Fix macOS transparent windows on OpenJDK (#1008)

Fixes
https://youtrack.jetbrains.com/issue/CMP-7352
https://youtrack.jetbrains.com/issue/CMP-7345

skiko/src/awtMain/objectiveC/macos/DisplayLinkThrottler.mm

@@ -88,7 +88,25 @@ static CVReturn displayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeSt
             [weakSelf onScreenDidChange];
         }];
 
+        if (NSThread.currentThread.isMainThread) {
             [self onScreenDidChange];
+        } else {
+            // In case of OpenJDK, EDT thread != NSThread main thread
+            // There is one thing we should keep in mind. Postponing creation of vsync throttler will cause that for sometime there won't be any waiting:
+            //
+            // ```
+            // create window
+            // (10x) schedule render -> render
+            // onScreenDidChange
+            // schedule render -> wait vsync -> render
+            // ```
+            //
+            // It is probably okay, but possible alternative would be to wait for throttler creation. It is difficult, so we can just keep the current code.
+            __weak DisplayLinkThrottler *weakSelf = self;
+            dispatch_async(dispatch_get_main_queue(), ^{
+                [weakSelf onScreenDidChange];
+            });
+        }
     }
 
     return self;

skiko/src/awtMain/objectiveC/macos/MetalRedrawer.mm

@@ -115,6 +115,26 @@ static jmethodID getOnOcclusionStateChangedMethodID(JNIEnv *env, jobject redrawe
     return onOcclusionStateChanged;
 }
 
+
+static void setWindowPropertiesUnsafe(NSWindow* window, jboolean transparency) {
+    if (window == NULL) return;
+    if (transparency) {
+        window.hasShadow = NO;
+    }
+}
+
+static void setWindowProperties(NSWindow* window, jboolean transparency) {
+    if (NSThread.currentThread.isMainThread) {
+        setWindowPropertiesUnsafe(window, transparency);
+    } else {
+        // In case of OpenJDK, EDT thread != NSThread main thread
+        __weak NSWindow *weakWindow = window;
+        dispatch_async(dispatch_get_main_queue(), ^{
+            setWindowPropertiesUnsafe(weakWindow, transparency);
+        });
+    }
+}
+
 extern "C"
 {
 
@@ -161,10 +181,7 @@ JNIEXPORT jlong JNICALL Java_org_jetbrains_skiko_redrawer_MetalRedrawer_createMe
         device.inflightSemaphore = dispatch_semaphore_create(device.layer.maximumDrawableCount);
 
         NSWindow* window = (__bridge NSWindow*) (void *) windowPtr;
-
-        if (transparency) {
-            window.hasShadow = NO;
-        }
+        setWindowProperties(window, transparency);
 
         jmethodID onOcclusionStateChanged = getOnOcclusionStateChangedMethodID(env, redrawer);
         device.occlusionObserver =