Fix dark styling for popup shells in workspace selection

Use display.addFilter instead of addListener for SWT.Show so the
listener actually fires for child popup shells (e.g. the content
proposal popup in the workspace selection combo). Re-apply styles
asynchronously to cover widgets populated after the Show event.

Reproducible on Windows; not reproducible on Linux.

Author: vogella

bundles/org.eclipse.ui.ide.application/src/org/eclipse/ui/internal/ide/application/IDEApplication.java

@@ -901,9 +901,16 @@ protected void initializeDefaultTheme(Display display) {
 			darkThemeShowListener = event -> {
 				if (event.widget instanceof Shell shell) {
 					applyDarkStyles(shell);
+					// Re-apply after the current event to cover popup shells (e.g. content
+					// proposal) whose content is populated after the SWT.Show event fires.
+					display.asyncExec(() -> {
+						if (!shell.isDisposed()) {
+							applyDarkStyles(shell);
+						}
+					});
 				}
 			};
-			display.addListener(SWT.Show, darkThemeShowListener);
+			display.addFilter(SWT.Show, darkThemeShowListener);
 		}
 	}
 
@@ -914,7 +921,7 @@ protected void initializeDefaultTheme(Display display) {
 	 */
 	protected void resetEarlyDarkTheme(Display display) {
 		if (darkThemeShowListener != null) {
-			display.removeListener(SWT.Show, darkThemeShowListener);
+			display.removeFilter(SWT.Show, darkThemeShowListener);
 			darkThemeShowListener = null;
 		}
 		if (isDark) {