a workaround to fix black screen on macOS 10.14 (cocos2d#19090)

Author: drelaptop

cocos/platform/CCGLView.h

@@ -433,6 +433,7 @@ class CC_DLL GLView : public Ref
 
 #if (CC_TARGET_PLATFORM == CC_PLATFORM_MAC)
     virtual id getCocoaWindow() = 0;
+    virtual id getNSGLContext() = 0; // stevetranby: added
 #endif /* (CC_TARGET_PLATFORM == CC_PLATFORM_MAC) */
 
     /**

cocos/platform/desktop/CCGLViewImpl-desktop.h

@@ -138,6 +138,7 @@ class CC_DLL GLViewImpl : public GLView
 
 #if (CC_TARGET_PLATFORM == CC_PLATFORM_MAC)
     id getCocoaWindow() override { return glfwGetCocoaWindow(_mainWindow); }
+    id getNSGLContext() override { return glfwGetNSGLContext(_mainWindow); } // stevetranby: added
 #endif // #if (CC_TARGET_PLATFORM == CC_PLATFORM_MAC)
 
 protected:

cocos/platform/mac/CCApplication-mac.mm

@@ -79,11 +79,21 @@ static long getCurrentMillSecond()
 
     // Retain glview to avoid glview being released in the while loop
     glview->retain();
-    
+
+    unsigned int ctx_updated_count = 0;
+
     while (!glview->windowShouldClose())
     {
         lastTime = getCurrentMillSecond();
-        
+
+        // hack to fix issue #19080, black screen on macOS 10.14
+        // stevetranby: look into doing this outside loop to get rid of condition test per frame
+        if(ctx_updated_count < 2) {
+            ctx_updated_count++;
+            NSOpenGLContext* ctx = (NSOpenGLContext*)glview->getNSGLContext();
+            [ctx update];
+        }
+
         director->mainLoop();
         glview->pollEvents();