Implementation of GC to enable multi zoom level support for win32 whi…

…ch can be

extended by other resources and widgets.

Contributes to
eclipse-platform#62 and eclipse-platform#131

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/GCData.java

@@ -15,6 +15,7 @@
 
 
 import org.eclipse.swt.*;
+import org.eclipse.swt.internal.*;
 import org.eclipse.swt.internal.win32.*;
 
 /**
@@ -47,6 +48,8 @@ public final class GCData {
 	public float[] lineDashes;
 	public float lineMiterLimit = 10;
 	public int alpha = 0xFF;
+	public int deviceZoom;
+	public int nativeDeviceZoom;
 
 	public Image image;
 	public PAINTSTRUCT ps;
@@ -57,4 +60,13 @@ public final class GCData {
 	public float gdipXOffset, gdipYOffset;
 	public int uiState = 0;
 	public boolean focusDrawn;
+
+	int getNativeDeviceZoom() {
+		return nativeDeviceZoom;
+	}
+
+	void setNativeDeviceZoom(int nativeDeviceZoom) {
+		this.nativeDeviceZoom = nativeDeviceZoom;
+		this.deviceZoom = DPIUtil.getZoomForAutoscaleProperty(nativeDeviceZoom);
+	}
 }

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/Image.java

@@ -139,7 +139,7 @@ public final class Image extends Resource implements Drawable {
 	/**
 	 * Attribute to cache current device zoom level
 	 */
-	private int currentDeviceZoom = 100;
+	int currentDeviceZoom = 100;
 
 	/**
 	 * width of the image

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

@@ -3563,6 +3563,12 @@ public void setMenu (Menu menu) {
 	this.menu = menu;
 }
 
+void setNativeZoomForGCData(GCData data) {
+	int nativeDeviceZoom = getShell().getNativeZoom();
+	data.nativeDeviceZoom = nativeDeviceZoom;
+	data.deviceZoom = DPIUtil.getZoomForAutoscaleProperty(nativeDeviceZoom);
+}
+
 /**
  * Sets the orientation of the receiver, which must be one
  * of the constants <code>SWT.LEFT_TO_RIGHT</code> or <code>SWT.RIGHT_TO_LEFT</code>.
@@ -3657,6 +3663,14 @@ public void setRedraw (boolean redraw) {
 	}
 }
 
+@Override
+void sendEvent(int eventType, Event event, boolean send) {
+	if(event != null && event.gc != null && event.gc.getGCData() != null) {
+		setNativeZoomForGCData(event.gc.getGCData());
+	}
+	super.sendEvent(eventType, event, send);
+}
+
 /**
  * Sets the shape of the control to the region specified
  * by the argument.  When the argument is null, the

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

@@ -563,6 +563,7 @@ void wmDrawChildImage(DRAWITEMSTRUCT struct) {
 	}
 
 	GCData data = new GCData();
+	setNativeZoomForGCData(data);
 	data.device = display;
 	GC gc = GC.win32_new (struct.hDC, data);
 	Image image = getEnabled () ? this.image : new Image (display, this.image, SWT.IMAGE_DISABLE);

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

@@ -125,7 +125,20 @@ public class Shell extends Decorations {
 	ToolTip [] toolTips;
 	long hwndMDIClient, lpstrTip, toolTipHandle, balloonTipHandle, menuItemToolTipHandle;
 	int minWidth = SWT.DEFAULT, minHeight = SWT.DEFAULT, maxWidth = SWT.DEFAULT, maxHeight = SWT.DEFAULT;
-	private int nativeZoom;
+	/**
+	 * the native zoom of the monitor the shell is drawn on
+	 * (Warning: This field is platform dependent)
+	 * <p>
+	 * <b>IMPORTANT:</b> This field is <em>not</em> part of the SWT
+	 * public API. 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 accessed from application code.
+	 * </p>
+	 *
+	 * @noreference This field is not intended to be referenced by clients.
+	 * @since 3.126
+	 */
+	public int nativeZoom;
 	long [] brushes;
 	boolean showWithParent, fullScreen, wasMaximized, modified, center;
 	String toolTitle, balloonTitle;

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

@@ -52,7 +52,20 @@
  */
 public abstract class Widget {
 
-	private int zoom;
+	/**
+	 * the zoom level of the widget
+	 * (Warning: This field is platform dependent)
+	 * <p>
+	 * <b>IMPORTANT:</b> This field is <em>not</em> part of the SWT
+	 * public API. 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 accessed from application code.
+	 * </p>
+	 *
+	 * @noreference This field is not intended to be referenced by clients.
+	 * @since 3.126
+	 */
+	public int zoom;
 	int style, state;
 	Display display;
 	EventTable eventTable;

tests/org.eclipse.swt.tests.win32/JUnit Tests/org/eclipse/swt/graphics/GCWin32Tests.java

@@ -0,0 +1,84 @@
+/*******************************************************************************
+ * Copyright (c) 2024 Yatta Solutions
+ *
+ * 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.graphics;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.concurrent.CompletableFuture;
+
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.internal.DPIUtil;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Event;
+import org.eclipse.swt.widgets.Shell;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class GCWin32Tests {
+	private Display display;
+	private int initialZoom;
+
+	@Before
+	public void setUp() {
+		initialZoom = DPIUtil.getDeviceZoom();
+		display = Display.getDefault();
+		DPIUtil.setDeviceZoom(100);
+	}
+
+	@After
+	public void tearDown() {
+		DPIUtil.setDeviceZoom(initialZoom);
+	}
+
+	@Test
+	public void gcZoomLevelMustChangeOnShellZoomChange() {
+		CompletableFuture<Integer> deviceZoom1 = new CompletableFuture<>();
+		CompletableFuture<Integer> deviceZoom2 = new CompletableFuture<>();
+		int zoom = DPIUtil.getDeviceZoom();
+		Shell shell = new Shell(display);
+		shell.addListener(SWT.Paint, event -> {
+			deviceZoom1.complete(event.gc.getGCData().deviceZoom);
+		});
+		shell.addListener(SWT.ZoomChanged, event -> {
+			deviceZoom2.complete(event.gc.getGCData().deviceZoom);
+		});
+		shell.open();
+		assertEquals("GCData must have a zoom level equal to the actual zoom level of the widget/shell", shell.zoom, (int) deviceZoom1.join());
+
+		int newSWTZoom = zoom * 2;
+		Event swtEvent = new Event();
+		swtEvent.type = SWT.ZoomChanged;
+		swtEvent.gc = GC.win32_new(shell, new GCData());
+		swtEvent.widget = shell;
+		DPIUtil.setDeviceZoom(newSWTZoom);
+		shell.zoom = newSWTZoom;
+		shell.nativeZoom = DPIUtil.getZoomForAutoscaleProperty(newSWTZoom);
+		shell.notifyListeners(SWT.ZoomChanged, swtEvent);
+
+		assertEquals("GCData must have a zoom level equal to the actual zoom level of the widget/shell on zoomChanged event", shell.zoom, (int) deviceZoom2.join());
+	}
+
+	@Test
+	public void drawnElementsShouldScaleUpToTheRightZoomLevel() {
+		int zoom = DPIUtil.getDeviceZoom();
+		int scalingFactor = 2;
+		Shell shell = new Shell(display);
+		GC gc = GC.win32_new(shell, new GCData());
+		gc.getGCData().deviceZoom = zoom * scalingFactor;
+		gc.getGCData().lineWidth = 10;
+		assertEquals("DPIUtil calls with getDeviceZoom should scale to the right value", gc.getGCData().lineWidth, gc.getLineWidth() * scalingFactor, 0);
+	}
+
+}