Scaling of Color/Font Dialog not working properly after DPI change

Creating a separate UI thread to set the DPI Awareness context to use
UNAWARE GDI scale before opening the either dialogs since windows has
issues with dialog scaling in AWARE context

Author: ShahzaibIbrahim

bundles/org.eclipse.swt/Eclipse SWT PI/win32/org/eclipse/swt/internal/win32/OS.java

@@ -370,6 +370,7 @@ public class OS extends C {
 	public static final short DMDUP_VERTICAL = 2;
 	public static final short DMDUP_HORIZONTAL = 3;
 	public static final int DPI_AWARENESS_CONTEXT_UNAWARE = 24592;
+	public static final int DPI_AWARENESS_CONTEXT_UNAWARE_GDISCALED = 1073766416;
 	public static final int DPI_AWARENESS_CONTEXT_SYSTEM_AWARE = 24593;
 	public static final int DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE = 18;
 	public static final int DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2 = 34;

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

@@ -233,6 +233,13 @@ public RGB open () {
 
 	display.externalEventLoop = true;
 	display.sendPreExternalEventDispatchEvent ();
+
+	/* Temporarily setting the thread dpi awareness to gdi scaling because window dialog has weird resize handling */
+	long currentDpiAwarenessContext = OS.GetThreadDpiAwarenessContext();
+	if(display.isRescalingAtRuntime()) {
+		currentDpiAwarenessContext = OS.SetThreadDpiAwarenessContext(OS.DPI_AWARENESS_CONTEXT_UNAWARE_GDISCALED);
+	}
+
 	/* Open the dialog */
 	boolean success = OS.ChooseColor (lpcc);
 	display.externalEventLoop = false;
@@ -270,6 +277,11 @@ public RGB open () {
 		rgb = new RGB (red, green, blue);
 	}
 
+	/* Reset the dpi awareness context */
+	if(display.isRescalingAtRuntime()) {
+		OS.SetThreadDpiAwarenessContext(currentDpiAwarenessContext);
+	}
+
 	/* Free the CCHookProc */
 	callback.dispose ();
 

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

@@ -226,6 +226,13 @@ public FontData open () {
 
 	display.externalEventLoop = true;
 	display.sendPreExternalEventDispatchEvent ();
+
+	/* Temporarily setting the thread dpi awareness to gdi scaling because window dialog has weird resize handling */
+	long currentDpiAwarenessContext = OS.GetThreadDpiAwarenessContext();
+	if(display.isRescalingAtRuntime()) {
+		currentDpiAwarenessContext = OS.SetThreadDpiAwarenessContext(OS.DPI_AWARENESS_CONTEXT_UNAWARE_GDISCALED);
+	}
+
 	/* Open the dialog */
 	boolean success = OS.ChooseFont (lpcf);
 	display.externalEventLoop = false;
@@ -279,6 +286,11 @@ public FontData open () {
 		}
 	}
 
+	/* Reset the dpi awareness context */
+	if(display.isRescalingAtRuntime()) {
+		OS.SetThreadDpiAwarenessContext(currentDpiAwarenessContext);
+	}
+
 	/* Free the OS memory */
 	if (lpLogFont != 0) OS.HeapFree (hHeap, 0, lpLogFont);