New approach for GPU font atlas

src/gpu/GrDistanceFieldTextContext.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrDistanceFieldTextContext.h"
 #include "GrAtlas.h"
 #include "GrDrawTarget.h"
@@ skipping 143 matching lines @@
     if (true || NULL == glyph->fPlot) {
         int x = vx >> 16;
         int y = vy >> 16;
         if (fClipRect.quickReject(x, y, x + width, y + height)) {
 //            SkCLZ(3);    // so we can set a break-point in the debugger
             return;
         }
     }
 */
     if (NULL == glyph->fPlot) {
-        if (fStrike->getGlyphAtlas(glyph, scaler)) {
+        if (fStrike->addGlyphToAtlas(glyph, scaler)) {
             goto HAS_ATLAS;
         }
 
         // try to clear out an unused plot before we flush
-        fContext->getFontCache()->freePlotExceptFor(fStrike);
-        if (fStrike->getGlyphAtlas(glyph, scaler)) {
+        if (fContext->getFontCache()->freeUnusedPlot(fStrike) &&
+            fStrike->addGlyphToAtlas(glyph, scaler)) {
             goto HAS_ATLAS;
         }
 
         if (c_DumpFontCache) {
 #ifdef SK_DEVELOPER
             fContext->getFontCache()->dump();
 #endif
         }
 
         // before we purge the cache, we must flush any accumulated draws
         this->flushGlyphs();
         fContext->flush();
 
-        // try to purge
-        fContext->getFontCache()->purgeExceptFor(fStrike);
-        // need to use new flush count here
-        if (fStrike->getGlyphAtlas(glyph, scaler)) {
+        // we should have an unused plot now
+        if (fContext->getFontCache()->freeUnusedPlot(fStrike) &&
+            fStrike->addGlyphToAtlas(glyph, scaler)) {
             goto HAS_ATLAS;
         }
 
         if (NULL == glyph->fPath) {
             SkPath* path = SkNEW(SkPath);
             if (!scaler->getGlyphPath(glyph->glyphID(), path)) {
                 // flag the glyph as being dead?
                 delete path;
                 return;
             }
@@ skipping 245 matching lines @@
                                       SkScalarToFixed(y) - (glyph.fAdvanceY >> alignShift)
                                         + SK_FixedHalf, //d1g.fHalfSampleY,
                                       fontScaler);
             }
             pos += scalarsPerPosition;
         }
     }
 
     this->finish();
 }