9.Vsync第二部分
在上一篇中我们讲到，视图的刷新需要很多步骤，
void SurfaceFlinger::handleMessageRefresh() {
ATRACE_CALL();
preComposition(); //合成前的准备
rebuildLayerStacks();//重新建立layer堆栈
setUpHWComposer();//HWComposer的设定
#ifdef QCOM_BSP
setUpTiledDr();
#endif
doDebugFlashRegions();
doComposition(); //正式合成工作
postComposition(); //合成的后期工作
}
本文将继续分析这些过程。
9.1 handlerMessageInvalidate
invalidate 字面意思就是使无效，更进一步就是当前的buffer已经无限，请刷新界面。
啥也没干，buffer已经无效，我换下一个，就是handlePageFlip
void SurfaceFlinger::handleMessageInvalidate() {
ATRACE_CALL();
handlePageFlip();
}
再来看这个函数：handlePageFlip
bool SurfaceFlinger::handlePageFlip()
{
Region dirtyRegion; bool visibleRegions = false;
const LayerVector& layers(mDrawingState.layersSortedByZ);
bool frameQueued = false; // Store the set of layers that need updates. This set must not change as
// buffers are being latched, as this could result in a deadlock.
// Example: Two producers share the same command stream and:
// 1.) Layer 0 is latched
// 2.) Layer 0 gets a new frame
// 2.) Layer 1 gets a new frame
// 3.) Layer 1 is latched.
// Display is now waiting on Layer 1's frame, which is behind layer 0's
// second frame. But layer 0's second frame could be waiting on display.
Vector<Layer*> layersWithQueuedFrames;
for (size_t i = , count = layers.size(); i<count ; i++) {
const sp<Layer>& layer(layers[i]);
if (layer->hasQueuedFrame()) {
frameQueued = true;
if (layer->shouldPresentNow(mPrimaryDispSync)) {
layersWithQueuedFrames.push_back(layer.get());
}
}
}
for (size_t i = , count = layersWithQueuedFrames.size() ; i<count ; i++) {
Layer* layer = layersWithQueuedFrames[i];
const Region dirty(layer->latchBuffer(visibleRegions));
const Layer::State& s(layer->getDrawingState());
invalidateLayerStack(s.layerStack, dirty);
} mVisibleRegionsDirty |= visibleRegions; // If we will need to wake up at some time in the future to deal with a
// queued frame that shouldn't be displayed during this vsync period, wake
// up during the next vsync period to check again.
if (frameQueued && layersWithQueuedFrames.empty()) {
signalLayerUpdate();
} // Only continue with the refresh if there is actually new work to do
return !layersWithQueuedFrames.empty();
}
handlePageFlip
@step1:layer->latchBuffer(visibleRegions) 通过该函数锁定各layer的缓冲区。可以理解这个函数一定与BufferQueue有关。
status_t updateResult = mSurfaceFlingerConsumer->updateTexImage(&r,
mFlinger->mPrimaryDispSync);
上面是latchBuffer的核心语句。SurfaceFlingerConsumer前文已经提过，是client端操作bufferqueue的一个端口。所以这个函数一定是操作bufferqueue的。
// Acquire the next buffer.
// In asynchronous mode the list is guaranteed to be one buffer
// deep, while in synchronous mode we use the oldest buffer.
err = acquireBufferLocked(&item, computeExpectedPresent(dispSync));
if (err != NO_ERROR) {
if (err == BufferQueue::NO_BUFFER_AVAILABLE) {
err = NO_ERROR;
} else if (err == BufferQueue::PRESENT_LATER) {
// return the error, without logging
} else {
ALOGE("updateTexImage: acquire failed: %s (%d)",
strerror(-err), err);
}
return err;
} // We call the rejecter here, in case the caller has a reason to
// not accept this buffer. This is used by SurfaceFlinger to
// reject buffers which have the wrong size
int buf = item.mBuf;
if (rejecter && rejecter->reject(mSlots[buf].mGraphicBuffer, item)) {
releaseBufferLocked(buf, mSlots[buf].mGraphicBuffer, EGL_NO_SYNC_KHR);
return NO_ERROR;
} // Release the previous buffer.
err = updateAndReleaseLocked(item);
if (err != NO_ERROR) {
return err;
}
看了注释，基本解释了大体的过程。
1) 请求新的buffer
2）通过rejecter来判断申请的buffer是否满足surfaceflinger的要求。
3）释放之前的buffer
具体流程可以参考如下：
@step2：SurfaceFlinger:invalidateLayerStack来更新各个区域。
9.2 preComposition 合成前的准备
首先来看2个Vsync Rate相关的代码：
virtual void setVsyncRate(uint32_t count)
virtual void requestNextVsync()
当count为1时，表示每个信号都要报告，当count =2 时，表示信号 一个间隔一个报告，当count =0时，表示不自动报告，除非主动触发requestNextVsync
void SurfaceFlinger::preComposition()
{
bool needExtraInvalidate = false;
const LayerVector& layers(mDrawingState.layersSortedByZ);
const size_t count = layers.size();
for (size_t i= ; i<count ; i++) {
if (layers[i]->onPreComposition()) {
needExtraInvalidate = true;
}
}
if (needExtraInvalidate) {
signalLayerUpdate();
}
}
代码很简单，其实一共就3步，
1）获取全部的layer
2）每个layer onPrecomposition
3) layer update
bool Layer::onPreComposition() {
mRefreshPending = false;
return mQueuedFrames > || mSidebandStreamChanged;
}
也就是说，当layer里存放被queue的frame以后，就会出发layer update.
void SurfaceFlinger::signalLayerUpdate() {
mEventQueue.invalidate();
}
最终会调用：
void EventThread::Connection::requestNextVsync() {
mEventThread->requestNextVsync(this);
}
void EventThread::requestNextVsync(
const sp<EventThread::Connection>& connection) {
Mutex::Autolock _l(mLock);
if (connection->count < ) {
connection->count = ;
mCondition.broadcast();//通知对vsync感兴趣的类
}
}
那么谁在等待这个broadcast呢？
还是EventThread
void EventThread::onVSyncEvent(nsecs_t timestamp) {
Mutex::Autolock _l(mLock);
mVSyncEvent[].header.type = DisplayEventReceiver::DISPLAY_EVENT_VSYNC;
mVSyncEvent[].header.id = ;
mVSyncEvent[].header.timestamp = timestamp;
mVSyncEvent[].vsync.count++;
mCondition.broadcast();
}
9.3可见区域rebuildlayerStack
void SurfaceFlinger::rebuildLayerStacks() {
#ifdef QCOM_BSP
char prop[PROPERTY_VALUE_MAX];
property_get("sys.extended_mode", prop, "");
sExtendedMode = atoi(prop) ? true : false;
#endif
// rebuild the visible layer list per screen
if (CC_UNLIKELY(mVisibleRegionsDirty)) {
ATRACE_CALL();
mVisibleRegionsDirty = false;
invalidateHwcGeometry();
const LayerVector& layers(mDrawingState.layersSortedByZ);
for (size_t dpy= ; dpy<mDisplays.size() ; dpy++) {
Region opaqueRegion;
Region dirtyRegion;
Vector< sp<Layer> > layersSortedByZ;
const sp<DisplayDevice>& hw(mDisplays[dpy]);
const Transform& tr(hw->getTransform());
const Rect bounds(hw->getBounds());
int dpyId = hw->getHwcDisplayId();
if (hw->isDisplayOn()) {
SurfaceFlinger::computeVisibleRegions(dpyId, layers,
hw->getLayerStack(), dirtyRegion, opaqueRegion);
const size_t count = layers.size();
for (size_t i= ; i<count ; i++) {
const sp<Layer>& layer(layers[i]);
const Layer::State& s(layer->getDrawingState());
Region drawRegion(tr.transform(
layer->visibleNonTransparentRegion));
drawRegion.andSelf(bounds);
if (!drawRegion.isEmpty()) {
layersSortedByZ.add(layer);
}
}
}
hw->setVisibleLayersSortedByZ(layersSortedByZ);
hw->undefinedRegion.set(bounds);
hw->undefinedRegion.subtractSelf(tr.transform(opaqueRegion));
hw->dirtyRegion.orSelf(dirtyRegion);
}
}
}
rebuildLayerStacks
前文提到mVisibleRegionsDirty这个变量是标记要刷新的可见区域的，我们按字面意思解释下：脏的可见区域，顾名思义，这就是要刷新的区域，因为buffer已经“脏”了。
@step1：系统的display可能不止一个，存在与mDisplays中。
@step2：computeVisibleRegions这个函数根据所有的layer状态，得到2个重要的变量。opaqueRegion & dirtyRegion
dirtyRegion是需要被刷新的。 opaqueRegion 不透明区域，应为layer是按Z-order排序的，左右排在前面的opaqueRegion 会挡住后面的layer。
@step3：Region drawRegion(tr.transform( layer->visibleNonTransparentRegion));程序需要进一步得出每个layer 绘制的区域。
系统的display（显示器）可能不止一个，但是所有的layer都记录在layersSortedByZ里面。记录每个layer属于那个display的变量是 hw->getLayerStack()
@step4：将结果保存到hw中。
这里的不透明区域 是很有意义的一个概念，就是我们在Z-order 上，越靠近用户的时候，值越大，所以是递减操作。
9.4 setUpHWComposer 搭建环境
用于合成surface的功能模块可以有2个，OpenGL ES & HWC，它的管理实在HWC里面实现的。
setUpHWComposer 总的来说就干了3件事情。
1）构造Worklist，并且给DisplayData:list 申请空间
2）填充各layer数据
3）报告HWC（有其他地方决定使用那个）
9.5 doCompostion
关键地方来了，上面的setUpHWComposer 只是交给HWC来负责显示，真正显示的地方就在这里。
1）如何合成
2）如何显示到屏幕上
合成的流程大体如上图。
有了概念后，分析源码：
void SurfaceFlinger::doComposition() {
ATRACE_CALL();
const bool repaintEverything = android_atomic_and(, &mRepaintEverything);
for (size_t dpy= ; dpy<mDisplays.size() ; dpy++) {
const sp<DisplayDevice>& hw(mDisplays[dpy]);
if (hw->isDisplayOn()) {
// transform the dirty region into this screen's coordinate space
const Region dirtyRegion(hw->getDirtyRegion(repaintEverything));
// repaint the framebuffer (if needed)
doDisplayComposition(hw, dirtyRegion);
++mActiveFrameSequence;
hw->dirtyRegion.clear();
hw->flip(hw->swapRegion);
hw->swapRegion.clear();
}
// inform the h/w that we're done compositing
hw->compositionComplete();
}
postFramebuffer();
}
变量mRepaintEverything用于说明，是否需要全部重绘所有内容。如果为true的化，那么dirtyRegion就是displaydevice的 width & height构成的RECT。
否则由dirtyRegion转换而来。
doDisplayComposition是每个Display来处理，有可能会用到OpenGL 的接口来交换buffer。
hw->compositionComplete(); 通知HWC合成结束了。
postFramebuffer HWC的Set接口调用。
9.5.1 doDisplayComposition
void SurfaceFlinger::doDisplayComposition(const sp<const DisplayDevice>& hw,
const Region& inDirtyRegion)
{
// We only need to actually compose the display if:
// 1) It is being handled by hardware composer, which may need this to
// keep its virtual display state machine in sync, or
// 2) There is work to be done (the dirty region isn't empty)
bool isHwcDisplay = hw->getHwcDisplayId() >= ;
if (!isHwcDisplay && inDirtyRegion.isEmpty()) {
return;
} Region dirtyRegion(inDirtyRegion); // compute the invalid region
hw->swapRegion.orSelf(dirtyRegion); uint32_t flags = hw->getFlags();
if (flags & DisplayDevice::SWAP_RECTANGLE) {
// we can redraw only what's dirty, but since SWAP_RECTANGLE only
// takes a rectangle, we must make sure to update that whole
// rectangle in that case
dirtyRegion.set(hw->swapRegion.bounds());
} else {
if (flags & DisplayDevice::PARTIAL_UPDATES) {
// We need to redraw the rectangle that will be updated
// (pushed to the framebuffer).
// This is needed because PARTIAL_UPDATES only takes one
// rectangle instead of a region (see DisplayDevice::flip())
dirtyRegion.set(hw->swapRegion.bounds());
} else {
// we need to redraw everything (the whole screen)
dirtyRegion.set(hw->bounds());
hw->swapRegion = dirtyRegion;
}
} if (CC_LIKELY(!mDaltonize && !mHasColorMatrix)) {
if (!doComposeSurfaces(hw, dirtyRegion)) return;
} else {
RenderEngine& engine(getRenderEngine());
mat4 colorMatrix = mColorMatrix;
if (mDaltonize) {
colorMatrix = colorMatrix * mDaltonizer();
}
mat4 oldMatrix = engine.setupColorTransform(colorMatrix);
doComposeSurfaces(hw, dirtyRegion);
engine.setupColorTransform(oldMatrix);
} // update the swap region and clear the dirty region
hw->swapRegion.orSelf(dirtyRegion); // swap buffers (presentation)
hw->swapBuffers(getHwComposer());
}
doDisplayComposition
传入的参数inDirtyRegion，这就是要刷新的“脏”区域，but，我们的刷新机制，决定了必须是矩形的区域。
So，需要一个最小的矩形，能够包裹inDirtyRegion的区域。
SWAP_RECTANGLE：系统支持软件层面的部分刷新，就需要计算这个最小矩形。
PARTIAL_UPDATES：硬件层面的部分刷新，同理需要这个最小矩形。
最后就是重绘这个区域。
bool SurfaceFlinger::doComposeSurfaces(const sp<const DisplayDevice>& hw, const Region& dirty)
{
RenderEngine& engine(getRenderEngine());
const int32_t id = hw->getHwcDisplayId();
HWComposer& hwc(getHwComposer());
HWComposer::LayerListIterator cur = hwc.begin(id);
const HWComposer::LayerListIterator end = hwc.end(id); Region clearRegion;
bool hasGlesComposition = hwc.hasGlesComposition(id);
const bool hasHwcComposition = hwc.hasHwcComposition(id);
if (hasGlesComposition) {
if (!hw->makeCurrent(mEGLDisplay, mEGLContext)) {
ALOGW("DisplayDevice::makeCurrent failed. Aborting surface composition for display %s",
hw->getDisplayName().string());
eglMakeCurrent(mEGLDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
if(!getDefaultDisplayDevice()->makeCurrent(mEGLDisplay, mEGLContext)) {
ALOGE("DisplayDevice::makeCurrent on default display failed. Aborting.");
}
return false;
} // Never touch the framebuffer if we don't have any framebuffer layers
if (hasHwcComposition) {
// when using overlays, we assume a fully transparent framebuffer
// NOTE: we could reduce how much we need to clear, for instance
// remove where there are opaque FB layers. however, on some
// GPUs doing a "clean slate" clear might be more efficient.
// We'll revisit later if needed.
if(!(mGpuTileRenderEnable && (mDisplays.size()==)))
engine.clearWithColor(, , , );
} else {
// we start with the whole screen area
const Region bounds(hw->getBounds()); // we remove the scissor part
// we're left with the letterbox region
// (common case is that letterbox ends-up being empty)
const Region letterbox(bounds.subtract(hw->getScissor())); // compute the area to clear
Region region(hw->undefinedRegion.merge(letterbox)); // but limit it to the dirty region
region.andSelf(dirty); // screen is already cleared here
#ifdef QCOM_BSP
clearRegion.clear();
if(mGpuTileRenderEnable && (mDisplays.size()==)) {
clearRegion = region;
if (cur == end) {
drawWormhole(hw, region);
} else if(mCanUseGpuTileRender) {
/* If GPUTileRect DR optimization on clear only the UnionDR
* (computed by computeTiledDr) which is the actual region
* that will be drawn on FB in this cycle.. */
clearRegion = clearRegion.andSelf(Region(mUnionDirtyRect));
}
} else
#endif
{
if (!region.isEmpty()) {
if (cur != end) {
if (cur->getCompositionType() != HWC_BLIT)
// can happen with SurfaceView
drawWormhole(hw, region);
} else
drawWormhole(hw, region);
}
}
} if (hw->getDisplayType() != DisplayDevice::DISPLAY_PRIMARY) {
// just to be on the safe side, we don't set the
// scissor on the main display. It should never be needed
// anyways (though in theory it could since the API allows it).
const Rect& bounds(hw->getBounds());
const Rect& scissor(hw->getScissor());
if (scissor != bounds) {
// scissor doesn't match the screen's dimensions, so we
// need to clear everything outside of it and enable
// the GL scissor so we don't draw anything where we shouldn't // enable scissor for this frame
const uint32_t height = hw->getHeight();
engine.setScissor(scissor.left, height - scissor.bottom,
scissor.getWidth(), scissor.getHeight());
}
}
} /*
* and then, render the layers targeted at the framebuffer
*/ const Vector< sp<Layer> >& layers(hw->getVisibleLayersSortedByZ());
const size_t count = layers.size();
const Transform& tr = hw->getTransform();
if (cur != end) {
// we're using h/w composer
#ifdef QCOM_BSP
int fbWidth= hw->getWidth();
int fbHeight= hw->getHeight();
/* if GPUTileRender optimization property is on & can be used
* i) Enable EGL_SWAP_PRESERVED flag
* ii) do startTile with union DirtyRect
* else , Disable EGL_SWAP_PRESERVED */
if(mGpuTileRenderEnable && (mDisplays.size()==)) {
if(mCanUseGpuTileRender && !mUnionDirtyRect.isEmpty()) {
hw->eglSwapPreserved(true);
Rect dr = mUnionDirtyRect;
engine.startTileComposition(dr.left, (fbHeight-dr.bottom),
(dr.right-dr.left),
(dr.bottom-dr.top), );
} else {
// Un Set EGL_SWAP_PRESERVED flag, if no tiling required.
hw->eglSwapPreserved(false);
}
// DrawWormHole/Any Draw has to be within startTile & EndTile
if (hasGlesComposition) {
if (hasHwcComposition) {
if(mCanUseGpuTileRender && !mUnionDirtyRect.isEmpty()) {
const Rect& scissor(mUnionDirtyRect);
engine.setScissor(scissor.left,
hw->getHeight()- scissor.bottom,
scissor.getWidth(), scissor.getHeight());
engine.clearWithColor(, , , );
engine.disableScissor();
} else {
engine.clearWithColor(, , , );
}
} else {
if (cur->getCompositionType() != HWC_BLIT &&
!clearRegion.isEmpty()) {
drawWormhole(hw, clearRegion);
}
}
}
}
#endif for (size_t i= ; i<count && cur!=end ; ++i, ++cur) {
const sp<Layer>& layer(layers[i]);
const Region clip(dirty.intersect(tr.transform(layer->visibleRegion)));
if (!clip.isEmpty()) {
switch (cur->getCompositionType()) {
case HWC_CURSOR_OVERLAY:
case HWC_OVERLAY: {
const Layer::State& state(layer->getDrawingState());
if ((cur->getHints() & HWC_HINT_CLEAR_FB)
&& i
&& layer->isOpaque(state) && (state.alpha == 0xFF)
&& hasGlesComposition) {
// never clear the very first layer since we're
// guaranteed the FB is already cleared
layer->clearWithOpenGL(hw, clip);
}
break;
}
case HWC_FRAMEBUFFER: {
layer->draw(hw, clip);
break;
}
case HWC_BLIT:
//Do nothing
break;
case HWC_FRAMEBUFFER_TARGET: {
// this should not happen as the iterator shouldn't
// let us get there.
ALOGW("HWC_FRAMEBUFFER_TARGET found in hwc list (index=%zu)", i);
break;
}
}
}
layer->setAcquireFence(hw, *cur);
} #ifdef QCOM_BSP
// call EndTile, if starTile has been called in this cycle.
if(mGpuTileRenderEnable && (mDisplays.size()==)) {
if(mCanUseGpuTileRender && !mUnionDirtyRect.isEmpty()) {
engine.endTileComposition(GL_PRESERVE);
}
}
#endif
} else {
// we're not using h/w composer
for (size_t i= ; i<count ; ++i) {
const sp<Layer>& layer(layers[i]);
const Region clip(dirty.intersect(
tr.transform(layer->visibleRegion)));
if (!clip.isEmpty()) {
layer->draw(hw, clip);
}
}
} // disable scissor at the end of the frame
engine.disableScissor();
return true;
}
doComposeSurfaces
依次分析：hasGlesComposition需要Open GL来合成的layer，hasHwcComposition需要HWC来合成的layer。
这2各变量不是互斥的，有同时存在需要Open GL layer & HWC layer。
hasHwcComposition在2种情况下是true。
1）layer的类型是HWC_Framebuffer的时候，通常情况下是true。
2)cur ==end 核心实现layer->draw 来完成。
3）cur!=end, 将有hwc来实现。
{
ATRACE_CALL();
if (CC_UNLIKELY(mActiveBuffer == )) {
// the texture has not been created yet, this Layer has
// in fact never been drawn into. This happens frequently with
// SurfaceView because the WindowManager can't know when the client
// has drawn the first time.
// If there is nothing under us, we paint the screen in black, otherwise
// we just skip this update.
// figure out if there is something below us
Region under;
const SurfaceFlinger::LayerVector& drawingLayers(
mFlinger->mDrawingState.layersSortedByZ);
const size_t count = drawingLayers.size();
for (size_t i= ; i<count ; ++i) {
const sp<Layer>& layer(drawingLayers[i]);
if (layer.get() == static_cast<Layer const*>(this))
break;
under.orSelf( hw->getTransform().transform(layer->visibleRegion) );
}
// if not everything below us is covered, we plug the holes!
Region holes(clip.subtract(under));
if (!holes.isEmpty()) {
clearWithOpenGL(hw, holes, , , , );
}
return;
}
// Bind the current buffer to the GL texture, and wait for it to be
// ready for us to draw into.
status_t err = mSurfaceFlingerConsumer->bindTextureImage();
if (err != NO_ERROR) {
ALOGW("onDraw: bindTextureImage failed (err=%d)", err);
// Go ahead and draw the buffer anyway; no matter what we do the screen
// is probably going to have something visibly wrong.
}
bool blackOutLayer = isProtected() || (isSecure() && !hw->isSecure());
RenderEngine& engine(mFlinger->getRenderEngine());
if (!blackOutLayer) {
// TODO: we could be more subtle with isFixedSize()
const bool useFiltering = getFiltering() || needsFiltering(hw) || isFixedSize();
// Query the texture matrix given our current filtering mode.
float textureMatrix[];
mSurfaceFlingerConsumer->setFilteringEnabled(useFiltering);
mSurfaceFlingerConsumer->getTransformMatrix(textureMatrix);
if (mSurfaceFlingerConsumer->getTransformToDisplayInverse()) {
/*
* the code below applies the display's inverse transform to the texture transform
*/
// create a 4x4 transform matrix from the display transform flags
const mat4 flipH(-,,,, ,,,, ,,,, ,,,);
const mat4 flipV( ,,,, ,-,,, ,,,, ,,,);
const mat4 rot90( ,,,, -,,,, ,,,, ,,,);
mat4 tr;
uint32_t transform = hw->getOrientationTransform();
if (transform & NATIVE_WINDOW_TRANSFORM_ROT_90)
tr = tr * rot90;
if (transform & NATIVE_WINDOW_TRANSFORM_FLIP_H)
tr = tr * flipH;
if (transform & NATIVE_WINDOW_TRANSFORM_FLIP_V)
tr = tr * flipV;
// calculate the inverse
tr = inverse(tr);
// and finally apply it to the original texture matrix
const mat4 texTransform(mat4(static_cast<const float*>(textureMatrix)) * tr);
memcpy(textureMatrix, texTransform.asArray(), sizeof(textureMatrix));
}
// Set things up for texturing.
mTexture.setDimensions(mActiveBuffer->getWidth(), mActiveBuffer->getHeight());
mTexture.setFiltering(useFiltering);
mTexture.setMatrix(textureMatrix);
engine.setupLayerTexturing(mTexture);
} else {
engine.setupLayerBlackedOut();
}
drawWithOpenGL(hw, clip, useIdentityTransform);
engine.disableTexturing();
}
里面关键就是drawwithOpenGL，可见是由Open GL来合成layer。