android_frameworks_base/libs/hwui/SkiaDisplayList.h

/*
 * Copyright (C) 2016 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 "DisplayList.h"
#include "SkiaDrawables.h"

#include <deque>
#include <SkLiteDL.h>
#include <SkPictureRecorder.h>

namespace android {
namespace uirenderer {

/**
 * This class is intended to be self contained, but still subclasses from
 * DisplayList to make it easier to support switching between the two at
 * runtime.  The downside of this inheritance is that we pay for the overhead
 * of the parent class construction/destruction without any real benefit.
 */
class SkiaDisplayList : public DisplayList {
public:
    SkiaDisplayList(SkRect bounds);
    virtual ~SkiaDisplayList() {
        /* Given that we are using a LinearStdAllocator to store some of the
         * SkDrawable contents we must ensure that any other object that is
         * holding a reference to those drawables is destroyed prior to their
         * deletion.
         */
        mDrawable.reset();
    }

    /**
     * This resets the DisplayList so that it behaves as if the object were newly
     * constructed with the provided bounds.  The reuse avoids any overhead
     * associated with destroying the SkLiteDL as well as the deques and vectors.
     */
    void reset(GrContext* context, SkRect bounds);

    /**
     * Use the linear allocator to create any SkDrawables needed by the display
     * list. This could be dangerous as these objects are ref-counted, so we
     * need to monitor that they don't extend beyond the lifetime of the class
     * that creates them.
     */
    template<class T, typename... Params>
    SkDrawable* allocateDrawable(Params&&... params) {
        return allocator.create<T>(std::forward<Params>(params)...);
    }

    bool isSkiaDL() const override { return true; }

    /**
     * Returns true if the DisplayList does not have any recorded content
     */
    bool isEmpty() const override { return mDrawable->empty(); }

    /**
     * Returns true if this list directly contains a GLFunctor drawing command.
     */
    bool hasFunctor() const override { return !mChildFunctors.empty(); }

    /**
     * Returns true if this list directly contains a VectorDrawable drawing command.
     */
    bool hasVectorDrawables() const override { return !mVectorDrawables.empty(); }

    /**
     * Attempts to reset and reuse this DisplayList.
     *
     * @return true if the displayList will be reused and therefore should not be deleted
     */
    bool reuseDisplayList(RenderNode* node, renderthread::CanvasContext* context) override;

    /**
     * ONLY to be called by RenderNode::syncDisplayList so that we can notify any
     * contained VectorDrawables or GLFunctors to sync their state.
     *
     * NOTE: This function can be folded into RenderNode when we no longer need
     *       to subclass from DisplayList
     */
    void syncContents() override;

    /**
     * ONLY to be called by RenderNode::prepareTree in order to prepare this
     * list while the UI thread is blocked.  Here we can upload mutable bitmaps
     * and notify our parent if any of our content has been invalidated and in
     * need of a redraw.  If the renderNode has any children then they are also
     * call in order to prepare them.
     *
     * @return true if any content change requires the node to be invalidated
     *
     * NOTE: This function can be folded into RenderNode when we no longer need
     *       to subclass from DisplayList
     */

    bool prepareListAndChildren(TreeInfo& info, bool functorsNeedLayer,
            std::function<void(RenderNode*, TreeInfo&, bool)> childFn) override;

    /**
     *  Calls the provided function once for each child of this DisplayList
     */
    void updateChildren(std::function<void(RenderNode*)> updateFn) override;

    /**
     * Pin/Unpin any mutable images to the GPU cache. A pinned images is
     * guaranteed to be remain in the cache until it has been unpinned which
     * we leverage to avoid making a CPU copy of the pixels.
     */
    void pinImages(GrContext* context);
    void unpinImages(GrContext* context);

    /**
     * If a SkiaDisplayList is deleted on the UI thread we cache a list of any
     * images that need unpinned from the GPU cache and call this function on
     * a subsequent frame to perform that cleanup.
     */
    static void cleanupImages(GrContext* context);

    /**
     * We use std::deque here because (1) we need to iterate through these
     * elements and (2) mDrawable holds pointers to the elements, so they cannot
     * relocate.
     */
    std::deque<RenderNodeDrawable> mChildNodes;
    std::deque<GLFunctorDrawable> mChildFunctors;
    std::vector<SkImage*> mMutableImages;
    std::vector<VectorDrawableRoot*> mVectorDrawables;
    sk_sp<SkLiteDL> mDrawable;

    bool mIsProjectionReceiver = false;

private:
    bool mPinnedImages = false;
};

}; // namespace uirenderer
}; // namespace android