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93 lines
2.9 KiB
93 lines
2.9 KiB
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Surface 的绘制原理
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---
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1. Surface 绘制的 buffer 是怎么来的？
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2. buffer 绘制完了又是怎么提交的？
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```java
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private void performTraversals(){
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performMeasure();
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performLayout();
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performDraw();
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}
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private void draw(boolean fullRedrawNeeded){
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Surface surface = mSurface;
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drawSoftware(surface, mAttachInfo, ..., dirty);
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}
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private boolean drawSoftware(Surface surface, ...){
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final Canvas canvas;
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canvas = mSurface.lockCanvas(dirty);
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mView.draw(canvas);
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surface.unlockCanvasAndPost(canvas);
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}
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static jlong nativeLockCanvas(JNIEnv* env, jclass clazz, jlong nativeObject, jobject canvasObj, jobject dirtyRectObj){
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sp<Surface> surface(reinterpert_cast<Surface *>(nativeObject));
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ANativeWindow_Buffer outBuffer;
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surface->lock(&outBuffer, dirtyRectPtr);
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SkBitmap bitmap;
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bitmap.setPixels(outBuffer.bits);
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Canvas* nativeCanvas = GraphicsJNI::getNativeCanvas(env, canvasObj);
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nativeCanvas->setBitmap(bitmap);
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sp<Surface> lockedSurface(surface);
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return (jlong)lockedSurface.get();
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}
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```
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每次绘制都要重新申请一块 buffer，它是怎么申请的？
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```c++
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status_t Surface::lock(ANativeWindow_Buffer* outBuffer, ...){
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ANativeWindowBuffer* out;
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dequeueBuffer(&out, &fenceFd);
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sp<GraphicBuffer> backBuffer(GraphicBuffer::getSelf(out));
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void* vaddr;
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status_t res = backBuffer->lockAsync(..., &vaddr, fenceFd);
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mLockedBuffer = backBuffer;
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outBuffer->bits = vaddr;
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}
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int Surface::dequeueBuffer(android_native_buffer_t** buffer, ...){
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int buf = -1;
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status_t result = mGraphicBufferProduct->dequeueBuffer(&buf, ...);
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sp<GraphicBuffer>& gbuf(mSlot[buf].buffer);
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if((result&IGraphicBufferProduct::BUFFER_NEEDS_REALLOCATION)||gbuf == 0){
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result = mGraphicBufferProduct->requestBuffer(buf, &gbuf);
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}
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*buffer = gbuf.get();
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return OK;
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}
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```
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Buffer 是怎么提交的？
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```c++
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public void unlockCanvasAndPost(Canvas canvas){
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synchronized(mLock){
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unlockSwCanvasAndPost(canvas);
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}
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}
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private void unlockSwCanvasAndPost(Canvas canvas){
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nativeUnlockCanvasAndPost(mLockedObject, canvas);
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nativeRelease(mLockedObject);
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mLockedObject = 0;
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}
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static void nativeUnlockCanvasAndPost(JNIEnv* env, jclass clazz, jlong nativeObject, jobject canvasObj) {
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sp<Surface> surface(reinterpret_cast<Surface *>(nativeObject));
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Canvas* nativeCanvas = GraphicsJNI::getNativeCanvas(env, canvasObj);
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nativeCanvas->setBitmap(SkBitmap());
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surface->unlockAndPost();
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}
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status_t Surface::unlockAndPost(){
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mLockedBuffer->unlockAsync(...);
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queueBuffer(mLockedBuffer.get(), ...);
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mPostedBuffer = mLockedBuffer;
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mLockedBuffer = 0;
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return err;
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}
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int Surface::queueBuffer(android_native_buffer_t* buffer, ...){
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int i = getSlotFromBufferLocked(buffer);
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mGraphicBufferProducer->queueBuffer(i, ...);
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}
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```
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