Add an empty typeface as a default-default.

src/core/SkTypeface.cpp

 /*
  * Copyright 2011 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkAdvancedTypefaceMetrics.h"
 #include "SkFontDescriptor.h"
 #include "SkFontHost.h"
@@ skipping 18 matching lines @@
 
 SkTypeface::~SkTypeface() {
 #ifdef TRACE_LIFECYCLE
     SkDebugf("SkTypeface: destroy %p fontID %d total %d\n",
              this, fUniqueID, --gTypefaceCounter);
 #endif
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
+class SkEmptyTypeface : public SkTypeface {
+public:
+    SkEmptyTypeface() : SkTypeface(SkTypeface::kNormal, 0, true) { }
+protected:
+    virtual SkStream* onOpenStream(int* ttcIndex) const SK_OVERRIDE { return NULL; }
+    virtual SkScalerContext* onCreateScalerContext(const SkDescriptor*) const SK_OVERRIDE {
+        return NULL;
+    }
+    virtual void onFilterRec(SkScalerContextRec*) const SK_OVERRIDE { }
+    virtual SkAdvancedTypefaceMetrics* onGetAdvancedTypefaceMetrics(
+                                SkAdvancedTypefaceMetrics::PerGlyphInfo,
+                                const uint32_t*, uint32_t) const SK_OVERRIDE { return NULL; }
+    virtual void onGetFontDescriptor(SkFontDescriptor*, bool*) const SK_OVERRIDE { }
+    virtual int onCountGlyphs() const SK_OVERRIDE { return 0; };
+    virtual int onGetUPEM() const SK_OVERRIDE { return 0; };
+    class EmptyLocalizedStrings : public SkTypeface::LocalizedStrings {
+    public:
+        virtual bool next(SkTypeface::LocalizedString*) SK_OVERRIDE { return false; }
+    };
+    virtual SkTypeface::LocalizedStrings* onCreateFamilyNameIterator() const SK_OVERRIDE {
+        return SkNEW(EmptyLocalizedStrings);
+    };
+    virtual int onGetTableTags(SkFontTableTag tags[]) const SK_OVERRIDE { return 0; }
+    virtual size_t onGetTableData(SkFontTableTag, size_t, size_t, void*) const SK_OVERRIDE {
+        return 0;
+    }
+    virtual SkTypeface* onRefMatchingStyle(Style) const SK_OVERRIDE { return NULL; }
+};
+
 SkTypeface* SkTypeface::GetDefaultTypeface(Style style) {
     // we keep a reference to this guy for all time, since if we return its
     // fontID, the font cache may later on ask to resolve that back into a
     // typeface object.
     static const uint32_t FONT_STYLE_COUNT = 4;
     static SkTypeface* gDefaultTypefaces[FONT_STYLE_COUNT];
     SkASSERT((unsigned)style < FONT_STYLE_COUNT);
 
     // mask off any other bits to avoid a crash in SK_RELEASE
     style = (Style)(style & 0x03);
 
     if (NULL == gDefaultTypefaces[style]) {
-        gDefaultTypefaces[style] =
-        SkFontHost::CreateTypeface(NULL, NULL, style);
+        gDefaultTypefaces[style] = SkFontHost::CreateTypeface(NULL, NULL, style);
     }
+    if (NULL == gDefaultTypefaces[style]) {
+        gDefaultTypefaces[style] = SkNEW(SkEmptyTypeface);
+    }
+
     return gDefaultTypefaces[style];
 }
 
 SkTypeface* SkTypeface::RefDefault(Style style) {
     return SkRef(GetDefaultTypeface(style));
 }
 
 uint32_t SkTypeface::UniqueID(const SkTypeface* face) {
     if (NULL == face) {
         face = GetDefaultTypeface();
@@ skipping 156 matching lines @@
 ///////////////////////////////////////////////////////////////////////////////
 
 int SkTypeface::onCharsToGlyphs(const void* chars, Encoding encoding,
                                 uint16_t glyphs[], int glyphCount) const {
     SkDebugf("onCharsToGlyphs unimplemented\n");
     if (glyphs && glyphCount > 0) {
         sk_bzero(glyphs, glyphCount * sizeof(glyphs[0]));
     }
     return 0;
 }