This is a simple narrative description of the multi application included with the Lumen library as a demo.

The multi demo can accept several optional command-line parameters, identical to those accepted by the text2 demo. Full documentation of the command line parameters can be found on the demo "manual" page.

You invoke multi by typing its name, optionally followed by a font-file pathname, and further optionally followed by attribute override values, like ./multi ../data/fsb.txf if you're sitting in the bin directory, or bin/multi data/fsb.txf a0 d16 if you're in the lumen directory and want to select a visual different from the default, in this case one with 0 bits required for an alpha channel and 16 bits in the depth buffer. (Or, of course, simply as ./multi or bin/multi, to use the default font and attributes.) The fsb.txf and chopin.txf files are two sample texture-mapped fonts provided for the demo programs; you can create others using the tools/make-txf tool. The "Chopin" sample font will work with multi, but as with text2 it will look awful.

When run, multi creates two windows, a scene window and a data window. The scene window has a light grey background with a rotating blue and red sphere. The data window is black, with the frame number and the current framerate (which should be close to 30) displayed in green. You can speed up or slow down the rotation of the sphere using the Up and Down arrow keys, pause/restart it with the spacebar, or set it back to its default with the equals sign. Note that the updating of the displayed data is independent of the sphere's rotation. Terminate the app by pressing "q" or the Esc key, or by closing either window.

The multi demo started life as a clone of the text2 demo, but has code added to open two separate windows. It shows how to create and manage the two windows, using the Lumen.Window.Make_Current call to select which window gets the OpenGL activity at any given point. One aspect of its behavior may not be readily evident: Event handling is attached to the scene window, because the events mechanism needs some window to use, but keyboard events are processed the same regardless of which window has focus. We're not entirely sure why it works that way, and are not sure it's the way we want it to work, so keep an eye out for changes in this area.

Last Updated: 14 Dec 2011 09:32:33