Refactor: Move Cocoa-specific DPI methods to CocoaDPIUtil

The `autoScale` methods no longer have relevance in the Win32
implementation, so this commit extracts the macOS-specific DPI scaling
logic into a dedicated `CocoaDPIUtil` class. This improves platform
separation and maintains cleaner, OS-specific code boundaries.

Author: ShahzaibIbrahim

bundles/org.eclipse.swt/Eclipse SWT/cocoa/org/eclipse/swt/graphics/Image.java

@@ -1822,11 +1822,11 @@ public String toString () {
  * @noreference This method is not intended to be referenced by clients.
  */
 public static void drawScaled(GC gc, Image original, int width, int height, float scaleFactor) {
-	gc.drawImage (original, 0, 0, DPIUtil.autoScaleDown (width), DPIUtil.autoScaleDown (height),
+	gc.drawImage (original, 0, 0, CocoaDPIUtil.autoScaleDown (width), CocoaDPIUtil.autoScaleDown (height),
 			/* E.g. destWidth here is effectively DPIUtil.autoScaleDown (scaledWidth), but avoiding rounding errors.
 			 * Nevertheless, we still have some rounding errors due to the point-based API GC#drawImage(..).
 			 */
-			0, 0, Math.round (DPIUtil.autoScaleDown (width * scaleFactor)), Math.round (DPIUtil.autoScaleDown (height * scaleFactor)));
+			0, 0, Math.round (CocoaDPIUtil.autoScaleDown (width * scaleFactor)), Math.round (CocoaDPIUtil.autoScaleDown (height * scaleFactor)));
 }
 
 }

bundles/org.eclipse.swt/Eclipse SWT/cocoa/org/eclipse/swt/internal/CocoaDPIUtil.java

@@ -0,0 +1,48 @@
+/*******************************************************************************
+ * Copyright (c) 2022 IBM Corporation 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:
+ *     IBM Corporation - initial API and implementation
+ *     Daniel Kruegler - #420 - [High DPI] "swt.autoScale" should add new "half" option
+ *     Yatta Solutions - #131 - Additional methods to specify target zoom directly
+ *******************************************************************************/
+package org.eclipse.swt.internal;
+
+/**
+ * This class hold common constants and utility functions w.r.t. to SWT high DPI
+ * functionality.
+ * <p>
+ * The {@code autoScaleUp(..)} methods convert from API coordinates (in SWT
+ * points) to internal high DPI coordinates (in pixels) that interface with
+ * native widgets.
+ * </p>
+ * <p>
+ * The {@code autoScaleDown(..)} convert from high DPI pixels to API coordinates
+ * (in SWT points).
+ * </p>
+ *
+ * @since 3.105
+ */
+public class CocoaDPIUtil {
+
+	/**
+	 * Auto-scale down int dimensions.
+	 */
+	public static int autoScaleDown(int size) {
+		return DPIUtil.scaleDown(size, DPIUtil.getDeviceZoom());
+	}
+
+	/**
+	 * Auto-scale down float dimensions.
+	 */
+	public static float autoScaleDown(float size) {
+		return DPIUtil.scaleDown(size, DPIUtil.getDeviceZoom());
+	}
+}