[win32] Refresh thread dpi awareness on hooks

This commit resets the DPI awareness for the WH_MSGFILTER hook, if called.
For performance reasons that is only done, when runAsyncMessages will be
triggered, as this can cause UI updates, which would be executed with the
wrong DPI awareness context and cause UI glitches.

Author: akoch-yatta

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Display.java

@@ -1456,31 +1456,39 @@ public Widget findWidget (Widget widget, long id) {
 long foregroundIdleProc (long code, long wParam, long lParam) {
 	if (code >= 0) {
 		if (!synchronizer.isMessagesEmpty()) {
-			sendPostExternalEventDispatchEvent ();
-			if (runMessagesInIdle) {
-				if (runMessagesInMessageProc) {
-					OS.PostMessage (hwndMessage, SWT_RUNASYNC, 0, 0);
-				} else {
-					runAsyncMessages (false);
+			// Windows hooks will inherit the thread DPI awareness from
+			// the process. Whatever DPI awareness was set before on
+			// the thread will be overwritten before the hook is called.
+			// This requires to reset the thread DPi awareness to make
+			// sure, all UI updates caused by this will be executed
+			// with the correct DPI awareness
+			runWithProperDPIAwareness(() -> {
+				sendPostExternalEventDispatchEvent ();
+				if (runMessagesInIdle) {
+					if (runMessagesInMessageProc) {
+						OS.PostMessage (hwndMessage, SWT_RUNASYNC, 0, 0);
+					} else {
+						runAsyncMessages (false);
+					}
 				}
-			}
-			/*
-			* Bug in Windows.  For some reason, input events can be lost
-			* when a message is posted to the queue from a foreground idle
-			* hook.  The fix is to detect that there are outstanding input
-			* events and avoid posting the wake event.
-			*
-			* Note that PeekMessage() changes the state of events on the
-			* queue to no longer be considered new. If we peek for input
-			* events and posted messages (PM_QS_INPUT | PM_QS_POSTMESSAGE),
-			* it is possible to cause WaitMessage() to sleep until a new
-			* input event is generated causing sync runnables not to be
-			* executed.
-			*/
-			MSG msg = new MSG();
-			int flags = OS.PM_NOREMOVE | OS.PM_NOYIELD | OS.PM_QS_INPUT;
-			if (!OS.PeekMessage (msg, 0, 0, 0, flags)) wakeThread ();
-			sendPreExternalEventDispatchEvent ();
+				/*
+				* Bug in Windows.  For some reason, input events can be lost
+				* when a message is posted to the queue from a foreground idle
+				* hook.  The fix is to detect that there are outstanding input
+				* events and avoid posting the wake event.
+				*
+				* Note that PeekMessage() changes the state of events on the
+				* queue to no longer be considered new. If we peek for input
+				* events and posted messages (PM_QS_INPUT | PM_QS_POSTMESSAGE),
+				* it is possible to cause WaitMessage() to sleep until a new
+				* input event is generated causing sync runnables not to be
+				* executed.
+				*/
+				MSG msg = new MSG();
+				int flags = OS.PM_NOREMOVE | OS.PM_NOYIELD | OS.PM_QS_INPUT;
+				if (!OS.PeekMessage (msg, 0, 0, 0, flags)) wakeThread ();
+				sendPreExternalEventDispatchEvent ();
+			});
 		}
 	}
 	return OS.CallNextHookEx (idleHook, (int)code, wParam, lParam);
@@ -3425,7 +3433,15 @@ long msgFilterProc (long code, long wParam, long lParam) {
 				MSG msg = new MSG ();
 				int flags = OS.PM_NOREMOVE | OS.PM_NOYIELD | OS.PM_QS_INPUT | OS.PM_QS_POSTMESSAGE;
 				if (!OS.PeekMessage (msg, 0, 0, 0, flags)) {
-					if (runAsyncMessages (false)) wakeThread ();
+					// Windows hooks will inherit the thread DPI awareness from
+					// the process. Whatever DPI awareness was set before on
+					// the thread will be overwritten before the hook is called.
+					// This requires to reset the thread DPi awareness to make
+					// sure, all UI updates caused by this will be executed
+					// with the correct DPI awareness
+					runWithProperDPIAwareness(() -> {
+						if (runAsyncMessages (false)) wakeThread ();
+					});
 				}
 			}
 			break;
@@ -5382,4 +5398,18 @@ private boolean setDPIAwareness(int desiredDpiAwareness) {
 	return true;
 }
 
+private void runWithProperDPIAwareness(Runnable operation) {
+	if (isRescalingAtRuntime()) {
+		// refreshing is only necessary, when monitor specific scaling is active
+		long previousDPIAwareness = OS.GetThreadDpiAwarenessContext();
+		if (!setDPIAwareness(OS.DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2)) {
+			// awareness was not changed, so no need to reset it
+			previousDPIAwareness = 0;
+		}
+		operation.run();
+		if (previousDPIAwareness > 0) {
+			OS.SetThreadDpiAwarenessContext(previousDPIAwareness);
+		}
+	}
+}
 }