[GTK][HiDpi] Code cleanup for removal of non-cairo scale path

Fixes #1300

tests/org.eclipse.swt.tests/ManualTests/org/eclipse/swt/tests/manual/Bug568641_GC_drawImage_IAE.java

@@ -0,0 +1,147 @@
+package org.eclipse.swt.tests.manual;
+/*******************************************************************************
+ * Copyright (c) 2020 Syntevo 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
+ *
+ * Contributors:
+ *     Syntevo - initial API and implementation
+ *******************************************************************************/
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.custom.CLabel;
+import org.eclipse.swt.graphics.GC;
+import org.eclipse.swt.graphics.Image;
+import org.eclipse.swt.graphics.ImageDataProvider;
+import org.eclipse.swt.graphics.Rectangle;
+import org.eclipse.swt.internal.DPIUtil;
+import org.eclipse.swt.layout.GridData;
+import org.eclipse.swt.layout.GridLayout;
+import org.eclipse.swt.widgets.Canvas;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Label;
+import org.eclipse.swt.widgets.Shell;
+public class Bug568641_GC_drawImage_IAE {
+	static final int imageSZ = 20;
+	static Image createTestImage(Display display) {
+		final Image image = new Image(display, 20, 20);
+		final GC gc = new GC(image);
+		final int halfSZ = imageSZ / 2;
+		gc.setBackground(display.getSystemColor(SWT.COLOR_RED));
+		gc.fillRectangle(0, 0, halfSZ, halfSZ);
+		gc.setBackground(display.getSystemColor(SWT.COLOR_GREEN));
+		gc.fillRectangle(halfSZ, 0, halfSZ, halfSZ);
+		gc.setBackground(display.getSystemColor(SWT.COLOR_BLUE));
+		gc.fillRectangle(0, halfSZ, halfSZ, halfSZ);
+		gc.setBackground(display.getSystemColor(SWT.COLOR_MAGENTA));
+		gc.fillRectangle(halfSZ, halfSZ, halfSZ, halfSZ);
+		return image;
+	}
+	static Image createImageWithZoom(Image srcImage, int zoom, boolean isProvider) {
+		final int oldZoom = DPIUtil.getDeviceZoom();
+		DPIUtil.setDeviceZoom(zoom);
+		final Image image;
+		if (isProvider) {
+			ImageDataProvider imageProvider = _zoom -> srcImage.getImageData(_zoom);
+			image = new Image(srcImage.getDevice(), imageProvider);
+		} else {
+			image = new Image(srcImage.getDevice(), srcImage.getImageData());
+		}
+		DPIUtil.setDeviceZoom(oldZoom);
+		return image;
+	}
+	static void drawImage(GC gc, Image srcImage, int zoom, boolean isProvider, int x, int y, boolean simple) {
+		// Image needs to be created each time, because painting it once
+		// will update internal state and prevent proper testing
+		final Image image = createImageWithZoom(srcImage, zoom, isProvider);
+		if (simple)
+			gc.drawImage(image, x, y);
+		else {
+			final Rectangle bounds = image.getBounds();
+			gc.drawImage(image, bounds.x, bounds.y, bounds.width, bounds.height, x, y, bounds.width, bounds.height);
+		}
+	}
+	static void verifyBounds(Image srcImage, int zoom, boolean isProvider) {
+		final Image image = createImageWithZoom(srcImage, zoom, isProvider);
+		{
+			final Rectangle bounds = image.getBounds();
+			int expected = imageSZ;
+			if ((bounds.x != 0) || (bounds.y != 0) || (bounds.width != expected) || (bounds.height != expected)) {
+				System.out.println(
+					"ERROR: Incorrect Image.getBounds(): zoom=" + zoom +
+						" provider=" + (isProvider ? 'Y' : 'N') +
+						" expected=" + expected +
+						" actual=" + bounds.width);
+			}
+		}
+		{
+			final Rectangle bounds = image.getBounds();
+			int expected = imageSZ * zoom / 100;
+			if ((bounds.x != 0) || (bounds.y != 0) || (bounds.width != expected) || (bounds.height != expected)) {
+				System.out.println(
+					"ERROR: Incorrect Image.getBoundsInPixels(): zoom=" + zoom +
+						" provider=" + (isProvider ? 'Y' : 'N') +
+						" expected=" + expected +
+						" actual=" + bounds.width);
+			}
+		}
+	}
+	public static void main(String[] args) {
+		// System.setProperty("swt.autoScale", "false");
+		final Display display = new Display();
+		final Shell shell = new Shell(display);
+		shell.setLayout(new GridLayout(1, true));
+		Label hint = new Label(shell, 0);
+		hint.setText(
+			"1) Start snippet at DPI=100%\n" +
+			"2) Check console for errors\n" +
+			"3) Snippet will crash with IllegalArgumentException in GC.drawImage()\n" +
+			"\n" +
+			"For CLabel demo:\n" +
+			"1) Go to your OS system settings and change Display DPI to 200%\n" +
+			"2) Start this snippet\n" +
+			"3) Change Display DPI to 100%\n" +
+			"4) Snippet will crash with IllegalArgumentException in GC.drawImage()"
+		);
+		final Image image = createTestImage(display);
+		// A demonstration that bug occurs even without trickery
+		ImageDataProvider imageProvider = zoom -> image.getImageData(zoom);
+		CLabel label = new CLabel(shell, 0);
+		label.setImage(new Image(display, imageProvider));
+		// A more detailed test of all combinations
+		final int margin = imageSZ;
+		Canvas canvas = new Canvas(shell, 0);
+		canvas.setLayoutData(new GridData(10*imageSZ, 5*imageSZ));
+		canvas.addListener(SWT.Paint, event -> {
+			int y = 0;
+			for (int iIsProvider = 0; iIsProvider < 2; iIsProvider++)
+			{
+				boolean isProvider = (iIsProvider == 0) ? false : true;
+				int x = 3;
+				verifyBounds(image, 100, isProvider);
+				drawImage(event.gc, image, 100, isProvider,  x, y, true);
+				x += imageSZ + margin;
+				drawImage(event.gc, image, 100, isProvider, x, y, false);
+				x += imageSZ + margin;
+				verifyBounds(image, 200, isProvider);
+				drawImage(event.gc, image, 200, isProvider, x, y, true);
+				x += imageSZ + margin;
+				drawImage(event.gc, image, 200, isProvider, x, y, false);
+				x += imageSZ + margin;
+				y += imageSZ + margin;
+			}
+		});
+		shell.pack();
+		shell.open();
+		while (!shell.isDisposed()) {
+			if (!display.readAndDispatch()) {
+				display.sleep();
+			}
+		}
+		display.dispose();
+	}
+}