Fills @visible_rect with the currently-visible region of the
buffer, in tree coordinates. Convert to bin_window coordinates with
gtk_tree_view_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.
Fills @visible_rect with the currently-visible region of the buffer, in tree coordinates. Convert to bin_window coordinates with gtk_tree_view_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.