Color selector swatches misdrawn at 200% scale eclipse-platform#261

Use a ImageDataProvider to provide the image data at the correct scale
based on the current zoom given to us by SWT.

Also provides a JFace example snippet for this widget because we didn't
have one.

Fixes eclipse-platform#261

Signed-off-by: Mat Booth <mat.booth@gmail.com>

bundles/org.eclipse.jface/src/org/eclipse/jface/preference/ColorSelector.java

@@ -1,5 +1,5 @@
 /*******************************************************************************
- * Copyright (c) 2000, 2015 IBM Corporation and others.
+ * Copyright (c) 2000, 2022 IBM Corporation and others.
  *
  * This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License 2.0
@@ -26,6 +26,8 @@
 import org.eclipse.swt.graphics.Font;
 import org.eclipse.swt.graphics.GC;
 import org.eclipse.swt.graphics.Image;
+import org.eclipse.swt.graphics.ImageData;
+import org.eclipse.swt.graphics.ImageDataProvider;
 import org.eclipse.swt.graphics.Point;
 import org.eclipse.swt.graphics.RGB;
 import org.eclipse.swt.widgets.Button;
@@ -36,7 +38,8 @@
 
 /**
  * The <code>ColorSelector</code> is a wrapper for a button that displays a
- * selected <code>Color</code> and allows the user to change the selection.
+ * swatch of the selected color and allows the user to change the selection
+ * using the operating system's native color chooser dialog.
  */
 public class ColorSelector extends EventManager {
 	/**
@@ -65,12 +68,7 @@ public class ColorSelector extends EventManager {
 	public ColorSelector(Composite parent) {
 		fButton = new Button(parent, SWT.PUSH);
 		fExtent = computeImageSize(parent);
-		fImage = new Image(parent.getDisplay(), fExtent.x, fExtent.y);
-		GC gc = new GC(fImage);
-		gc.setBackground(parent.getDisplay().getSystemColor(SWT.COLOR_WIDGET_BORDER));
-		gc.fillRectangle(0, 0, fExtent.x, fExtent.y);
-		gc.dispose();
-		fButton.setImage(fImage);
+		updateColorImage();
 		fButton.addSelectionListener(widgetSelectedAdapter(event -> open()));
 		fButton.addDisposeListener(event -> {
 			if (fImage != null) {
@@ -173,12 +171,34 @@ public void setEnabled(boolean state) {
 	 * setting.
 	 */
 	protected void updateColorImage() {
-		Display display = fButton.getDisplay();
-		GC gc = new GC(fImage);
-		Color color = new Color(display, fColorValue);
-		gc.setBackground(color);
-		gc.fillRectangle(1, 1, fExtent.x - 2, fExtent.y - 2);
-		gc.dispose();
+		if (fImage != null) {
+			fImage.dispose();
+		}
+
+		final Display display = fButton.getDisplay();
+
+		fImage = new Image(display, new ImageDataProvider() {
+
+			@Override
+			public ImageData getImageData(int zoom) {
+				Image image = new Image(display, fExtent.x, fExtent.y);
+				GC gc = new GC(image);
+
+				RGB color = getColorValue();
+				gc.setForeground(display.getSystemColor(SWT.COLOR_WIDGET_BORDER));
+				if (color != null) {
+					gc.setBackground(new Color(display, color));
+					gc.fillRectangle(image.getBounds());
+				}
+				gc.setLineWidth(2);
+				gc.drawRectangle(image.getBounds());
+				gc.dispose();
+
+				ImageData data = image.getImageData(zoom);
+				image.dispose();
+				return data;
+			}
+		});
 		fButton.setImage(fImage);
 	}
 

examples/org.eclipse.jface.snippets/Eclipse JFace Snippets/org/eclipse/jface/snippets/dialogs/Snippet082ColorSelectDialog.java

@@ -0,0 +1,70 @@
+/*******************************************************************************
+ * Copyright (c) 2022 Mat Booth 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
+ *******************************************************************************/
+package org.eclipse.jface.snippets.dialogs;
+
+import org.eclipse.jface.preference.ColorSelector;
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.events.SelectionListener;
+import org.eclipse.swt.graphics.Color;
+import org.eclipse.swt.layout.GridLayout;
+import org.eclipse.swt.widgets.Button;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Label;
+import org.eclipse.swt.widgets.Shell;
+
+/**
+ * Demo of the JFace {@link ColorSelector} which is compound widget comprising a
+ * color swatch button and the native color chooser dialog.
+ */
+public class Snippet082ColorSelectDialog {
+
+	public static void main(String[] args) {
+		Display display = new Display();
+		Shell shell = new Shell(display);
+		shell.setLayout(new GridLayout(2, false));
+		shell.setText("Color Select Dialog Demo");
+		shell.setSize(320, 240);
+		shell.setBackgroundMode(SWT.INHERIT_DEFAULT);
+
+		Label bgLabel = new Label(shell, SWT.NONE);
+		bgLabel.setText("Background Color:");
+		ColorSelector bgColorSelector = new ColorSelector(shell);
+		bgColorSelector.setColorValue(shell.getBackground().getRGB());
+		Button bgColorButton = bgColorSelector.getButton();
+
+		Label fgLabel = new Label(shell, SWT.NONE);
+		fgLabel.setText("Foreground Color:");
+		ColorSelector fgColorSelector = new ColorSelector(shell);
+		fgColorSelector.setColorValue(shell.getForeground().getRGB());
+		Button fgColorButton = fgColorSelector.getButton();
+
+		bgColorButton.addSelectionListener(SelectionListener.widgetSelectedAdapter(e -> {
+			shell.setBackground(new Color(bgColorSelector.getColorValue()));
+		}));
+
+		fgColorButton.addSelectionListener(SelectionListener.widgetSelectedAdapter(e -> {
+			Color color = new Color(fgColorSelector.getColorValue());
+			shell.setForeground(color);
+			// On Windows 10, foreground color is not automatically inherited by default
+			bgLabel.setForeground(color);
+			fgLabel.setForeground(color);
+		}));
+
+		shell.open();
+		while (!shell.isDisposed()) {
+			if (!display.readAndDispatch()) {
+				display.sleep();
+			}
+		}
+
+		display.dispose();
+	}
+}