Change monitor-specific scaling setting before Display creation

The method Display#setRescalingAtRuntime() allows to activate the
monitor-specific scaling mechanism on Windows. This must, however,
actually be activated before the Display is instantiated, like it is
done during the Display constructor execution if the VM argument for
global activation of monitor-specific scaling is specified. In
consequence, calling #setRescalingAtRuntime() does not take the full
intended effect.

This change deprecated the method (along with its according
accessor #isRescalingAtRuntime()) and adds a new method to activate
monitor-specific scaling on the Display class instead of an instance to
be used for subsequent displays to be instantiated.

Author: HeikoKlare

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

@@ -6833,6 +6833,22 @@ static boolean isActivateShellOnForceFocus() {
 	return "true".equals(System.getProperty("org.eclipse.swt.internal.activateShellOnForceFocus", "true")); //$NON-NLS-1$
 }
 
+/**
+ * Activates or deactivates monitor-specific scaling of shells at runtime for
+ * all Displays subsequently created whenever the DPI scaling of the shell's
+ * monitor changes. This only affects displays created after calling this
+ * method.
+ * <p>
+ * <b>Note:</b> This functionality is only available on Windows. Calling this
+ * method on other operating system will have no effect.
+ *
+ * @param activated whether monitor-specific scaling shall be activated or
+ *                  deactivated
+ * @since 3.129
+ */
+public static void setMonitorSpecificScaling(boolean activated) {
+}
+
 /**
  * {@return whether rescaling of shells at runtime when the DPI scaling of a
  * shell's monitor changes is activated for this device}
@@ -6841,7 +6857,10 @@ static boolean isActivateShellOnForceFocus() {
  * method on other operating system will always return false.
  *
  * @since 3.127
+ * @deprecated this method should not be used as the corresponding
+ *             {@link #setRescalingAtRuntime(boolean)} should not be used either
  */
+@Deprecated(since = "2025-03", forRemoval = true)
 public boolean isRescalingAtRuntime() {
 	return false;
 }
@@ -6858,7 +6877,12 @@ public boolean isRescalingAtRuntime() {
  * @param activate whether rescaling shall be activated or deactivated
  * @return whether activating or deactivating the rescaling was successful
  * @since 3.127
+ * @deprecated this method should not be used as it needs to be called already
+ *             during instantiation to take proper effect; use
+ *             {@link #setMonitorSpecificScaling(boolean)} before creating a
+ *             Display instead
  */
+@Deprecated(since = "2025-03", forRemoval = true)
 public boolean setRescalingAtRuntime(boolean activate) {
 	// not implemented for Cocoa
 	return false;

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

@@ -6269,6 +6269,22 @@ static boolean isActivateShellOnForceFocus() {
 	return "true".equals(System.getProperty("org.eclipse.swt.internal.activateShellOnForceFocus", "true")); //$NON-NLS-1$
 }
 
+/**
+ * Activates or deactivates monitor-specific scaling of shells at runtime for
+ * all Displays subsequently created whenever the DPI scaling of the shell's
+ * monitor changes. This only affects displays created after calling this
+ * method.
+ * <p>
+ * <b>Note:</b> This functionality is only available on Windows. Calling this
+ * method on other operating system will have no effect.
+ *
+ * @param activated whether monitor-specific scaling shall be activated or
+ *                  deactivated
+ * @since 3.129
+ */
+public static void setMonitorSpecificScaling(boolean activated) {
+}
+
 /**
  * {@return whether rescaling of shells at runtime when the DPI scaling of a
  * shell's monitor changes is activated for this device}
@@ -6277,7 +6293,10 @@ static boolean isActivateShellOnForceFocus() {
  * method on other operating system will always return false.
  *
  * @since 3.127
+ * @deprecated this method should not be used as the corresponding
+ *             {@link #setRescalingAtRuntime(boolean)} should not be used either
  */
+@Deprecated(since = "2025-03", forRemoval = true)
 public boolean isRescalingAtRuntime() {
 	return false;
 }
@@ -6294,7 +6313,12 @@ public boolean isRescalingAtRuntime() {
  * @param activate whether rescaling shall be activated or deactivated
  * @return whether activating or deactivating the rescaling was successful
  * @since 3.127
+ * @deprecated this method should not be used as it needs to be called already
+ *             during instantiation to take proper effect; use
+ *             {@link #setMonitorSpecificScaling(boolean)} before creating a
+ *             Display instead
  */
+@Deprecated(since = "2025-03", forRemoval = true)
 public boolean setRescalingAtRuntime(boolean activate) {
 	// not implemented for GTK
 	return false;

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

@@ -139,6 +139,7 @@ public class Display extends Device implements Executor {
 	boolean useOwnDC;
 	boolean externalEventLoop; // events are dispatched outside SWT, e.g. TrackPopupMenu or DoDragDrop
 	private CoordinateSystemMapper coordinateSystemMapper;
+	private static boolean monitorSpecificScaling;
 	private boolean rescalingAtRuntime;
 
 	/* Widget Table */
@@ -948,7 +949,7 @@ public void close () {
 protected void create (DeviceData data) {
 	checkSubclass ();
 	checkDisplay (thread = Thread.currentThread (), true);
-	if (DPIUtil.isAutoScaleOnRuntimeActive()) {
+	if (monitorSpecificScaling || DPIUtil.isAutoScaleOnRuntimeActive()) {
 		setRescalingAtRuntime(true);
 	}
 	createDisplay (data);
@@ -5270,6 +5271,24 @@ private long openThemeData(final char[] themeName) {
 		return OS.OpenThemeData(hwndMessage, themeName, dpi);
 	}
 }
+
+/**
+ * Activates or deactivates monitor-specific scaling of shells at runtime for
+ * all Displays subsequently created whenever the DPI scaling of the shell's
+ * monitor changes. This only affects displays created after calling this
+ * method.
+ * <p>
+ * <b>Note:</b> This functionality is only available on Windows. Calling this
+ * method on other operating system will have no effect.
+ *
+ * @param activated whether monitor-specific scaling shall be activated or
+ *                  deactivated
+ * @since 3.129
+ */
+public static void setMonitorSpecificScaling(boolean activated) {
+	monitorSpecificScaling = activated;
+}
+
 /**
  * {@return whether rescaling of shells at runtime when the DPI scaling of a
  * shell's monitor changes is activated for this device}
@@ -5278,7 +5297,10 @@ private long openThemeData(final char[] themeName) {
  * method on other operating system will always return false.
  *
  * @since 3.127
+ * @deprecated this method should not be used as the corresponding
+ *             {@link #setRescalingAtRuntime(boolean)} should not be used either
  */
+@Deprecated(since = "2025-03", forRemoval = true)
 public boolean isRescalingAtRuntime() {
 	return rescalingAtRuntime;
 }
@@ -5295,7 +5317,12 @@ public boolean isRescalingAtRuntime() {
  * @param activate whether rescaling shall be activated or deactivated
  * @return whether activating or deactivating the rescaling was successful
  * @since 3.127
+ * @deprecated this method should not be used as it needs to be called already
+ *             during instantiation to take proper effect; use
+ *             {@link #setMonitorSpecificScaling(boolean)} before creating a
+ *             Display instead
  */
+@Deprecated(since = "2025-03", forRemoval = true)
 public boolean setRescalingAtRuntime(boolean activate) {
 	int desiredApiAwareness = activate ? OS.DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2 : OS.DPI_AWARENESS_CONTEXT_SYSTEM_AWARE;
 	if (setDPIAwareness(desiredApiAwareness)) {