4.13.1 Panels Basics

The #<panel> object is a window that is implicitly treated as part of a deck including all other panel objects. The deck is treated as a stack with the top panel being completely visible and the other panels may or may not be obscured according to their positions. So the basic idea is to create a stack of overlapping panels and use panels library to display them correctly. There is a function similar to refresh which, when called , displays panels in the correct order. Functions are provided to hide or show panels, move panels, change its size etc.. The overlapping problem is managed by the panels library during all the calls to these functions.

The general flow of a panel program goes like this:

1. Create the windows (with newwin) to be attached to the panels.
2. Create panels with the chosen visibility order. Stack them up according to the desired visibility. The function new-panel is used to create panels.
3. Call update-panels to write the panels to the virtual screen in correct visibility order. Do a doupdate to show it on the screen.
4. Manipulate the panels with show-panel, hide-panel, move-panel etc. Make use of helper functions like panel-hidden and panel-window.
5. When you are done with the panel use del-panel to delete the panel.

Let’s make the concepts clear, with some programs. The following is a simple program which creates 3 overlapping panels and shows them on the screen.