Gtk.TreeView.prototype.get_visible_rect

function get_visible_rect():void {
    // Gjs wrapper for gtk_tree_view_get_visible_rect()
}

Fills visible_rect with the currently-visible region of the buffer, in tree coordinates. Convert to bin_window coordinates with Gtk.TreeView.prototype.convert_tree_to_bin_window_coords. Tree coordinates start at 0,0 for row 0 of the tree, and cover the entire scrollable area of the tree.