Recycle OffscreenBuffers

Change-Id: Ia2e219026f211a5308ecf8209c5f986bb888aadd
diff --git a/libs/hwui/renderstate/OffscreenBufferPool.cpp b/libs/hwui/renderstate/OffscreenBufferPool.cpp
new file mode 100644
index 0000000..6b44557
--- /dev/null
+++ b/libs/hwui/renderstate/OffscreenBufferPool.cpp
@@ -0,0 +1,196 @@
+/*
+ * Copyright (C) 2015 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 "OffscreenBufferPool.h"
+
+#include "Caches.h"
+#include "Properties.h"
+#include "renderstate/RenderState.h"
+#include "utils/FatVector.h"
+
+#include <utils/Log.h>
+
+#include <GLES2/gl2.h>
+
+namespace android {
+namespace uirenderer {
+
+////////////////////////////////////////////////////////////////////////////////
+// OffscreenBuffer
+////////////////////////////////////////////////////////////////////////////////
+
+OffscreenBuffer::OffscreenBuffer(RenderState& renderState, Caches& caches,
+        uint32_t viewportWidth, uint32_t viewportHeight)
+        : renderState(renderState)
+        , viewportWidth(viewportWidth)
+        , viewportHeight(viewportHeight)
+        , texture(caches) {
+    texture.width = computeIdealDimension(viewportWidth);
+    texture.height = computeIdealDimension(viewportHeight);
+    texture.blend = true;
+
+    caches.textureState().activateTexture(0);
+    glGenTextures(1, &texture.id);
+    caches.textureState().bindTexture(GL_TEXTURE_2D, texture.id);
+
+    texture.setWrap(GL_CLAMP_TO_EDGE, false, false, GL_TEXTURE_2D);
+    // not setting filter on texture, since it's set when drawing, based on transform
+
+    glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, texture.width, texture.height, 0,
+            GL_RGBA, GL_UNSIGNED_BYTE, nullptr);
+}
+
+void OffscreenBuffer::updateMeshFromRegion() {
+    // avoid T-junctions as they cause artifacts in between the resultant
+    // geometry when complex transforms occur.
+    // TODO: generate the safeRegion only if necessary based on drawing transform
+    Region safeRegion = Region::createTJunctionFreeRegion(region);
+
+    size_t count;
+    const android::Rect* rects = safeRegion.getArray(&count);
+
+    const float texX = 1.0f / float(texture.width);
+    const float texY = 1.0f / float(texture.height);
+
+    FatVector<TextureVertex, 64> meshVector(count * 4); // uses heap if more than 64 vertices needed
+    TextureVertex* mesh = &meshVector[0];
+    for (size_t i = 0; i < count; i++) {
+        const android::Rect* r = &rects[i];
+
+        const float u1 = r->left * texX;
+        const float v1 = (viewportHeight - r->top) * texY;
+        const float u2 = r->right * texX;
+        const float v2 = (viewportHeight - r->bottom) * texY;
+
+        TextureVertex::set(mesh++, r->left, r->top, u1, v1);
+        TextureVertex::set(mesh++, r->right, r->top, u2, v1);
+        TextureVertex::set(mesh++, r->left, r->bottom, u1, v2);
+        TextureVertex::set(mesh++, r->right, r->bottom, u2, v2);
+    }
+    elementCount = count * 6;
+    renderState.meshState().genOrUpdateMeshBuffer(&vbo,
+            sizeof(TextureVertex) * count * 4,
+            &meshVector[0],
+            GL_DYNAMIC_DRAW); // TODO: GL_STATIC_DRAW if savelayer
+}
+
+uint32_t OffscreenBuffer::computeIdealDimension(uint32_t dimension) {
+    return uint32_t(ceilf(dimension / float(LAYER_SIZE)) * LAYER_SIZE);
+}
+
+OffscreenBuffer::~OffscreenBuffer() {
+    texture.deleteTexture();
+    renderState.meshState().deleteMeshBuffer(vbo);
+    elementCount = 0;
+    vbo = 0;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// OffscreenBufferPool
+///////////////////////////////////////////////////////////////////////////////
+
+OffscreenBufferPool::OffscreenBufferPool()
+    : mMaxSize(Properties::layerPoolSize) {
+}
+
+OffscreenBufferPool::~OffscreenBufferPool() {
+    clear(); // TODO: unique_ptr?
+}
+
+int OffscreenBufferPool::Entry::compare(const Entry& lhs, const Entry& rhs) {
+    int deltaInt = int(lhs.width) - int(rhs.width);
+    if (deltaInt != 0) return deltaInt;
+
+    return int(lhs.height) - int(rhs.height);
+}
+
+void OffscreenBufferPool::clear() {
+    for (auto entry : mPool) {
+        delete entry.layer;
+    }
+    mPool.clear();
+    mSize = 0;
+}
+
+OffscreenBuffer* OffscreenBufferPool::get(RenderState& renderState,
+        const uint32_t width, const uint32_t height) {
+    OffscreenBuffer* layer = nullptr;
+
+    Entry entry(width, height);
+    auto iter = mPool.find(entry);
+
+    if (iter != mPool.end()) {
+        entry = *iter;
+        mPool.erase(iter);
+
+        layer = entry.layer;
+        layer->viewportWidth = width;
+        layer->viewportHeight = height;
+        mSize -= layer->getSizeInBytes();
+    } else {
+        layer = new OffscreenBuffer(renderState, Caches::getInstance(), width, height);
+    }
+
+    return layer;
+}
+
+OffscreenBuffer* OffscreenBufferPool::resize(OffscreenBuffer* layer,
+        const uint32_t width, const uint32_t height) {
+    RenderState& renderState = layer->renderState;
+    if (layer->texture.width == OffscreenBuffer::computeIdealDimension(width)
+            && layer->texture.height == OffscreenBuffer::computeIdealDimension(height)) {
+        // resize in place
+        layer->viewportWidth = width;
+        layer->viewportHeight = height;
+        return layer;
+    }
+    putOrDelete(layer);
+    return get(renderState, width, height);
+}
+
+void OffscreenBufferPool::dump() {
+    for (auto entry : mPool) {
+        ALOGD("  Layer size %dx%d", entry.width, entry.height);
+    }
+}
+
+void OffscreenBufferPool::putOrDelete(OffscreenBuffer* layer) {
+    const uint32_t size = layer->getSizeInBytes();
+    // Don't even try to cache a layer that's bigger than the cache
+    if (size < mMaxSize) {
+        // TODO: Use an LRU
+        while (mSize + size > mMaxSize) {
+            OffscreenBuffer* victim = mPool.begin()->layer;
+            mSize -= victim->getSizeInBytes();
+            delete victim;
+            mPool.erase(mPool.begin());
+        }
+
+        // clear region, since it's no longer valid
+        layer->region.clear();
+
+        Entry entry(layer);
+
+        mPool.insert(entry);
+        mSize += size;
+    } else {
+        delete layer;
+    }
+}
+
+}; // namespace uirenderer
+}; // namespace android
diff --git a/libs/hwui/renderstate/OffscreenBufferPool.h b/libs/hwui/renderstate/OffscreenBufferPool.h
new file mode 100644
index 0000000..f0fd82d
--- /dev/null
+++ b/libs/hwui/renderstate/OffscreenBufferPool.h
@@ -0,0 +1,142 @@
+/*
+ * Copyright (C) 2015 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.
+ */
+
+#ifndef ANDROID_HWUI_OFFSCREEN_BUFFER_POOL_H
+#define ANDROID_HWUI_OFFSCREEN_BUFFER_POOL_H
+
+#include "Caches.h"
+#include "Texture.h"
+#include "utils/Macros.h"
+
+#include <ui/Region.h>
+
+#include <set>
+
+namespace android {
+namespace uirenderer {
+
+class RenderState;
+
+/**
+ * Lightweight alternative to Layer. Owns the persistent state of an offscreen render target, and
+ * encompasses enough information to draw it back on screen (minus paint properties, which are held
+ * by LayerOp).
+ */
+class OffscreenBuffer {
+public:
+    OffscreenBuffer(RenderState& renderState, Caches& caches,
+            uint32_t viewportWidth, uint32_t viewportHeight);
+    ~OffscreenBuffer();
+
+    // must be called prior to rendering, to construct/update vertex buffer
+    void updateMeshFromRegion();
+
+    static uint32_t computeIdealDimension(uint32_t dimension);
+
+    uint32_t getSizeInBytes() { return texture.width * texture.height * 4; }
+
+    RenderState& renderState;
+    uint32_t viewportWidth;
+    uint32_t viewportHeight;
+    Texture texture;
+
+    // Portion of layer that has been drawn to. Used to minimize drawing area when
+    // drawing back to screen / parent FBO.
+    Region region;
+    GLsizei elementCount = 0;
+    GLuint vbo = 0;
+};
+
+/**
+ * Pool of OffscreenBuffers allocated, but not currently in use.
+ */
+class OffscreenBufferPool {
+public:
+    OffscreenBufferPool();
+    ~OffscreenBufferPool();
+
+    WARN_UNUSED_RESULT OffscreenBuffer* get(RenderState& renderState,
+            const uint32_t width, const uint32_t height);
+
+    WARN_UNUSED_RESULT OffscreenBuffer* resize(OffscreenBuffer* layer,
+            const uint32_t width, const uint32_t height);
+
+    void putOrDelete(OffscreenBuffer* layer);
+
+    /**
+     * Clears the pool. This causes all layers to be deleted.
+     */
+    void clear();
+
+    /**
+     * Returns the maximum size of the pool in bytes.
+     */
+    uint32_t getMaxSize() { return mMaxSize; }
+
+    /**
+     * Returns the current size of the pool in bytes.
+     */
+    uint32_t getSize() { return mSize; }
+
+    size_t getCount() { return mPool.size(); }
+
+    /**
+     * Prints out the content of the pool.
+     */
+    void dump();
+private:
+    struct Entry {
+        Entry() {}
+
+        Entry(const uint32_t layerWidth, const uint32_t layerHeight)
+                : width(OffscreenBuffer::computeIdealDimension(layerWidth))
+                , height(OffscreenBuffer::computeIdealDimension(layerHeight)) {}
+
+        Entry(OffscreenBuffer* layer)
+                : layer(layer)
+                , width(layer->texture.width)
+                , height(layer->texture.height) {
+        }
+
+        static int compare(const Entry& lhs, const Entry& rhs);
+
+        bool operator==(const Entry& other) const {
+            return compare(*this, other) == 0;
+        }
+
+        bool operator!=(const Entry& other) const {
+            return compare(*this, other) != 0;
+        }
+
+        bool operator<(const Entry& other) const {
+            return Entry::compare(*this, other) < 0;
+        }
+
+        OffscreenBuffer* layer = nullptr;
+        uint32_t width = 0;
+        uint32_t height = 0;
+    }; // struct Entry
+
+    std::multiset<Entry> mPool;
+
+    uint32_t mSize = 0;
+    uint32_t mMaxSize;
+}; // class OffscreenBufferCache
+
+}; // namespace uirenderer
+}; // namespace android
+
+#endif // ANDROID_HWUI_OFFSCREEN_BUFFER_POOL_H
diff --git a/libs/hwui/renderstate/RenderState.cpp b/libs/hwui/renderstate/RenderState.cpp
index 9637117..4fa8200 100644
--- a/libs/hwui/renderstate/RenderState.cpp
+++ b/libs/hwui/renderstate/RenderState.cpp
@@ -90,6 +90,8 @@
     }
 */
 
+    mLayerPool.clear();
+
     // TODO: reset all cached state in state objects
     std::for_each(mActiveLayers.begin(), mActiveLayers.end(), layerLostGlContext);
     mAssetAtlas.terminate();
@@ -106,6 +108,19 @@
     mStencil = nullptr;
 }
 
+void RenderState::flush(Caches::FlushMode mode) {
+    switch (mode) {
+        case Caches::FlushMode::Full:
+            // fall through
+        case Caches::FlushMode::Moderate:
+            // fall through
+        case Caches::FlushMode::Layers:
+            mLayerPool.clear();
+            break;
+    }
+    mCaches->flush(mode);
+}
+
 void RenderState::setViewport(GLsizei width, GLsizei height) {
     mViewportWidth = width;
     mViewportHeight = height;
diff --git a/libs/hwui/renderstate/RenderState.h b/libs/hwui/renderstate/RenderState.h
index 3cda170..dcd5ea6 100644
--- a/libs/hwui/renderstate/RenderState.h
+++ b/libs/hwui/renderstate/RenderState.h
@@ -21,6 +21,7 @@
 #include "Glop.h"
 #include "renderstate/Blend.h"
 #include "renderstate/MeshState.h"
+#include "renderstate/OffscreenBufferPool.h"
 #include "renderstate/PixelBufferState.h"
 #include "renderstate/Scissor.h"
 #include "renderstate/Stencil.h"
@@ -56,6 +57,8 @@
     void onGLContextCreated();
     void onGLContextDestroyed();
 
+    void flush(Caches::FlushMode flushMode);
+
     void setViewport(GLsizei width, GLsizei height);
     void getViewport(GLsizei* outWidth, GLsizei* outHeight);
 
@@ -97,6 +100,8 @@
     Scissor& scissor() { return *mScissor; }
     Stencil& stencil() { return *mStencil; }
 
+    OffscreenBufferPool& layerPool() { return mLayerPool; }
+
     void dump();
 
 private:
@@ -116,6 +121,8 @@
     Scissor* mScissor = nullptr;
     Stencil* mStencil = nullptr;
 
+    OffscreenBufferPool mLayerPool;
+
     AssetAtlas mAssetAtlas;
     std::set<Layer*> mActiveLayers;
     std::set<renderthread::CanvasContext*> mRegisteredContexts;