Always set disabled icons in AbstractContributionItem

AbstractionContributionItems only set a disabled icon on the ToolItem in
case such a disabled icon is specified via an explicit URI to that icon.
If no such URI is specified, the ToolItem creates a disabled icon on the
fly. Since the ToolItem creates a new image every time the enablement
state of the ToolItem changes, this leads to unnecessary repeated
creation of images.
In contrast, ActionContributionItems always set the disabled icon for
their ToolItem, even if no disabled image descriptor is specified for
them, to avoid that the ToolItem repeatedly created that icon.

This change align the AbstractContributionItem handling for disabled
icons with the one of ActionContributionItems: in case no URI to a
disabled icon is specified, the SWT disablement mechanism is used to
create a disabled version and to explicitly set it at the ToolItem. This
avoids unnecessary repeated creation of the disabled version of an icon
for those items.

Author: HeikoKlare

bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/workbench/renderers/swt/AbstractContributionItem.java

@@ -149,10 +149,17 @@ void setResourceUtils(IResourceUtilities<ImageDescriptor> utils) {
 	}
 
 	protected Image getImage(String iconURI, LocalResourceManager resourceManager) {
+		return createImage(iconURI, resourceManager, false);
+	}
+
+	private Image createImage(String iconURI, LocalResourceManager resourceManager, boolean disabled) {
 		Image image = null;
 
 		if (iconURI != null && iconURI.length() > 0) {
 			ImageDescriptor iconDescriptor = resUtils.imageDescriptorFromURI(URI.createURI(iconURI));
+			if (disabled) {
+				iconDescriptor = ImageDescriptor.createWithFlags(iconDescriptor, SWT.IMAGE_DISABLE);
+			}
 			if (iconDescriptor != null) {
 				try {
 					image = resourceManager.create(iconDescriptor);
@@ -169,6 +176,10 @@ protected Image getImage(String iconURI, LocalResourceManager resourceManager) {
 		return image;
 	}
 
+	private Image getDisabledImage(String iconURI, LocalResourceManager resourceManager) {
+		return createImage(iconURI, resourceManager, true);
+	}
+
 	protected void updateIcons() {
 		if (!(widget instanceof Item)) {
 			return;
@@ -184,14 +195,23 @@ protected void updateIcons() {
 			Image iconImage = getImage(iconURI, resourceManager);
 			item.setImage(iconImage);
 			item.setData(ICON_URI, iconURI);
-			if (item instanceof ToolItem) {
+			if (item instanceof ToolItem toolItem) {
 				iconImage = getImage(disabledURI, resourceManager);
-				((ToolItem) item).setDisabledImage(iconImage);
-				item.setData(DISABLED_URI, disabledURI);
+				toolItem.setDisabledImage(iconImage);
+				toolItem.setData(DISABLED_URI, disabledURI);
 			}
 			disposeOldImages();
 			localResourceManager = resourceManager;
 		}
+		// if there is no explicit disabled icon and the element becomes disabled,
+		// create it
+		boolean hasExplicitDisabledImage = "".equals(disabledURI); //$NON-NLS-1$
+		if (!modelItem.isEnabled() && !hasExplicitDisabledImage && item instanceof ToolItem toolItem) {
+			if (toolItem.getDisabledImage() == null) {
+				Image iconImage = getDisabledImage(iconURI, localResourceManager);
+				toolItem.setDisabledImage(iconImage);
+			}
+		}
 	}
 
 	private String getDisabledIconURI(MItem toolItem) {