[GTK] Factor out common image initialization functionality (#1892)

The GTK implementation of the Image class currently contains the
basically same piece of code for initializing and image based on an
ImageFileNameProvider and ImageDataProvider twice, once in the Image
constructors and once in the refresh logic for changing the zoom.

This change factors out the common functionality in reused methods and
streamlines the implementation for the ImageFileNameProvider.

Author: HeikoKlare

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

@@ -613,19 +613,7 @@ public Image(Device device, ImageFileNameProvider imageFileNameProvider) {
 	super(device);
 	this.imageFileNameProvider = imageFileNameProvider;
 	currentDeviceZoom = DPIUtil.getDeviceZoom();
-	ElementAtZoom<String> filename = DPIUtil.validateAndGetImagePathAtZoom (imageFileNameProvider, currentDeviceZoom);
-	if (filename.zoom() == currentDeviceZoom) {
-		initNative (filename.element());
-
-		if (this.surface == 0) {
-			ImageData data = new ImageData(filename.element());
-			init(data);
-		}
-	} else {
-		ImageData imageData = new ImageData (filename.element());
-		ImageData resizedData = DPIUtil.autoScaleImageData (device, imageData, filename.zoom());
-		init(resizedData);
-	}
+	initFromFileNameProvider(currentDeviceZoom);
 	init ();
 }
 
@@ -662,9 +650,7 @@ public Image(Device device, ImageDataProvider imageDataProvider) {
 	super(device);
 	this.imageDataProvider = imageDataProvider;
 	currentDeviceZoom = DPIUtil.getDeviceZoom();
-	ElementAtZoom<ImageData> data =  DPIUtil.validateAndGetImageDataAtZoom(imageDataProvider, currentDeviceZoom);
-	ImageData resizedData = DPIUtil.autoScaleImageData(device, data.element(), data.zoom());
-	init (resizedData);
+	initFromImageDataProvider(currentDeviceZoom);
 	init ();
 }
 
@@ -724,37 +710,19 @@ boolean refreshImageForZoom () {
 	if (imageFileNameProvider != null) {
 		int deviceZoomLevel = deviceZoom;
 		if (deviceZoomLevel != currentDeviceZoom) {
-			ElementAtZoom<String> filename = DPIUtil.validateAndGetImagePathAtZoom (imageFileNameProvider, deviceZoomLevel);
-			/* Avoid re-creating the fall-back image, when current zoom is already 100% */
-			if (filename.zoom() == deviceZoomLevel) {
-				/* Release current native resources */
-				destroy ();
-				initNative(filename.element());
-				if (this.surface == 0) {
-					ImageData data = new ImageData(filename.element());
-					init(data);
-				}
-				init ();
-				refreshed = true;
-			} else {
-				/* Release current native resources */
-				destroy ();
-				ImageData imageData = new ImageData (filename.element());
-				ImageData resizedData = DPIUtil.autoScaleImageData (device, imageData, filename.zoom());
-				init(resizedData);
-				init ();
-				refreshed = true;
-			}
+			/* Release current native resources */
+			destroy ();
+			initFromFileNameProvider(deviceZoomLevel);
+			init ();
+			refreshed = true;
 			currentDeviceZoom = deviceZoomLevel;
 		}
 	} else if (imageDataProvider != null) {
 		int deviceZoomLevel = deviceZoom;
 		if (deviceZoomLevel != currentDeviceZoom) {
-			ElementAtZoom<ImageData> data = DPIUtil.validateAndGetImageDataAtZoom (imageDataProvider, deviceZoomLevel);
 			/* Release current native resources */
 			destroy ();
-			ImageData resizedData = DPIUtil.autoScaleImageData (device, data.element(), data.zoom());
-			init(resizedData);
+			initFromImageDataProvider(deviceZoomLevel);
 			init();
 			refreshed = true;
 			currentDeviceZoom = deviceZoomLevel;
@@ -801,6 +769,26 @@ void initNative(String filename) {
 	} catch (SWTException e) {}
 }
 
+private void initFromFileNameProvider(int zoom) {
+	ElementAtZoom<String> fileForZoom = DPIUtil.validateAndGetImagePathAtZoom (imageFileNameProvider, zoom);
+	if (fileForZoom.zoom() == zoom) {
+		initNative(fileForZoom.element());
+	}
+	if (this.surface == 0) {
+		ImageData imageData = new ImageData(fileForZoom.element());
+		if (fileForZoom.zoom() != zoom) {
+			imageData = DPIUtil.scaleImageData(device, imageData, zoom, fileForZoom.zoom());
+		}
+		init(imageData);
+	}
+}
+
+private void initFromImageDataProvider(int zoom) {
+	ElementAtZoom<ImageData> data = DPIUtil.validateAndGetImageDataAtZoom (imageDataProvider, zoom);
+	ImageData resizedData = DPIUtil.scaleImageData (device, data.element(), zoom, data.zoom());
+	init(resizedData);
+}
+
 void createFromPixbuf(int type, long pixbuf) {
 	this.type = type;