Implementation of Pattern to enable multi zoom level support for win32

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

@@ -198,9 +198,9 @@ void checkGC(int mask) {
 			Pattern pattern = data.foregroundPattern;
 			if (pattern != null) {
 				if(data.alpha == 0xFF) {
-					brush = pattern.handle;
+					brush = pattern.getHandle(getZoom());
 				} else {
-					brush = data.gdipFgPatternBrushAlpha != 0 ? Gdip.Brush_Clone(data.gdipFgPatternBrushAlpha) : createAlphaTextureBrush(pattern.handle, data.alpha);
+					brush = data.gdipFgPatternBrushAlpha != 0 ? Gdip.Brush_Clone(data.gdipFgPatternBrushAlpha) : createAlphaTextureBrush(pattern.getHandle(getZoom()), data.alpha);
 					data.gdipFgPatternBrushAlpha = brush;
 				}
 				if ((data.style & SWT.MIRRORED) != 0) {
@@ -289,9 +289,9 @@ void checkGC(int mask) {
 			Pattern pattern = data.backgroundPattern;
 			if (pattern != null) {
 				if(data.alpha == 0xFF) {
-					data.gdipBrush = pattern.handle;
+					data.gdipBrush = pattern.getHandle(getZoom());
 				} else {
-					long brush = data.gdipBgPatternBrushAlpha != 0 ? Gdip.Brush_Clone(data.gdipBgPatternBrushAlpha) : createAlphaTextureBrush(pattern.handle, data.alpha);
+					long brush = data.gdipBgPatternBrushAlpha != 0 ? Gdip.Brush_Clone(data.gdipBgPatternBrushAlpha) : createAlphaTextureBrush(pattern.getHandle(getZoom()), data.alpha);
 					data.gdipBrush = data.gdipBgBrush /*= data.gdipBgPatternBrushAlpha */ = brush;
 				}
 				if ((data.style & SWT.MIRRORED) != 0) {
@@ -3440,7 +3440,7 @@ public void getClipping (Region region) {
 }
 
 long getFgBrush() {
-	return data.foregroundPattern != null ? data.foregroundPattern.handle : data.gdipFgBrush;
+	return data.foregroundPattern != null ? data.foregroundPattern.getHandle(getZoom()) : data.gdipFgBrush;
 }
 
 /**

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

@@ -13,6 +13,8 @@
  *******************************************************************************/
 package org.eclipse.swt.graphics;
 
+import java.util.*;
+
 import org.eclipse.swt.*;
 import org.eclipse.swt.internal.*;
 import org.eclipse.swt.internal.gdip.*;
@@ -39,22 +41,18 @@
  */
 public class Pattern extends Resource {
 
-	/**
-	 * the OS resource for the Pattern
-	 * (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.
-	 */
-	public long handle;
+	private int initialZoom;
 
 	private Runnable bitmapDestructor;
 
+	// These are the possible fields with which a pattern can be initialized from the appropriate constructors.
+	private final Image image;
+	private float baseX1, baseY1, baseX2, baseY2;
+	private Color color1, color2;
+	private int alpha1, alpha2;
+
+	private final Map<Integer, Long> zoomLevelToHandle = new HashMap<>();
+
 /**
  * Constructs a new Pattern given an image. Drawing with the resulting
  * pattern will cause the image to be tiled over the resulting area.
@@ -88,22 +86,9 @@ public Pattern(Device device, Image image) {
 	if (image == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
 	if (image.isDisposed()) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
 	this.device.checkGDIP();
-	long[] gdipImage = image.createGdipImage();
-	long img = gdipImage[0];
-	int width = Gdip.Image_GetWidth(img);
-	int height = Gdip.Image_GetHeight(img);
-	handle = Gdip.TextureBrush_new(img, Gdip.WrapModeTile, 0, 0, width, height);
-	bitmapDestructor = () -> {
-		Gdip.Bitmap_delete(img);
-		if (gdipImage[1] != 0) {
-			long hHeap = OS.GetProcessHeap ();
-			OS.HeapFree(hHeap, 0, gdipImage[1]);
-		}
-	};
-	if (handle == 0) {
-		bitmapDestructor.run();
-		SWT.error(SWT.ERROR_NO_HANDLES);
-	}
+	this.image = image;
+	initialZoom = DPIUtil.getDeviceZoom();
+	setImageHandle(image, initialZoom);
 	init();
 }
 
@@ -187,10 +172,36 @@ public Pattern(Device device, float x1, float y1, float x2, float y2, Color colo
  */
 public Pattern(Device device, float x1, float y1, float x2, float y2, Color color1, int alpha1, Color color2, int alpha2) {
 	super(device);
-	x1 = DPIUtil.autoScaleUp(x1);
-	y1 = DPIUtil.autoScaleUp(y1);
-	x2 = DPIUtil.autoScaleUp(x2);
-	y2 = DPIUtil.autoScaleUp(y2);
+	this.baseX1 = x1;
+	this.baseX2 = x2;
+	this.baseY1 = y1;
+	this.baseY2 = y2;
+	this.color1 = color1;
+	this.color2 = color2;
+	this.alpha1 = alpha1;
+	this.alpha2 = alpha2;
+	this.image = null;
+	initialZoom = DPIUtil.getDeviceZoom();
+	initializeSize(initialZoom);
+}
+
+long getHandle(int zoom) {
+	if (!this.zoomLevelToHandle.containsKey(zoom)) {
+		if (isImagePattern()) {
+			setImageHandle(image, zoom);
+		} else {
+			initializeSize(zoom);
+		}
+	}
+	return this.zoomLevelToHandle.get(zoom);
+}
+
+private void initializeSize(int zoom) {
+	long handle;
+	float x1 = DPIUtil.autoScaleUp(this.baseX1, zoom);
+	float y1 = DPIUtil.autoScaleUp(this.baseY1, zoom);
+	float x2 = DPIUtil.autoScaleUp(this.baseX2, zoom);
+	float y2 = DPIUtil.autoScaleUp(this.baseY2, zoom);
 	if (color1 == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
 	if (color1.isDisposed()) SWT.error(SWT.ERROR_INVALID_ARGUMENT);
 	if (color2 == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
@@ -221,27 +232,51 @@ public Pattern(Device device, float x1, float y1, float x2, float y2, Color colo
 			Gdip.LinearGradientBrush_SetInterpolationColors(handle, new int [] {foreColor, midColor, backColor}, new float[]{0, 0.5f, 1}, 3);
 		}
 	}
+	this.zoomLevelToHandle.put(zoom, handle);
 	init();
 }
 
+void setImageHandle(Image image, int zoom) {
+	long[] gdipImage = image.createGdipImage(zoom);
+	long img = gdipImage[0];
+	int width = Gdip.Image_GetWidth(img);
+	int height = Gdip.Image_GetHeight(img);
+	long handle = Gdip.TextureBrush_new(img, Gdip.WrapModeTile, 0, 0, width, height);
+	bitmapDestructor = () -> {
+		Gdip.Bitmap_delete(img);
+		if (gdipImage[1] != 0) {
+			long hHeap = OS.GetProcessHeap ();
+			OS.HeapFree(hHeap, 0, gdipImage[1]);
+		}
+	};
+	if (handle == 0) {
+		bitmapDestructor.run();
+		SWT.error(SWT.ERROR_NO_HANDLES);
+	} else {
+		zoomLevelToHandle.put(zoom, handle);
+	}
+}
+
 @Override
 void destroy() {
-	int type = Gdip.Brush_GetType(handle);
-	switch (type) {
-		case Gdip.BrushTypeSolidColor:
-			Gdip.SolidBrush_delete(handle);
-			break;
-		case Gdip.BrushTypeHatchFill:
-			Gdip.HatchBrush_delete(handle);
-			break;
-		case Gdip.BrushTypeLinearGradient:
-			Gdip.LinearGradientBrush_delete(handle);
-			break;
-		case Gdip.BrushTypeTextureFill:
-			Gdip.TextureBrush_delete(handle);
-			break;
+	for (long handle: zoomLevelToHandle.values()) {
+		int type = Gdip.Brush_GetType(handle);
+		switch (type) {
+			case Gdip.BrushTypeSolidColor:
+				Gdip.SolidBrush_delete(handle);
+				break;
+			case Gdip.BrushTypeHatchFill:
+				Gdip.HatchBrush_delete(handle);
+				break;
+			case Gdip.BrushTypeLinearGradient:
+				Gdip.LinearGradientBrush_delete(handle);
+				break;
+			case Gdip.BrushTypeTextureFill:
+				Gdip.TextureBrush_delete(handle);
+				break;
+		}
 	}
-	handle = 0;
+	zoomLevelToHandle.clear();
 	if (bitmapDestructor != null) {
 		bitmapDestructor.run();
 		bitmapDestructor = null;
@@ -260,7 +295,7 @@ void destroy() {
  */
 @Override
 public boolean isDisposed() {
-	return handle == 0;
+	return zoomLevelToHandle.isEmpty();
 }
 
 /**
@@ -272,7 +307,11 @@ public boolean isDisposed() {
 @Override
 public String toString() {
 	if (isDisposed()) return "Pattern {*DISPOSED*}";
-	return "Pattern {" + handle + "}";
+	return "Pattern {" + zoomLevelToHandle + "}";
+}
+
+private boolean isImagePattern() {
+	return image != null;
 }
 
 }

tests/org.eclipse.swt.tests.win32/ManualTests/org/eclipse/swt/widgets/PatternWin32ManualTest.java

@@ -0,0 +1,71 @@
+/*******************************************************************************
+ * 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.widgets;
+
+import org.eclipse.swt.graphics.Color;
+import org.eclipse.swt.graphics.Pattern;
+import org.eclipse.swt.internal.DPIUtil;
+
+/*
+ * This Snippet tests a pattern at multiple zoom levels.
+ *
+ * It is difficult to test the pattern at multiple zoom level automatically since we also need
+ * to test the visual behavior. It is important to make sure that the pattern looks the same
+ * regardless of its size as per the zoom level. On the execution, 2 shells are
+ * opened at 2 different zoom levels. The pattern is a gradient of 2 colors. On both the
+ * shells, the pattern should be uniformly drawn and the size difference of both the patterns
+ * should be clearly visible without any visual difference except for the size. The size
+ * difference should be equal to the scalingFactor in the snippet.
+ *
+ */
+public class PatternWin32ManualTest {
+	private static Display display = Display.getDefault();
+
+	public static void main (String [] args) {
+		int zoom = DPIUtil.getDeviceZoom();
+		int scalingFactor = 3;
+		int scaledZoom = zoom * scalingFactor;
+		int width = 400;
+		int height = 300;
+		final Pattern pat = new Pattern(display, 0, 0, width, height, new Color(null, 200, 200, 200), 0, new Color(null, 255, 0, 0), 255);
+
+		Shell shell1 = createShellWithPattern(width, height, pat, zoom);
+		Shell shell2 = createShellWithPattern(width, height, pat, scaledZoom);
+
+		while (!shell1.isDisposed() || !shell2.isDisposed()) {
+			if (!display.readAndDispatch()) {
+				display.sleep();
+			}
+		}
+		pat.dispose();
+		shell1.dispose();
+		shell2.dispose();
+	}
+
+	private static Shell createShellWithPattern(int width, int height, final Pattern pat, int nativeZoom) {
+		Shell shell = new Shell(display);
+		shell.nativeZoom = nativeZoom;
+		shell.setText("Unscaled shell");
+		shell.setSize(width, height);
+		shell.addPaintListener(e -> {
+			e.gc.setBackground(new Color(null, 100, 200, 0));
+			e.gc.fillRectangle(0, 0, shell.getBounds().width, shell.getBounds().height);
+			e.gc.setBackground(new Color(null, 255, 0, 0));
+			e.gc.setBackgroundPattern(pat);
+			e.gc.fillRectangle(0, 0, shell.getBounds().width, shell.getBounds().height);
+		});
+		shell.open();
+		return shell;
+	}
+}