Add tests for drawing scaled image with GC#drawImage()

This adds test cases for the GC#drawImage(ImageIIII) method to draw a
scaled version of the given image. With the introduction of the
ImageDataAtSizeProvider, an image can be provided at the desired size
instead of rescaling the best fitting zoomed image. The added tests
cover those use cases and ensure that based on the kind of
ImageDataProvider the appropriately scaled data is used.

The tests for the ImageDataAtSizeProvider are limited to Windows until
the implementation is extended to GTK and Cocoa.

Author: HeikoKlare

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

@@ -37,6 +37,8 @@
 import org.eclipse.swt.graphics.GC;
 import org.eclipse.swt.graphics.Image;
 import org.eclipse.swt.graphics.ImageData;
+import org.eclipse.swt.graphics.ImageDataAtSizeProvider;
+import org.eclipse.swt.graphics.ImageDataProvider;
 import org.eclipse.swt.graphics.ImageGcDrawer;
 import org.eclipse.swt.graphics.LineAttributes;
 import org.eclipse.swt.graphics.PaletteData;
@@ -51,6 +53,8 @@
 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;
 
 /**
  * Automated Test Suite for class org.eclipse.swt.graphics.GC
@@ -390,6 +394,120 @@ public void test_drawImageLorg_eclipse_swt_graphics_ImageIIII() {
 	images.dispose();
 }
 
+@Test
+public void test_drawImageLorg_eclipse_swt_graphics_ImageIIII_ImageDataProvider() {
+	int width = 32;
+	int height = 48;
+	Image drawToImage = new Image(display, width, height);
+	GC gc = new GC(drawToImage);
+	gc.setAntialias(SWT.OFF);
+	RGB drawnRgb = new RGB(10, 0, 0);
+	RGB undrawnRgb = new RGB(0, 0, 0);
+	ImageDataProvider imageDataProvider = zoom -> {
+		if (zoom != 100) {
+			return null;
+		}
+		PaletteData palette = new PaletteData(0xFF0000, 0xFF00, 0xFF);
+		ImageData imageData = new ImageData(16, 16, 32, palette);
+		int redPixel = palette.getPixel(drawnRgb);
+		for (int i = 0; i < 16; i++) {
+			imageData.setPixel(i, 0, redPixel);
+			imageData.setPixel(i, 15, redPixel);
+			imageData.setPixel(0, i, redPixel);
+			imageData.setPixel(15, i, redPixel);
+		}
+		return imageData;
+	};
+	Image image = new Image(display, imageDataProvider);
+	try {
+		gc.drawImage(image, 0, 0, width, height);
+		ImageData printedImageData = drawToImage.getImageData();
+		PaletteData printedPalette = printedImageData.palette;
+		// Expect that image is blurry scaled to the desired extents
+		assertEquals(drawnRgb, printedPalette.getRGB(printedImageData.getPixel(0, 0)));
+		assertEquals(drawnRgb, printedPalette.getRGB(printedImageData.getPixel(1, 1)));
+		assertNotEquals(undrawnRgb, printedPalette.getRGB(printedImageData.getPixel(1, 2)));
+		assertNotEquals(undrawnRgb, printedPalette.getRGB(printedImageData.getPixel(width - 2, height - 3)));
+		assertEquals(drawnRgb, printedPalette.getRGB(printedImageData.getPixel(width - 2, height - 2)));
+		assertEquals(drawnRgb, printedPalette.getRGB(printedImageData.getPixel(width - 1, height - 1)));
+	} finally {
+		image.dispose();
+		drawToImage.dispose();
+	}
+}
+
+@Test
+@EnabledOnOs(value = OS.WINDOWS)
+public void test_drawImageLorg_eclipse_swt_graphics_ImageIIII_ImageDataAtSizeProvider_invalid() {
+	ImageDataAtSizeProvider provider = new ImageDataAtSizeProvider() {
+		@Override
+		public ImageData getImageData(int zoom) {
+			return new ImageData(1, 1, 32, new PaletteData(0xFF0000, 0xFF00, 0xFF));
+		}
+
+		@Override
+		public ImageData getImageData(int width, int height) {
+			return null;
+		}
+	};
+	Image image = new Image(display, provider);
+	Image drawToImage = new Image(display, 1, 1);
+	try {
+		GC gc = new GC(drawToImage);
+		Exception e = assertThrows(IllegalArgumentException.class, () -> gc.drawImage(image, 0, 0, 1, 1));
+		assertSWTProblem("Incorrect exception thrown for provider == null", SWT.ERROR_INVALID_ARGUMENT, e);
+	} finally {
+		image.dispose();
+		drawToImage.dispose();
+	}
+}
+
+@Test
+@EnabledOnOs(value = OS.WINDOWS)
+public void test_drawImageLorg_eclipse_swt_graphics_ImageIIII_ImageDataAtSizeProvider() {
+	int width = 50;
+	int height = 70;
+	Image drawToImage = new Image(display, width, height);
+	GC gc = new GC(drawToImage);
+	gc.setAntialias(SWT.OFF);
+	RGB drawnRgb = new RGB(10, 0, 0);
+	RGB undrawnRgb = new RGB(0, 0, 0);
+	ImageDataAtSizeProvider imageDataAtSizeProvider = new ImageDataAtSizeProvider() {
+		@Override
+		public ImageData getImageData(int width, int height) {
+			PaletteData palette = new PaletteData(0xFF0000, 0xFF00, 0xFF);
+			int redPixel = palette.getPixel(drawnRgb);
+			ImageData imageData = new ImageData(width, height, 32, palette);
+			for (int i = 0; i < width; i++) {
+				imageData.setPixel(i, 0, redPixel);
+				imageData.setPixel(i, height - 1, redPixel);
+			}
+			for (int i = 0; i < height; i++) {
+				imageData.setPixel(0, i, redPixel);
+				imageData.setPixel(width - 1, i, redPixel);
+			}
+			return imageData;
+		}
+		@Override
+		public ImageData getImageData(int zoom) {
+			return new ImageData(1, 1, 32, new PaletteData(0xFF0000, 0xFF00, 0xFF));
+		}
+	};
+	Image image = new Image(display, imageDataAtSizeProvider);
+	try {
+		gc.drawImage(image, 0, 0, width, height);
+		ImageData printedImageData = drawToImage.getImageData();
+		PaletteData printedPalette = printedImageData.palette;
+		assertEquals(drawnRgb, printedPalette.getRGB(printedImageData.getPixel(0, 0)));
+		assertEquals(undrawnRgb, printedPalette.getRGB(printedImageData.getPixel(1, 1)));
+		assertEquals(undrawnRgb, printedPalette.getRGB(printedImageData.getPixel(width - 2, height - 2)));
+		assertEquals(drawnRgb, printedPalette.getRGB(printedImageData.getPixel(width -1 , height - 2)));
+	} finally {
+		image.dispose();
+		drawToImage.dispose();
+	}
+}
+
 @Test
 public void test_drawLineIIII() {
 	gc.drawLine(0,0,0,20);