Function on_pre_mouse_down 

pub fn on_pre_mouse_down(
    child: impl IntoUiNode,
    handler: Box<dyn FnMut(&MouseInputArgs) -> HandlerResult + Send>,
) -> UiNode

P Mouse button pressed while the cursor is over the widget, the widget is enabled and cursor capture allows it.

Route

This event property uses the preview route, that is, the handler is called before the children widget handlers and before the $pn_ident handlers.