Implement OpenGL backend in Android viewer app

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2032623002

Review-Url: https://codereview.chromium.org/2032623002

8 files changed, 219 insertions, 38 deletions

diff --git a/tools/viewer/Viewer.cpp b/tools/viewer/Viewer.cpp
index 5228a0fd12..c73b1ba9ce 100644
--- a/tools/viewer/Viewer.cpp
+++ b/tools/viewer/Viewer.cpp
@@ -424,9 +424,11 @@ void Viewer::updateUIState() {
     // We will be able to change the backend too.
     Json::Value backendState(Json::objectValue);
     backendState[kName] = kBackendStateName;
-    backendState[kValue] = fBackendType == sk_app::Window::kVulkan_BackendType ?
-            "Vulkan" : "Other than Vulkan";
+    backendState[kValue] = kBackendTypeStrings[fBackendType];
     backendState[kOptions] = Json::Value(Json::arrayValue);
+    for(auto str : kBackendTypeStrings) {
+        backendState[kOptions].append(Json::Value(str));
+    }
 
     Json::Value state(Json::arrayValue);
     state.append(slideState);
@@ -436,7 +438,10 @@ void Viewer::updateUIState() {
 }
 
 void Viewer::onUIStateChanged(const SkString& stateName, const SkString& stateValue) {
-    // Currently, we only recognize the Slide state
+    // For those who will add more features to handle the state change in this function:
+    // After the change, please call updateUIState no notify the frontend (e.g., Android app).
+    // For example, after slide change, updateUIState is called inside setupCurrentSlide;
+    // after backend change, updateUIState is called in this function.
     if (stateName.equals(kSlideStateName)) {
         int previousSlide = fCurrentSlide;
         fCurrentSlide = 0;
@@ -451,6 +456,20 @@ void Viewer::onUIStateChanged(const SkString& stateName, const SkString& stateVa
             fCurrentSlide = previousSlide;
             SkDebugf("Slide not found: %s", stateValue.c_str());
         }
+    } else if (stateName.equals(kBackendStateName)) {
+        for (int i = 0; i < sk_app::Window::kBackendTypeCount; i++) {
+            if (stateValue.equals(kBackendTypeStrings[i])) {
+                if (fBackendType != i) {
+                    fBackendType = (sk_app::Window::BackendType)i;
+                    fWindow->detach();
+                    fWindow->attach(fBackendType, DisplayParams());
+                    fWindow->inval();
+                    updateTitle();
+                    updateUIState();
+                }
+                break;
+            }
+        }
     } else {
         SkDebugf("Unknown stateName: %s", stateName.c_str());
     }
diff --git a/tools/viewer/sk_app/GLWindowContext.h b/tools/viewer/sk_app/GLWindowContext.h
index 6fb5e09889..acf15a332e 100644
--- a/tools/viewer/sk_app/GLWindowContext.h
+++ b/tools/viewer/sk_app/GLWindowContext.h
@@ -52,6 +52,8 @@ protected:
     sk_sp<SkSurface>                  fSurface;
 
     // parameters obtained from the native window
+    // Note that the platform .cpp file is responsible for
+    // initializing fSampleCount, fStencilBits, and fColorBits!
     int                               fSampleCount;
     int                               fStencilBits;
     int                               fColorBits;
diff --git a/tools/viewer/sk_app/android/GLWindowContext_android.cpp b/tools/viewer/sk_app/android/GLWindowContext_android.cpp
new file mode 100644
index 0000000000..a98b5553f8
--- /dev/null
+++ b/tools/viewer/sk_app/android/GLWindowContext_android.cpp
@@ -0,0 +1,122 @@
+
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include <GLES/gl.h> 
+
+#include "GLWindowContext_android.h"
+
+#include <android/native_window_jni.h>
+
+namespace sk_app {
+
+// Most of the following 3 functions (GLWindowContext::Create, constructor, desctructor)
+// are copied from Unix/Win platform with unix/win changed to android
+
+// platform-dependent create
+GLWindowContext* GLWindowContext::Create(void* platformData, const DisplayParams& params) {
+    GLWindowContext_android* ctx = new GLWindowContext_android(platformData, params);
+    if (!ctx->isValid()) {
+        delete ctx;
+        return nullptr;
+    }
+    return ctx;
+}
+
+GLWindowContext_android::GLWindowContext_android(void* platformData, const DisplayParams& params)
+    : GLWindowContext(platformData, params)
+    , fDisplay(EGL_NO_DISPLAY)
+    , fEGLContext(EGL_NO_CONTEXT)
+    , fSurface(EGL_NO_SURFACE) {
+
+    // any config code here (particularly for msaa)?
+
+    this->initializeContext(platformData, params);
+}
+
+GLWindowContext_android::~GLWindowContext_android() {
+    this->destroyContext();
+}
+
+void GLWindowContext_android::onInitializeContext(void* platformData, const DisplayParams& params) {
+    ContextPlatformData_android* androidPlatformData = 
+            reinterpret_cast<ContextPlatformData_android*>(platformData);
+
+    fWidth = ANativeWindow_getWidth(androidPlatformData->fNativeWindow);
+    fHeight = ANativeWindow_getHeight(androidPlatformData->fNativeWindow);
+
+    fDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
+
+    EGLint majorVersion;
+    EGLint minorVersion;
+    eglInitialize(fDisplay, &majorVersion, &minorVersion);
+
+    SkAssertResult(eglBindAPI(EGL_OPENGL_ES_API));
+
+    EGLint numConfigs = 0;
+    const EGLint configAttribs[] = {
+        EGL_SURFACE_TYPE, EGL_PBUFFER_BIT,
+        EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
+        EGL_RED_SIZE, 8,
+        EGL_GREEN_SIZE, 8,
+        EGL_BLUE_SIZE, 8,
+        EGL_ALPHA_SIZE, 8,
+        EGL_NONE
+    };
+
+    EGLConfig surfaceConfig;
+    SkAssertResult(eglChooseConfig(fDisplay, configAttribs, &surfaceConfig, 1, &numConfigs));
+    SkASSERT(numConfigs > 0);
+
+    static const EGLint kEGLContextAttribsForOpenGLES[] = {
+        EGL_CONTEXT_CLIENT_VERSION, 2,
+        EGL_NONE
+    };
+    fEGLContext = eglCreateContext(
+            fDisplay, surfaceConfig, nullptr, kEGLContextAttribsForOpenGLES);
+    SkASSERT(EGL_NO_CONTEXT != fEGLContext);
+
+    fSurface = eglCreateWindowSurface(
+            fDisplay, surfaceConfig, androidPlatformData->fNativeWindow, nullptr);
+    SkASSERT(EGL_NO_SURFACE != fSurface);
+
+    SkAssertResult(eglMakeCurrent(fDisplay, fSurface, fSurface, fEGLContext));
+    // GLWindowContext::initializeContext will call GrGLCreateNativeInterface so we
+    // won't call it here.
+
+    glClearStencil(0);
+    glClearColor(0, 0, 0, 0);
+    glStencilMask(0xffffffff);
+    glClear(GL_STENCIL_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
+
+    int redBits, greenBits, blueBits;
+    eglGetConfigAttrib(fDisplay, surfaceConfig, EGL_RED_SIZE, &redBits);
+    eglGetConfigAttrib(fDisplay, surfaceConfig, EGL_GREEN_SIZE, &greenBits);
+    eglGetConfigAttrib(fDisplay, surfaceConfig, EGL_BLUE_SIZE, &blueBits);
+    fColorBits = redBits + greenBits + blueBits;
+    eglGetConfigAttrib(fDisplay, surfaceConfig, EGL_STENCIL_SIZE, &fStencilBits);
+    eglGetConfigAttrib(fDisplay, surfaceConfig, EGL_SAMPLES, &fSampleCount);
+}
+
+void GLWindowContext_android::onDestroyContext() {
+    if (!fDisplay || !fEGLContext || !fSurface) {
+        return;
+    }
+    eglMakeCurrent(fDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
+    SkAssertResult(eglDestroySurface(fDisplay, fSurface));
+    SkAssertResult(eglDestroyContext(fDisplay, fEGLContext));
+    fEGLContext = EGL_NO_CONTEXT;
+    fSurface = EGL_NO_SURFACE;
+}
+
+void GLWindowContext_android::onSwapBuffers() {
+    if (fDisplay && fEGLContext && fSurface) {
+        eglSwapBuffers(fDisplay, fSurface);
+    }
+}
+
+}
diff --git a/tools/viewer/sk_app/android/GLWindowContext_android.h b/tools/viewer/sk_app/android/GLWindowContext_android.h
new file mode 100644
index 0000000000..85e65beaa2
--- /dev/null
+++ b/tools/viewer/sk_app/android/GLWindowContext_android.h
@@ -0,0 +1,40 @@
+
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#ifndef GLWindowContext_android_DEFINED
+#define GLWindowContext_android_DEFINED
+
+#include "../GLWindowContext.h"
+#include "Window_android.h"
+
+#include <EGL/egl.h>
+
+namespace sk_app {
+
+class GLWindowContext_android : public GLWindowContext {
+public:
+    friend GLWindowContext* GLWindowContext::Create(void* platformData, const DisplayParams&);
+
+    ~GLWindowContext_android() override;
+
+    void onSwapBuffers() override;
+
+    void onInitializeContext(void*, const DisplayParams&) override;
+    void onDestroyContext() override;
+
+private:
+    GLWindowContext_android(void*, const DisplayParams&);
+
+    EGLDisplay fDisplay;
+    EGLContext fEGLContext;
+    EGLSurface fSurface;
+};
+
+
+}
+
+#endif
diff --git a/tools/viewer/sk_app/android/VulkanWindowContext_android.cpp b/tools/viewer/sk_app/android/VulkanWindowContext_android.cpp
index 555f8a692b..5c6b7416a2 100644
--- a/tools/viewer/sk_app/android/VulkanWindowContext_android.cpp
+++ b/tools/viewer/sk_app/android/VulkanWindowContext_android.cpp
@@ -6,7 +6,8 @@
  * found in the LICENSE file.
  */
 
-#include "VulkanWindowContext_android.h"
+#include "Window_android.h"
+#include "../VulkanWindowContext.h"
 
 #include "vk/GrVkInterface.h"
 #include "vk/GrVkUtil.h"
diff --git a/tools/viewer/sk_app/android/VulkanWindowContext_android.h b/tools/viewer/sk_app/android/VulkanWindowContext_android.h
deleted file mode 100644
index dd53e13b69..0000000000
--- a/tools/viewer/sk_app/android/VulkanWindowContext_android.h
+++ /dev/null
@@ -1,26 +0,0 @@
-
-/*
- * Copyright 2016 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-#ifndef VULKANTESTCONTEXT_ANDROID_DEFINED
-#define VULKANTESTCONTEXT_ANDROID_DEFINED
-
-#ifdef SK_VULKAN
-
-#include "../VulkanWindowContext.h"
-
-struct ANativeWindow;
-
-namespace sk_app {
-
-struct ContextPlatformData_android {
-    ANativeWindow* fNativeWindow;
-};
-
-}
-#endif // SK_VULKAN
-
-#endif
diff --git a/tools/viewer/sk_app/android/Window_android.cpp b/tools/viewer/sk_app/android/Window_android.cpp
index 4f33870c1a..926c7cd17d 100644
--- a/tools/viewer/sk_app/android/Window_android.cpp
+++ b/tools/viewer/sk_app/android/Window_android.cpp
@@ -6,8 +6,8 @@
 */
 
 #include "Window_android.h"
-
-#include "VulkanWindowContext_android.h"
+#include "../GLWindowContext.h"
+#include "../VulkanWindowContext.h"
 
 namespace sk_app {
 
@@ -46,26 +46,39 @@ void Window_android::setUIState(const Json::Value& state) {
 }
 
 bool Window_android::attach(BackendType attachType, const DisplayParams& params) {
-    if (kVulkan_BackendType != attachType) {
-        return false;
-    }
-
+    fBackendType = attachType;
     fDisplayParams = params;
 
-    // We delay the creation of fTestContext until Android informs us that
+    if (fNativeWindow) {
+        this->initDisplay(fNativeWindow);
+    }
+    // If fNativeWindow is not set,
+    // we delay the creation of fWindowContext until Android informs us that
     // the native window is ready to use.
+    // The creation will be done in initDisplay, which is initiated by kSurfaceCreated event.
     return true;
 }
 
 void Window_android::initDisplay(ANativeWindow* window) {
     SkASSERT(window);
+    fNativeWindow = window;
     ContextPlatformData_android platformData;
     platformData.fNativeWindow = window;
-    fWindowContext = VulkanWindowContext::Create((void*)&platformData, fDisplayParams);
+    switch (fBackendType) {
+        case kNativeGL_BackendType:
+            fWindowContext = GLWindowContext::Create((void*)&platformData, fDisplayParams);
+            break;
+
+        case kVulkan_BackendType:
+        default:
+            fWindowContext = VulkanWindowContext::Create((void*)&platformData, fDisplayParams);
+            break;
+    }
 }
 
 void Window_android::onDisplayDestroyed() {
     detach();
+    fNativeWindow = nullptr;
 }
 
 void Window_android::onInval() {
diff --git a/tools/viewer/sk_app/android/Window_android.h b/tools/viewer/sk_app/android/Window_android.h
index f1c079835b..2a7ff4730a 100644
--- a/tools/viewer/sk_app/android/Window_android.h
+++ b/tools/viewer/sk_app/android/Window_android.h
@@ -8,11 +8,17 @@
 #ifndef Window_android_DEFINED
 #define Window_android_DEFINED
 
+#include <android/native_window_jni.h>
+
 #include "../Window.h"
 #include "surface_glue_android.h"
 
 namespace sk_app {
 
+struct ContextPlatformData_android {
+    ANativeWindow* fNativeWindow;
+};
+
 class Window_android : public Window {
 public:
     Window_android() : Window() {}
@@ -38,9 +44,13 @@ public:
     void setContentRect(int l, int t, int r, int b) { fContentRect.set(l,t,r,b); }
 
 private:
+    // We need fNativeWindow for attaching with another backend.
+    // (in that case, attach is called without initDisplay being called later)
+    ANativeWindow* fNativeWindow = nullptr;
     SkiaAndroidApp* fSkiaAndroidApp = nullptr;
     SkRect fContentRect;
     DisplayParams fDisplayParams;
+    BackendType fBackendType;
 };
 
 }   // namespace sk_app