Avoid attempt to draw images with target width/height of 0

Recently, the ability to scale images for the desired target size of a
drawImage operation executed on a GC and the incorporation of a
Transform potentially applied to that GC have been implemented. With
this, the target size for an image to be drawn can become 0 and the
request of a handle of that size can fail, in particular when trying to
rasterize an SVG at that size.

This change adapts the implementation of the handle retrieval for a
desired size in the Image implementation so that the minimum size of the
provided handle is 1 in both of the dimensions. The draw operation in
the GC will then take care of potentially not drawing anything at all
when the actual intended size is really 0.
It also adds a test case for the specific case of requesting a handle at
size 0 and also adds a test for the general correctness of image handle
retrieval when a transform is applied to the GC.

Fixes #3078

Author: HeikoKlare

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

@@ -1878,7 +1878,7 @@ public static void drawAtSize(GC gc, ImageData imageData, int width, int height)
 }
 
 void executeOnImageAtSizeBestFittingSize(Consumer<Image> imageAtBestFittingSizeConsumer, int destWidth, int destHeight) {
-	Optional<Image> imageAtSize = cachedImageAtSize.refresh(destWidth, destHeight);
+	Optional<Image> imageAtSize = cachedImageAtSize.refresh(Math.max(1, destWidth), Math.max(1, destHeight));
 	imageAtBestFittingSizeConsumer.accept(imageAtSize.orElse(this));
 }
 

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

@@ -1025,7 +1025,7 @@ private Optional<ImageData> loadImageDataAtExactSize(int targetWidth, int target
 }
 
 void executeOnImageAtSize(Consumer<Image> imageAtBestFittingSizeConsumer, int destWidth, int destHeight) {
-	Optional<Image> imageAtSize = cachedImageAtSize.refresh(destWidth, destHeight);
+	Optional<Image> imageAtSize = cachedImageAtSize.refresh(Math.max(1, destWidth), Math.max(1, destHeight));
 	imageAtBestFittingSizeConsumer.accept(imageAtSize.orElse(this));
 }
 

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

@@ -941,8 +941,8 @@ ImageHandle getHandle (int targetZoom, int nativeZoom) {
 	return imageHandleManager.getOrCreate(targetZoom, () -> imageProvider.newImageHandle(zoomContext));
 }
 
-void executeOnImageHandleAtBestFittingSize(Consumer<ImageHandle> handleAtSizeConsumer, int widthHint, int heightHint) {
-	ImageHandle imageHandle = lastRequestedHandle.refresh(widthHint, heightHint);
+void executeOnImageHandleAtBestFittingSize(Consumer<ImageHandle> handleAtSizeConsumer, int destWidth, int destHeight) {
+	ImageHandle imageHandle = lastRequestedHandle.refresh(Math.max(1, destWidth), Math.max(1, destHeight));
 	handleAtSizeConsumer.accept(imageHandle);
 }
 

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

@@ -27,6 +27,8 @@
 import static org.junit.jupiter.api.Assumptions.assumeFalse;
 import static org.junit.jupiter.api.Assumptions.assumeTrue;
 
+import java.io.IOException;
+import java.io.InputStream;
 import java.lang.ref.WeakReference;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
@@ -48,12 +50,15 @@
 import org.eclipse.swt.graphics.Rectangle;
 import org.eclipse.swt.graphics.Transform;
 import org.eclipse.swt.internal.DPIUtil;
+import org.eclipse.swt.tests.graphics.ImageDataTestHelper;
 import org.eclipse.swt.widgets.Canvas;
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.swt.widgets.Shell;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.EnabledOnOs;
+import org.junit.jupiter.api.condition.OS;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
 
@@ -394,6 +399,50 @@ public void test_drawImageLorg_eclipse_swt_graphics_ImageIIII() {
 	images.dispose();
 }
 
+@Test
+@EnabledOnOs(OS.WINDOWS)
+public void test_drawImageLorg_eclipse_swt_graphics_ImageIIII_withTransform() throws IOException {
+	Image image = null;
+	try (InputStream is = getClass().getResourceAsStream("collapseall.svg")) {
+		image = new Image(Display.getDefault(), is);
+	}
+	Transform transform = new Transform(display, 2, 0, 0, 2, 0, 0);
+	gc.setTransform(transform);
+	gc.drawImage(image, 0, 0, 2, 2);
+	ImageData resultImageDataWithTransform = getImageDataFromGC(gc, 0, 0, 4, 4);
+
+	gc.setTransform(null);
+	gc.drawImage(image, 10, 10, 4, 4);
+	ImageData resultImageDataWithoutTransform = getImageDataFromGC(gc, 10, 10, 4, 4);
+
+	ImageDataTestHelper.assertImageDataEqual(resultImageDataWithoutTransform, resultImageDataWithoutTransform, resultImageDataWithTransform);
+
+	image.dispose();
+	transform.dispose();
+}
+
+private ImageData getImageDataFromGC(GC gc, int x, int y, int width, int height) {
+	Image extractionImage = new Image(display, width, height);
+	gc.copyArea(extractionImage, x, y);
+	ImageData resultImageData = extractionImage.getImageData();
+	extractionImage.dispose();
+	return resultImageData;
+}
+
+public void test_drawImageLorg_eclipse_swt_graphics_ImageIIII_withTransform_zeroTargetSize() throws IOException {
+	Image image = null;
+	try (InputStream is = getClass().getResourceAsStream("collapseall.svg")) {
+		image = new Image(Display.getDefault(), is);
+	}
+	Transform transform = new Transform(display, 0.1f, 0, 0, 0.1f, 0, 0);
+	gc.setTransform(transform);
+	// The destination size will become 0, but no exception should be thrown.
+	gc.drawImage(image, 0, 0, 2, 2);
+
+	image.dispose();
+	transform.dispose();
+}
+
 @Test
 public void test_drawImageLorg_eclipse_swt_graphics_ImageIIII_ImageDataProvider() {
 	int width = 32;