Add Snippet 386: Demonstrates Cursor constructors and DPI scaling in SWT

examples/org.eclipse.swt.snippets/Snippets.md

@@ -125,6 +125,7 @@ To contribute a new snippet, [create a snippet contribution as a pull request](h
 - [create a color cursor from a source and a mask](https://github.com/eclipse-platform/eclipse.platform.swt/tree/master/examples/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet119.java) – [(preview)](https://github.com/eclipse-platform/eclipse.platform.swt/blob/master/examples/org.eclipse.swt.snippets/previews/Snippet119.png "Preview for Snippet 119")
 - [create a color cursor from an image file](https://github.com/eclipse-platform/eclipse.platform.swt/tree/master/examples/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet118.java) – [(preview)](https://github.com/eclipse-platform/eclipse.platform.swt/blob/master/examples/org.eclipse.swt.snippets/previews/Snippet118.png "Preview for Snippet 118")
 - [hide the Cursor over a control](https://github.com/eclipse-platform/eclipse.platform.swt/tree/master/examples/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet242.java) – [(preview)](https://github.com/eclipse-platform/eclipse.platform.swt/blob/master/examples/org.eclipse.swt.snippets/previews/Snippet242.png "Preview for Snippet 242")
+- [demonstrates various ways to construct and use custom cursors in an SWT application](https://github.com/eclipse-platform/eclipse.platform.swt/tree/master/examples/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet386.java) – [(preview)](https://github.com/eclipse-platform/eclipse.platform.swt/blob/master/examples/org.eclipse.swt.snippets/previews/Snippet386.png "Preview for Snippet 386")
 
 ### **DateTime**
 - [create a DateTime calendar and a DateTime time](https://github.com/eclipse-platform/eclipse.platform.swt/tree/master/examples/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet250.java) – [(preview)](https://github.com/eclipse-platform/eclipse.platform.swt/blob/master/examples/org.eclipse.swt.snippets/previews/Snippet250.png "Preview for Snippet 250")

examples/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet386.java

@@ -0,0 +1,227 @@
+/*******************************************************************************
+ * Copyright (c) 2025 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.snippets;
+
+import org.eclipse.swt.*;
+import org.eclipse.swt.graphics.*;
+import org.eclipse.swt.layout.*;
+import org.eclipse.swt.widgets.*;
+
+/**
+ * Demonstrates various ways to construct and use custom cursors in an SWT
+ * application.
+ * <p>
+ * This example provides a graphical user interface that allows users to select
+ * from several different {@link org.eclipse.swt.graphics.Cursor} constructors,
+ * showing the resulting cursor in real time on the application shell. It also
+ * dynamically updates to reflect changes in system DPI scaling (zoom),
+ * displaying the expected cursor size and drawing a set of reference ticks to
+ * help visualize scaling.
+ * <p>
+ * Features of this snippet include:
+ * <ul>
+ * <li>Combo box to choose between multiple cursor constructors, including
+ * system, custom image, and DPI-aware providers.</li>
+ * <li>Live update of the shell cursor based on the user's selection.</li>
+ * <li>Display of current system zoom level and expected cursor size for visual
+ * reference.</li>
+ * <li>Painted tick marks and labels to visualize scaling and cursor positioning
+ * at different zooms.</li>
+ * <li>DPI change listener to update UI when system zoom changes.</li>
+ * </ul>
+ *
+ * This snippet is intended for educational and demonstration purposes to aid
+ * understanding of cursor creation and DPI handling in SWT.
+ *
+ * <p>
+ * For a list of all SWT example snippets see
+ * http://www.eclipse.org/swt/snippets/
+ * </p>
+ */
+public class Snippet386 {
+
+	private static final int IMAGE_SIZE_IN_POINTS = 16;
+
+	public static void main(String[] args) {
+		Display display = new Display();
+		Shell shell = createShell(display);
+
+		Combo combo = createConstructorCombo(shell);
+		Label zoomLabel = createZoomLabel(shell);
+
+		addZoomChangedListener(shell, zoomLabel);
+		Group section = new Group(shell, SWT.NONE);
+		section.setText("Scale");
+		section.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
+		section.setLayout(new FillLayout());
+		addPaintTicks(section);
+
+		CursorManager cursorManager = new CursorManager(display, shell, combo);
+		combo.addListener(SWT.Selection, e -> cursorManager.updateCursor());
+		cursorManager.updateCursor();
+
+		shell.setSize(400, 400);
+		shell.open();
+
+		eventLoop(display, shell);
+		display.dispose();
+	}
+
+	private static Shell createShell(Display display) {
+		Shell shell = new Shell(display);
+		shell.setText("Snippet 386");
+		shell.setLayout(new GridLayout(1, false));
+		return shell;
+	}
+
+	private static Combo createConstructorCombo(Composite parent) {
+		Label label = new Label(parent, SWT.NONE);
+		label.setText("Choose Cursor Constructor:");
+
+		Combo combo = new Combo(parent, SWT.READ_ONLY);
+		combo.setItems("Cursor(Device, int)", "Cursor(Device, ImageData, ImageData, int, int)",
+				"Cursor(Device, ImageData, int, int)", "Cursor(Device, ImageDataProvider, int, int)");
+		combo.select(0);
+		return combo;
+	}
+
+	private static Label createZoomLabel(Shell parent) {
+		Label zoomLabel = new Label(parent, SWT.NONE);
+		zoomLabel.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true, false));
+		setZoomLabelText(parent, zoomLabel);
+		return zoomLabel;
+	}
+
+	private static void setZoomLabelText(Shell shell, Label label) {
+		int zoom = shell.getMonitor().getZoom();
+		int expectedCursorSize = Math.round(IMAGE_SIZE_IN_POINTS * (zoom / 100f));
+		label.setText("Current zoom: " + zoom + "% \nExpected Cursor Size = " + expectedCursorSize);
+	}
+
+	private static void addZoomChangedListener(Shell shell, Label zoomLabel) {
+		shell.addListener(SWT.Resize, event -> {
+			setZoomLabelText(shell, zoomLabel);
+			shell.layout();
+		});
+	}
+
+	private static void addPaintTicks(Composite composite) {
+		composite.addPaintListener(event -> {
+			drawTicks(composite, event.gc);
+		});
+	}
+
+	private static void drawTicks(Composite shell, GC gc) {
+		int deviceZoom = shell.getMonitor().getZoom();
+		float devScale = deviceZoom / 100f;
+		Point client = shell.getSize();
+		int xPos = (int) ((client.x / 2) - (6 * (IMAGE_SIZE_IN_POINTS / devScale)));
+		int tickHeight = 10;
+		int yPos = 20;
+
+		for (int tickIndex = 0; tickIndex < 6; tickIndex++) {
+			xPos += (IMAGE_SIZE_IN_POINTS / devScale);
+			int yOffset = (tickIndex % 3 == 1) ? 20 : (tickIndex % 3 == 2) ? 40 : 0;
+
+			gc.drawLine(xPos, yPos, xPos, yPos + tickHeight);
+			gc.drawText(Integer.toString(tickIndex * IMAGE_SIZE_IN_POINTS), xPos - 5, yPos + 12 + yOffset);
+		}
+	}
+
+	private static void eventLoop(Display display, Shell shell) {
+		while (!shell.isDisposed()) {
+			if (!display.readAndDispatch())
+				display.sleep();
+		}
+	}
+
+	public static ImageData createSolidColorImageData(int size, RGB color) {
+		PaletteData palette = new PaletteData(0xFF0000, 0x00FF00, 0x0000FF);
+		ImageData imageData = new ImageData(size, size, 24, palette);
+
+		int pixel = palette.getPixel(color);
+		for (int y = 0; y < size; y++) {
+			for (int x = 0; x < size; x++) {
+				imageData.setPixel(x, y, pixel);
+			}
+		}
+		return imageData;
+	}
+
+	private static class CursorManager {
+		private final Display display;
+		private final Shell shell;
+		private final Combo combo;
+
+		CursorManager(Display display, Shell shell, Combo combo) {
+			this.display = display;
+			this.shell = shell;
+			this.combo = combo;
+		}
+
+		void updateCursor() {
+			int selection = combo.getSelectionIndex();
+			Cursor oldCursor = shell.getCursor();
+			if (oldCursor != null && !oldCursor.isDisposed()) {
+				oldCursor.dispose();
+			}
+			Cursor cursor = createCursor(selection);
+			if (cursor != null) {
+				shell.setCursor(cursor);
+			}
+		}
+
+		private Cursor createCursor(int selection) {
+			switch (selection) {
+			case 0:
+				return new Cursor(display, SWT.CURSOR_HAND);
+			case 1: {
+				PaletteData rgbPalette = new PaletteData(0xFF0000, 0x00FF00, 0x0000FF);
+				int bluePixel = rgbPalette.getPixel(new RGB(0, 0, 255));
+				ImageData source = new ImageData(IMAGE_SIZE_IN_POINTS, IMAGE_SIZE_IN_POINTS, 24,
+						new PaletteData(0xFF0000, 0x00FF00, 0x0000FF));
+
+				for (int x = 0; x < IMAGE_SIZE_IN_POINTS; x++) {
+					for (int y = 0; y < IMAGE_SIZE_IN_POINTS; y++) {
+						source.setPixel(x, y, bluePixel);
+					}
+				}
+
+				ImageData mask = new ImageData(IMAGE_SIZE_IN_POINTS, IMAGE_SIZE_IN_POINTS, 1,
+						new PaletteData(new RGB[] { new RGB(0, 0, 0), new RGB(255, 255, 255) }));
+				for (int x = 0; x < IMAGE_SIZE_IN_POINTS; x++) {
+					for (int y = 0; y < IMAGE_SIZE_IN_POINTS; y++) {
+						mask.setPixel(x, y, x % 2);
+					}
+				}
+
+				return new Cursor(display, source, mask, IMAGE_SIZE_IN_POINTS / 2, IMAGE_SIZE_IN_POINTS / 2);
+			}
+			case 2:
+				RGB red = new RGB(255, 0, 0);
+				return new Cursor(display, createSolidColorImageData(IMAGE_SIZE_IN_POINTS, red), 0, 0);
+
+			case 3: {
+				RGB green = new RGB(0, 255, 0);
+				ImageDataProvider provider = zoom -> {
+					return createSolidColorImageData(IMAGE_SIZE_IN_POINTS * zoom / 100, green);
+				};
+				return new Cursor(display, provider, 0, 0);
+			}
+			default:
+				return null;
+			}
+		}
+	}
+}