Added ability to flush context to GrTextBlobCache

src/gpu/GrTextBlobCache.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrTextBlobCache_DEFINED
 #define GrTextBlobCache_DEFINED
 
 #include "GrAtlasTextContext.h"
 #include "SkTDynamicHash.h"
 #include "SkTextBlob.h"
 
 class GrTextBlobCache {
 public:
     typedef GrAtlasTextContext::BitmapTextBlob BitmapTextBlob;
 
-    GrTextBlobCache() : fPool(kPreAllocSize, kMinGrowthSize) {}
+    /**
+     * The callback function used by the cache when it is still over budget after a purge. The
+     * passed in 'data' is the same 'data' handed to setOverbudgetCallback.
+     */
+    typedef void (*PFOverBudgetCB)(void* data);
+
+    GrTextBlobCache(PFOverBudgetCB cb, void* data)
+        : fPool(kPreAllocSize, kMinGrowthSize)
+        , fCallback(cb)
+        , fData(data) {
+        SkASSERT(cb && data);
+    }
     ~GrTextBlobCache();
 
     // creates an uncached blob
     BitmapTextBlob* createBlob(int glyphCount, int runCount, size_t maxVASize);
 
     BitmapTextBlob* createCachedBlob(const SkTextBlob* blob, size_t maxVAStride) {
         int glyphCount = 0;
         int runCount = 0;
         BlobGlyphCount(&glyphCount, &runCount, blob);
         BitmapTextBlob* cacheBlob = this->createBlob(glyphCount, runCount, maxVAStride);
@@ skipping 15 matching lines @@
     void add(BitmapTextBlob* blob) {
         fCache.add(blob);
         fBlobList.addToHead(blob);
 
         // If we are overbudget, then unref until we are below budget again
         if (fPool.size() > kBudget) {
             BitmapBlobList::Iter iter;
             iter.init(fBlobList, BitmapBlobList::Iter::kTail_IterStart);
             BitmapTextBlob* lruBlob = iter.get();
             SkASSERT(lruBlob);
-            do {
+            while (fPool.size() > kBudget && (lruBlob = iter.get()) && lruBlob != blob) {
                 fCache.remove(lruBlob->fUniqueID);
                 fBlobList.remove(lruBlob);
+                iter.prev();
                 lruBlob->unref();
-                iter.prev();
-            } while (fPool.size() > kBudget && (lruBlob = iter.get()));
+            }
+
+            // If we break out of the loop with lruBlob == blob, then we haven't purged enough
+            // use the call back and try to free some more.  If we are still overbudget after this,
+            // then this single textblob is over our budget
+            if (lruBlob == blob) {
+                (*fCallback)(fData);
+            }
+
+#ifdef SK_DEBUG
+            if (fPool.size() > kBudget) {
+                SkDebugf("Single textblob is larger than our whole budget");
+            }
+#endif
         }
     }
 
     void makeMRU(BitmapTextBlob* blob) {
         if (fBlobList.head() == blob) {
             return;
         }
 
         fBlobList.remove(blob);
         fBlobList.addToHead(blob);
     }
 
 private:
     // TODO move to SkTextBlob
     void BlobGlyphCount(int* glyphCount, int* runCount, const SkTextBlob* blob) {
         SkTextBlob::RunIterator itCounter(blob);
         for (; !itCounter.done(); itCounter.next(), (*runCount)++) {
             *glyphCount += itCounter.glyphCount();
         }
     }
 
     typedef SkTInternalLList<BitmapTextBlob> BitmapBlobList;
 
     // Budget was chosen to be ~4 megabytes.  The min alloc and pre alloc sizes in the pool are
     // based off of the largest cached textblob I have seen in the skps(a couple of kilobytes).
     static const int kPreAllocSize = 1 << 17;
     static const int kMinGrowthSize = 1 << 17;
-    static const int kBudget = 1 << 20;
+    static const int kBudget = 1 << 22;
     BitmapBlobList fBlobList;
     SkTDynamicHash<BitmapTextBlob, uint32_t> fCache;
     GrMemoryPool fPool;
+    PFOverBudgetCB fCallback;
+    void* fData;
 };
 
 #endif