9.2 An example interface

Here is a simple example of interface definition done with define-interface :

(define-interface demo ()

  ()

  (:panes

   (page-up push-button 

            :text "Page Up")

   (page-down push-button

              :text "Page Down")

   (open-file push-button

              :text "Open File"))

  (:layouts

   (row-of-buttons row-layout

                   '(page-up page-down open-file)))

  (:default-initargs :title "Demo"))

An instance of this interface can be displayed as follows:

At the moment the buttons do nothing, but they will eventually do the following:

• Open File will bring up a file prompter and allow you to select a filename from a directory. Later on, we will add an editor pane to display the chosen file's contents.
• Page Down will scroll downwards so that you can view the lower parts of the file that cannot be seen initially.
• Page Up will scroll upwards so that you can return to parts of the file seen before.

Figure 9.1 A demonstration of a CAPI interface

Later on, we will specify callbacks for these buttons to provide this functionality.

The (:default-initargs :title "Demo") part at the end is necessary to give the interface a title. If no title is given, the default name is "Untitled CAPI Interface".

9.2.1 How the example works