prototype for kerning api

include/core/SkTypeface.h

Index: include/core/SkTypeface.h
diff --git a/include/core/SkTypeface.h b/include/core/SkTypeface.h
index eebb1276f7cd535606aa562f55a2606ef6529bde..d79f5a03802bccfbd4d349634b591f7aeb4d11a3 100644
--- a/include/core/SkTypeface.h
+++ b/include/core/SkTypeface.h
@@ -225,6 +225,23 @@ public:
      */
     int getUnitsPerEm() const;
 
+    /**
+     *  If the typeface does not support kerning, returns false and all
+     *  parameters are ignored.
+     *
+     *  If the typeface does support kerning, returns true. If the adjustments
+     *  parameter is not NULL, then it must have room for at least count-1

[bungeman-skia, 2013/10/29 21:38:41]

This seems a bit odd. I would thing that if we wanted a magic set of values to
pass in to determine if we support kerning, it would be to pass NULL for glyphs,
(and imply that count should be 0 and adjustments NULL as well). This seems to
more ask the question "If I tried to get kerning information for no glyphs,
would that work?"

[reed1, 2013/10/30 13:59:37]

Done.

+     *  entries. These will be filled in with the kerning values that correspond
+     *  to the associated pairs of glyphs.
+     *
+     *  e.g. adjustment[i] is relative to glyphs[i] and glyphs[i+1]
+     *
+     *  These values are in design units, which are relative to the typeface's
+     *  units-per-em (see getUnitsPerEm).
+     */
+    bool getKerningPairAdjustments(const uint16_t glyphs[], int count,
+                                   int32_t adjustments[]) const;
+
     struct LocalizedString {
         SkString fString;
         SkString fLanguage;
@@ -303,6 +320,7 @@ protected:
                         SkAdvancedTypefaceMetrics::PerGlyphInfo perGlyphInfo,
                         const uint32_t* glyphIDs,
                         uint32_t glyphIDsCount) const = 0;
+
     virtual SkStream* onOpenStream(int* ttcIndex) const = 0;
     virtual void onGetFontDescriptor(SkFontDescriptor*, bool* isLocal) const = 0;
 
@@ -311,6 +329,8 @@ protected:
     virtual int onCountGlyphs() const = 0;
 
     virtual int onGetUPEM() const = 0;
+    virtual bool onGetKerningPairAdjustments(const uint16_t glyphs[], int count,
+                                             int32_t adjustments[]) const;
 
     virtual LocalizedStrings* onCreateFamilyNameIterator() const = 0;