Revise the Cursor class to support scaling

Previously, cursors were initialized with a single ImageData, which
caused issues on systems with varying zoom levels, for example, cursors
were not scaled at all on Linux, or were blurrily auto-scaled on
Windows.

This commit introduces a new constructor for the Cursor class that
accepts an ImageDataProvider object instead of ImageData. This allows the code
instantiating the cursor to pass an imageDataProvider capable of providing
appropriately scaled image data based on the current zoom level.

Author: arunjose696

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

@@ -382,6 +382,10 @@ void createNSCursor(int hotspotX, int hotspotY, byte[] buffer, int width, int he
  */
 public Cursor(Device device, ImageData source, int hotspotX, int hotspotY) {
 	super(device);
+	setupCursorFromImageData(source, hotspotX, hotspotY);
+}
+
+private void setupCursorFromImageData(ImageData source, int hotspotX, int hotspotY) {
 	if (source == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
 	if (hotspotX >= source.width || hotspotX < 0 ||
 		hotspotY >= source.height || hotspotY < 0) {
@@ -448,6 +452,41 @@ public Cursor(Device device, ImageData source, int hotspotX, int hotspotY) {
 	}
 }
 
+/**
+ * Constructs a new cursor given a device, image describing
+ * the desired cursor appearance, and the x and y coordinates of
+ * the <em>hotspot</em> (that is, the point within the area
+ * covered by the cursor which is considered to be where the
+ * on-screen pointer is "pointing").
+ * <p>
+ * You must dispose the cursor when it is no longer required.
+ * </p>
+ *
+ * @param device the device on which to allocate the cursor
+ * @param imageDataProvider the ImageDataProvider for the cursor
+ * @param hotspotX the x coordinate of the cursor's hotspot
+ * @param hotspotY the y coordinate of the cursor's hotspot
+ *
+ * @exception IllegalArgumentException <ul>
+ *    <li>ERROR_NULL_ARGUMENT - if device is null and there is no current device</li>
+ *    <li>ERROR_NULL_ARGUMENT - if the image is null</li>
+ *    <li>ERROR_INVALID_ARGUMENT - if the hotspot is outside the bounds of the
+ * 		 image</li>
+ * </ul>
+ * @exception SWTError <ul>
+ *    <li>ERROR_NO_HANDLES - if a handle could not be obtained for cursor creation</li>
+ * </ul>
+ *
+ * @see #dispose()
+ *
+ * @since 3.131
+ */
+public Cursor(Device device, ImageDataProvider imageDataProvider, int hotspotX, int hotspotY) {
+	super(device);
+	if (imageDataProvider == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
+	setupCursorFromImageData(imageDataProvider.getImageData(100), hotspotX, hotspotY);
+}
+
 @Override
 void destroy() {
 	handle.release();

bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/graphics/Cursor.java

@@ -272,6 +272,11 @@ public Cursor(Device device, ImageData source, ImageData mask, int hotspotX, int
  */
 public Cursor(Device device, ImageData source, int hotspotX, int hotspotY) {
 	super(device);
+	setupCursorFromImageData(source, hotspotX, hotspotY);
+
+}
+
+private void setupCursorFromImageData(ImageData source, int hotspotX, int hotspotY) {
 	if (source == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
 	if (hotspotX >= source.width || hotspotX < 0 ||
 		hotspotY >= source.height || hotspotY < 0) {
@@ -355,6 +360,41 @@ public Cursor(Device device, ImageData source, int hotspotX, int hotspotY) {
 	init();
 }
 
+/**
+ * Constructs a new cursor given a device, image describing
+ * the desired cursor appearance, and the x and y coordinates of
+ * the <em>hotspot</em> (that is, the point within the area
+ * covered by the cursor which is considered to be where the
+ * on-screen pointer is "pointing").
+ * <p>
+ * You must dispose the cursor when it is no longer required.
+ * </p>
+ *
+ * @param device the device on which to allocate the cursor
+ * @param imageDataProvider the ImageDataProvider for the cursor
+ * @param hotspotX the x coordinate of the cursor's hotspot
+ * @param hotspotY the y coordinate of the cursor's hotspot
+ *
+ * @exception IllegalArgumentException <ul>
+ *    <li>ERROR_NULL_ARGUMENT - if device is null and there is no current device</li>
+ *    <li>ERROR_NULL_ARGUMENT - if the image is null</li>
+ *    <li>ERROR_INVALID_ARGUMENT - if the hotspot is outside the bounds of the
+ * 		 image</li>
+ * </ul>
+ * @exception SWTError <ul>
+ *    <li>ERROR_NO_HANDLES - if a handle could not be obtained for cursor creation</li>
+ * </ul>
+ *
+ * @see #dispose()
+ *
+ * @since 3.131
+ */
+public Cursor(Device device, ImageDataProvider imageDataProvider, int hotspotX, int hotspotY) {
+	super(device);
+	if (imageDataProvider == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
+	setupCursorFromImageData(imageDataProvider.getImageData(100), hotspotX, hotspotY);
+}
+
 long createCursor(byte[] sourceData, byte[] maskData, int width, int height, int hotspotX, int hotspotY, boolean reverse) {
 	for (int i = 0; i < sourceData.length; i++) {
 		byte s = sourceData[i];

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

@@ -69,6 +69,7 @@ public final class Cursor extends Resource {
 	private HashMap<Integer, Long> zoomLevelToHandle = new HashMap<>();
 
 	boolean isIcon;
+	private final ImageDataProvider imageDataProvider;
 	private final ImageData source;
 	private final ImageData mask;
 	private final int hotspotX;
@@ -79,6 +80,7 @@ public final class Cursor extends Resource {
 Cursor(Device device) {
 	super(device);
 	this.source = null;
+	this.imageDataProvider = null;
 	this.mask = null;
 	this.hotspotX = -1;
 	this.hotspotY = -1;
@@ -204,6 +206,7 @@ public Cursor(Device device, ImageData source, ImageData mask, int hotspotX, int
 	this.mask = mask;
 	this.hotspotX = hotspotX;
 	this.hotspotY = hotspotY;
+	this.imageDataProvider = null;
 	if (source == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
 	if (mask == null) {
 		if (source.getTransparencyType() != SWT.TRANSPARENCY_MASK) {
@@ -271,6 +274,11 @@ public Cursor(Device device, ImageData source, int hotspotX, int hotspotY) {
 	this.mask = null;
 	this.hotspotX = hotspotX;
 	this.hotspotY = hotspotY;
+	this.imageDataProvider = null;
+	setupCursorFromImageData(source);
+}
+
+private void setupCursorFromImageData(ImageData source) {
 	if (source == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
 	/* Check the hotspots */
 	if (hotspotX >= source.width || hotspotX < 0 ||
@@ -345,6 +353,46 @@ public Cursor(Device device, ImageData source, int hotspotX, int hotspotY) {
 	this.device.registerResourceWithZoomSupport(this);
 }
 
+/**
+ * Constructs a new cursor given a device, image describing
+ * the desired cursor appearance, and the x and y coordinates of
+ * the <em>hotspot</em> (that is, the point within the area
+ * covered by the cursor which is considered to be where the
+ * on-screen pointer is "pointing").
+ * <p>
+ * You must dispose the cursor when it is no longer required.
+ * </p>
+ *
+ * @param device the device on which to allocate the cursor
+ * @param imageDataProvider the ImageDataProvider for the cursor
+ * @param hotspotX the x coordinate of the cursor's hotspot
+ * @param hotspotY the y coordinate of the cursor's hotspot
+ *
+ * @exception IllegalArgumentException <ul>
+ *    <li>ERROR_NULL_ARGUMENT - if device is null and there is no current device</li>
+ *    <li>ERROR_NULL_ARGUMENT - if the image is null</li>
+ *    <li>ERROR_INVALID_ARGUMENT - if the hotspot is outside the bounds of the
+ * 		 image</li>
+ * </ul>
+ * @exception SWTError <ul>
+ *    <li>ERROR_NO_HANDLES - if a handle could not be obtained for cursor creation</li>
+ * </ul>
+ *
+ * @see #dispose()
+ *
+ * @since 3.131
+ */
+public Cursor(Device device, ImageDataProvider imageDataProvider, int hotspotX, int hotspotY) {
+	super(device);
+	if (imageDataProvider == null) SWT.error(SWT.ERROR_NULL_ARGUMENT);
+	this.imageDataProvider = imageDataProvider;
+	this.source = imageDataProvider.getImageData(100);
+	this.mask = null;
+	this.hotspotX = hotspotX;
+	this.hotspotY = hotspotY;
+	setupCursorFromImageData(this.source);
+}
+
 /**
  * <b>IMPORTANT:</b> This method is not part of the public
  * API for Image. It is marked public only so that it
@@ -371,7 +419,13 @@ public static Long win32_getHandle (Cursor cursor, int zoom) {
 	if (cursor.source == null) {
 		cursor.setHandleForZoomLevel(cursor.handle, zoom);
 	} else {
-		ImageData source = DPIUtil.scaleImageData(cursor.device, cursor.source, zoom, DEFAULT_ZOOM);
+		ImageData source;
+		if (cursor.imageDataProvider != null) {
+			source = DPIUtil.validateAndGetImageDataAtZoom(cursor.imageDataProvider, zoom).element();
+		}
+		else {
+			source = DPIUtil.scaleImageData(cursor.device, cursor.source, zoom, DEFAULT_ZOOM);
+		}
 		if (cursor.isIcon) {
 			Cursor newCursor = new Cursor(cursor.device, source, cursor.hotspotX, cursor.hotspotY);
 			cursor.setHandleForZoomLevel(newCursor.handle, zoom);

tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_graphics_Cursor.java

@@ -24,7 +24,9 @@
 
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.graphics.Cursor;
+import org.eclipse.swt.graphics.Image;
 import org.eclipse.swt.graphics.ImageData;
+import org.eclipse.swt.graphics.ImageDataProvider;
 import org.eclipse.swt.graphics.ImageLoader;
 import org.eclipse.swt.widgets.Display;
 import org.junit.Before;
@@ -153,6 +155,23 @@ public void test_ConstructorLorg_eclipse_swt_graphics_DeviceLorg_eclipse_swt_gra
 	}
 }
 
+@Test
+public void test_ConstructorWithImageDataProvider() {
+	// Test new Cursor(Device device, ImageData source, ImageData mask, int
+	// hotspotX, int hotspotY)
+	Image sourceImage = new Image(display, 10, 10);
+	Cursor cursor = new Cursor(display, sourceImage::getImageData, 0, 0);
+	cursor.dispose();
+	sourceImage.dispose();
+
+	try {
+		cursor = new Cursor(display, (ImageDataProvider) null, 0, 0);
+		cursor.dispose();
+		fail("No exception thrown when ImageDataProvider is null");
+	} catch (IllegalArgumentException e) {
+	}
+}
+
 @Test
 public void test_equalsLjava_lang_Object() {
 	/* Note: Two cursors are only considered equal if their handles are equal.