Purge GrTextBlobCache entries on SkTextBlob deletion

Similar to the SkImage purge mechanism.

Change-Id: I0b7fb1bad507a3c7f30a4f7514bedd894d1748ac
Reviewed-on: https://skia-review.googlesource.com/9631
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>

include/core/SkTextBlob.h

@@ -9,6 +9,7 @@
 #define SkTextBlob_DEFINED
 
 #include "../private/SkTemplates.h"
+#include "../private/SkAtomics.h"
 #include "SkPaint.h"
 #include "SkString.h"
 #include "SkRefCnt.h"
@@ -75,11 +76,19 @@ private:
 
     static unsigned ScalarsPerGlyph(GlyphPositioning pos);
 
+    // Call when this blob is part of the key to a cache entry. This allows the cache
+    // to know automatically those entries can be purged when this SkTextBlob is deleted.
+    void notifyAddedToCache() const {
+        fAddedToCache.store(true);
+    }
+
+    friend class GrTextBlobCache;
     friend class SkTextBlobBuilder;
     friend class SkTextBlobRunIterator;
 
-    const SkRect   fBounds;
-    const uint32_t fUniqueID;
+    const SkRect           fBounds;
+    const uint32_t         fUniqueID;
+    mutable SkAtomic<bool> fAddedToCache;
 
     SkDEBUGCODE(size_t fStorageSize;)
 

src/core/SkTextBlob.cpp

@@ -11,6 +11,10 @@
 #include "SkTypeface.h"
 #include "SkWriteBuffer.h"
 
+#if SK_SUPPORT_GPU
+#include "text/GrTextBlobCache.h"
+#endif
+
 namespace {
 
 // TODO(fmalita): replace with SkFont.
@@ -286,10 +290,16 @@ static int32_t next_id() {
 
 SkTextBlob::SkTextBlob(const SkRect& bounds)
     : fBounds(bounds)
-    , fUniqueID(next_id()) {
-}
+    , fUniqueID(next_id())
+    , fAddedToCache(false) {}
 
 SkTextBlob::~SkTextBlob() {
+#if SK_SUPPORT_GPU
+    if (fAddedToCache.load()) {
+        GrTextBlobCache::PostPurgeBlobMessage(fUniqueID);
+    }
+#endif
+
     const auto* run = RunRecord::First(this);
     do {
         const auto* nextRun = RunRecord::Next(run);

src/gpu/text/GrTextBlobCache.cpp

@@ -7,6 +7,8 @@
 
 #include "GrTextBlobCache.h"
 
+DECLARE_SKMESSAGEBUS_MESSAGE(GrTextBlobCache::PurgeBlobMessage)
+
 GrTextBlobCache::~GrTextBlobCache() {
     SkDEBUGCODE(this->freeAll();)
 }
@@ -24,3 +26,8 @@ void GrTextBlobCache::freeAll() {
     SkASSERT(fPool.isEmpty());
     SkASSERT(fBlobList.isEmpty());
 }
+
+void GrTextBlobCache::PostPurgeBlobMessage(uint32_t id) {
+    SkASSERT(id != SK_InvalidGenID);
+    SkMessageBus<PurgeBlobMessage>::Post(PurgeBlobMessage({id}));
+}

src/gpu/text/GrTextBlobCache.h

@@ -9,6 +9,7 @@
 #define GrTextBlobCache_DEFINED
 
 #include "GrAtlasTextContext.h"
+#include "SkMessageBus.h"
 #include "SkRefCnt.h"
 #include "SkTArray.h"
 #include "SkTextBlobRunIterator.h"
@@ -50,6 +51,7 @@ public:
         sk_sp<GrAtlasTextBlob> cacheBlob(this->makeBlob(blob));
         cacheBlob->setupKey(key, blurRec, paint);
         this->add(cacheBlob);
+        blob->notifyAddedToCache();
         return cacheBlob;
     }
 
@@ -94,6 +96,12 @@ public:
         this->checkPurge();
     }
 
+    struct PurgeBlobMessage {
+        uint32_t fID;
+    };
+
+    static void PostPurgeBlobMessage(uint32_t);
+
 private:
     using BitmapBlobList = SkTInternalLList<GrAtlasTextBlob>;
 
@@ -159,7 +167,30 @@ private:
     }
 
     void checkPurge(GrAtlasTextBlob* blob = nullptr) {
-        // If we are overbudget, then unref until we are below budget again
+        // First, purge all stale blob IDs.
+        {
+            // TODO: tweak poll to allow mem-movable arrays, and update.
+            SkSTArray<128, PurgeBlobMessage, false> msgs;
+            fPurgeBlobInbox.poll(&msgs);
+
+            for (const auto& msg : msgs) {
+                auto* idEntry = fBlobIDCache.find(msg.fID);
+                if (!idEntry) {
+                    // no cache entries for id
+                    continue;
+                }
+
+                // remove all blob entries from the LRU list
+                for (const auto& blob : idEntry->fBlobs) {
+                    fBlobList.remove(blob.get());
+                }
+
+                // drop the idEntry itself (unrefs all blobs)
+                fBlobIDCache.remove(msg.fID);
+            }
+        }
+
+        // If we are still overbudget, then unref until we are below budget again
         if (fPool.size() > fBudget) {
             BitmapBlobList::Iter iter;
             iter.init(fBlobList, BitmapBlobList::Iter::kTail_IterStart);
@@ -197,6 +228,7 @@ private:
     PFOverBudgetCB fCallback;
     void* fData;
     size_t fBudget;
+    SkMessageBus<PurgeBlobMessage>::Inbox fPurgeBlobInbox;
 };
 
 #endif