[win32] Ensure correct DPI awareness for DnD

bundles/org.eclipse.swt/Eclipse SWT Drag and Drop/win32/org/eclipse/swt/dnd/DropTarget.java

@@ -242,29 +242,35 @@ void createCOMInterfaces() {
 		public long method2(long[] args) {return Release();}
 		@Override
 		public long method3(long[] args) {
-			if (args.length == 5) {
-				return DragEnter(args[0], (int)args[1], (int)args[2], (int)args[3], args[4]);
-			} else {
-				return DragEnter_64(args[0], (int)args[1], args[2], args[3]);
-			}
+			return Win32DPIUtils.runWithProperDPIAwareness(() -> {
+				if (args.length == 5) {
+					return DragEnter(args[0], (int)args[1], (int)args[2], (int)args[3], args[4]);
+				} else {
+					return DragEnter_64(args[0], (int)args[1], args[2], args[3]);
+				}
+			});
 		}
 		@Override
 		public long method4(long[] args) {
-			if (args.length == 4) {
-				return DragOver((int)args[0], (int)args[1], (int)args[2], args[3]);
-			} else {
-				return DragOver_64((int)args[0], args[1], args[2]);
-			}
+			return Win32DPIUtils.runWithProperDPIAwareness(() -> {
+				if (args.length == 4) {
+					return DragOver((int)args[0], (int)args[1], (int)args[2], args[3]);
+				} else {
+					return DragOver_64((int)args[0], args[1], args[2]);
+				}
+			});
 		}
 		@Override
 		public long method5(long[] args) {return DragLeave();}
 		@Override
 		public long method6(long[] args) {
-			if (args.length == 5) {
-				return Drop(args[0], (int)args[1], (int)args[2], (int)args[3], args[4]);
-			} else {
-				return Drop_64(args[0], (int)args[1], args[2], args[3]);
-			}
+			return Win32DPIUtils.runWithProperDPIAwareness(() -> {
+				if (args.length == 5) {
+					return Drop(args[0], (int)args[1], (int)args[2], (int)args[3], args[4]);
+				} else {
+					return Drop_64(args[0], (int)args[1], args[2], args[3]);
+				}
+			});
 		}
 	};
 }

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/internal/Win32DPIUtils.java

@@ -0,0 +1,68 @@
+/*******************************************************************************
+ * Copyright (c) 2025 Yatta Solutions and others.
+ *
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Yatta Solutions - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.swt.internal;
+
+import java.util.function.*;
+
+import org.eclipse.swt.internal.win32.*;
+import org.eclipse.swt.internal.win32.version.*;
+
+/**
+ * This class is used in the win32 implementation only to provide
+ * DPI related utility methods.
+ * <p>
+ * <b>IMPORTANT:</b> This class is <em>not</em> part of the public
+ * API for SWT. It is marked public only so that it can be shared
+ * within the packages provided by SWT. It is not available on all
+ * platforms, and should never be called from application code.
+ * </p>
+ * @noreference This class is not intended to be referenced by clients
+ */
+public class Win32DPIUtils {
+	public static boolean setDPIAwareness(int desiredDpiAwareness) {
+		if (desiredDpiAwareness == OS.GetThreadDpiAwarenessContext()) {
+			return true;
+		}
+		if (desiredDpiAwareness == OS.DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2) {
+			// "Per Monitor V2" only available in more recent Windows version
+			boolean perMonitorV2Available = OsVersion.IS_WIN10_1809;
+			if (!perMonitorV2Available) {
+				System.err.println("***WARNING: the OS version does not support DPI awareness mode PerMonitorV2.");
+				return false;
+			}
+		}
+		long setDpiAwarenessResult = OS.SetThreadDpiAwarenessContext(desiredDpiAwareness);
+		if (setDpiAwarenessResult == 0L) {
+			System.err.println("***WARNING: setting DPI awareness failed.");
+			return false;
+		}
+		return true;
+	}
+
+	public static <T> T runWithProperDPIAwareness(Supplier<T> operation) {
+		// refreshing is only necessary, when monitor specific scaling is active
+		long previousDPIAwareness = OS.GetThreadDpiAwarenessContext();
+		try {
+			if (!setDPIAwareness(OS.DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2)) {
+				// awareness was not changed, so no need to reset it
+				previousDPIAwareness = 0;
+			}
+			return operation.get();
+		} finally {
+			if (previousDPIAwareness > 0) {
+				OS.SetThreadDpiAwarenessContext(previousDPIAwareness);
+			}
+		}
+	}
+}

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

@@ -5404,7 +5404,7 @@ public boolean setRescalingAtRuntime(boolean activate) {
 
 private boolean setMonitorSpecificScaling(boolean activate) {
 	int desiredApiAwareness = activate ? OS.DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2 : OS.DPI_AWARENESS_CONTEXT_SYSTEM_AWARE;
-	if (setDPIAwareness(desiredApiAwareness)) {
+	if (Win32DPIUtils.setDPIAwareness(desiredApiAwareness)) {
 		rescalingAtRuntime = activate;
 		coordinateSystemMapper = activate ? new MultiZoomCoordinateSystemMapper(this, this::getMonitors) : new SingleZoomCoordinateSystemMapper(this);
 		// dispose a existing font registry for the default display
@@ -5414,38 +5414,12 @@ private boolean setMonitorSpecificScaling(boolean activate) {
 	return false;
 }
 
-private boolean setDPIAwareness(int desiredDpiAwareness) {
-	if (desiredDpiAwareness == OS.GetThreadDpiAwarenessContext()) {
-		return true;
-	}
-	if (desiredDpiAwareness == OS.DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2) {
-		// "Per Monitor V2" only available in more recent Windows version
-		boolean perMonitorV2Available = OsVersion.IS_WIN10_1809;
-		if (!perMonitorV2Available) {
-			System.err.println("***WARNING: the OS version does not support DPI awareness mode PerMonitorV2.");
-			return false;
-		}
-	}
-	long setDpiAwarenessResult = OS.SetThreadDpiAwarenessContext(desiredDpiAwareness);
-	if (setDpiAwarenessResult == 0L) {
-		System.err.println("***WARNING: setting DPI awareness failed.");
-		return false;
-	}
-	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);
-		}
+		Win32DPIUtils.runWithProperDPIAwareness(() -> {
+			operation.run();
+			return true;
+		});
 	} else {
 		operation.run();
 	}