Refactor SkGLContext to be actually extendable

Refactor SkGLContext to be actually extendable. Before, non-trivial subclass
would need to destroy the GL connection upon running the destructor. However,
the base class would run GL commands in its own destructor (with destroyed GL
connection)

Refactor so that SkGLContext subclass object creation is completely done by
the factory function. If the factory function returns a non-NULL ptr, it means the context
is usable.

The destruction is done with the destructor instead of virtual function called
upon destruction. Make the destructors not to call virtual functions, for
clarity.

Remove custom 1x1 FBO setup code from the base class. It appears not to be used
anymore.

BUG=skia:2992

Review URL: https://codereview.chromium.org/640283004

1 files changed, 45 insertions, 42 deletions

diff --git a/src/gpu/gl/win/SkCreatePlatformGLContext_win.cpp b/src/gpu/gl/win/SkCreatePlatformGLContext_win.cpp
index d362556a4e..b53d46ced3 100644
--- a/src/gpu/gl/win/SkCreatePlatformGLContext_win.cpp
+++ b/src/gpu/gl/win/SkCreatePlatformGLContext_win.cpp
@@ -19,17 +19,14 @@ namespace {
 
 class WinGLContext : public SkGLContext {
 public:
-    WinGLContext();
-
-    virtual ~WinGLContext();
-
+    WinGLContext(GrGLStandard forcedGpuAPI);
+	virtual ~WinGLContext() SK_OVERRIDE;
     virtual void makeCurrent() const SK_OVERRIDE;
     virtual void swapBuffers() const SK_OVERRIDE;
-protected:
-    virtual const GrGLInterface* createGLContext(GrGLStandard forcedGpuAPI) SK_OVERRIDE;
-    virtual void destroyGLContext() SK_OVERRIDE;
 
 private:
+    void destroyGLContext();
+
     HWND fWindow;
     HDC fDeviceContext;
     HGLRC fGlRenderContext;
@@ -39,34 +36,11 @@ private:
 
 ATOM WinGLContext::gWC = 0;
 
-WinGLContext::WinGLContext()
+WinGLContext::WinGLContext(GrGLStandard forcedGpuAPI)
     : fWindow(NULL)
     , fDeviceContext(NULL)
     , fGlRenderContext(0)
     , fPbufferContext(NULL) {
-}
-
-WinGLContext::~WinGLContext() {
-    this->destroyGLContext();
-}
-
-void WinGLContext::destroyGLContext() {
-    SkSafeSetNull(fPbufferContext);
-    if (fGlRenderContext) {
-        wglDeleteContext(fGlRenderContext);
-        fGlRenderContext = 0;
-    }
-    if (fWindow && fDeviceContext) {
-        ReleaseDC(fWindow, fDeviceContext);
-        fDeviceContext = 0;
-    }
-    if (fWindow) {
-        DestroyWindow(fWindow);
-        fWindow = 0;
-    }
-}
-
-const GrGLInterface* WinGLContext::createGLContext(GrGLStandard forcedGpuAPI) {
     HINSTANCE hInstance = (HINSTANCE)GetModuleHandle(NULL);
 
     if (!gWC) {
@@ -85,7 +59,7 @@ const GrGLInterface* WinGLContext::createGLContext(GrGLStandard forcedGpuAPI) {
         gWC = RegisterClass(&wc);
         if (!gWC) {
             SkDebugf("Could not register window class.\n");
-            return NULL;
+            return;
         }
     }
 
@@ -96,13 +70,13 @@ const GrGLInterface* WinGLContext::createGLContext(GrGLStandard forcedGpuAPI) {
                                  NULL, NULL,
                                  hInstance, NULL))) {
         SkDebugf("Could not create window.\n");
-        return NULL;
+        return;
     }
 
     if (!(fDeviceContext = GetDC(fWindow))) {
         SkDebugf("Could not get device context.\n");
         this->destroyGLContext();
-        return NULL;
+        return;
     }
     // Requesting a Core profile would bar us from using NVPR. So we request
     // compatibility profile or GL ES.
@@ -119,7 +93,7 @@ const GrGLInterface* WinGLContext::createGLContext(GrGLStandard forcedGpuAPI) {
         if (!(fGlRenderContext = SkCreateWGLContext(fDeviceContext, 0, contextType))) {
             SkDebugf("Could not create rendering context.\n");
             this->destroyGLContext();
-            return NULL;
+            return;
         }
         dc = fDeviceContext;
         glrc = fGlRenderContext;
@@ -136,17 +110,41 @@ const GrGLInterface* WinGLContext::createGLContext(GrGLStandard forcedGpuAPI) {
     if (!(wglMakeCurrent(dc, glrc))) {
         SkDebugf("Could not set the context.\n");
         this->destroyGLContext();
-        return NULL;
+        return;
     }
 
-    const GrGLInterface* interface = GrGLCreateNativeInterface();
-    if (NULL == interface) {
+    fGL.reset(GrGLCreateNativeInterface());
+    if (NULL == fGL.get()) {
         SkDebugf("Could not create GL interface.\n");
         this->destroyGLContext();
-        return NULL;
+        return;
     }
+    if (!fGL->validate()) {
+        SkDebugf("Could not validate GL interface.\n");
+        this->destroyGLContext();
+        return;
+    }
+}
 
-    return interface;
+WinGLContext::~WinGLContext() {
+    this->destroyGLContext();
+}
+
+void WinGLContext::destroyGLContext() {
+    fGL.reset(NULL);
+    SkSafeSetNull(fPbufferContext);
+    if (fGlRenderContext) {
+        wglDeleteContext(fGlRenderContext);
+        fGlRenderContext = 0;
+    }
+    if (fWindow && fDeviceContext) {
+        ReleaseDC(fWindow, fDeviceContext);
+        fDeviceContext = 0;
+    }
+    if (fWindow) {
+        DestroyWindow(fWindow);
+        fWindow = 0;
+    }
 }
 
 void WinGLContext::makeCurrent() const {
@@ -181,7 +179,12 @@ void WinGLContext::swapBuffers() const {
 
 } // anonymous namespace
 
-SkGLContext* SkCreatePlatformGLContext() {
-    return SkNEW(WinGLContext);
+SkGLContext* SkCreatePlatformGLContext(GrGLStandard forcedGpuAPI) {
+    WinGLContext* ctx = SkNEW_ARGS(WinGLContext, (forcedGpuAPI));
+    if (!ctx->isValid()) {
+        SkDELETE(ctx);
+        return NULL;
+    }
+    return ctx;
 }