Fix flicker when changing backend on Mac viewer

Tie the SDL GL context to the Window, not the context. Deleting the context
causes the window to render a frame of black - this keeps the context alive
along with the window, so that never happens.

Change-Id: Id4df18a6f2fe09f617ec2ff1809d000f18f547ba
Reviewed-on: https://skia-review.googlesource.com/107941
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

5 files changed, 29 insertions, 33 deletions

diff --git a/tools/sk_app/mac/GLWindowContext_mac.cpp b/tools/sk_app/mac/GLWindowContext_mac.cpp
index 67fb853fee..f7e56ccb62 100644
--- a/tools/sk_app/mac/GLWindowContext_mac.cpp
+++ b/tools/sk_app/mac/GLWindowContext_mac.cpp
@@ -27,7 +27,7 @@ public:
     void onSwapBuffers() override;
 
     sk_sp<const GrGLInterface> onInitializeContext() override;
-    void onDestroyContext() override;
+    void onDestroyContext() override {}
 
 private:
     SDL_Window*   fWindow;
@@ -39,7 +39,7 @@ private:
 GLWindowContext_mac::GLWindowContext_mac(const MacWindowInfo& info, const DisplayParams& params)
     : INHERITED(params)
     , fWindow(info.fWindow)
-    , fGLContext(nullptr) {
+    , fGLContext(info.fGLContext) {
 
     // any config code here (particularly for msaa)?
 
@@ -52,12 +52,7 @@ GLWindowContext_mac::~GLWindowContext_mac() {
 
 sk_sp<const GrGLInterface> GLWindowContext_mac::onInitializeContext() {
     SkASSERT(fWindow);
-
-    fGLContext = SDL_GL_CreateContext(fWindow);
-    if (!fGLContext) {
-        SkDebugf("%s\n", SDL_GetError());
-        return nullptr;
-    }
+    SkASSERT(fGLContext);
 
     if (0 == SDL_GL_MakeCurrent(fWindow, fGLContext)) {
         glClearStencil(0);
@@ -77,15 +72,6 @@ sk_sp<const GrGLInterface> GLWindowContext_mac::onInitializeContext() {
     return GrGLMakeNativeInterface();
 }
 
-void GLWindowContext_mac::onDestroyContext() {
-    if (!fWindow || !fGLContext) {
-        return;
-    }
-    SDL_GL_DeleteContext(fGLContext);
-    fGLContext = nullptr;
-}
-
-
 void GLWindowContext_mac::onSwapBuffers() {
     if (fWindow && fGLContext) {
         SDL_GL_SwapWindow(fWindow);
diff --git a/tools/sk_app/mac/RasterWindowContext_mac.cpp b/tools/sk_app/mac/RasterWindowContext_mac.cpp
index fbe9837911..b66ba407fa 100644
--- a/tools/sk_app/mac/RasterWindowContext_mac.cpp
+++ b/tools/sk_app/mac/RasterWindowContext_mac.cpp
@@ -51,7 +51,7 @@ RasterWindowContext_mac::RasterWindowContext_mac(const MacWindowInfo& info,
                                                  const DisplayParams& params)
     : INHERITED(params)
     , fWindow(info.fWindow)
-    , fGLContext(nullptr) {
+    , fGLContext(info.fGLContext) {
 
     // any config code here (particularly for msaa)?
 
@@ -64,12 +64,7 @@ RasterWindowContext_mac::~RasterWindowContext_mac() {
 
 sk_sp<const GrGLInterface> RasterWindowContext_mac::onInitializeContext() {
     SkASSERT(fWindow);
-
-    fGLContext = SDL_GL_CreateContext(fWindow);
-    if (!fGLContext) {
-        SkDebugf("%s\n", SDL_GetError());
-        return nullptr;
-    }
+    SkASSERT(fGLContext);
 
     if (0 == SDL_GL_MakeCurrent(fWindow, fGLContext)) {
         glClearStencil(0);
@@ -95,12 +90,7 @@ sk_sp<const GrGLInterface> RasterWindowContext_mac::onInitializeContext() {
 }
 
 void RasterWindowContext_mac::onDestroyContext() {
-    if (!fWindow || !fGLContext) {
-        return;
-    }
     fBackbufferSurface.reset(nullptr);
-    SDL_GL_DeleteContext(fGLContext);
-    fGLContext = nullptr;
 }
 
 sk_sp<SkSurface> RasterWindowContext_mac::getBackbufferSurface() { return fBackbufferSurface; }
diff --git a/tools/sk_app/mac/WindowContextFactory_mac.h b/tools/sk_app/mac/WindowContextFactory_mac.h
index 3adc68bbc2..c195c24daa 100644
--- a/tools/sk_app/mac/WindowContextFactory_mac.h
+++ b/tools/sk_app/mac/WindowContextFactory_mac.h
@@ -19,7 +19,8 @@ struct DisplayParams;
 namespace window_context_factory {
 
 struct MacWindowInfo {
-    SDL_Window*  fWindow;
+    SDL_Window*   fWindow;
+    SDL_GLContext fGLContext;
 };
 
 inline WindowContext* NewVulkanForMac(const MacWindowInfo&, const DisplayParams&) {
diff --git a/tools/sk_app/mac/Window_mac.cpp b/tools/sk_app/mac/Window_mac.cpp
index f2620518a2..309c8bbf36 100644
--- a/tools/sk_app/mac/Window_mac.cpp
+++ b/tools/sk_app/mac/Window_mac.cpp
@@ -71,10 +71,22 @@ bool Window_mac::initWindow() {
     fWindowID = SDL_GetWindowID(fWindow);
     gWindowMap.add(this);
 
+    fGLContext = SDL_GL_CreateContext(fWindow);
+    if (!fGLContext) {
+        SkDebugf("%s\n", SDL_GetError());
+        this->closeWindow();
+        return false;
+    }
+
     return true;
 }
 
 void Window_mac::closeWindow() {
+    if (fGLContext) {
+        SDL_GL_DeleteContext(fGLContext);
+        fGLContext = nullptr;
+    }
+
     if (fWindow) {
         gWindowMap.remove(fWindowID);
         SDL_DestroyWindow(fWindow);
@@ -251,6 +263,7 @@ bool Window_mac::attach(BackendType attachType) {
 
     window_context_factory::MacWindowInfo info;
     info.fWindow = fWindow;
+    info.fGLContext = fGLContext;
     switch (attachType) {
         case kRaster_BackendType:
             fWindowContext = NewRasterForMac(info, fRequestedDisplayParams);
diff --git a/tools/sk_app/mac/Window_mac.h b/tools/sk_app/mac/Window_mac.h
index 35cba095fa..8b34b7c902 100644
--- a/tools/sk_app/mac/Window_mac.h
+++ b/tools/sk_app/mac/Window_mac.h
@@ -18,7 +18,12 @@ namespace sk_app {
 
 class Window_mac : public Window {
 public:
-    Window_mac() : INHERITED(), fWindow(nullptr), fWindowID(0), fMSAASampleCount(1) {}
+    Window_mac()
+            : INHERITED()
+            , fWindow(nullptr)
+            , fWindowID(0)
+            , fGLContext(nullptr)
+            , fMSAASampleCount(1) {}
     ~Window_mac() override { this->closeWindow(); }
 
     bool initWindow();
@@ -47,8 +52,9 @@ private:
 
     static SkTDynamicHash<Window_mac, Uint32> gWindowMap;
 
-    SDL_Window*  fWindow;
-    Uint32       fWindowID;
+    SDL_Window*   fWindow;
+    Uint32        fWindowID;
+    SDL_GLContext fGLContext;
 
     int          fMSAASampleCount;