[GTK] Support loading and drawing images at desired size

This change introduces support for loading and drawing images at custom sizes in the GTK versions of GC and Image.
The GC#drawImage() method, which  only accepts the destination position and size, now attempts to load image at the destination size in case if it is provided by
ImageFilenameProvider returning svgs or if the image is created with a imageDataAtSizeProvider.

Author: arunjose696

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

@@ -913,7 +913,7 @@ public void drawImage(Image image, int destX, int destY, int destWidth, int dest
 	if (image.isDisposed()) {
 		SWT.error(SWT.ERROR_INVALID_ARGUMENT);
 	}
-	drawImage(image, 0, 0, 0, 0, destX, destY, destWidth, destHeight, false);
+	image.executeOnImageAtSize(imageAtSize -> drawImage(imageAtSize, 0, 0, 0, 0, destX, destY, destWidth, destHeight, false), destWidth, destHeight);
 }
 
 void drawImage(Image srcImage, int srcX, int srcY, int srcWidth, int srcHeight, int destX, int destY, int destWidth, int destHeight, boolean simple) {

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

@@ -18,6 +18,7 @@
 
 import java.io.*;
 import java.util.*;
+import java.util.function.*;
 
 import org.eclipse.swt.*;
 import org.eclipse.swt.internal.*;
@@ -929,6 +930,74 @@ void destroy() {
 	memGC = null;
 }
 
+private CachedImageAtSize cachedImageAtSize = new CachedImageAtSize();
+
+private class CachedImageAtSize {
+	private Image image;
+
+	public void destroy() {
+		if (image != null) {
+			image.dispose();
+			image = null;
+		}
+	}
+
+	private Optional<Image> refresh(int destWidth, int destHeight) {
+		int scaledWidth = DPIUtil.pointToPixel(destWidth, DPIUtil.getDeviceZoom());
+		int scaledHeight = DPIUtil.pointToPixel(destHeight, DPIUtil.getDeviceZoom());
+		if (isReusable(scaledWidth, scaledHeight)) {
+			return Optional.of(image);
+		} else {
+			destroy();
+			Optional<Image> imageAtSize = loadImageAtSize(scaledWidth, scaledHeight);
+			image = imageAtSize.orElse(null);
+			return imageAtSize;
+		}
+	}
+
+	private boolean isReusable(int width, int height) {
+		return image != null && image.height == height && image.width == width;
+	}
+
+	private Optional<Image> loadImageAtSize(int destWidth, int destHeight) {
+		Optional<ImageData> imageData = loadImageDataAtExactSize(destWidth, destHeight);
+		if (imageData.isEmpty()) {
+			return Optional.empty();
+		}
+		Image image = new Image(device, imageData.get(), DPIUtil.getDeviceZoom());
+		if (styleFlag != SWT.IMAGE_COPY) {
+			Image styledImage = new Image(device, image, styleFlag);
+			image.dispose();
+			image = styledImage;
+		}
+		return Optional.of(image);
+	}
+
+	private Optional<ImageData> loadImageDataAtExactSize(int targetWidth, int targetHeight) {
+		if (imageDataProvider instanceof ImageDataAtSizeProvider imageDataAtSizeProvider) {
+			ImageData imageData = imageDataAtSizeProvider.getImageData(targetWidth, targetHeight);
+			if (imageData == null) {
+				SWT.error(SWT.ERROR_INVALID_ARGUMENT, null,
+						" ImageDataAtSizeProvider returned null for width=" + targetWidth + ", height=" + targetHeight);
+			}
+			return Optional.of(imageData);
+		}
+		if (imageFileNameProvider != null) {
+			String fileName = DPIUtil.validateAndGetImagePathAtZoom(imageFileNameProvider, 100).element();
+			if (ImageDataLoader.isDynamicallySizable(fileName)) {
+				ImageData imageDataAtSize = ImageDataLoader.loadBySize(fileName, targetWidth, targetHeight);
+				return Optional.of(imageDataAtSize);
+			}
+		}
+		return Optional.empty();
+	}
+}
+
+void executeOnImageAtSize(Consumer<Image> imageAtBestFittingSizeConsumer, int destWidth, int destHeight) {
+	Optional<Image> imageAtSize = cachedImageAtSize.refresh(destWidth, destHeight);
+	imageAtBestFittingSizeConsumer.accept(imageAtSize.orElse(this));
+}
+
 /**
  * Compares the argument to the receiver, and returns true
  * if they represent the <em>same</em> object using a class

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

@@ -54,8 +54,6 @@
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.condition.DisabledOnOs;
-import org.junit.jupiter.api.condition.OS;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
 
@@ -442,7 +440,6 @@ public void test_drawImageLorg_eclipse_swt_graphics_ImageIIII_ImageDataProvider(
 }
 
 @Test
-@DisabledOnOs(value = OS.LINUX)
 public void test_drawImageLorg_eclipse_swt_graphics_ImageIIII_ImageDataAtSizeProvider_invalid() {
 	ImageDataAtSizeProvider provider = new ImageDataAtSizeProvider() {
 		@Override
@@ -469,11 +466,10 @@ public ImageData getImageData(int width, int height) {
 
 @ParameterizedTest
 @ValueSource(ints = {SWT.IMAGE_COPY, SWT.IMAGE_DISABLE, SWT.IMAGE_GRAY, -1})
-@DisabledOnOs(value = OS.LINUX)
 public void test_drawImageLorg_eclipse_swt_graphics_ImageIIII_ImageDataAtSizeProvider(int styleFlag) {
 	int width = 50;
 	int height = 70;
-	Image drawToImage = new Image(display, width, height);
+	Image drawToImage = new Image(display, new ImageData(width, height, 32, new PaletteData(0xFF0000, 0xFF00, 0xFF)));
 	GC gc = new GC(drawToImage);
 	gc.setAntialias(SWT.OFF);
 	RGB drawnRgb = new RGB(255, 255, 255);