Playing with Sheeple-based GUI atop CL-OpenGL November 19th, 2009
Patrick Stein

Inspired by the previous TC Lispers meeting and spurred on by the probable topic of the next TC Lispers meeting, I have spent the little bit of coding time I’ve had over the past two weeks on making a GUI layer using Sheeple atop CL-OpenGL and employing ZPB-TTF for font-loading.

I have dubbed this project Woolly (because it’s made from Sheeple and because Woolly sounds sorta like GUI).

woolly-peekI spent about half of my coding time so far getting the basic framework in place (proven through clickable buttons with labels). I am trying to keep it cleanly separated between generic GUI stuff and the CL-OpenGL specifics in the event that someone would like to port it to some other I/O spec.

The other half of my coding time was spent getting the font-rendering to be anti-aliased. I promise to write more about how I accomplished the font-rendering in a future post so that if you’re ever stuck rendering fonts in OpenGL, you won’t be stuck with pixelated blockiness or resorting to rendering to a texture-map and letting the mipmapper figure it out.

For this post, however, I’ll just show you the code that sets up the interface depicted here.

(require :asdf)
(asdf:operate 'asdf:load-op 'woolly-gl :verbose nil)

;; make it easier to change renderer/controller later
(rename-package 'woolly-gl 'toolkit)

(defun test ()
  (let ((font (sheeple:object :parents toolkit:=font=
                              :em-size 48
                              :pathname "okolaks/okolaksRegular.ttf")))
    (let ((app (sheeple:object :parents toolkit:=app=))
          (win (sheeple:object :parents toolkit:=window=
                               :title "Woolly Window 1"
                               :width 640
                               :height 480))
          (but (sheeple:object :parents toolkit:=button=
                               :offset-x 40
                               :offset-y 40
                               :width 300
                               :height 100
                               :font font
                               :label "Button")))
      (woolly:display-window win)
      (woolly:add win but)
      (woolly:main-loop app)
      (woolly:destroy-window win))))

Next up on my agenda is to make the background and button prettier. It should be easy enough to do with GL_LIGHTING and some vertex-coloring for gradations. After that, it’s on to more controls like labels, panels, checkboxes, drop-downs, borders, and (my dread) text input boxes. Then, it’s on to a layout manager.

woolly-peekEdit: Here’s the same GUI a day later. I’m using a simple lighting scheme and rendering the button in 3D. I haven’t yet hooked in the bit to render it depressed when the button is pressed. I’ve tested the code that draws it the other way, but I haven’t hooked it into the mouse handlers yet.

Edit #2: Actually, it only took a few minutes for me to hook in the rendering it pressed vs. unpressed. When I did it though, it looked like the label was sliding around because the effect of the contrast between the light and dark edges of the button was so great that you perceive the whole button sliding when it’s pressed. So, I added a little bit in there to actually slide the text by an amount close to what is perceived. So, now… it looks pretty spiffy.