Create CTabFolder images with ImageDataProvider

This commit changes the createButtonImage method in CTabFolder. Until now the requested image data were created once and are scaled to other zoom settings with an AutoScaleImageDataProvider, which is a destructive operation when scaling it to a smaller zoom. With this change the whole logic is moved into an ImageDataProvider, so each time ImageData for a specific zoom value is requested, it will be created from scratch for this zoom value.

Contributes to #62 and #131

Author: akoch-yatta

bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/CTabFolder.java

@@ -17,8 +17,6 @@
 import org.eclipse.swt.accessibility.*;
 import org.eclipse.swt.events.*;
 import org.eclipse.swt.graphics.*;
-import org.eclipse.swt.internal.*;
-import org.eclipse.swt.internal.DPIUtil.*;
 import org.eclipse.swt.widgets.*;
 
 /**
@@ -720,24 +718,25 @@ public Rectangle computeTrim (int x, int y, int width, int height) {
 	return trim;
 }
 Image createButtonImage(Display display, int button) {
-	GC tempGC = new GC (this);
-	Point size = renderer.computeSize(button, SWT.NONE, tempGC, SWT.DEFAULT, SWT.DEFAULT);
-	tempGC.dispose();
-
-	Rectangle trim = renderer.computeTrim(button, SWT.NONE, 0, 0, 0, 0);
-	Image image = new Image (display, size.x - trim.width, size.y - trim.height);
-	GC gc = new GC (image);
-	Color transColor = renderer.parent.getBackground();
-	gc.setBackground(transColor);
-	gc.fillRectangle(image.getBounds());
-	renderer.draw(button, SWT.NONE, new Rectangle(trim.x, trim.y, size.x, size.y), gc);
-	gc.dispose ();
-
-	final ImageData imageData = image.getImageData (DPIUtil.getDeviceZoom ());
-	imageData.transparentPixel = imageData.palette.getPixel(transColor.getRGB());
-	image.dispose();
-	image = new Image(display, new AutoScaleImageDataProvider(display, imageData, DPIUtil.getDeviceZoom()));
-	return image;
+	return new Image(display, (ImageDataProvider) zoom -> {
+		GC tempGC = new GC (CTabFolder.this);
+		Point size = renderer.computeSize(button, SWT.NONE, tempGC, SWT.DEFAULT, SWT.DEFAULT);
+		tempGC.dispose();
+
+		Rectangle trim = renderer.computeTrim(button, SWT.NONE, 0, 0, 0, 0);
+		Image image = new Image (display, size.x - trim.width, size.y - trim.height);
+		GC gc = new GC (image);
+		Color transColor = renderer.parent.getBackground();
+		gc.setBackground(transColor);
+		gc.fillRectangle(image.getBounds());
+		renderer.draw(button, SWT.NONE, new Rectangle(trim.x, trim.y, size.x, size.y), gc);
+		gc.dispose ();
+
+		final ImageData imageData = image.getImageData (zoom);
+		imageData.transparentPixel = imageData.palette.getPixel(transColor.getRGB());
+		image.dispose();
+		return imageData;
+	});
 }
 
 private void notifyItemCountChange() {