Prevent shutdown hang when changing theme and disabling theming

When changing the current theme via the Appearance preference page, and
disabling theming, two calls to IWorkbench.restart() are triggered
during ViewsPreferencePage.performOk(). This results in a hang at
shutdown, during the second restart call.

This change ensures only one restart is triggered, preventing the hang.

Fixes: #2950
Signed-off-by: Simeon Andreev <[email protected]>

Author: trancexpress

bundles/org.eclipse.ui.workbench/eclipseui/org/eclipse/ui/internal/dialogs/ViewsPreferencePage.java

@@ -381,6 +381,10 @@ public boolean performOk() {
 			WorkbenchPlugin.log("Failed to set SWT renderer preferences", e); //$NON-NLS-1$
 		}
 
+		boolean showRestartDialog = false;
+		String restartDialogTitle = null;
+		String restartDialogMessage = null;
+
 		if (engine != null) {
 			ITheme theme = getSelectedTheme();
 			boolean themeChanged = theme != null && !theme.equals(currentTheme);
@@ -400,15 +404,24 @@ public boolean performOk() {
 			colorFontsDecorator.hide();
 
 			if (themeChanged || colorsAndFontsThemeChanged) {
-				showRestartDialog(WorkbenchMessages.ThemeChangeWarningTitle, WorkbenchMessages.ThemeChangeWarningText);
+				showRestartDialog = true;
+				restartDialogTitle = WorkbenchMessages.ThemeChangeWarningTitle;
+				restartDialogMessage = WorkbenchMessages.ThemeChangeWarningText;
 			}
 		}
 		if (themingEnabledChanged) {
-			showRestartDialog(WorkbenchMessages.ThemeChangeWarningTitle, WorkbenchMessages.ThemeChangeWarningText);
+			showRestartDialog = true;
+			restartDialogTitle = WorkbenchMessages.ThemeChangeWarningTitle;
+			restartDialogMessage = WorkbenchMessages.ThemeChangeWarningText;
 		}
 		if (isRescaleAtRuntimeChanged) {
-			showRestartDialog(WorkbenchMessages.RescaleAtRuntimeSettingChangeWarningTitle,
-					WorkbenchMessages.RescaleAtRuntimeSettingChangeWarningText);
+			showRestartDialog = true;
+			restartDialogTitle = WorkbenchMessages.RescaleAtRuntimeSettingChangeWarningTitle;
+			restartDialogMessage = WorkbenchMessages.RescaleAtRuntimeSettingChangeWarningText;
+		}
+
+		if (showRestartDialog) {
+			showRestartDialog(restartDialogTitle, restartDialogMessage);
 		}
 
 		return super.performOk();