Replace RenderEngineResult with FenceResult

Bug: b/232535621
Test: atest librenderengine_test
Test: atest SurfaceFlinger_test

Change-Id: If036ab847024751b8da97d6ed856db447db19f6f
diff --git a/libs/renderengine/RenderEngine.cpp b/libs/renderengine/RenderEngine.cpp
index c7ad058..9d9cb6b 100644
--- a/libs/renderengine/RenderEngine.cpp
+++ b/libs/renderengine/RenderEngine.cpp
@@ -63,12 +63,13 @@
                         "output buffer not gpu writeable");
 }
 
-std::future<RenderEngineResult> RenderEngine::drawLayers(
-        const DisplaySettings& display, const std::vector<LayerSettings>& layers,
-        const std::shared_ptr<ExternalTexture>& buffer, const bool useFramebufferCache,
-        base::unique_fd&& bufferFence) {
-    const auto resultPromise = std::make_shared<std::promise<RenderEngineResult>>();
-    std::future<RenderEngineResult> resultFuture = resultPromise->get_future();
+ftl::Future<FenceResult> RenderEngine::drawLayers(const DisplaySettings& display,
+                                                  const std::vector<LayerSettings>& layers,
+                                                  const std::shared_ptr<ExternalTexture>& buffer,
+                                                  const bool useFramebufferCache,
+                                                  base::unique_fd&& bufferFence) {
+    const auto resultPromise = std::make_shared<std::promise<FenceResult>>();
+    std::future<FenceResult> resultFuture = resultPromise->get_future();
     drawLayersInternal(std::move(resultPromise), display, layers, buffer, useFramebufferCache,
                        std::move(bufferFence));
     return resultFuture;
diff --git a/libs/renderengine/benchmark/RenderEngineBench.cpp b/libs/renderengine/benchmark/RenderEngineBench.cpp
index 7bcfff5..739f3fa 100644
--- a/libs/renderengine/benchmark/RenderEngineBench.cpp
+++ b/libs/renderengine/benchmark/RenderEngineBench.cpp
@@ -159,9 +159,10 @@
     };
     auto layers = std::vector<LayerSettings>{layer};
 
-    auto [status, drawFence] =
-            re.drawLayers(display, layers, texture, kUseFrameBufferCache, base::unique_fd()).get();
-    sp<Fence> waitFence = sp<Fence>::make(std::move(drawFence));
+    sp<Fence> waitFence =
+            re.drawLayers(display, layers, texture, kUseFrameBufferCache, base::unique_fd())
+                    .get()
+                    .value();
     waitFence->waitForever(LOG_TAG);
     return texture;
 }
@@ -190,10 +191,10 @@
 
     // This loop starts and stops the timer.
     for (auto _ : benchState) {
-        auto [status, drawFence] = re.drawLayers(display, layers, outputBuffer,
-                                                 kUseFrameBufferCache, base::unique_fd())
-                                           .get();
-        sp<Fence> waitFence = sp<Fence>::make(std::move(drawFence));
+        sp<Fence> waitFence = re.drawLayers(display, layers, outputBuffer, kUseFrameBufferCache,
+                                            base::unique_fd())
+                                      .get()
+                                      .value();
         waitFence->waitForever(LOG_TAG);
     }
 
diff --git a/libs/renderengine/gl/GLESRenderEngine.cpp b/libs/renderengine/gl/GLESRenderEngine.cpp
index 9a5ff54..13f766c 100644
--- a/libs/renderengine/gl/GLESRenderEngine.cpp
+++ b/libs/renderengine/gl/GLESRenderEngine.cpp
@@ -1081,14 +1081,14 @@
 }
 
 void GLESRenderEngine::drawLayersInternal(
-        const std::shared_ptr<std::promise<RenderEngineResult>>&& resultPromise,
+        const std::shared_ptr<std::promise<FenceResult>>&& resultPromise,
         const DisplaySettings& display, const std::vector<LayerSettings>& layers,
         const std::shared_ptr<ExternalTexture>& buffer, const bool useFramebufferCache,
         base::unique_fd&& bufferFence) {
     ATRACE_CALL();
     if (layers.empty()) {
         ALOGV("Drawing empty layer stack");
-        resultPromise->set_value({NO_ERROR, base::unique_fd()});
+        resultPromise->set_value(Fence::NO_FENCE);
         return;
     }
 
@@ -1103,7 +1103,7 @@
 
     if (buffer == nullptr) {
         ALOGE("No output buffer provided. Aborting GPU composition.");
-        resultPromise->set_value({BAD_VALUE, base::unique_fd()});
+        resultPromise->set_value(base::unexpected(BAD_VALUE));
         return;
     }
 
@@ -1132,7 +1132,7 @@
             ALOGE("Failed to bind framebuffer! Aborting GPU composition for buffer (%p).",
                   buffer->getBuffer()->handle);
             checkErrors();
-            resultPromise->set_value({fbo->getStatus(), base::unique_fd()});
+            resultPromise->set_value(base::unexpected(fbo->getStatus()));
             return;
         }
         setViewportAndProjection(display.physicalDisplay, display.clip);
@@ -1144,7 +1144,7 @@
             ALOGE("Failed to prepare blur filter! Aborting GPU composition for buffer (%p).",
                   buffer->getBuffer()->handle);
             checkErrors();
-            resultPromise->set_value({status, base::unique_fd()});
+            resultPromise->set_value(base::unexpected(status));
             return;
         }
     }
@@ -1178,7 +1178,7 @@
                 ALOGE("Failed to render blur effect! Aborting GPU composition for buffer (%p).",
                       buffer->getBuffer()->handle);
                 checkErrors("Can't render first blur pass");
-                resultPromise->set_value({status, base::unique_fd()});
+                resultPromise->set_value(base::unexpected(status));
                 return;
             }
 
@@ -1201,7 +1201,7 @@
                 ALOGE("Failed to bind framebuffer! Aborting GPU composition for buffer (%p).",
                       buffer->getBuffer()->handle);
                 checkErrors("Can't bind native framebuffer");
-                resultPromise->set_value({status, base::unique_fd()});
+                resultPromise->set_value(base::unexpected(status));
                 return;
             }
 
@@ -1210,7 +1210,7 @@
                 ALOGE("Failed to render blur effect! Aborting GPU composition for buffer (%p).",
                       buffer->getBuffer()->handle);
                 checkErrors("Can't render blur filter");
-                resultPromise->set_value({status, base::unique_fd()});
+                resultPromise->set_value(base::unexpected(status));
                 return;
             }
         }
@@ -1310,7 +1310,7 @@
             checkErrors();
             // Chances are, something illegal happened (either the caller passed
             // us bad parameters, or we messed up our shader generation).
-            resultPromise->set_value({INVALID_OPERATION, std::move(drawFence)});
+            resultPromise->set_value(base::unexpected(INVALID_OPERATION));
             return;
         }
         mLastDrawFence = nullptr;
@@ -1322,8 +1322,7 @@
     mPriorResourcesCleaned = false;
 
     checkErrors();
-    resultPromise->set_value({NO_ERROR, std::move(drawFence)});
-    return;
+    resultPromise->set_value(sp<Fence>::make(std::move(drawFence)));
 }
 
 void GLESRenderEngine::setViewportAndProjection(Rect viewport, Rect clip) {
diff --git a/libs/renderengine/gl/GLESRenderEngine.h b/libs/renderengine/gl/GLESRenderEngine.h
index 1d7c2ca..1ee5cba 100644
--- a/libs/renderengine/gl/GLESRenderEngine.h
+++ b/libs/renderengine/gl/GLESRenderEngine.h
@@ -31,6 +31,7 @@
 #include <renderengine/RenderEngine.h>
 #include <renderengine/private/Description.h>
 #include <sys/types.h>
+#include <ui/FenceResult.h>
 #include "GLShadowTexture.h"
 #include "ImageManager.h"
 
@@ -102,7 +103,7 @@
             EXCLUDES(mRenderingMutex);
     void unmapExternalTextureBuffer(const sp<GraphicBuffer>& buffer) EXCLUDES(mRenderingMutex);
     bool canSkipPostRenderCleanup() const override;
-    void drawLayersInternal(const std::shared_ptr<std::promise<RenderEngineResult>>&& resultPromise,
+    void drawLayersInternal(const std::shared_ptr<std::promise<FenceResult>>&& resultPromise,
                             const DisplaySettings& display,
                             const std::vector<LayerSettings>& layers,
                             const std::shared_ptr<ExternalTexture>& buffer,
diff --git a/libs/renderengine/include/renderengine/RenderEngine.h b/libs/renderengine/include/renderengine/RenderEngine.h
index 3e7f69c..199392c 100644
--- a/libs/renderengine/include/renderengine/RenderEngine.h
+++ b/libs/renderengine/include/renderengine/RenderEngine.h
@@ -18,6 +18,7 @@
 #define SF_RENDERENGINE_H_
 
 #include <android-base/unique_fd.h>
+#include <ftl/future.h>
 #include <math/mat4.h>
 #include <renderengine/DisplaySettings.h>
 #include <renderengine/ExternalTexture.h>
@@ -26,6 +27,7 @@
 #include <renderengine/LayerSettings.h>
 #include <stdint.h>
 #include <sys/types.h>
+#include <ui/FenceResult.h>
 #include <ui/GraphicTypes.h>
 #include <ui/Transform.h>
 
@@ -68,7 +70,6 @@
 class Mesh;
 class Texture;
 struct RenderEngineCreationArgs;
-struct RenderEngineResult;
 
 namespace threaded {
 class RenderEngineThreaded;
@@ -158,12 +159,13 @@
     // parameter does nothing.
     // @param bufferFence Fence signalling that the buffer is ready to be drawn
     // to.
-    // @return A future object of RenderEngineResult struct indicating whether
-    // drawing was successful in async mode.
-    virtual std::future<RenderEngineResult> drawLayers(
-            const DisplaySettings& display, const std::vector<LayerSettings>& layers,
-            const std::shared_ptr<ExternalTexture>& buffer, const bool useFramebufferCache,
-            base::unique_fd&& bufferFence);
+    // @return A future object of FenceResult indicating whether drawing was
+    // successful in async mode.
+    virtual ftl::Future<FenceResult> drawLayers(const DisplaySettings& display,
+                                                const std::vector<LayerSettings>& layers,
+                                                const std::shared_ptr<ExternalTexture>& buffer,
+                                                const bool useFramebufferCache,
+                                                base::unique_fd&& bufferFence);
 
     // Clean-up method that should be called on the main thread after the
     // drawFence returned by drawLayers fires. This method will free up
@@ -237,7 +239,7 @@
     const RenderEngineType mRenderEngineType;
 
     virtual void drawLayersInternal(
-            const std::shared_ptr<std::promise<RenderEngineResult>>&& resultPromise,
+            const std::shared_ptr<std::promise<FenceResult>>&& resultPromise,
             const DisplaySettings& display, const std::vector<LayerSettings>& layers,
             const std::shared_ptr<ExternalTexture>& buffer, const bool useFramebufferCache,
             base::unique_fd&& bufferFence) = 0;
@@ -327,13 +329,6 @@
             RenderEngine::RenderEngineType::SKIA_GL_THREADED;
 };
 
-struct RenderEngineResult {
-    // status indicates if drawing is successful
-    status_t status;
-    // drawFence will fire when the buffer has been drawn to and is ready to be examined.
-    base::unique_fd drawFence;
-};
-
 } // namespace renderengine
 } // namespace android
 
diff --git a/libs/renderengine/include/renderengine/mock/RenderEngine.h b/libs/renderengine/include/renderengine/mock/RenderEngine.h
index 248bd65..e3ce85d 100644
--- a/libs/renderengine/include/renderengine/mock/RenderEngine.h
+++ b/libs/renderengine/include/renderengine/mock/RenderEngine.h
@@ -48,14 +48,13 @@
     MOCK_METHOD0(cleanupPostRender, void());
     MOCK_CONST_METHOD0(canSkipPostRenderCleanup, bool());
     MOCK_METHOD5(drawLayers,
-                 std::future<RenderEngineResult>(const DisplaySettings&,
-                                                 const std::vector<LayerSettings>&,
-                                                 const std::shared_ptr<ExternalTexture>&,
-                                                 const bool, base::unique_fd&&));
+                 ftl::Future<FenceResult>(const DisplaySettings&, const std::vector<LayerSettings>&,
+                                          const std::shared_ptr<ExternalTexture>&, const bool,
+                                          base::unique_fd&&));
     MOCK_METHOD6(drawLayersInternal,
-                 void(const std::shared_ptr<std::promise<RenderEngineResult>>&&,
-                      const DisplaySettings&, const std::vector<LayerSettings>&,
-                      const std::shared_ptr<ExternalTexture>&, const bool, base::unique_fd&&));
+                 void(const std::shared_ptr<std::promise<FenceResult>>&&, const DisplaySettings&,
+                      const std::vector<LayerSettings>&, const std::shared_ptr<ExternalTexture>&,
+                      const bool, base::unique_fd&&));
     MOCK_METHOD0(cleanFramebufferCache, void());
     MOCK_METHOD0(getContextPriority, int());
     MOCK_METHOD0(supportsBackgroundBlur, bool());
diff --git a/libs/renderengine/skia/SkiaRenderEngine.cpp b/libs/renderengine/skia/SkiaRenderEngine.cpp
index db983a8..b9aa5ac 100644
--- a/libs/renderengine/skia/SkiaRenderEngine.cpp
+++ b/libs/renderengine/skia/SkiaRenderEngine.cpp
@@ -632,7 +632,7 @@
 };
 
 void SkiaRenderEngine::drawLayersInternal(
-        const std::shared_ptr<std::promise<RenderEngineResult>>&& resultPromise,
+        const std::shared_ptr<std::promise<FenceResult>>&& resultPromise,
         const DisplaySettings& display, const std::vector<LayerSettings>& layers,
         const std::shared_ptr<ExternalTexture>& buffer, const bool /*useFramebufferCache*/,
         base::unique_fd&& bufferFence) {
@@ -642,7 +642,7 @@
 
     if (buffer == nullptr) {
         ALOGE("No output buffer provided. Aborting GPU composition.");
-        resultPromise->set_value({BAD_VALUE, base::unique_fd()});
+        resultPromise->set_value(base::unexpected(BAD_VALUE));
         return;
     }
 
@@ -675,7 +675,7 @@
     SkCanvas* dstCanvas = mCapture->tryCapture(dstSurface.get());
     if (dstCanvas == nullptr) {
         ALOGE("Cannot acquire canvas from Skia.");
-        resultPromise->set_value({BAD_VALUE, base::unique_fd()});
+        resultPromise->set_value(base::unexpected(BAD_VALUE));
         return;
     }
 
@@ -1126,8 +1126,7 @@
     }
 
     base::unique_fd drawFence = flushAndSubmit(grContext);
-    resultPromise->set_value({NO_ERROR, std::move(drawFence)});
-    return;
+    resultPromise->set_value(sp<Fence>::make(std::move(drawFence)));
 }
 
 size_t SkiaRenderEngine::getMaxTextureSize() const {
diff --git a/libs/renderengine/skia/SkiaRenderEngine.h b/libs/renderengine/skia/SkiaRenderEngine.h
index a5cd278..e7c5b8f 100644
--- a/libs/renderengine/skia/SkiaRenderEngine.h
+++ b/libs/renderengine/skia/SkiaRenderEngine.h
@@ -135,7 +135,7 @@
     void initCanvas(SkCanvas* canvas, const DisplaySettings& display);
     void drawShadow(SkCanvas* canvas, const SkRRect& casterRRect,
                     const ShadowSettings& shadowSettings);
-    void drawLayersInternal(const std::shared_ptr<std::promise<RenderEngineResult>>&& resultPromise,
+    void drawLayersInternal(const std::shared_ptr<std::promise<FenceResult>>&& resultPromise,
                             const DisplaySettings& display,
                             const std::vector<LayerSettings>& layers,
                             const std::shared_ptr<ExternalTexture>& buffer,
diff --git a/libs/renderengine/tests/RenderEngineTest.cpp b/libs/renderengine/tests/RenderEngineTest.cpp
index d23063c..9d8b2df 100644
--- a/libs/renderengine/tests/RenderEngineTest.cpp
+++ b/libs/renderengine/tests/RenderEngineTest.cpp
@@ -528,16 +528,15 @@
 
     void invokeDraw(const renderengine::DisplaySettings& settings,
                     const std::vector<renderengine::LayerSettings>& layers) {
-        std::future<renderengine::RenderEngineResult> result =
+        ftl::Future<FenceResult> future =
                 mRE->drawLayers(settings, layers, mBuffer, true, base::unique_fd());
+        ASSERT_TRUE(future.valid());
 
-        ASSERT_TRUE(result.valid());
-        auto [status, fence] = result.get();
+        auto result = future.get();
+        ASSERT_TRUE(result.ok());
 
-        ASSERT_EQ(NO_ERROR, status);
-        if (fence.ok()) {
-            sync_wait(fence.get(), -1);
-        }
+        auto fence = result.value();
+        fence->waitForever(LOG_TAG);
 
         if (layers.size() > 0 && mGLESRE != nullptr) {
             ASSERT_TRUE(mGLESRE->isFramebufferImageCachedForTesting(mBuffer->getBuffer()->getId()));
@@ -1681,13 +1680,13 @@
     layer.geometry.boundaries = fullscreenRect().toFloatRect();
     BufferSourceVariant<ForceOpaqueBufferVariant>::fillColor(layer, 1.0f, 0.0f, 0.0f, this);
     layers.push_back(layer);
-    std::future<renderengine::RenderEngineResult> result =
+    ftl::Future<FenceResult> future =
             mRE->drawLayers(settings, layers, nullptr, true, base::unique_fd());
 
-    ASSERT_TRUE(result.valid());
-    auto [status, fence] = result.get();
-    ASSERT_EQ(BAD_VALUE, status);
-    ASSERT_FALSE(fence.ok());
+    ASSERT_TRUE(future.valid());
+    auto result = future.get();
+    ASSERT_FALSE(result.ok());
+    ASSERT_EQ(BAD_VALUE, result.error());
 }
 
 TEST_P(RenderEngineTest, drawLayers_doesNotCacheFramebuffer) {
@@ -1712,15 +1711,14 @@
     layer.alpha = 1.0;
     layers.push_back(layer);
 
-    std::future<renderengine::RenderEngineResult> result =
+    ftl::Future<FenceResult> future =
             mRE->drawLayers(settings, layers, mBuffer, false, base::unique_fd());
-    ASSERT_TRUE(result.valid());
-    auto [status, fence] = result.get();
+    ASSERT_TRUE(future.valid());
+    auto result = future.get();
 
-    ASSERT_EQ(NO_ERROR, status);
-    if (fence.ok()) {
-        sync_wait(fence.get(), -1);
-    }
+    ASSERT_TRUE(result.ok());
+    auto fence = result.value();
+    fence->waitForever(LOG_TAG);
 
     ASSERT_FALSE(mGLESRE->isFramebufferImageCachedForTesting(mBuffer->getBuffer()->getId()));
     expectBufferColor(fullscreenRect(), 255, 0, 0, 255);
@@ -2219,20 +2217,20 @@
     layer.alpha = 1.0;
     layers.push_back(layer);
 
-    std::future<renderengine::RenderEngineResult> resultOne =
+    ftl::Future<FenceResult> futureOne =
             mRE->drawLayers(settings, layers, mBuffer, true, base::unique_fd());
-    ASSERT_TRUE(resultOne.valid());
-    auto [statusOne, fenceOne] = resultOne.get();
-    ASSERT_EQ(NO_ERROR, statusOne);
+    ASSERT_TRUE(futureOne.valid());
+    auto resultOne = futureOne.get();
+    ASSERT_TRUE(resultOne.ok());
+    auto fenceOne = resultOne.value();
 
-    std::future<renderengine::RenderEngineResult> resultTwo =
-            mRE->drawLayers(settings, layers, mBuffer, true, std::move(fenceOne));
-    ASSERT_TRUE(resultTwo.valid());
-    auto [statusTwo, fenceTwo] = resultTwo.get();
-    ASSERT_EQ(NO_ERROR, statusTwo);
-    if (fenceTwo.ok()) {
-        sync_wait(fenceTwo.get(), -1);
-    }
+    ftl::Future<FenceResult> futureTwo =
+            mRE->drawLayers(settings, layers, mBuffer, true, base::unique_fd(fenceOne->dup()));
+    ASSERT_TRUE(futureTwo.valid());
+    auto resultTwo = futureTwo.get();
+    ASSERT_TRUE(resultTwo.ok());
+    auto fenceTwo = resultTwo.value();
+    fenceTwo->waitForever(LOG_TAG);
 
     // Only cleanup the first time.
     EXPECT_FALSE(mRE->canSkipPostRenderCleanup());
diff --git a/libs/renderengine/tests/RenderEngineThreadedTest.cpp b/libs/renderengine/tests/RenderEngineThreadedTest.cpp
index 909ded3..1a96289 100644
--- a/libs/renderengine/tests/RenderEngineThreadedTest.cpp
+++ b/libs/renderengine/tests/RenderEngineThreadedTest.cpp
@@ -183,20 +183,17 @@
     base::unique_fd bufferFence;
 
     EXPECT_CALL(*mRenderEngine, drawLayersInternal)
-            .WillOnce([&](const std::shared_ptr<std::promise<renderengine::RenderEngineResult>>&&
-                                  resultPromise,
+            .WillOnce([&](const std::shared_ptr<std::promise<FenceResult>>&& resultPromise,
                           const renderengine::DisplaySettings&,
                           const std::vector<renderengine::LayerSettings>&,
                           const std::shared_ptr<renderengine::ExternalTexture>&, const bool,
-                          base::unique_fd&&) -> void {
-                resultPromise->set_value({NO_ERROR, base::unique_fd()});
-            });
+                          base::unique_fd&&) { resultPromise->set_value(Fence::NO_FENCE); });
 
-    std::future<renderengine::RenderEngineResult> result =
+    ftl::Future<FenceResult> future =
             mThreadedRE->drawLayers(settings, layers, buffer, false, std::move(bufferFence));
-    ASSERT_TRUE(result.valid());
-    auto [status, _] = result.get();
-    ASSERT_EQ(NO_ERROR, status);
+    ASSERT_TRUE(future.valid());
+    auto result = future.get();
+    ASSERT_TRUE(result.ok());
 }
 
 } // namespace android
diff --git a/libs/renderengine/threaded/RenderEngineThreaded.cpp b/libs/renderengine/threaded/RenderEngineThreaded.cpp
index 203bb54..b41e843 100644
--- a/libs/renderengine/threaded/RenderEngineThreaded.cpp
+++ b/libs/renderengine/threaded/RenderEngineThreaded.cpp
@@ -313,21 +313,21 @@
 }
 
 void RenderEngineThreaded::drawLayersInternal(
-        const std::shared_ptr<std::promise<RenderEngineResult>>&& resultPromise,
+        const std::shared_ptr<std::promise<FenceResult>>&& resultPromise,
         const DisplaySettings& display, const std::vector<LayerSettings>& layers,
         const std::shared_ptr<ExternalTexture>& buffer, const bool useFramebufferCache,
         base::unique_fd&& bufferFence) {
-    resultPromise->set_value({NO_ERROR, base::unique_fd()});
+    resultPromise->set_value(Fence::NO_FENCE);
     return;
 }
 
-std::future<RenderEngineResult> RenderEngineThreaded::drawLayers(
+ftl::Future<FenceResult> RenderEngineThreaded::drawLayers(
         const DisplaySettings& display, const std::vector<LayerSettings>& layers,
         const std::shared_ptr<ExternalTexture>& buffer, const bool useFramebufferCache,
         base::unique_fd&& bufferFence) {
     ATRACE_CALL();
-    const auto resultPromise = std::make_shared<std::promise<RenderEngineResult>>();
-    std::future<RenderEngineResult> resultFuture = resultPromise->get_future();
+    const auto resultPromise = std::make_shared<std::promise<FenceResult>>();
+    std::future<FenceResult> resultFuture = resultPromise->get_future();
     int fd = bufferFence.release();
     {
         std::lock_guard lock(mThreadMutex);
diff --git a/libs/renderengine/threaded/RenderEngineThreaded.h b/libs/renderengine/threaded/RenderEngineThreaded.h
index 1340902..bf2ebea 100644
--- a/libs/renderengine/threaded/RenderEngineThreaded.h
+++ b/libs/renderengine/threaded/RenderEngineThreaded.h
@@ -56,11 +56,11 @@
     void useProtectedContext(bool useProtectedContext) override;
     void cleanupPostRender() override;
 
-    std::future<RenderEngineResult> drawLayers(const DisplaySettings& display,
-                                               const std::vector<LayerSettings>& layers,
-                                               const std::shared_ptr<ExternalTexture>& buffer,
-                                               const bool useFramebufferCache,
-                                               base::unique_fd&& bufferFence) override;
+    ftl::Future<FenceResult> drawLayers(const DisplaySettings& display,
+                                        const std::vector<LayerSettings>& layers,
+                                        const std::shared_ptr<ExternalTexture>& buffer,
+                                        const bool useFramebufferCache,
+                                        base::unique_fd&& bufferFence) override;
 
     void cleanFramebufferCache() override;
     int getContextPriority() override;
@@ -73,7 +73,7 @@
     void mapExternalTextureBuffer(const sp<GraphicBuffer>& buffer, bool isRenderable) override;
     void unmapExternalTextureBuffer(const sp<GraphicBuffer>& buffer) override;
     bool canSkipPostRenderCleanup() const override;
-    void drawLayersInternal(const std::shared_ptr<std::promise<RenderEngineResult>>&& resultPromise,
+    void drawLayersInternal(const std::shared_ptr<std::promise<FenceResult>>&& resultPromise,
                             const DisplaySettings& display,
                             const std::vector<LayerSettings>& layers,
                             const std::shared_ptr<ExternalTexture>& buffer,
diff --git a/libs/ui/include/ui/FenceResult.h b/libs/ui/include/ui/FenceResult.h
new file mode 100644
index 0000000..6d63fc9
--- /dev/null
+++ b/libs/ui/include/ui/FenceResult.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright 2022 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/expected.h>
+#include <utils/Errors.h>
+#include <utils/StrongPointer.h>
+
+namespace android {
+
+class Fence;
+
+using FenceResult = base::expected<sp<Fence>, status_t>;
+
+inline status_t fenceStatus(const FenceResult& fenceResult) {
+    return fenceResult.ok() ? NO_ERROR : fenceResult.error();
+}
+
+} // namespace android