Pressing 'enter' in treeview loses focus

it goes from the dialog to the document. This can be seen in
the chapter/heading dialog in writer. Open the dialog, press twice
to ensure the focus can be seen in the treeview, press return,
the focus disappears and up/down no longer had an effect.

Signed-off-by: Caolán McNamara <caolan.mcnamara@collabora.com>
Change-Id: Iede45ff2bdd3ebdd46776ba48ee3ca009e3023a0

Author: caolanm

browser/src/control/jsdialog/Widget.TreeView.ts

@@ -1012,6 +1012,11 @@ class TreeViewControl {
 			return;
 		}
 
+		// Remember if the focused element is inside this treeview,
+		// because clearing selections removes tabindex which drops
+		// focus to BODY for non-natively-focusable elements.
+		const hadFocus = this._container.contains(document.activeElement);
+
 		// Clear existing selections
 		this._container
 			.querySelectorAll('.ui-treeview-entry.selected')
@@ -1021,7 +1026,7 @@ class TreeViewControl {
 
 		// Select the target row
 		const checkbox = rowElement.querySelector('input') as HTMLInputElement;
-		this.selectEntry(rowElement, checkbox, shouldFocus);
+		this.selectEntry(rowElement, checkbox, shouldFocus || hadFocus);
 	}
 
 	unselectEntry(item: HTMLElement) {