetBool(kPrefName, false);
+    Preferences::SetBool(kPrefName, !fontInternalChange);
+}
+
 void
 gfxPlatform::FontsPrefsChanged(const char *aPref)
 {

gfx/thebes/gfxPlatform.h

@@ -557,6 +557,14 @@ public:
 
     int32_t GetBidiNumeralOption();
 
+    /**
+     * This is a bit ugly, but useful... force all presContexts to reflow,
+     * by toggling a preference that they observe. This is used when
+     * something about platform settings changes that might have an effect
+     * on layout, such as font rendering settings that influence metrics.
+     */
+    static void ForceGlobalReflow();
+
     static void
     FlushFontAndWordCaches();
 

gfx/thebes/gfxPlatformFontList.cpp

@@ -1583,15 +1583,6 @@ gfxPlatformFontList::GetPrefsAndStartLoader()
     StartLoader(delay, interval);
 }
 
-void
-gfxPlatformFontList::ForceGlobalReflow()
-{
-    // modify a preference that will trigger reflow everywhere
-    static const char kPrefName[] = "font.internaluseonly.changed";
-    bool fontInternalChange = Preferences::GetBool(kPrefName, false);
-    Preferences::SetBool(kPrefName, !fontInternalChange);
-}
-
 void
 gfxPlatformFontList::RebuildLocalFonts()
 {

gfx/thebes/gfxPlatformFontList.h

@@ -485,7 +485,9 @@ protected:
     void GetPrefsAndStartLoader();
 
     // for font list changes that affect all documents
-    void ForceGlobalReflow();
+    void ForceGlobalReflow() {
+        gfxPlatform::ForceGlobalReflow();
+    }
 
     void RebuildLocalFonts();