Update Layer Hoisting to store its atlas texture in the resource cache

src/gpu/GrLayerCache.cpp

Index: src/gpu/GrLayerCache.cpp
diff --git a/src/gpu/GrLayerCache.cpp b/src/gpu/GrLayerCache.cpp
index 9af89a34665664e42499623bab05e46cc60cd156..105ee04e53cd1a26f6ab78238211229bc3916225 100644
--- a/src/gpu/GrLayerCache.cpp
+++ b/src/gpu/GrLayerCache.cpp
@@ -27,9 +27,11 @@ void GrCachedLayer::validate(const GrTexture* backingTexture) const {
         SkASSERT(fRect.isEmpty());
         SkASSERT(nullptr == fPlot);
         SkASSERT(!fLocked);     // layers without a texture cannot be locked
+        SkASSERT(!fAtlased);    // can't be atlased if it doesn't have a texture
     }
 
     if (fPlot) {
+        SkASSERT(fAtlased);
         // If a layer has a plot (i.e., is atlased) then it must point to
         // the backing texture. Additionally, its rect should be non-empty.
         SkASSERT(fTexture && backingTexture == fTexture);
@@ -119,8 +121,10 @@ void GrLayerCache::freeAll() {
     }
     fLayerHash.rewind();
 
-    // The atlas only lets go of its texture when the atlas is deleted.
-    fAtlas.free();
+    if (fAtlas) {
+        fAtlas->resetPlots();
+        fAtlas->detachBackingTexture();
+    }
 }
 
 GrCachedLayer* GrLayerCache::createLayer(uint32_t pictureID,
@@ -167,7 +171,7 @@ GrCachedLayer* GrLayerCache::findLayerOrCreate(uint32_t pictureID,
 bool GrLayerCache::tryToAtlas(GrCachedLayer* layer,
                               const GrSurfaceDesc& desc,
                               bool* needsRendering) {
-    SkDEBUGCODE(GrAutoValidateLayer avl(fAtlas ? fAtlas->getTexture() : nullptr, layer);)
+    SkDEBUGCODE(GrAutoValidateLayer avl(fAtlas ? fAtlas->getTextureOrNull() : nullptr, layer);)
 
     SkASSERT(PlausiblyAtlasable(desc.fWidth, desc.fHeight));
     SkASSERT(0 == desc.fSampleCnt);
@@ -217,7 +221,7 @@ bool GrLayerCache::tryToAtlas(GrCachedLayer* layer,
                 // The layer was successfully added to the atlas
                 const SkIRect bounds = SkIRect::MakeXYWH(loc.fX, loc.fY,
                                                          desc.fWidth, desc.fHeight);
-                layer->setTexture(fAtlas->getTexture(), bounds);
+                layer->setTexture(fAtlas->getTexture(), bounds, true);
                 layer->setPlot(plot);
                 layer->setLocked(true);
                 this->incPlotLock(layer->plot()->id());
@@ -227,7 +231,7 @@ bool GrLayerCache::tryToAtlas(GrCachedLayer* layer,
 
             // The layer was rejected by the atlas (even though we know it is
             // plausibly atlas-able). See if a plot can be purged and try again.
-            if (!this->purgePlot()) {
+            if (!this->purgePlots(true)) {
                 break;  // We weren't able to purge any plots
             }
         }
@@ -260,14 +264,14 @@ bool GrLayerCache::lock(GrCachedLayer* layer, const GrSurfaceDesc& desc, bool* n
         return false;
     }
 
-    layer->setTexture(tex, SkIRect::MakeWH(desc.fWidth, desc.fHeight));
+    layer->setTexture(tex, SkIRect::MakeWH(desc.fWidth, desc.fHeight), false);
     layer->setLocked(true);
     *needsRendering = true;
     return true;
 }
 
 void GrLayerCache::unlock(GrCachedLayer* layer) {
-    SkDEBUGCODE(GrAutoValidateLayer avl(fAtlas ? fAtlas->getTexture() : nullptr, layer);)
+    SkDEBUGCODE(GrAutoValidateLayer avl(fAtlas ? fAtlas->getTextureOrNull() : nullptr, layer);)
 
     if (nullptr == layer || !layer->locked()) {
         // invalid or not locked
@@ -299,11 +303,11 @@ void GrLayerCache::unlock(GrCachedLayer* layer) {
         }
 
         layer->setPlot(nullptr);
-        layer->setTexture(nullptr, SkIRect::MakeEmpty());
+        layer->setTexture(nullptr, SkIRect::MakeEmpty(), false);
 #endif
 
     } else {
-        layer->setTexture(nullptr, SkIRect::MakeEmpty());
+        layer->setTexture(nullptr, SkIRect::MakeEmpty(), false);
     }
 
     layer->setLocked(false);
@@ -318,7 +322,7 @@ void GrLayerCache::validate() const {
     for (; !iter.done(); ++iter) {
         const GrCachedLayer* layer = &(*iter);
 
-        layer->validate(fAtlas.get() ? fAtlas->getTexture() : nullptr);
+        layer->validate(fAtlas.get() ? fAtlas->getTextureOrNull() : nullptr);
 
         const GrPictureInfo* pictInfo = fPictureHash.find(layer->pictureID());
         if (!pictInfo) {
@@ -389,10 +393,11 @@ void GrLayerCache::purge(uint32_t pictureID) {
     }
 }
 
-bool GrLayerCache::purgePlot() {
+bool GrLayerCache::purgePlots(bool justOne) {
     SkDEBUGCODE(GrAutoValidateCache avc(this);)
     SkASSERT(fAtlas);
 
+    bool anyPurged = false;
     GrLayerAtlas::PlotIter iter;
     GrLayerAtlas::Plot* plot;
     for (plot = fAtlas->iterInit(&iter, GrLayerAtlas::kLRUFirst_IterOrder);
@@ -402,11 +407,14 @@ bool GrLayerCache::purgePlot() {
             continue;
         }
 
+        anyPurged = true;
         this->purgePlot(plot);
-        return true;
+        if (justOne) {
+            break;
+        }
     }
 
-    return false;
+    return anyPurged;
 }
 
 void GrLayerCache::purgePlot(GrLayerAtlas::Plot* plot) {
@@ -455,27 +463,57 @@ void GrLayerCache::purgeAll() {
         return;
     }
 
-    GrLayerAtlas::PlotIter iter;
-    GrLayerAtlas::Plot* plot;
-    for (plot = fAtlas->iterInit(&iter, GrLayerAtlas::kLRUFirst_IterOrder);
-         plot;
-         plot = iter.prev()) {
-        SkASSERT(0 == fPlotLocks[plot->id()]);
-
-        this->purgePlot(plot);
-    }
+    this->purgePlots(false); // clear them all out
 
     SkASSERT(0 == fPictureHash.count());
 
-    SkAutoTUnref<GrDrawContext> drawContext(
-                                fContext->drawContext(fAtlas->getTexture()->asRenderTarget()));
+    if (fAtlas->getTextureOrNull()) {
+        SkAutoTUnref<GrDrawContext> drawContext(
+                                    fContext->drawContext(fAtlas->getTexture()->asRenderTarget()));
 
-    if (drawContext) {
-        drawContext->discard();
+        if (drawContext) {
+            drawContext->discard();
+        }
     }
 }
 #endif
 
+void GrLayerCache::begin() {
+    if (!fAtlas) {
+        return;
+    }
+
+    if (!fAtlas->reattachBackingTexture()) {
+        // We weren't able to re-attach. Clear out all the atlased layers.
+        this->purgePlots(false);
+        SkASSERT(0 == fPictureHash.count());
+    }
+#ifdef SK_DEBUG
+    else {
+        // we've reattached - everything had better make sense
+        SkTDynamicHash<GrCachedLayer, GrCachedLayer::Key>::Iter iter(&fLayerHash);
+        for (; !iter.done(); ++iter) {
+            GrCachedLayer* layer = &(*iter);
+
+            if (layer->isAtlased()) {
+                SkASSERT(fAtlas->getTexture() == layer->texture());
+            }
+        }
+    }
+#endif
+}
+
+void GrLayerCache::end() {
+    if (!fAtlas) {
+        return;
+    }
+
+    // Adding this call will clear out all the layers in the atlas
+    //this->purgePlots(false);
+
+    fAtlas->detachBackingTexture();
+}
+
 void GrLayerCache::processDeletedPictures() {
     SkTArray<SkPicture::DeletionMessage> deletedPictures;
     fPictDeletionInbox.poll(&deletedPictures);
@@ -489,7 +527,7 @@ void GrLayerCache::processDeletedPictures() {
 void GrLayerCache::writeLayersToDisk(const SkString& dirName) {
 
     if (fAtlas) {
-        GrTexture* atlasTexture = fAtlas->getTexture();
+        GrTexture* atlasTexture = fAtlas->getTextureOrNull();
         if (nullptr != atlasTexture) {
             SkString fileName(dirName);
             fileName.append("\\atlas.png");