Set a local grab on this widget. A grab confines pointer events to this widget and its descendants: while the pointer is outside the widget’s subtree, button presses and releases and pointer motion are reported to the grab widget, and windows outside the subtree become insensitive until the grab is released. A local grab affects only the grabbing application. Any grab previously set by this application on the widget’s display is automatically released. Setting a grab is the usual way to make a dialog modal: while the grab is in effect the user cannot interact with the other windows of the application.