Bug 418479. Allow antialiased text rendering to be disabled for small text sizes via a pref. r+sr=vlad, a=damons

gfx/thebes/public/gfxPlatformMac.h

@@ -80,14 +80,21 @@ public:
     // Ex: Mac OS X 10.4.x ==> 0x104x 
     PRInt32 OSXVersion();
 
+    // lower threshold on font anti-aliasing
+    PRUint32 GetAntiAliasingThreshold() { return mFontAntiAliasingThreshold; }
+    
 private:
     void gfxPlatformMac::AppendCJKPrefLangs(eFontPrefLang aPrefLangs[], PRUint32 &aLen, 
                                             eFontPrefLang aCharLang, eFontPrefLang aPageLang);
                                                
     virtual cmsHPROFILE GetPlatformCMSOutputProfile();
     
+    // read in the pref value for the lower threshold on font anti-aliasing
+    static PRUint32 ReadAntiAliasingThreshold();    
+    
     nsTArray<PRUint32> mCJKPrefLangs;
     PRInt32 mOSXVersion;
+    PRUint32 mFontAntiAliasingThreshold;
 };
 
 #endif /* GFX_PLATFORM_MAC_H */

gfx/thebes/src/gfxAtsuiFonts.cpp

@@ -140,6 +140,13 @@ gfxAtsuiFont::gfxAtsuiFont(MacOSFontEntry *aFontEntry,
     }
 
     cairo_font_options_t *fontOptions = cairo_font_options_create();
+    
+    // turn off font anti-aliasing based on user pref setting
+    if (mAdjustedSize <= (float) gfxPlatformMac::GetPlatform()->GetAntiAliasingThreshold()) {
+        cairo_font_options_set_antialias(fontOptions, CAIRO_ANTIALIAS_NONE); 
+        //printf("font: %s, size: %f, disabling anti-aliasing\n", NS_ConvertUTF16toUTF8(mName).get(), mAdjustedSize);
+    }
+    
     mScaledFont = cairo_scaled_font_create(mFontFace, &sizeMatrix, &ctm, fontOptions);
     cairo_font_options_destroy(fontOptions);
     NS_ASSERTION(cairo_scaled_font_status(mScaledFont) == CAIRO_STATUS_SUCCESS,

gfx/thebes/src/gfxPlatformMac.cpp

@@ -65,6 +65,7 @@ gfxPlatformMac::gfxPlatformMac()
         glitz_agl_init();
 #endif
     mOSXVersion = 0;
+    mFontAntiAliasingThreshold = ReadAntiAliasingThreshold();
 }
 
 already_AddRefed<gfxASurface>
@@ -336,6 +337,39 @@ gfxPlatformMac::AppendCJKPrefLangs(eFontPrefLang aPrefLangs[], PRUint32 &aLen, e
         
 }
 
+PRUint32
+gfxPlatformMac::ReadAntiAliasingThreshold()
+{
+    PRUint32 threshold = 0;  // default == no threshold
+    
+    // first read prefs flag to determine whether to use the setting or not
+    PRBool useAntiAliasingThreshold = PR_FALSE;
+    nsCOMPtr<nsIPrefBranch> prefs = do_GetService(NS_PREFSERVICE_CONTRACTID);
+    if (prefs) {
+        PRBool enabled;
+        nsresult rv =
+            prefs->GetBoolPref("gfx.use_text_smoothing_setting", &enabled);
+        if (NS_SUCCEEDED(rv)) {
+            useAntiAliasingThreshold = enabled;
+        }
+    }
+    
+    // if the pref setting is disabled, return 0 which effectively disables this feature
+    if (!useAntiAliasingThreshold)
+        return threshold;
+        
+    // value set via Appearance pref panel, "Turn off text smoothing for font sizes xxx and smaller"
+    CFNumberRef prefValue = (CFNumberRef)CFPreferencesCopyAppValue(CFSTR("AppleAntiAliasingThreshold"), kCFPreferencesCurrentApplication);
+
+    if (prefValue) {
+        if (!CFNumberGetValue(prefValue, kCFNumberIntType, &threshold)) {
+            threshold = 0;
+        }
+        CFRelease(prefValue);
+    }
+
+    return threshold;
+}
 
 cmsHPROFILE
 gfxPlatformMac::GetPlatformCMSOutputProfile()

modules/libpref/src/init/all.js

@@ -172,6 +172,9 @@ pref("accessibility.typeaheadfind.soundURL", "beep");
 pref("accessibility.typeaheadfind.enablesound", true);
 pref("accessibility.typeaheadfind.prefillwithselection", true);
 
+// use Mac OS X Appearance panel text smoothing setting when rendering text, disabled by default
+pref("gfx.use_text_smoothing_setting", false);
+
 pref("browser.history_expire_days", 9);
 
 // loading and rendering of framesets and iframes