android屏幕旋转显示流程

PAD默认屏幕显示方向是竖着显示,改成默认横屏显示需要将屏幕的默认显示方向顺时针旋转90度.

android显示系统的核心是surfaceflinger,它为所有的应用程序提供显示服务,它能够将各种应用程序的2D,3D surface进行组合,合并最终得到的一个main surface数据送入framebuffer,显示的翻转和旋转也是由surfaceflinger完成的,我们大致分析下surfaceflinger的旋转流程:

1.surfaceflinger启动后首先进行初始化操作,设置surfaceflinger的相关属性并创建了DisplayDevice对象

void SurfaceFlinger::init() {
...
#ifdef MTK_AOSP_ENHANCEMENT// make sure 3D init successif (mEGLContext == EGL_NO_CONTEXT){ALOGE("FATAL: couldn't create EGLContext");delete mHwc;eglTerminate(mEGLDisplay);exit(0);}// init properties setting firstsetMTKProperties();   //设置MTK相关属性
#elseLOG_ALWAYS_FATAL_IF(mEGLContext == EGL_NO_CONTEXT,"couldn't create EGLContext");
#endif
...// initialize our non-virtual displaysfor (size_t i=0 ; i<DisplayDevice::NUM_BUILTIN_DISPLAY_TYPES ; i++) {DisplayDevice::DisplayType type((DisplayDevice::DisplayType)i);// set-up the displays that are already connectedif (mHwc->isConnected(i) || type==DisplayDevice::DISPLAY_PRIMARY) {// All non-virtual displays are currently considered secure.bool isSecure = true;createBuiltinDisplayLocked(type);wp<IBinder> token = mBuiltinDisplays[i];sp<IGraphicBufferProducer> producer;sp<IGraphicBufferConsumer> consumer;BufferQueue::createBufferQueue(&producer, &consumer,new GraphicBufferAlloc());sp<FramebufferSurface> fbs = new FramebufferSurface(*mHwc, i,consumer);int32_t hwcId = allocateHwcDisplayId(type);sp<DisplayDevice> hw = new DisplayDevice(this,  //初始化各个DisplayDevice对象type, hwcId, mHwc->getFormat(hwcId), isSecure, token,fbs, producer,mRenderEngine->getEGLConfig());if (i > DisplayDevice::DISPLAY_PRIMARY) {// FIXME: currently we don't get blank/unblank requests// for displays other than the main display, so we always// assume a connected display is unblanked.ALOGD("marking display %zu as acquired/unblanked", i);hw->setPowerMode(HWC_POWER_MODE_NORMAL);}mDisplays.add(token, hw);}}
}

setMTKProperties()中会设置surfaceflinger的相关属性:

void SurfaceFlinger::setMTKProperties(String8 &result) {
...// get info for panel physical rotationproperty_get("ro.sf.hwrotation", value, "0");sPropertiesState.mHwRotation = atoi(value);snprintf(buffer, sizeof(buffer), "    ro.sf.hwrotation (mHwRotation): %d\n", sPropertiesState.mHwRotation);result.append(buffer);
...
}

此处会读取 ro.sf.hwrotation系统属性,这个系统属性决定了显示屏的初始旋转方向,并保存到全局变量sPropertiesState.mHwRotation中

2.DisplayDevice中会调用显示的旋转函数setProjection()

DisplayDevice::DisplayDevice(const sp<SurfaceFlinger>& flinger,DisplayType type,int32_t hwcId,int format,bool isSecure,const wp<IBinder>& displayToken,const sp<DisplaySurface>& displaySurface,const sp<IGraphicBufferProducer>& producer,EGLConfig config)(
<span style="font-family: Arial, Helvetica, sans-serif;">...
</span><pre code_snippet_id="1939821" snippet_file_name="blog_20161020_4_9852155" name="code" class="cpp">#ifdef MTK_AOSP_ENHANCEMENTmHwOrientation = DisplayState::eOrientationDefault;   //读取默认的显示屏方向// Name the display.  The name will be replaced shortly if the display// was created with createDisplay().switch (mType) {case DISPLAY_PRIMARY:mDisplayName = "Built-in Screen";
#ifdef MTK_AOSP_ENHANCEMENTswitch (mFlinger->sPropertiesState.mHwRotation) {     //读取显示屏初始旋转方向case 90:mHwOrientation = DisplayState::eOrientation90;break;case 180:mHwOrientation = DisplayState::eOrientation180;break;case 270:mHwOrientation = DisplayState::eOrientation270;break;}
#endifbreak;case DISPLAY_EXTERNAL:mDisplayName = "HDMI Screen";break;default:mDisplayName = "Virtual Screen";    // e.g. Overlay #nbreak;}// initialize the display orientation transform.setProjection(DisplayState::eOrientationDefault, mViewport, mFrame);  //设置显示屏初始旋转方向
}

void DisplayDevice::setProjection(int orientation,const Rect& newViewport, const Rect& newFrame) {Rect viewport(newViewport);Rect frame(newFrame);const int w = mDisplayWidth;const int h = mDisplayHeight;Transform R;DisplayDevice::orientationToTransfrom(orientation, w, h, &R);if (!frame.isValid()) {// the destination frame can be invalid if it has never been set,// in that case we assume the whole display frame.frame = Rect(w, h);}if (viewport.isEmpty()) {// viewport can be invalid if it has never been set, in that case// we assume the whole display size.// it's also invalid to have an empty viewport, so we handle that// case in the same way.viewport = Rect(w, h);if (R.getOrientation() & Transform::ROT_90) {// viewport is always specified in the logical orientation// of the display (ie: post-rotation).swap(viewport.right, viewport.bottom);}}dirtyRegion.set(getBounds());#ifdef MTK_AOSP_ENHANCEMENT// for boot animation black screen issueif ((false == mFlinger->getBootFinished()) && (DISPLAY_PRIMARY == mType)) {ALOGI("[%s] clear DisplayDevice(type:%d) dirty region while booting",__FUNCTION__, mType);dirtyRegion.clear();}
#endifTransform TL, TP, S;float src_width  = viewport.width();float src_height = viewport.height();float dst_width  = frame.width();float dst_height = frame.height();if (src_width != dst_width || src_height != dst_height) {float sx = dst_width  / src_width;float sy = dst_height / src_height;S.set(sx, 0, 0, sy);}float src_x = viewport.left;float src_y = viewport.top;float dst_x = frame.left;float dst_y = frame.top;TL.set(-src_x, -src_y);TP.set(dst_x, dst_y);#ifdef MTK_AOSP_ENHANCEMENT// need to take care of HW rotation for mGlobalTransform// for case if the panel is not installed align with device orientationif (DisplayState::eOrientationDefault != mHwOrientation) {    DisplayDevice::orientationToTransfrom((orientation + mHwOrientation) % (DisplayState::eOrientation270 + 1),w, h, &R);}
#endif// The viewport and frame are both in the logical orientation.// Apply the logical translation, scale to physical size, apply the// physical translation and finally rotate to the physical orientation.mGlobalTransform = R * TP * S * TL;const uint8_t type = mGlobalTransform.getType();mNeedsFiltering = (!mGlobalTransform.preserveRects() ||(type >= Transform::SCALE));mScissor = mGlobalTransform.transform(viewport);if (mScissor.isEmpty()) {mScissor = getBounds();}mOrientation = orientation;mViewport = viewport;mFrame = frame;
}

接着调用DisplayDevice类的orientationToTransfrom()方法构造成一个变换矩阵R,然后得到mGlobalTransform这个全局变换矩阵,最后通过mGlobalTransform.transform()这个方法进行显示的旋转

status_t DisplayDevice::orientationToTransfrom(int orientation, int w, int h, Transform* tr)
{uint32_t flags = 0;switch (orientation) {case DisplayState::eOrientationDefault:flags = Transform::ROT_0;break;case DisplayState::eOrientation90:flags = Transform::ROT_90;break;case DisplayState::eOrientation180:flags = Transform::ROT_180;break;case DisplayState::eOrientation270:flags = Transform::ROT_270;break;default:return BAD_VALUE;}tr->set(flags, w, h);return NO_ERROR;
}

这里调用Transform::set()方法设置矩阵,有兴趣可以深入分析

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android屏幕旋转显示流程

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