這個簡單的框架服務允許供應商進程在 HAL 實作中使用 SurfaceFlinger/EGL,而無需連結 libgui。 AOSP 提供了該服務的預設實現,該實現功能齊全。但是,供應商也必須實作 API 才能在其平台上提供此服務。
package android.frameworks.automotive.display@1.0; import android.hardware.graphics.bufferqueue@2.0::IGraphicBufferProducer; interface IAutomotiveDisplayProxyService { /** * Gets an IGraphicBufferProducer instance from the service. * * @param id Target's stable display identifier * * @return igbp Returns an IGraphicBufferProducer object, that can be * converted to an ANativeWindow object. */ getIGraphicBufferProducer(uint64_t id) generates (IGraphicBufferProducer igbp); /** * Sets the ANativeWindow, which is associated with the * IGraphicBufferProducer, to be visible and to take over the display. * * @param id Target display ID * * @return success Returns true on success. */ showWindow(uint64_t id) generates (bool success); /** * Sets the ANativeWindow, which is associated with the * IGraphicBufferProducer, to be invisible and to release the control * over display. * * @param id Target display ID * * @return success Returns true on success. */ hideWindow(uint64_t id) generates (bool success); /** * Returns the stable identifiers of all available displays. * * @return ids A list of stable display identifiers. */ getDisplayIdList() generates (vec<uint64_t> ids); /** * Returns the descriptor of the target display. * * @param id Stable ID of a target display. * @return cfg DisplayConfig of the active display. * @return state Current state of the active display. */ getDisplayInfo(uint64_t id) generates (HwDisplayConfig cfg, HwDisplayState state); }
若要使用此服務:
- 取得
IAutomotiveDisplayProxyService
。android::sp<IAutomotiveDisplayProxyService> windowProxyService = IAutomotiveDisplayProxyService::getService("default"); if (windowProxyService == nullptr) { LOG(ERROR) << "Cannot use AutomotiveDisplayProxyService. Exiting."; return 1; }
- 從服務檢索活動顯示資訊以確定解析度。
// We use the first display in the list as the primary. pWindowProxy->getDisplayInfo(displayId, [this](auto dpyConfig, auto dpyState) { DisplayConfig *pConfig = (DisplayConfig*)dpyConfig.data(); mWidth = pConfig->resolution.getWidth(); mHeight = pConfig->resolution.getHeight(); ui::DisplayState* pState = (ui::DisplayState*)dpyState.data(); if (pState->orientation != ui::ROTATION_0 && pState->orientation != ui::ROTATION_180) { // rotate std::swap(mWidth, mHeight); } LOG(DEBUG) << "Display resolution is " << mWidth << " x " << mHeight; });
- 從
IAutomotiveDisplayProxyService
擷取硬體IGraphicBufferProducer
(或 HIDL GraphicBufferProducer (HGBP)):mGfxBufferProducer = pWindowProxy->getIGraphicBufferProducer(displayId); if (mGfxBufferProducer == nullptr) { LOG(ERROR) << "Failed to get IGraphicBufferProducer from " << "IAutomotiveDisplayProxyService."; return false; }
- 使用 API
libbufferqueueconverter
從檢索到的 HGBP 取得SurfaceHolder
:mSurfaceHolder = getSurfaceFromHGBP(mGfxBufferProducer); if (mSurfaceHolder == nullptr) { LOG(ERROR) << "Failed to get a Surface from HGBP."; return false; }
- 使用 API
libbufferqueueconverter
將SurfaceHolder
轉換為本機視窗:mWindow = getNativeWindow(mSurfaceHolder.get()); if (mWindow == nullptr) { LOG(ERROR) << "Failed to get a native window from Surface."; return false; }
- 使用本機視窗建立 EGL 視窗表面,然後渲染:
// Set up our OpenGL ES context associated with the default display mDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY); if (mDisplay == EGL_NO_DISPLAY) { LOG(ERROR) << "Failed to get egl display"; return false; } ... // Create the EGL render target surface mSurface = eglCreateWindowSurface(mDisplay, egl_config, mWindow, nullptr); if (mSurface == EGL_NO_SURFACE) { LOG(ERROR) << "eglCreateWindowSurface failed."; return false; } ...
- 呼叫
IAutomotiveDisplayProxyService::showWindow()
在螢幕上顯示渲染的視圖。該服務具有最高優先級,因此始終從當前所有者手中控制螢幕:mAutomotiveDisplayProxyService->showWindow();
如需更多實作細節,請參閱$ANDROID_BUILD_TOP/packages/services/Car/evs/sampleDriver/
中的service.cpp
和GlWrapper.cpp
。
EVS HAL 實作需要下面以粗體顯示的附加函式庫。
cc_binary { name: "android.hardware.automotive.evs@1.1-sample", vendor: true, srcs: [ ... ], shared_libs: [ ... "libbufferqueueconverter", "android.hidl.token@1.0-utils", "android.frameworks.automotive.display@1.0", "android.hardware.graphics.bufferqueue@1.0", "android.hardware.graphics.bufferqueue@2.0", ],
多顯示器支援
顯示設備枚舉並檢索顯示訊息
與相機設備枚舉一樣,EVS 框架提供了一種列舉可用顯示器的方法。靜態顯示標識符對長類型標識符進行編碼,顯示連接埠資訊位於低位元組中, Extended Display IDentification Data
位於高位元中。 IAutomotiveDisplayProxyService::getDisplayIdList()
傳回可用於 EVS 服務的實體本機顯示器的顯示器 ID 列表, IEvsEnumerator::getDisplayIdList()
傳回偵測到的顯示器連接到的顯示連接埠清單。清單中的第一個 ID 始終是主顯示器的 ID。
interface IEvsEnumerator extends @1.0::IEvsEnumerator { ... /** * Returns a list of all EVS displays available to the system * * @return displayIds Identifiers of available displays. */ getDisplayIdList() generates (vec<uint8_t> displayIds); };
開啟目標顯示設備
EVS 應用程式使用目標顯示連接埠號碼呼叫 IEvsEnumerator::openDisplay_1_1():
android::sp<IEvsDisplay> pDisplay = pEvs->openDisplay_1_1(displayId); if (pDisplay.get() == nullptr) { LOG(ERROR) << "EVS Display unavailable. Exiting."; return 1; }
注意:一次只能使用一個顯示器,這表示當另一個 EVS 用戶端要求開啟顯示器時,當前 EVS 用戶端將會遺失其顯示器,即使它們不相同。