Add ExternalTexture class into RenderEngine interface

ExternalTexture is an RAII structure that wraps raw GraphicBuffers that
are passed into RenderEngine. ExternalTexture's role is to help with
managing GPU resources of GraphicBuffers by mapping buffers into
textures, EGLImages, or AutoBackendTextures depending on the
RenderEngine backend. Under the hood, mapExternalTextureBuffer and
unmapExternalTextureBuffer (renamed from cacheExternalTextureBuffer and
unbindExternalTextureBuffer respectively) are used to help tie
resource management to the ExternalTexture lifetime.

The main motivation for this is that currently managing buffer
lifecycle has historically been errorprone and caused memory leaks, so
this improves code health.

As part of this:
* mapExternalTextureBuffer and unmapExternalTextureBuffer
are now protected methods, and are never called outside of RenderEngine
with the exception of creating and destroying ExternalTextures.
* Because GLESRenderEngine's output buffers are cached differently from
Skia RenderEngine, if there are output-only buffers then disable the
mapExternalTextureBuffer calls whenever GLESRenderEngine is used.
* Custom RAII classes in the Planner and in BufferLayerConsumer are now
removed since they're subsumed by ExternalTexture
* RenderSurface now controls its own management of ExternalTextures in a
small queue
* cleanFramebufferCache is now unimplemented for Skia, because
ExternalTextures are now deleted whenever a RenderSurface is deleted.

Bug: 180767535
Test: libsurfaceflinger_unittest
Test: libcompositionengine_test
Test: librenderengine_test
Test: Simulate virtual displays
Test: Screen reotation
Test: Movie playback on Google TV
Test: Force GPU composition
Test: screenshot

Change-Id: I222c71e6e1c67485cdeac49e2cb829289af9efec
diff --git a/libs/renderengine/Android.bp b/libs/renderengine/Android.bp
index ec39137..f395ab4 100644
--- a/libs/renderengine/Android.bp
+++ b/libs/renderengine/Android.bp
@@ -48,6 +48,7 @@
     name: "librenderengine_sources",
     srcs: [
         "Description.cpp",
+        "ExternalTexture.cpp",
         "Mesh.cpp",
         "RenderEngine.cpp",
         "Texture.cpp",
diff --git a/libs/renderengine/ExternalTexture.cpp b/libs/renderengine/ExternalTexture.cpp
new file mode 100644
index 0000000..eabff58
--- /dev/null
+++ b/libs/renderengine/ExternalTexture.cpp
@@ -0,0 +1,43 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <renderengine/ExternalTexture.h>
+#include <renderengine/RenderEngine.h>
+#include <ui/GraphicBuffer.h>
+
+#include "log/log_main.h"
+
+namespace android::renderengine {
+
+ExternalTexture::ExternalTexture(const sp<GraphicBuffer>& buffer, RenderEngine& renderEngine,
+                                 uint32_t usage)
+      : mBuffer(buffer), mRenderEngine(renderEngine) {
+    LOG_ALWAYS_FATAL_IF(buffer == nullptr,
+                        "Attempted to bind a null buffer to an external texture!");
+    // GLESRenderEngine has a separate texture cache for output buffers,
+    if (usage == Usage::WRITEABLE &&
+        (mRenderEngine.getRenderEngineType() == RenderEngine::RenderEngineType::GLES ||
+         mRenderEngine.getRenderEngineType() == RenderEngine::RenderEngineType::THREADED)) {
+        return;
+    }
+    mRenderEngine.mapExternalTextureBuffer(mBuffer, usage & Usage::WRITEABLE);
+}
+
+ExternalTexture::~ExternalTexture() {
+    mRenderEngine.unmapExternalTextureBuffer(mBuffer);
+}
+
+} // namespace android::renderengine
diff --git a/libs/renderengine/gl/GLESRenderEngine.cpp b/libs/renderengine/gl/GLESRenderEngine.cpp
index a2963a7..d87315f 100644
--- a/libs/renderengine/gl/GLESRenderEngine.cpp
+++ b/libs/renderengine/gl/GLESRenderEngine.cpp
@@ -746,7 +746,8 @@
     return;
 }
 
-void GLESRenderEngine::cacheExternalTextureBuffer(const sp<GraphicBuffer>& buffer) {
+void GLESRenderEngine::mapExternalTextureBuffer(const sp<GraphicBuffer>& buffer,
+                                                bool /*isRenderable*/) {
     ATRACE_CALL();
     mImageManager->cacheAsync(buffer, nullptr);
 }
@@ -797,8 +798,8 @@
     return NO_ERROR;
 }
 
-void GLESRenderEngine::unbindExternalTextureBuffer(uint64_t bufferId) {
-    mImageManager->releaseAsync(bufferId, nullptr);
+void GLESRenderEngine::unmapExternalTextureBuffer(const sp<GraphicBuffer>& buffer) {
+    mImageManager->releaseAsync(buffer->getId(), nullptr);
 }
 
 std::shared_ptr<ImageManager::Barrier> GLESRenderEngine::unbindExternalTextureBufferForTesting(
@@ -1102,7 +1103,7 @@
 
 status_t GLESRenderEngine::drawLayers(const DisplaySettings& display,
                                       const std::vector<const LayerSettings*>& layers,
-                                      const sp<GraphicBuffer>& buffer,
+                                      const std::shared_ptr<ExternalTexture>& buffer,
                                       const bool useFramebufferCache, base::unique_fd&& bufferFence,
                                       base::unique_fd* drawFence) {
     ATRACE_CALL();
@@ -1125,7 +1126,7 @@
         return BAD_VALUE;
     }
 
-    validateOutputBufferUsage(buffer);
+    validateOutputBufferUsage(buffer->getBuffer());
 
     std::unique_ptr<BindNativeBufferAsFramebuffer> fbo;
     // Gathering layers that requested blur, we'll need them to decide when to render to an
@@ -1142,11 +1143,13 @@
 
     if (blurLayersSize == 0) {
         fbo = std::make_unique<BindNativeBufferAsFramebuffer>(*this,
-                                                              buffer.get()->getNativeBuffer(),
+                                                              buffer->getBuffer()
+                                                                      .get()
+                                                                      ->getNativeBuffer(),
                                                               useFramebufferCache);
         if (fbo->getStatus() != NO_ERROR) {
             ALOGE("Failed to bind framebuffer! Aborting GPU composition for buffer (%p).",
-                  buffer->handle);
+                  buffer->getBuffer()->handle);
             checkErrors();
             return fbo->getStatus();
         }
@@ -1157,7 +1160,7 @@
                 mBlurFilter->setAsDrawTarget(display, blurLayers.front()->backgroundBlurRadius);
         if (status != NO_ERROR) {
             ALOGE("Failed to prepare blur filter! Aborting GPU composition for buffer (%p).",
-                  buffer->handle);
+                  buffer->getBuffer()->handle);
             checkErrors();
             return status;
         }
@@ -1194,7 +1197,7 @@
             auto status = mBlurFilter->prepare();
             if (status != NO_ERROR) {
                 ALOGE("Failed to render blur effect! Aborting GPU composition for buffer (%p).",
-                      buffer->handle);
+                      buffer->getBuffer()->handle);
                 checkErrors("Can't render first blur pass");
                 return status;
             }
@@ -1203,6 +1206,7 @@
                 // Done blurring, time to bind the native FBO and render our blur onto it.
                 fbo = std::make_unique<BindNativeBufferAsFramebuffer>(*this,
                                                                       buffer.get()
+                                                                              ->getBuffer()
                                                                               ->getNativeBuffer(),
                                                                       useFramebufferCache);
                 status = fbo->getStatus();
@@ -1215,7 +1219,7 @@
             }
             if (status != NO_ERROR) {
                 ALOGE("Failed to bind framebuffer! Aborting GPU composition for buffer (%p).",
-                      buffer->handle);
+                      buffer->getBuffer()->handle);
                 checkErrors("Can't bind native framebuffer");
                 return status;
             }
@@ -1223,7 +1227,7 @@
             status = mBlurFilter->render(blurLayersSize > 1);
             if (status != NO_ERROR) {
                 ALOGE("Failed to render blur effect! Aborting GPU composition for buffer (%p).",
-                      buffer->handle);
+                      buffer->getBuffer()->handle);
                 checkErrors("Can't render blur filter");
                 return status;
             }
@@ -1250,7 +1254,7 @@
             disableTexture = false;
             isOpaque = layer->source.buffer.isOpaque;
 
-            sp<GraphicBuffer> gBuf = layer->source.buffer.buffer;
+            sp<GraphicBuffer> gBuf = layer->source.buffer.buffer->getBuffer();
             validateInputBufferUsage(gBuf);
             bindExternalTextureBuffer(layer->source.buffer.textureName, gBuf,
                                       layer->source.buffer.fence);
@@ -1274,7 +1278,7 @@
 
             // Do not cache protected EGLImage, protected memory is limited.
             if (gBuf->getUsage() & GRALLOC_USAGE_PROTECTED) {
-                unbindExternalTextureBuffer(gBuf->getId());
+                unmapExternalTextureBuffer(gBuf);
             }
         }
 
diff --git a/libs/renderengine/gl/GLESRenderEngine.h b/libs/renderengine/gl/GLESRenderEngine.h
index cd7a86b..e7ed9c0 100644
--- a/libs/renderengine/gl/GLESRenderEngine.h
+++ b/libs/renderengine/gl/GLESRenderEngine.h
@@ -60,16 +60,14 @@
     void primeCache() override;
     void genTextures(size_t count, uint32_t* names) override;
     void deleteTextures(size_t count, uint32_t const* names) override;
-    void cacheExternalTextureBuffer(const sp<GraphicBuffer>& buffer) EXCLUDES(mRenderingMutex);
-    void unbindExternalTextureBuffer(uint64_t bufferId) EXCLUDES(mRenderingMutex);
-
     bool isProtected() const override { return mInProtectedContext; }
     bool supportsProtectedContent() const override;
     bool useProtectedContext(bool useProtectedContext) override;
     status_t drawLayers(const DisplaySettings& display,
                         const std::vector<const LayerSettings*>& layers,
-                        const sp<GraphicBuffer>& buffer, const bool useFramebufferCache,
-                        base::unique_fd&& bufferFence, base::unique_fd* drawFence) override;
+                        const std::shared_ptr<ExternalTexture>& buffer,
+                        const bool useFramebufferCache, base::unique_fd&& bufferFence,
+                        base::unique_fd* drawFence) override;
     bool cleanupPostRender(CleanupMode mode) override;
     int getContextPriority() override;
     bool supportsBackgroundBlur() override { return mBlurFilter != nullptr; }
@@ -105,6 +103,9 @@
             EXCLUDES(mFramebufferImageCacheMutex);
     size_t getMaxTextureSize() const override;
     size_t getMaxViewportDims() const override;
+    void mapExternalTextureBuffer(const sp<GraphicBuffer>& buffer, bool isRenderable)
+            EXCLUDES(mRenderingMutex);
+    void unmapExternalTextureBuffer(const sp<GraphicBuffer>& buffer) EXCLUDES(mRenderingMutex);
 
 private:
     friend class BindNativeBufferAsFramebuffer;
diff --git a/libs/renderengine/include/renderengine/ExternalTexture.h b/libs/renderengine/include/renderengine/ExternalTexture.h
new file mode 100644
index 0000000..07f0833
--- /dev/null
+++ b/libs/renderengine/include/renderengine/ExternalTexture.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <android-base/macros.h>
+#include <ui/GraphicBuffer.h>
+
+namespace android::renderengine {
+
+class RenderEngine;
+
+/**
+ * Manages GPU image resources on behalf of clients using RenderEngine.
+ *
+ * Clients of RenderEngine are required to wrap their GraphicBuffer objects as an ExternalTexture,
+ * which is then mapped into GPU resources required by RenderEngine. When a client no longer needs
+ * to use the GraphicBuffer as input into RenderEngine::drawLayers, then the client should delete
+ * their ExternalTexture so that resources may be freed.
+ */
+class ExternalTexture {
+public:
+    // Usage specifies the rendering intent for the buffer.
+    enum Usage : uint32_t {
+        // When a buffer is not READABLE but is WRITEABLE, then GLESRenderEngine will use that as a
+        // hint to load the buffer into a separate cache
+        READABLE = 1 << 0,
+
+        // The buffer needs to be mapped as a 2D texture if set, otherwise must be mapped as an
+        // external texture
+        WRITEABLE = 1 << 1,
+    };
+    // Creates an ExternalTexture for the provided buffer and RenderEngine instance, with the given
+    // usage hint of type Usage.
+    ExternalTexture(const sp<GraphicBuffer>& buffer, RenderEngine& renderEngine, uint32_t usage);
+
+    ~ExternalTexture();
+
+    // Retrieves the buffer that is bound to this texture.
+    const sp<GraphicBuffer>& getBuffer() const { return mBuffer; }
+
+private:
+    sp<GraphicBuffer> mBuffer;
+    RenderEngine& mRenderEngine;
+    DISALLOW_COPY_AND_ASSIGN(ExternalTexture);
+};
+
+} // namespace android::renderengine
diff --git a/libs/renderengine/include/renderengine/LayerSettings.h b/libs/renderengine/include/renderengine/LayerSettings.h
index 7661233..c54c5ba 100644
--- a/libs/renderengine/include/renderengine/LayerSettings.h
+++ b/libs/renderengine/include/renderengine/LayerSettings.h
@@ -16,11 +16,9 @@
 
 #pragma once
 
-#include <iosfwd>
-
 #include <math/mat4.h>
 #include <math/vec3.h>
-#include <renderengine/Texture.h>
+#include <renderengine/ExternalTexture.h>
 #include <ui/BlurRegion.h>
 #include <ui/Fence.h>
 #include <ui/FloatRect.h>
@@ -31,6 +29,8 @@
 #include <ui/StretchEffect.h>
 #include <ui/Transform.h>
 
+#include <iosfwd>
+
 namespace android {
 namespace renderengine {
 
@@ -39,7 +39,7 @@
     // Buffer containing the image that we will render.
     // If buffer == nullptr, then the rest of the fields in this struct will be
     // ignored.
-    sp<GraphicBuffer> buffer = nullptr;
+    std::shared_ptr<ExternalTexture> buffer = nullptr;
 
     // Fence that will fire when the buffer is ready to be bound.
     sp<Fence> fence = nullptr;
diff --git a/libs/renderengine/include/renderengine/RenderEngine.h b/libs/renderengine/include/renderengine/RenderEngine.h
index 8dd98c3..c8a0f0a 100644
--- a/libs/renderengine/include/renderengine/RenderEngine.h
+++ b/libs/renderengine/include/renderengine/RenderEngine.h
@@ -17,19 +17,20 @@
 #ifndef SF_RENDERENGINE_H_
 #define SF_RENDERENGINE_H_
 
-#include <stdint.h>
-#include <sys/types.h>
-#include <memory>
-
 #include <android-base/unique_fd.h>
 #include <math/mat4.h>
 #include <renderengine/DisplaySettings.h>
+#include <renderengine/ExternalTexture.h>
 #include <renderengine/Framebuffer.h>
 #include <renderengine/Image.h>
 #include <renderengine/LayerSettings.h>
+#include <stdint.h>
+#include <sys/types.h>
 #include <ui/GraphicTypes.h>
 #include <ui/Transform.h>
 
+#include <memory>
+
 /**
  * Allows to set RenderEngine backend to GLES (default) or SkiaGL (NOT yet supported).
  */
@@ -51,6 +52,7 @@
 
 namespace renderengine {
 
+class ExternalTexture;
 class Image;
 class Mesh;
 class Texture;
@@ -104,23 +106,6 @@
 
     virtual void genTextures(size_t count, uint32_t* names) = 0;
     virtual void deleteTextures(size_t count, uint32_t const* names) = 0;
-    // Caches Image resources for this buffer, but does not bind the buffer to
-    // a particular texture.
-    // Note that work is deferred to an additional thread, i.e. this call
-    // is made asynchronously, but the caller can expect that cache/unbind calls
-    // are performed in a manner that's conflict serializable, i.e. unbinding
-    // a buffer should never occur before binding the buffer if the caller
-    // called {bind, cache}ExternalTextureBuffer before calling unbind.
-    virtual void cacheExternalTextureBuffer(const sp<GraphicBuffer>& buffer) = 0;
-    // Removes internal resources referenced by the bufferId. This method should be
-    // invoked when the caller will no longer hold a reference to a GraphicBuffer
-    // and needs to clean up its resources.
-    // Note that work is deferred to an additional thread, i.e. this call
-    // is made asynchronously, but the caller can expect that cache/unbind calls
-    // are performed in a manner that's conflict serializable, i.e. unbinding
-    // a buffer should never occur before binding the buffer if the caller
-    // called {bind, cache}ExternalTextureBuffer before calling unbind.
-    virtual void unbindExternalTextureBuffer(uint64_t bufferId) = 0;
 
     enum class CleanupMode {
         CLEAN_OUTPUT_RESOURCES,
@@ -191,8 +176,9 @@
     // now, this always returns NO_ERROR.
     virtual status_t drawLayers(const DisplaySettings& display,
                                 const std::vector<const LayerSettings*>& layers,
-                                const sp<GraphicBuffer>& buffer, const bool useFramebufferCache,
-                                base::unique_fd&& bufferFence, base::unique_fd* drawFence) = 0;
+                                const std::shared_ptr<ExternalTexture>& buffer,
+                                const bool useFramebufferCache, base::unique_fd&& bufferFence,
+                                base::unique_fd* drawFence) = 0;
     virtual void cleanFramebufferCache() = 0;
     // Returns the priority this context was actually created with. Note: this may not be
     // the same as specified at context creation time, due to implementation limits on the
@@ -213,6 +199,31 @@
     static void validateOutputBufferUsage(const sp<GraphicBuffer>&);
 
 protected:
+    // Maps GPU resources for this buffer.
+    // Note that work may be deferred to an additional thread, i.e. this call
+    // is made asynchronously, but the caller can expect that map/unmap calls
+    // are performed in a manner that's conflict serializable, i.e. unmapping
+    // a buffer should never occur before binding the buffer if the caller
+    // called mapExternalTextureBuffer before calling unmap.
+    // Note also that if the buffer contains protected content, then mapping those GPU resources may
+    // be deferred until the buffer is really used for drawing. This is because typical SoCs that
+    // support protected memory only support a limited amount, so optimisitically mapping protected
+    // memory may be too burdensome. If a buffer contains protected content and the RenderEngine
+    // implementation supports protected context, then GPU resources may be mapped into both the
+    // protected and unprotected contexts.
+    // If the buffer may ever be written to by RenderEngine, then isRenderable must be true.
+    virtual void mapExternalTextureBuffer(const sp<GraphicBuffer>& buffer, bool isRenderable) = 0;
+    // Unmaps GPU resources used by this buffer. This method should be
+    // invoked when the caller will no longer hold a reference to a GraphicBuffer
+    // and needs to clean up its resources.
+    // Note that if there are multiple callers holding onto the same buffer, then the buffer's
+    // resources may be internally ref-counted to guard against use-after-free errors. Note that
+    // work may be deferred to an additional thread, i.e. this call is expected to be made
+    // asynchronously, but the caller can expect that map/unmap calls are performed in a manner
+    // that's conflict serializable, i.e. unmap a buffer should never occur before binding the
+    // buffer if the caller called mapExternalTextureBuffer before calling unmap.
+    virtual void unmapExternalTextureBuffer(const sp<GraphicBuffer>& buffer) = 0;
+    friend class ExternalTexture;
     friend class threaded::RenderEngineThreaded;
     const RenderEngineType mRenderEngineType;
 };
diff --git a/libs/renderengine/include/renderengine/mock/RenderEngine.h b/libs/renderengine/include/renderengine/mock/RenderEngine.h
index 228553d..27dbd1e 100644
--- a/libs/renderengine/include/renderengine/mock/RenderEngine.h
+++ b/libs/renderengine/include/renderengine/mock/RenderEngine.h
@@ -39,8 +39,6 @@
     MOCK_METHOD1(dump, void(std::string&));
     MOCK_METHOD2(genTextures, void(size_t, uint32_t*));
     MOCK_METHOD2(deleteTextures, void(size_t, uint32_t const*));
-    MOCK_METHOD1(cacheExternalTextureBuffer, void(const sp<GraphicBuffer>&));
-    MOCK_METHOD1(unbindExternalTextureBuffer, void(uint64_t));
     MOCK_METHOD1(drawMesh, void(const renderengine::Mesh&));
     MOCK_CONST_METHOD0(getMaxTextureSize, size_t());
     MOCK_CONST_METHOD0(getMaxViewportDims, size_t());
@@ -50,12 +48,17 @@
     MOCK_METHOD1(cleanupPostRender, bool(CleanupMode mode));
     MOCK_METHOD6(drawLayers,
                  status_t(const DisplaySettings&, const std::vector<const LayerSettings*>&,
-                          const sp<GraphicBuffer>&, const bool, base::unique_fd&&,
+                          const std::shared_ptr<ExternalTexture>&, const bool, base::unique_fd&&,
                           base::unique_fd*));
     MOCK_METHOD0(cleanFramebufferCache, void());
     MOCK_METHOD0(getContextPriority, int());
     MOCK_METHOD0(supportsBackgroundBlur, bool());
     MOCK_METHOD1(onPrimaryDisplaySizeChanged, void(ui::Size));
+
+protected:
+    // mock renderengine still needs to implement these, but callers should never need to call them.
+    void mapExternalTextureBuffer(const sp<GraphicBuffer>&, bool) {}
+    void unmapExternalTextureBuffer(const sp<GraphicBuffer>&) {}
 };
 
 } // namespace mock
diff --git a/libs/renderengine/skia/AutoBackendTexture.h b/libs/renderengine/skia/AutoBackendTexture.h
index bb75878..2d61cf8 100644
--- a/libs/renderengine/skia/AutoBackendTexture.h
+++ b/libs/renderengine/skia/AutoBackendTexture.h
@@ -21,9 +21,9 @@
 #include <SkImage.h>
 #include <SkSurface.h>
 #include <sys/types.h>
+#include <ui/GraphicTypes.h>
 
 #include "android-base/macros.h"
-#include "ui/GraphicTypes.h"
 
 namespace android {
 namespace renderengine {
@@ -41,13 +41,18 @@
     // of shared ownership with Skia objects, so we wrap it here instead.
     class LocalRef {
     public:
-        LocalRef() {}
+        LocalRef(AutoBackendTexture* texture) { setTexture(texture); }
 
         ~LocalRef() {
             // Destroying the texture is the same as setting it to null
             setTexture(nullptr);
         }
 
+        AutoBackendTexture* getTexture() const { return mTexture; }
+
+        DISALLOW_COPY_AND_ASSIGN(LocalRef);
+
+    private:
         // Sets the texture to locally ref-track.
         void setTexture(AutoBackendTexture* texture) {
             if (mTexture != nullptr) {
@@ -59,12 +64,6 @@
                 mTexture->ref();
             }
         }
-
-        AutoBackendTexture* getTexture() const { return mTexture; }
-
-        DISALLOW_COPY_AND_ASSIGN(LocalRef);
-
-    private:
         AutoBackendTexture* mTexture = nullptr;
     };
 
diff --git a/libs/renderengine/skia/Cache.cpp b/libs/renderengine/skia/Cache.cpp
index 1db20c0..1c2b2fc 100644
--- a/libs/renderengine/skia/Cache.cpp
+++ b/libs/renderengine/skia/Cache.cpp
@@ -46,7 +46,7 @@
 } // namespace
 
 static void drawShadowLayers(SkiaRenderEngine* renderengine, const DisplaySettings& display,
-                             sp<GraphicBuffer> dstBuffer) {
+                             const std::shared_ptr<ExternalTexture>& dstTexture) {
     // Somewhat arbitrary dimensions, but on screen and slightly shorter, based
     // on actual use.
     FloatRect rect(0, 0, display.physicalDisplay.width(), display.physicalDisplay.height() - 30);
@@ -73,7 +73,7 @@
 
     auto layers = std::vector<const LayerSettings*>{&layer};
     // The identity matrix will generate the fast shader
-    renderengine->drawLayers(display, layers, dstBuffer, kUseFrameBufferCache, base::unique_fd(),
+    renderengine->drawLayers(display, layers, dstTexture, kUseFrameBufferCache, base::unique_fd(),
                              nullptr);
     // This matrix, which has different scales for x and y, will
     // generate the slower (more general case) version, which has variants for translucent
@@ -86,13 +86,14 @@
     // clang-format on
     for (auto translucent : {false, true}) {
         layer.shadow.casterIsTranslucent = translucent;
-        renderengine->drawLayers(display, layers, dstBuffer, kUseFrameBufferCache,
+        renderengine->drawLayers(display, layers, dstTexture, kUseFrameBufferCache,
                                  base::unique_fd(), nullptr);
     }
 }
 
 static void drawImageLayers(SkiaRenderEngine* renderengine, const DisplaySettings& display,
-                            sp<GraphicBuffer> dstBuffer, sp<GraphicBuffer> srcBuffer) {
+                            const std::shared_ptr<ExternalTexture>& dstTexture,
+                            const std::shared_ptr<ExternalTexture>& srcTexture) {
     const Rect& displayRect = display.physicalDisplay;
     FloatRect rect(0, 0, displayRect.width(), displayRect.height());
     LayerSettings layer{
@@ -103,7 +104,7 @@
                     },
             .source = PixelSource{.buffer =
                                           Buffer{
-                                                  .buffer = srcBuffer,
+                                                  .buffer = srcTexture,
                                                   .maxMasteringLuminance = 1000.f,
                                                   .maxContentLuminance = 1000.f,
                                           }},
@@ -126,7 +127,7 @@
                 layer.source.buffer.isOpaque = isOpaque;
                 for (auto alpha : {half(.23999f), half(1.0f)}) {
                     layer.alpha = alpha;
-                    renderengine->drawLayers(display, layers, dstBuffer, kUseFrameBufferCache,
+                    renderengine->drawLayers(display, layers, dstTexture, kUseFrameBufferCache,
                                              base::unique_fd(), nullptr);
                 }
             }
@@ -135,7 +136,7 @@
 }
 
 static void drawSolidLayers(SkiaRenderEngine* renderengine, const DisplaySettings& display,
-                            sp<GraphicBuffer> dstBuffer) {
+                            const std::shared_ptr<ExternalTexture>& dstTexture) {
     const Rect& displayRect = display.physicalDisplay;
     FloatRect rect(0, 0, displayRect.width(), displayRect.height());
     LayerSettings layer{
@@ -143,11 +144,11 @@
                     Geometry{
                             .boundaries = rect,
                     },
-            .alpha = 1,
             .source =
                     PixelSource{
                             .solidColor = half3(0.1f, 0.2f, 0.3f),
                     },
+            .alpha = 1,
     };
 
     auto layers = std::vector<const LayerSettings*>{&layer};
@@ -155,14 +156,14 @@
         layer.geometry.positionTransform = transform;
         for (float roundedCornersRadius : {0.0f, 0.05f, 50.f}) {
             layer.geometry.roundedCornersRadius = roundedCornersRadius;
-            renderengine->drawLayers(display, layers, dstBuffer, kUseFrameBufferCache,
+            renderengine->drawLayers(display, layers, dstTexture, kUseFrameBufferCache,
                                      base::unique_fd(), nullptr);
         }
     }
 }
 
 static void drawBlurLayers(SkiaRenderEngine* renderengine, const DisplaySettings& display,
-                           sp<GraphicBuffer> dstBuffer) {
+                           const std::shared_ptr<ExternalTexture>& dstTexture) {
     const Rect& displayRect = display.physicalDisplay;
     FloatRect rect(0, 0, displayRect.width(), displayRect.height());
     LayerSettings layer{
@@ -176,7 +177,7 @@
     auto layers = std::vector<const LayerSettings*>{&layer};
     for (int radius : {9, 60}) {
         layer.backgroundBlurRadius = radius;
-        renderengine->drawLayers(display, layers, dstBuffer, kUseFrameBufferCache,
+        renderengine->drawLayers(display, layers, dstTexture, kUseFrameBufferCache,
                                  base::unique_fd(), nullptr);
     }
 }
@@ -214,6 +215,9 @@
     sp<GraphicBuffer> dstBuffer =
             new GraphicBuffer(displayRect.width(), displayRect.height(), PIXEL_FORMAT_RGBA_8888, 1,
                               usage, "primeShaderCache_dst");
+
+    const auto dstTexture = std::make_shared<ExternalTexture>(dstBuffer, *renderengine,
+                                                              ExternalTexture::Usage::WRITEABLE);
     // This buffer will be the source for the call to drawImageLayers. Draw
     // something to it as a placeholder for what an app draws. We should draw
     // something, but the details are not important. Make use of the shadow layer drawing step
@@ -222,11 +226,16 @@
             new GraphicBuffer(displayRect.width(), displayRect.height(), PIXEL_FORMAT_RGBA_8888, 1,
                               usage, "drawImageLayer_src");
 
-    drawSolidLayers(renderengine, display, dstBuffer);
-    drawShadowLayers(renderengine, display, srcBuffer);
-    drawBlurLayers(renderengine, display, dstBuffer);
+    const auto srcTexture =
+            std::make_shared<ExternalTexture>(srcBuffer, *renderengine,
+                                              ExternalTexture::Usage::READABLE |
+                                                      ExternalTexture::Usage::WRITEABLE);
+
+    drawSolidLayers(renderengine, display, dstTexture);
+    drawShadowLayers(renderengine, display, srcTexture);
+    drawBlurLayers(renderengine, display, dstTexture);
     // The majority of shaders are related to sampling images.
-    drawImageLayers(renderengine, display, dstBuffer, srcBuffer);
+    drawImageLayers(renderengine, display, dstTexture, srcTexture);
 
     // should be the same as AHARDWAREBUFFER_USAGE_GPU_SAMPLED_IMAGE;
     const int64_t usageExternal = GRALLOC_USAGE_HW_TEXTURE;
@@ -234,12 +243,12 @@
     sp<GraphicBuffer> externalBuffer =
             new GraphicBuffer(displayRect.width(), displayRect.height(), PIXEL_FORMAT_RGBA_8888, 1,
                               usageExternal, "primeShaderCache_external");
+    const auto externalTexture =
+            std::make_shared<ExternalTexture>(externalBuffer, *renderengine,
+                                              ExternalTexture::Usage::READABLE);
     // TODO(b/184665179) doubles number of image shader compilations, but only somewhere
     // between 6 and 8 will occur in real uses.
-    drawImageLayers(renderengine, display, dstBuffer, externalBuffer);
-    renderengine->unbindExternalTextureBuffer(externalBuffer->getId());
-
-    renderengine->unbindExternalTextureBuffer(srcBuffer->getId());
+    drawImageLayers(renderengine, display, dstTexture, externalTexture);
 
     const nsecs_t timeAfter = systemTime();
     const float compileTimeMs = static_cast<float>(timeAfter - timeBefore) / 1.0E6;
diff --git a/libs/renderengine/skia/SkiaGLRenderEngine.cpp b/libs/renderengine/skia/SkiaGLRenderEngine.cpp
index 3b2c7e5..e781584 100644
--- a/libs/renderengine/skia/SkiaGLRenderEngine.cpp
+++ b/libs/renderengine/skia/SkiaGLRenderEngine.cpp
@@ -329,8 +329,6 @@
 }
 
 SkiaGLRenderEngine::~SkiaGLRenderEngine() {
-    cleanFramebufferCache();
-
     std::lock_guard<std::mutex> lock(mRenderingMutex);
     if (mBlurFilter) {
         delete mBlurFilter;
@@ -484,7 +482,8 @@
             sourceTransfer != destTransfer;
 }
 
-void SkiaGLRenderEngine::cacheExternalTextureBuffer(const sp<GraphicBuffer>& buffer) {
+void SkiaGLRenderEngine::mapExternalTextureBuffer(const sp<GraphicBuffer>& buffer,
+                                                  bool isRenderable) {
     // Only run this if RE is running on its own thread. This way the access to GL
     // operations is guaranteed to be happening on the same thread.
     if (mRenderEngineType != RenderEngineType::SKIA_GL_THREADED) {
@@ -505,25 +504,41 @@
     auto& cache = mInProtectedContext ? mProtectedTextureCache : mTextureCache;
 
     std::lock_guard<std::mutex> lock(mRenderingMutex);
-    auto iter = cache.find(buffer->getId());
-    if (iter != cache.end()) {
-        ALOGV("Texture already exists in cache.");
-    } else {
+    mGraphicBufferExternalRefs[buffer->getId()]++;
+
+    if (const auto& iter = cache.find(buffer->getId()); iter == cache.end()) {
         std::shared_ptr<AutoBackendTexture::LocalRef> imageTextureRef =
-                std::make_shared<AutoBackendTexture::LocalRef>();
-        imageTextureRef->setTexture(
-                new AutoBackendTexture(grContext.get(), buffer->toAHardwareBuffer(), false));
+                std::make_shared<AutoBackendTexture::LocalRef>(
+                        new AutoBackendTexture(grContext.get(), buffer->toAHardwareBuffer(),
+                                               isRenderable));
         cache.insert({buffer->getId(), imageTextureRef});
     }
     // restore the original state of the protected context if necessary
     useProtectedContext(protectedContextState);
 }
 
-void SkiaGLRenderEngine::unbindExternalTextureBuffer(uint64_t bufferId) {
+void SkiaGLRenderEngine::unmapExternalTextureBuffer(const sp<GraphicBuffer>& buffer) {
     ATRACE_CALL();
     std::lock_guard<std::mutex> lock(mRenderingMutex);
-    mTextureCache.erase(bufferId);
-    mProtectedTextureCache.erase(bufferId);
+    if (const auto& iter = mGraphicBufferExternalRefs.find(buffer->getId());
+        iter != mGraphicBufferExternalRefs.end()) {
+        if (iter->second == 0) {
+            ALOGW("Attempted to unmap GraphicBuffer <id: %" PRId64
+                  "> from RenderEngine texture, but the "
+                  "ref count was already zero!",
+                  buffer->getId());
+            mGraphicBufferExternalRefs.erase(buffer->getId());
+            return;
+        }
+
+        iter->second--;
+
+        if (iter->second == 0) {
+            mTextureCache.erase(buffer->getId());
+            mProtectedTextureCache.erase(buffer->getId());
+            mGraphicBufferExternalRefs.erase(buffer->getId());
+        }
+    }
 }
 
 sk_sp<SkShader> SkiaGLRenderEngine::createRuntimeEffectShader(sk_sp<SkShader> shader,
@@ -621,8 +636,8 @@
 
 status_t SkiaGLRenderEngine::drawLayers(const DisplaySettings& display,
                                         const std::vector<const LayerSettings*>& layers,
-                                        const sp<GraphicBuffer>& buffer,
-                                        const bool useFramebufferCache,
+                                        const std::shared_ptr<ExternalTexture>& buffer,
+                                        const bool /*useFramebufferCache*/,
                                         base::unique_fd&& bufferFence, base::unique_fd* drawFence) {
     ATRACE_NAME("SkiaGL::drawLayers");
 
@@ -645,32 +660,18 @@
         return BAD_VALUE;
     }
 
-    validateOutputBufferUsage(buffer);
+    validateOutputBufferUsage(buffer->getBuffer());
 
     auto grContext = mInProtectedContext ? mProtectedGrContext : mGrContext;
     auto& cache = mInProtectedContext ? mProtectedTextureCache : mTextureCache;
-    AHardwareBuffer_Desc bufferDesc;
-    AHardwareBuffer_describe(buffer->toAHardwareBuffer(), &bufferDesc);
 
-    std::shared_ptr<AutoBackendTexture::LocalRef> surfaceTextureRef = nullptr;
-    if (useFramebufferCache) {
-        auto iter = cache.find(buffer->getId());
-        if (iter != cache.end()) {
-            ALOGV("Cache hit!");
-            ATRACE_NAME("Cache hit");
-            surfaceTextureRef = iter->second;
-        }
-    }
-
-    if (surfaceTextureRef == nullptr || surfaceTextureRef->getTexture() == nullptr) {
-        ATRACE_NAME("Cache miss");
-        surfaceTextureRef = std::make_shared<AutoBackendTexture::LocalRef>();
-        surfaceTextureRef->setTexture(
-                new AutoBackendTexture(grContext.get(), buffer->toAHardwareBuffer(), true));
-        if (useFramebufferCache) {
-            ALOGD("Adding to cache");
-            cache.insert({buffer->getId(), surfaceTextureRef});
-        }
+    std::shared_ptr<AutoBackendTexture::LocalRef> surfaceTextureRef;
+    if (const auto& it = cache.find(buffer->getBuffer()->getId()); it != cache.end()) {
+        surfaceTextureRef = it->second;
+    } else {
+        surfaceTextureRef = std::make_shared<AutoBackendTexture::LocalRef>(
+                new AutoBackendTexture(grContext.get(), buffer->getBuffer()->toAHardwareBuffer(),
+                                       true));
     }
 
     const ui::Dataspace dstDataspace =
@@ -876,18 +877,22 @@
         SkPaint paint;
         if (layer->source.buffer.buffer) {
             ATRACE_NAME("DrawImage");
-            validateInputBufferUsage(layer->source.buffer.buffer);
+            validateInputBufferUsage(layer->source.buffer.buffer->getBuffer());
             const auto& item = layer->source.buffer;
             std::shared_ptr<AutoBackendTexture::LocalRef> imageTextureRef = nullptr;
-            auto iter = cache.find(item.buffer->getId());
-            if (iter != cache.end()) {
+
+            if (const auto& iter = cache.find(item.buffer->getBuffer()->getId());
+                iter != cache.end()) {
                 imageTextureRef = iter->second;
             } else {
-                imageTextureRef = std::make_shared<AutoBackendTexture::LocalRef>();
-                imageTextureRef->setTexture(new AutoBackendTexture(grContext.get(),
-                                                                   item.buffer->toAHardwareBuffer(),
-                                                                   false));
-                cache.insert({item.buffer->getId(), imageTextureRef});
+                // If we didn't find the image in the cache, then create a local ref but don't cache
+                // it. If we're using skia, we're guaranteed to run on a dedicated GPU thread so if
+                // we didn't find anything in the cache then we intentionally did not cache this
+                // buffer's resources.
+                imageTextureRef = std::make_shared<AutoBackendTexture::LocalRef>(
+                        new AutoBackendTexture(grContext.get(),
+                                               item.buffer->getBuffer()->toAHardwareBuffer(),
+                                               false));
             }
 
             sk_sp<SkImage> image =
@@ -1200,15 +1205,6 @@
     return eglCreatePbufferSurface(display, placeholderConfig, attributes.data());
 }
 
-void SkiaGLRenderEngine::cleanFramebufferCache() {
-    // TODO(b/180767535) Remove this method and use b/180767535 instead, which would allow
-    // SF to control texture lifecycle more tightly rather than through custom hooks into RE.
-    std::lock_guard<std::mutex> lock(mRenderingMutex);
-    mRuntimeEffects.clear();
-    mProtectedTextureCache.clear();
-    mTextureCache.clear();
-}
-
 int SkiaGLRenderEngine::getContextPriority() {
     int value;
     eglQueryContext(mEGLDisplay, mEGLContext, EGL_CONTEXT_PRIORITY_LEVEL_IMG, &value);
@@ -1281,6 +1277,12 @@
         StringAppendF(&result, "Skia's Wrapped Objects:\n");
         gpuReporter.logOutput(result, true);
 
+        StringAppendF(&result, "RenderEngine tracked buffers: %zu\n",
+                      mGraphicBufferExternalRefs.size());
+        StringAppendF(&result, "Dumping buffer ids...\n");
+        for (const auto& [id, refCounts] : mGraphicBufferExternalRefs) {
+            StringAppendF(&result, "- 0x%" PRIx64 " - %d refs \n", id, refCounts);
+        }
         StringAppendF(&result, "RenderEngine AHB/BackendTexture cache size: %zu\n",
                       mTextureCache.size());
         StringAppendF(&result, "Dumping buffer ids...\n");
diff --git a/libs/renderengine/skia/SkiaGLRenderEngine.h b/libs/renderengine/skia/SkiaGLRenderEngine.h
index 8e77c16..e71c560 100644
--- a/libs/renderengine/skia/SkiaGLRenderEngine.h
+++ b/libs/renderengine/skia/SkiaGLRenderEngine.h
@@ -23,6 +23,7 @@
 #include <GrDirectContext.h>
 #include <SkSurface.h>
 #include <android-base/thread_annotations.h>
+#include <renderengine/ExternalTexture.h>
 #include <renderengine/RenderEngine.h>
 #include <sys/types.h>
 
@@ -52,13 +53,12 @@
     ~SkiaGLRenderEngine() override EXCLUDES(mRenderingMutex);
 
     void primeCache() override;
-    void cacheExternalTextureBuffer(const sp<GraphicBuffer>& buffer) override;
-    void unbindExternalTextureBuffer(uint64_t bufferId) override;
     status_t drawLayers(const DisplaySettings& display,
                         const std::vector<const LayerSettings*>& layers,
-                        const sp<GraphicBuffer>& buffer, const bool useFramebufferCache,
-                        base::unique_fd&& bufferFence, base::unique_fd* drawFence) override;
-    void cleanFramebufferCache() override;
+                        const std::shared_ptr<ExternalTexture>& buffer,
+                        const bool useFramebufferCache, base::unique_fd&& bufferFence,
+                        base::unique_fd* drawFence) override;
+    void cleanFramebufferCache() override {}
     int getContextPriority() override;
     bool isProtected() const override { return mInProtectedContext; }
     bool supportsProtectedContent() const override;
@@ -72,6 +72,8 @@
     void dump(std::string& result) override;
     size_t getMaxTextureSize() const override;
     size_t getMaxViewportDims() const override;
+    void mapExternalTextureBuffer(const sp<GraphicBuffer>& buffer, bool isRenderable) override;
+    void unmapExternalTextureBuffer(const sp<GraphicBuffer>& buffer) override;
 
 private:
     static EGLConfig chooseEglConfig(EGLDisplay display, int format, bool logConfig);
@@ -114,7 +116,9 @@
     const PixelFormat mDefaultPixelFormat;
     const bool mUseColorManagement;
 
-    // Cache of GL textures that we'll store per GraphicBuffer ID
+    // Number of external holders of ExternalTexture references, per GraphicBuffer ID.
+    std::unordered_map<uint64_t, int32_t> mGraphicBufferExternalRefs GUARDED_BY(mRenderingMutex);
+    // Cache of GL textures that we'll store per GraphicBuffer ID, sliced by GPU context.
     std::unordered_map<uint64_t, std::shared_ptr<AutoBackendTexture::LocalRef>> mTextureCache
             GUARDED_BY(mRenderingMutex);
     std::unordered_map<uint64_t, std::shared_ptr<AutoBackendTexture::LocalRef>>
diff --git a/libs/renderengine/skia/SkiaRenderEngine.h b/libs/renderengine/skia/SkiaRenderEngine.h
index 51ef088..308c5ff 100644
--- a/libs/renderengine/skia/SkiaRenderEngine.h
+++ b/libs/renderengine/skia/SkiaRenderEngine.h
@@ -42,15 +42,12 @@
     virtual void primeCache() override{};
     virtual void genTextures(size_t /*count*/, uint32_t* /*names*/) override{};
     virtual void deleteTextures(size_t /*count*/, uint32_t const* /*names*/) override{};
-    virtual void cacheExternalTextureBuffer(const sp<GraphicBuffer>& /*buffer*/){};
-    virtual void unbindExternalTextureBuffer(uint64_t /*bufferId*/){};
-
     virtual bool isProtected() const override { return false; } // mInProtectedContext; }
     virtual bool supportsProtectedContent() const override { return false; };
     virtual bool useProtectedContext(bool /*useProtectedContext*/) override { return false; };
     virtual status_t drawLayers(const DisplaySettings& /*display*/,
                                 const std::vector<const LayerSettings*>& /*layers*/,
-                                const sp<GraphicBuffer>& /*buffer*/,
+                                const std::shared_ptr<ExternalTexture>& /*buffer*/,
                                 const bool /*useFramebufferCache*/,
                                 base::unique_fd&& /*bufferFence*/,
                                 base::unique_fd* /*drawFence*/) override {
@@ -60,6 +57,11 @@
     virtual int getContextPriority() override { return 0; }
     virtual void assertShadersCompiled(int numShaders) {}
     virtual int reportShadersCompiled() { return 0; }
+
+protected:
+    virtual void mapExternalTextureBuffer(const sp<GraphicBuffer>& /*buffer*/,
+                                          bool /*isRenderable*/) override;
+    virtual void unmapExternalTextureBuffer(const sp<GraphicBuffer>& /*buffer*/) override;
 };
 
 } // namespace skia
diff --git a/libs/renderengine/tests/RenderEngineTest.cpp b/libs/renderengine/tests/RenderEngineTest.cpp
index 7846156..d63c88b 100644
--- a/libs/renderengine/tests/RenderEngineTest.cpp
+++ b/libs/renderengine/tests/RenderEngineTest.cpp
@@ -24,6 +24,7 @@
 
 #include <cutils/properties.h>
 #include <gtest/gtest.h>
+#include <renderengine/ExternalTexture.h>
 #include <renderengine/RenderEngine.h>
 #include <sync/sync.h>
 #include <ui/PixelFormat.h>
@@ -160,27 +161,42 @@
 
 class RenderEngineTest : public ::testing::TestWithParam<std::shared_ptr<RenderEngineFactory>> {
 public:
-    static sp<GraphicBuffer> allocateDefaultBuffer() {
-        return new GraphicBuffer(DEFAULT_DISPLAY_WIDTH, DEFAULT_DISPLAY_HEIGHT,
-                                 HAL_PIXEL_FORMAT_RGBA_8888, 1,
-                                 GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN |
-                                         GRALLOC_USAGE_HW_RENDER | GRALLOC_USAGE_HW_TEXTURE,
-                                 "output");
+    std::shared_ptr<renderengine::ExternalTexture> allocateDefaultBuffer() {
+        return std::make_shared<
+                renderengine::
+                        ExternalTexture>(new GraphicBuffer(DEFAULT_DISPLAY_WIDTH,
+                                                           DEFAULT_DISPLAY_HEIGHT,
+                                                           HAL_PIXEL_FORMAT_RGBA_8888, 1,
+                                                           GRALLOC_USAGE_SW_READ_OFTEN |
+                                                                   GRALLOC_USAGE_SW_WRITE_OFTEN |
+                                                                   GRALLOC_USAGE_HW_RENDER |
+                                                                   GRALLOC_USAGE_HW_TEXTURE,
+                                                           "output"),
+                                         *mRE,
+                                         renderengine::ExternalTexture::Usage::READABLE |
+                                                 renderengine::ExternalTexture::Usage::WRITEABLE);
     }
 
     // Allocates a 1x1 buffer to fill with a solid color
-    static sp<GraphicBuffer> allocateSourceBuffer(uint32_t width, uint32_t height) {
-        return new GraphicBuffer(width, height, HAL_PIXEL_FORMAT_RGBA_8888, 1,
-                                 GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN |
-                                         GRALLOC_USAGE_HW_TEXTURE,
-                                 "input");
+    std::shared_ptr<renderengine::ExternalTexture> allocateSourceBuffer(uint32_t width,
+                                                                        uint32_t height) {
+        return std::make_shared<
+                renderengine::
+                        ExternalTexture>(new GraphicBuffer(width, height,
+                                                           HAL_PIXEL_FORMAT_RGBA_8888, 1,
+                                                           GRALLOC_USAGE_SW_READ_OFTEN |
+                                                                   GRALLOC_USAGE_SW_WRITE_OFTEN |
+                                                                   GRALLOC_USAGE_HW_TEXTURE,
+                                                           "input"),
+                                         *mRE,
+                                         renderengine::ExternalTexture::Usage::READABLE |
+                                                 renderengine::ExternalTexture::Usage::WRITEABLE);
     }
 
     RenderEngineTest() {
         const ::testing::TestInfo* const test_info =
                 ::testing::UnitTest::GetInstance()->current_test_info();
         ALOGD("**** Setting up for %s.%s\n", test_info->test_case_name(), test_info->name());
-        mBuffer = allocateDefaultBuffer();
     }
 
     ~RenderEngineTest() {
@@ -211,20 +227,21 @@
         }
 
         uint8_t* pixels;
-        mBuffer->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
-                      reinterpret_cast<void**>(&pixels));
+        mBuffer->getBuffer()->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
+                                   reinterpret_cast<void**>(&pixels));
 
         file << "P6\n";
-        file << mBuffer->getWidth() << "\n";
-        file << mBuffer->getHeight() << "\n";
+        file << mBuffer->getBuffer()->getWidth() << "\n";
+        file << mBuffer->getBuffer()->getHeight() << "\n";
         file << 255 << "\n";
 
-        std::vector<uint8_t> outBuffer(mBuffer->getWidth() * mBuffer->getHeight() * 3);
+        std::vector<uint8_t> outBuffer(mBuffer->getBuffer()->getWidth() *
+                                       mBuffer->getBuffer()->getHeight() * 3);
         auto outPtr = reinterpret_cast<uint8_t*>(outBuffer.data());
 
-        for (int32_t j = 0; j < mBuffer->getHeight(); j++) {
-            const uint8_t* src = pixels + (mBuffer->getStride() * j) * 4;
-            for (int32_t i = 0; i < mBuffer->getWidth(); i++) {
+        for (int32_t j = 0; j < mBuffer->getBuffer()->getHeight(); j++) {
+            const uint8_t* src = pixels + (mBuffer->getBuffer()->getStride() * j) * 4;
+            for (int32_t i = 0; i < mBuffer->getBuffer()->getWidth(); i++) {
                 // Only copy R, G and B components
                 outPtr[0] = src[0];
                 outPtr[1] = src[1];
@@ -235,7 +252,7 @@
             }
         }
         file.write(reinterpret_cast<char*>(outBuffer.data()), outBuffer.size());
-        mBuffer->unlock();
+        mBuffer->getBuffer()->unlock();
     }
 
     void expectBufferColor(const Region& region, uint8_t r, uint8_t g, uint8_t b, uint8_t a) {
@@ -262,13 +279,13 @@
     void expectBufferColor(const Rect& region, uint8_t r, uint8_t g, uint8_t b, uint8_t a,
                            std::function<bool(const uint8_t* a, const uint8_t* b)> colorCompare) {
         uint8_t* pixels;
-        mBuffer->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
-                      reinterpret_cast<void**>(&pixels));
+        mBuffer->getBuffer()->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
+                                   reinterpret_cast<void**>(&pixels));
         int32_t maxFails = 10;
         int32_t fails = 0;
         for (int32_t j = 0; j < region.getHeight(); j++) {
-            const uint8_t* src =
-                    pixels + (mBuffer->getStride() * (region.top + j) + region.left) * 4;
+            const uint8_t* src = pixels +
+                    (mBuffer->getBuffer()->getStride() * (region.top + j) + region.left) * 4;
             for (int32_t i = 0; i < region.getWidth(); i++) {
                 const uint8_t expected[4] = {r, g, b, a};
                 bool equal = colorCompare(src, expected);
@@ -289,7 +306,7 @@
                 break;
             }
         }
-        mBuffer->unlock();
+        mBuffer->getBuffer()->unlock();
     }
 
     void expectAlpha(const Rect& rect, uint8_t a) {
@@ -387,7 +404,6 @@
         base::unique_fd fence;
         status_t status =
                 mRE->drawLayers(settings, layers, mBuffer, true, base::unique_fd(), &fence);
-        mCurrentBuffer = mBuffer;
 
         int fd = fence.release();
         if (fd >= 0) {
@@ -397,7 +413,7 @@
 
         ASSERT_EQ(NO_ERROR, status);
         if (layers.size() > 0 && mGLESRE != nullptr) {
-            ASSERT_TRUE(mGLESRE->isFramebufferImageCachedForTesting(mBuffer->getId()));
+            ASSERT_TRUE(mGLESRE->isFramebufferImageCachedForTesting(mBuffer->getBuffer()->getId()));
         }
     }
 
@@ -503,17 +519,11 @@
     void initializeRenderEngine();
 
     std::unique_ptr<renderengine::RenderEngine> mRE;
+    std::shared_ptr<renderengine::ExternalTexture> mBuffer;
     // GLESRenderEngine for testing GLES-specific behavior.
     // Owened by mRE, but this is downcasted.
     renderengine::gl::GLESRenderEngine* mGLESRE = nullptr;
 
-    // Dumb hack to avoid NPE in the EGL driver: the GraphicBuffer needs to
-    // be freed *after* RenderEngine is destroyed, so that the EGL image is
-    // destroyed first.
-    sp<GraphicBuffer> mCurrentBuffer;
-
-    sp<GraphicBuffer> mBuffer;
-
     std::vector<uint32_t> mTexNames;
 };
 
@@ -530,6 +540,7 @@
     } else {
         mRE = renderEngineFactory->createRenderEngine();
     }
+    mBuffer = allocateDefaultBuffer();
 }
 
 struct ColorSourceVariant {
@@ -566,18 +577,18 @@
 struct BufferSourceVariant {
     static void fillColor(renderengine::LayerSettings& layer, half r, half g, half b,
                           RenderEngineTest* fixture) {
-        sp<GraphicBuffer> buf = RenderEngineTest::allocateSourceBuffer(1, 1);
+        const auto buf = fixture->allocateSourceBuffer(1, 1);
         uint32_t texName;
         fixture->mRE->genTextures(1, &texName);
         fixture->mTexNames.push_back(texName);
 
         uint8_t* pixels;
-        buf->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
-                  reinterpret_cast<void**>(&pixels));
+        buf->getBuffer()->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
+                               reinterpret_cast<void**>(&pixels));
 
-        for (int32_t j = 0; j < buf->getHeight(); j++) {
-            uint8_t* iter = pixels + (buf->getStride() * j) * 4;
-            for (int32_t i = 0; i < buf->getWidth(); i++) {
+        for (int32_t j = 0; j < buf->getBuffer()->getHeight(); j++) {
+            uint8_t* iter = pixels + (buf->getBuffer()->getStride() * j) * 4;
+            for (int32_t i = 0; i < buf->getBuffer()->getWidth(); i++) {
                 iter[0] = uint8_t(r * 255);
                 iter[1] = uint8_t(g * 255);
                 iter[2] = uint8_t(b * 255);
@@ -586,7 +597,7 @@
             }
         }
 
-        buf->unlock();
+        buf->getBuffer()->unlock();
 
         layer.source.buffer.buffer = buf;
         layer.source.buffer.textureName = texName;
@@ -1012,14 +1023,14 @@
     layer.sourceDataspace = ui::Dataspace::V0_SRGB_LINEAR;
     // Here will allocate a checker board texture, but transform texture
     // coordinates so that only the upper left is applied.
-    sp<GraphicBuffer> buf = allocateSourceBuffer(2, 2);
+    const auto buf = allocateSourceBuffer(2, 2);
     uint32_t texName;
     RenderEngineTest::mRE->genTextures(1, &texName);
     this->mTexNames.push_back(texName);
 
     uint8_t* pixels;
-    buf->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
-              reinterpret_cast<void**>(&pixels));
+    buf->getBuffer()->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
+                           reinterpret_cast<void**>(&pixels));
     // Red top left, Green top right, Blue bottom left, Black bottom right
     pixels[0] = 255;
     pixels[1] = 0;
@@ -1033,7 +1044,7 @@
     pixels[9] = 0;
     pixels[10] = 255;
     pixels[11] = 255;
-    buf->unlock();
+    buf->getBuffer()->unlock();
 
     layer.source.buffer.buffer = buf;
     layer.source.buffer.textureName = texName;
@@ -1061,19 +1072,19 @@
     std::vector<const renderengine::LayerSettings*> layers;
 
     renderengine::LayerSettings layer;
-    sp<GraphicBuffer> buf = allocateSourceBuffer(1, 1);
+    const auto buf = allocateSourceBuffer(1, 1);
     uint32_t texName;
     RenderEngineTest::mRE->genTextures(1, &texName);
     this->mTexNames.push_back(texName);
 
     uint8_t* pixels;
-    buf->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
-              reinterpret_cast<void**>(&pixels));
+    buf->getBuffer()->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
+                           reinterpret_cast<void**>(&pixels));
     pixels[0] = 255;
     pixels[1] = 0;
     pixels[2] = 0;
     pixels[3] = 255;
-    buf->unlock();
+    buf->getBuffer()->unlock();
 
     layer.source.buffer.buffer = buf;
     layer.source.buffer.textureName = texName;
@@ -1100,19 +1111,19 @@
     std::vector<const renderengine::LayerSettings*> layers;
 
     renderengine::LayerSettings layer;
-    sp<GraphicBuffer> buf = allocateSourceBuffer(1, 1);
+    const auto buf = allocateSourceBuffer(1, 1);
     uint32_t texName;
     RenderEngineTest::mRE->genTextures(1, &texName);
     this->mTexNames.push_back(texName);
 
     uint8_t* pixels;
-    buf->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
-              reinterpret_cast<void**>(&pixels));
+    buf->getBuffer()->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
+                           reinterpret_cast<void**>(&pixels));
     pixels[0] = 255;
     pixels[1] = 0;
     pixels[2] = 0;
     pixels[3] = 255;
-    buf->unlock();
+    buf->getBuffer()->unlock();
 
     layer.source.buffer.buffer = buf;
     layer.source.buffer.textureName = texName;
@@ -1233,8 +1244,7 @@
 }
 
 TEST_P(RenderEngineTest, drawLayers_withoutBuffers_withColorTransform) {
-    const auto& renderEngineFactory = GetParam();
-    mRE = renderEngineFactory->createRenderEngine();
+    initializeRenderEngine();
 
     renderengine::DisplaySettings settings;
     settings.outputDataspace = ui::Dataspace::V0_SRGB_LINEAR;
@@ -1295,7 +1305,6 @@
     layers.push_back(&layer);
 
     status_t status = mRE->drawLayers(settings, layers, mBuffer, true, base::unique_fd(), nullptr);
-    mCurrentBuffer = mBuffer;
     ASSERT_EQ(NO_ERROR, status);
     expectBufferColor(fullscreenRect(), 255, 0, 0, 255);
 }
@@ -1323,9 +1332,8 @@
     layers.push_back(&layer);
 
     status_t status = mRE->drawLayers(settings, layers, mBuffer, false, base::unique_fd(), nullptr);
-    mCurrentBuffer = mBuffer;
     ASSERT_EQ(NO_ERROR, status);
-    ASSERT_FALSE(mGLESRE->isFramebufferImageCachedForTesting(mBuffer->getId()));
+    ASSERT_FALSE(mGLESRE->isFramebufferImageCachedForTesting(mBuffer->getBuffer()->getId()));
     expectBufferColor(fullscreenRect(), 255, 0, 0, 255);
 }
 
@@ -1574,98 +1582,6 @@
     clearRegion();
 }
 
-TEST_P(RenderEngineTest, drawLayers_fillsBufferAndCachesImages) {
-    const auto& renderEngineFactory = GetParam();
-
-    if (renderEngineFactory->type() != renderengine::RenderEngine::RenderEngineType::GLES) {
-        // GLES-specific test
-        return;
-    }
-
-    initializeRenderEngine();
-
-    renderengine::DisplaySettings settings;
-    settings.outputDataspace = ui::Dataspace::V0_SRGB_LINEAR;
-    settings.physicalDisplay = fullscreenRect();
-    settings.clip = fullscreenRect();
-
-    std::vector<const renderengine::LayerSettings*> layers;
-
-    renderengine::LayerSettings layer;
-    layer.geometry.boundaries = fullscreenRect().toFloatRect();
-    BufferSourceVariant<ForceOpaqueBufferVariant>::fillColor(layer, 1.0f, 0.0f, 0.0f, this);
-
-    layers.push_back(&layer);
-    invokeDraw(settings, layers);
-    uint64_t bufferId = layer.source.buffer.buffer->getId();
-    EXPECT_TRUE(mGLESRE->isImageCachedForTesting(bufferId));
-    std::shared_ptr<renderengine::gl::ImageManager::Barrier> barrier =
-            mGLESRE->unbindExternalTextureBufferForTesting(bufferId);
-    std::lock_guard<std::mutex> lock(barrier->mutex);
-    ASSERT_TRUE(barrier->condition.wait_for(barrier->mutex, std::chrono::seconds(5),
-                                            [&]() REQUIRES(barrier->mutex) {
-                                                return barrier->isOpen;
-                                            }));
-    EXPECT_FALSE(mGLESRE->isImageCachedForTesting(bufferId));
-    EXPECT_EQ(NO_ERROR, barrier->result);
-}
-
-TEST_P(RenderEngineTest, cacheExternalBuffer_withNullBuffer) {
-    const auto& renderEngineFactory = GetParam();
-
-    if (renderEngineFactory->type() != renderengine::RenderEngine::RenderEngineType::GLES) {
-        // GLES-specific test
-        return;
-    }
-
-    initializeRenderEngine();
-
-    std::shared_ptr<renderengine::gl::ImageManager::Barrier> barrier =
-            mGLESRE->cacheExternalTextureBufferForTesting(nullptr);
-    std::lock_guard<std::mutex> lock(barrier->mutex);
-    ASSERT_TRUE(barrier->condition.wait_for(barrier->mutex, std::chrono::seconds(5),
-                                            [&]() REQUIRES(barrier->mutex) {
-                                                return barrier->isOpen;
-                                            }));
-    EXPECT_TRUE(barrier->isOpen);
-    EXPECT_EQ(BAD_VALUE, barrier->result);
-}
-
-TEST_P(RenderEngineTest, cacheExternalBuffer_cachesImages) {
-    const auto& renderEngineFactory = GetParam();
-
-    if (renderEngineFactory->type() != renderengine::RenderEngine::RenderEngineType::GLES) {
-        // GLES-specific test
-        return;
-    }
-
-    initializeRenderEngine();
-
-    sp<GraphicBuffer> buf = allocateSourceBuffer(1, 1);
-    uint64_t bufferId = buf->getId();
-    std::shared_ptr<renderengine::gl::ImageManager::Barrier> barrier =
-            mGLESRE->cacheExternalTextureBufferForTesting(buf);
-    {
-        std::lock_guard<std::mutex> lock(barrier->mutex);
-        ASSERT_TRUE(barrier->condition.wait_for(barrier->mutex, std::chrono::seconds(5),
-                                                [&]() REQUIRES(barrier->mutex) {
-                                                    return barrier->isOpen;
-                                                }));
-        EXPECT_EQ(NO_ERROR, barrier->result);
-    }
-    EXPECT_TRUE(mGLESRE->isImageCachedForTesting(bufferId));
-    barrier = mGLESRE->unbindExternalTextureBufferForTesting(bufferId);
-    {
-        std::lock_guard<std::mutex> lock(barrier->mutex);
-        ASSERT_TRUE(barrier->condition.wait_for(barrier->mutex, std::chrono::seconds(5),
-                                                [&]() REQUIRES(barrier->mutex) {
-                                                    return barrier->isOpen;
-                                                }));
-        EXPECT_EQ(NO_ERROR, barrier->result);
-    }
-    EXPECT_FALSE(mGLESRE->isImageCachedForTesting(bufferId));
-}
-
 TEST_P(RenderEngineTest, drawLayers_fillShadow_castsWithoutCasterLayer) {
     initializeRenderEngine();
 
@@ -1858,7 +1774,7 @@
         sync_wait(fd, -1);
     }
 
-    uint64_t bufferId = layer.source.buffer.buffer->getId();
+    uint64_t bufferId = layer.source.buffer.buffer->getBuffer()->getId();
     uint32_t texName = layer.source.buffer.textureName;
     EXPECT_TRUE(mGLESRE->isImageCachedForTesting(bufferId));
     EXPECT_EQ(bufferId, mGLESRE->getBufferIdForTextureNameForTesting(texName));
@@ -1966,16 +1882,16 @@
 
     // The next layer will overwrite redLayer with a GraphicBuffer that is green
     // applied with a translucent alpha.
-    auto buf = allocateSourceBuffer(1, 1);
+    const auto buf = allocateSourceBuffer(1, 1);
     {
         uint8_t* pixels;
-        buf->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
-                  reinterpret_cast<void**>(&pixels));
+        buf->getBuffer()->lock(GRALLOC_USAGE_SW_READ_OFTEN | GRALLOC_USAGE_SW_WRITE_OFTEN,
+                               reinterpret_cast<void**>(&pixels));
         pixels[0] = 0;
         pixels[1] = 255;
         pixels[2] = 0;
         pixels[3] = 255;
-        buf->unlock();
+        buf->getBuffer()->unlock();
     }
 
     const renderengine::LayerSettings greenLayer{
diff --git a/libs/renderengine/tests/RenderEngineThreadedTest.cpp b/libs/renderengine/tests/RenderEngineThreadedTest.cpp
index b093e88..e3917cc 100644
--- a/libs/renderengine/tests/RenderEngineThreadedTest.cpp
+++ b/libs/renderengine/tests/RenderEngineThreadedTest.cpp
@@ -162,15 +162,18 @@
 TEST_F(RenderEngineThreadedTest, drawLayers) {
     renderengine::DisplaySettings settings;
     std::vector<const renderengine::LayerSettings*> layers;
-    sp<GraphicBuffer> buffer = new GraphicBuffer();
+    std::shared_ptr<renderengine::ExternalTexture> buffer = std::make_shared<
+            renderengine::ExternalTexture>(new GraphicBuffer(), *mRenderEngine,
+                                           renderengine::ExternalTexture::Usage::READABLE |
+                                                   renderengine::ExternalTexture::Usage::WRITEABLE);
     base::unique_fd bufferFence;
     base::unique_fd drawFence;
 
     EXPECT_CALL(*mRenderEngine, drawLayers)
             .WillOnce([](const renderengine::DisplaySettings&,
                          const std::vector<const renderengine::LayerSettings*>&,
-                         const sp<GraphicBuffer>&, const bool, base::unique_fd&&,
-                         base::unique_fd*) -> status_t { return NO_ERROR; });
+                         const std::shared_ptr<renderengine::ExternalTexture>&, const bool,
+                         base::unique_fd&&, base::unique_fd*) -> status_t { return NO_ERROR; });
 
     status_t result = mThreadedRE->drawLayers(settings, layers, buffer, false,
                                               std::move(bufferFence), &drawFence);
diff --git a/libs/renderengine/threaded/RenderEngineThreaded.cpp b/libs/renderengine/threaded/RenderEngineThreaded.cpp
index 194c7da..c9f6296 100644
--- a/libs/renderengine/threaded/RenderEngineThreaded.cpp
+++ b/libs/renderengine/threaded/RenderEngineThreaded.cpp
@@ -157,27 +157,28 @@
     resultFuture.wait();
 }
 
-void RenderEngineThreaded::cacheExternalTextureBuffer(const sp<GraphicBuffer>& buffer) {
+void RenderEngineThreaded::mapExternalTextureBuffer(const sp<GraphicBuffer>& buffer,
+                                                    bool isRenderable) {
     // This function is designed so it can run asynchronously, so we do not need to wait
     // for the futures.
     {
         std::lock_guard lock(mThreadMutex);
         mFunctionCalls.push([=](renderengine::RenderEngine& instance) {
-            ATRACE_NAME("REThreaded::cacheExternalTextureBuffer");
-            instance.cacheExternalTextureBuffer(buffer);
+            ATRACE_NAME("REThreaded::mapExternalTextureBuffer");
+            instance.mapExternalTextureBuffer(buffer, isRenderable);
         });
     }
     mCondition.notify_one();
 }
 
-void RenderEngineThreaded::unbindExternalTextureBuffer(uint64_t bufferId) {
+void RenderEngineThreaded::unmapExternalTextureBuffer(const sp<GraphicBuffer>& buffer) {
     // This function is designed so it can run asynchronously, so we do not need to wait
     // for the futures.
     {
         std::lock_guard lock(mThreadMutex);
         mFunctionCalls.push([=](renderengine::RenderEngine& instance) {
-            ATRACE_NAME("REThreaded::unbindExternalTextureBuffer");
-            instance.unbindExternalTextureBuffer(bufferId);
+            ATRACE_NAME("REThreaded::unmapExternalTextureBuffer");
+            instance.unmapExternalTextureBuffer(buffer);
         });
     }
     mCondition.notify_one();
@@ -239,7 +240,7 @@
 
 status_t RenderEngineThreaded::drawLayers(const DisplaySettings& display,
                                           const std::vector<const LayerSettings*>& layers,
-                                          const sp<GraphicBuffer>& buffer,
+                                          const std::shared_ptr<ExternalTexture>& buffer,
                                           const bool useFramebufferCache,
                                           base::unique_fd&& bufferFence,
                                           base::unique_fd* drawFence) {
diff --git a/libs/renderengine/threaded/RenderEngineThreaded.h b/libs/renderengine/threaded/RenderEngineThreaded.h
index 61ae9b8..eb6098e 100644
--- a/libs/renderengine/threaded/RenderEngineThreaded.h
+++ b/libs/renderengine/threaded/RenderEngineThreaded.h
@@ -48,8 +48,6 @@
 
     void genTextures(size_t count, uint32_t* names) override;
     void deleteTextures(size_t count, uint32_t const* names) override;
-    void cacheExternalTextureBuffer(const sp<GraphicBuffer>& buffer) override;
-    void unbindExternalTextureBuffer(uint64_t bufferId) override;
     size_t getMaxTextureSize() const override;
     size_t getMaxViewportDims() const override;
 
@@ -60,14 +58,19 @@
 
     status_t drawLayers(const DisplaySettings& display,
                         const std::vector<const LayerSettings*>& layers,
-                        const sp<GraphicBuffer>& buffer, const bool useFramebufferCache,
-                        base::unique_fd&& bufferFence, base::unique_fd* drawFence) override;
+                        const std::shared_ptr<ExternalTexture>& buffer,
+                        const bool useFramebufferCache, base::unique_fd&& bufferFence,
+                        base::unique_fd* drawFence) override;
 
     void cleanFramebufferCache() override;
     int getContextPriority() override;
     bool supportsBackgroundBlur() override;
     void onPrimaryDisplaySizeChanged(ui::Size size) override;
 
+protected:
+    void mapExternalTextureBuffer(const sp<GraphicBuffer>& buffer, bool isRenderable) override;
+    void unmapExternalTextureBuffer(const sp<GraphicBuffer>& buffer) override;
+
 private:
     void threadMain(CreateInstanceFactory factory);
     void waitUntilInitialized() const;