[e4] Improve User Experience for saving a single part

Currently when a single part is saved this gives a very bad user
experience as the user has to choose from a (single element) checkbox
list with option [OK] and [CANCEL], but to *not* save the part one has
to uncheck that part and then press [OK].

This now enhances the case of single element to asking the user with a
simple dialog and the choice to [SAVE] / [DON'T SAVE] / [CANCEL] how it
is done for the IDE with the e3 editors.

Author: laeubi

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

@@ -24,6 +24,10 @@ public class SWTRenderersMessages extends NLS {
 
 	public static String choosePartsToSaveTitle;
 	public static String choosePartsToSave;
+	public static String choosePartsToSave_Button_Save;
+	public static String choosePartsToSave_Button_Cancel;
+	public static String choosePartsToSave_Button_Dont_Save;
+	public static String saveSingleChangesQuestionTitle;
 
 	public static String menuClose;
 	public static String menuCloseOthers;

bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/internal/workbench/renderers/swt/messages.properties

@@ -16,10 +16,14 @@
 
 choosePartsToSaveTitle=Save Parts
 choosePartsToSave=Select the parts to save:
+choosePartsToSave_Button_Save=&Save
+choosePartsToSave_Button_Cancel=Cancel
+choosePartsToSave_Button_Dont_Save=Do&n't Save
+saveSingleChangesQuestionTitle=Save ''{0}''?
 menuClose = &Close
 menuCloseOthers = Close &Others
 menuCloseAll = Close &All
 menuCloseRight = Close Tabs to the &Right
 menuCloseLeft = Close Tabs to the &Left
 menuDetach= &Detach
-viewMenu = View Menu
+viewMenu = View Menu

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

@@ -62,12 +62,14 @@
 import org.eclipse.e4.ui.workbench.modeling.ISaveHandler;
 import org.eclipse.e4.ui.workbench.modeling.IWindowCloseHandler;
 import org.eclipse.jface.dialogs.Dialog;
+import org.eclipse.jface.dialogs.MessageDialog;
 import org.eclipse.jface.util.Geometry;
 import org.eclipse.jface.util.Util;
 import org.eclipse.jface.viewers.ArrayContentProvider;
 import org.eclipse.jface.viewers.CheckboxTableViewer;
 import org.eclipse.jface.window.IShellProvider;
 import org.eclipse.jface.window.Window;
+import org.eclipse.osgi.util.NLS;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.events.ControlEvent;
 import org.eclipse.swt.events.ControlListener;
@@ -446,7 +448,7 @@ public Object createWidget(MUIElement element, Object parent) {
 			@Override
 			public Save promptToSave(MPart dirtyPart) {
 				Shell shell = (Shell) context.get(IServiceConstants.ACTIVE_SHELL);
-				Object[] elements = promptForSave(shell, Collections.singleton(dirtyPart));
+				Object[] elements = promptForSave(shell, List.of(dirtyPart));
 				if (elements == null) {
 					return Save.CANCEL;
 				}
@@ -745,14 +747,36 @@ public void postProcess(MUIElement shellME) {
 		}
 	}
 
-	private Object[] promptForSave(Shell parentShell,
-			Collection<MPart> saveableParts) {
-		SaveablePartPromptDialog dialog = new SaveablePartPromptDialog(
-				parentShell, saveableParts);
+	private Object[] promptForSave(Shell parentShell, List<MPart> saveableParts) {
+		if (saveableParts.size() == 1) {
+			MPart part = saveableParts.get(0);
+			String[] buttons;
+			buttons = new String[] { SWTRenderersMessages.choosePartsToSave_Button_Save,
+					SWTRenderersMessages.choosePartsToSave_Button_Dont_Save,
+					SWTRenderersMessages.choosePartsToSave_Button_Cancel };
+
+			String message = NLS.bind(SWTRenderersMessages.saveSingleChangesQuestionTitle, part.getLabel());
+			MessageDialog dialog = new MessageDialog(parentShell, SWTRenderersMessages.choosePartsToSaveTitle, null,
+					message, MessageDialog.NONE, 0, buttons) {
+				@Override
+				protected int getShellStyle() {
+					return SWT.CLOSE | SWT.TITLE | SWT.BORDER | SWT.APPLICATION_MODAL | SWT.SHEET
+							| getDefaultOrientation();
+				}
+			};
+			switch (dialog.open()) {
+			case 0:
+				return new Object[] { part };
+			case 1:
+				return new Object[0];
+			default:
+				return null;
+			}
+		}
+		SaveablePartPromptDialog dialog = new SaveablePartPromptDialog(parentShell, saveableParts);
 		if (dialog.open() == Window.CANCEL) {
 			return null;
 		}
-
 		return dialog.getCheckedElements();
 	}