Ensure Consistent DPI Awareness in getDPI() for Font Calculation

The DPI computed in getDPI() is used to determine the font height for the OS.ChooseFont dialog. Following the change in b2c80a4, the thread DPI awareness is set to OS.DPI_AWARENESS_CONTEXT_UNAWARE_GDISCALED before opening the ChooseFont dialog. This commit ensures the same DPI awareness is applied in getDPI() for consistent font size calculation.

Fixes #2866

Author: arunjose696

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

@@ -278,14 +278,24 @@ public FontData open () {
 }
 
 private int getDPI() {
-	long hDC = OS.GetDC (0);
-	// We need to use OS.GetDeviceCaps, which is static throughout application
-	// lifecycle (System DPI Aware), because we use
-	// DPI_AWARENESS_CONTEXT_UNAWARE_GDISCALED which always depends on the DPI at
-	// application startup
-	int dpi = OS.GetDeviceCaps(hDC, OS.LOGPIXELSY);
-	OS.ReleaseDC (0, hDC);
-	return dpi;
+	long currentDpiAwarenessContext = OS.GetThreadDpiAwarenessContext();
+	try {
+		if (parent.getDisplay().isRescalingAtRuntime()) {
+			currentDpiAwarenessContext = OS.SetThreadDpiAwarenessContext(OS.DPI_AWARENESS_CONTEXT_UNAWARE_GDISCALED);
+		}
+		long hDC = OS.GetDC(0);
+		// We need to use OS.GetDeviceCaps, which is static throughout application
+		// lifecycle (System DPI Aware), because we use
+		// DPI_AWARENESS_CONTEXT_UNAWARE_GDISCALED which always depends on the DPI at
+		// application startup
+		int dpi = OS.GetDeviceCaps(hDC, OS.LOGPIXELSY);
+		OS.ReleaseDC(0, hDC);
+		return dpi;
+	} finally {
+		if (parent.getDisplay().isRescalingAtRuntime()) {
+			OS.SetThreadDpiAwarenessContext(currentDpiAwarenessContext);
+		}
+	}
 }
 
 /**