New approach for GPU font atlas

src/gpu/GrBitmapTextContext.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 "GrBitmapTextContext.h"
 #include "GrAtlas.h"
 #include "GrDrawTarget.h"
@@ skipping 500 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
+        // flush any accumulated draws to allow us to free up a plot
         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 74 matching lines @@
 
     fVertices[2*fCurrVertex].setRectFan(r.fLeft, r.fTop, r.fRight, r.fBottom,
                                         2 * sizeof(SkPoint));
     fVertices[2*fCurrVertex+1].setRectFan(SkFixedToFloat(texture->normalizeFixedX(tx)),
                                           SkFixedToFloat(texture->normalizeFixedY(ty)),
                                           SkFixedToFloat(texture->normalizeFixedX(tx + width)),
                                           SkFixedToFloat(texture->normalizeFixedY(ty + height)),
                                           2 * sizeof(SkPoint));
     fCurrVertex += 4;
 }