Lazy load disabled icons in AbstractContributionItem

AbstractionContributionItems load their disabled icons even if the
icon's widget is not disabled. This unnecessarily occupies resources
that may never be used.

This change updates the implementation to lazily load or create the
disabled icon once the element is actually disabled for the first time.

Author: HeikoKlare

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

@@ -188,29 +188,26 @@ protected void updateIcons() {
 		String iconURI = modelItem.getIconURI() != null ? modelItem.getIconURI() : ""; //$NON-NLS-1$
 		String disabledURI = getDisabledIconURI(modelItem);
 		Object disabledData = item.getData(DISABLED_URI);
-		if (disabledData == null)
-			disabledData = ""; //$NON-NLS-1$
-		if (!iconURI.equals(item.getData(ICON_URI)) || !disabledURI.equals(disabledData)) {
+		boolean enabledIconChanged = !iconURI.equals(item.getData(ICON_URI));
+		boolean disabledIconChanged = disabledData != null && !disabledURI.equals(disabledData);
+		if (enabledIconChanged || disabledIconChanged) {
 			LocalResourceManager resourceManager = new LocalResourceManager(JFaceResources.getResources());
 			Image iconImage = getImage(iconURI, resourceManager);
 			item.setImage(iconImage);
 			item.setData(ICON_URI, iconURI);
-			if (item instanceof ToolItem toolItem) {
-				iconImage = getImage(disabledURI, resourceManager);
-				toolItem.setDisabledImage(iconImage);
-				toolItem.setData(DISABLED_URI, disabledURI);
-			}
+			disabledData = null;
+			item.setData(DISABLED_URI, null);
 			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);
+		// If item is disabled, create disabled image if not done yet
+		if (!modelItem.isEnabled() && disabledData == null && item instanceof ToolItem toolItem) {
+			Image disabledImage = getImage(disabledURI, localResourceManager);
+			if (disabledImage == null) {
+				disabledImage = getDisabledImage(iconURI, localResourceManager);
 			}
+			toolItem.setDisabledImage(disabledImage);
+			toolItem.setData(DISABLED_URI, disabledURI);
 		}
 	}