Code Snippets

I have collected here some small code snippets, essentially the software equivalent of doodling. Feel free to copy this stuff as you see fit.

• Graphics related stuff
  • OpenGL shader based text terminal
  • Mandelbrot Renderer
• How do I do $THING with X11/Xlib
  • X11 Message Box
  • Sub-window compositing
  • Window that's always on top
  • Urgent window hint

Graphics

OpenGL shader based text terminal

An 8 bit per pixel texture holding ASCII-ish characters is mapped onto a rectangle in 3D space. The fragment shader uses the character value to index into a larger texture holding a font bitmap. A bit of linear equation fiddling is used to generate a ramp function over the character area to render the full character and effectively use mip-mapping for the font texture.

Mandelbrot Renderer

A self-contained program in less than 70 lines of verbously commented C that generates a rendering of the famous mandelbrot set, exported to a ppm file.

X11 Snippets

X11 Message Box

A self-contained function that tries to mimic the Windows® MessageBox function, without using any toolkits.

Sub-window compositing

The composite extension allows redirecting sub-windows to off-screen rendering surfaces.

This only affects rendering, not hit-detection. The mouse can still interact with where the window is supposed to be, and the server sends events like "mouse entered", "mouse clicked", etc. to the sub window, but the server won't render it. The application is expected to composite the window contents onto the parent.

The sample I pieced together creates a window with 3 levels of children. The top level is handled by the application (using XRender for the compositing), the lower level is handled by the XServer, since they aren't redirected.

Window that's always on top

Using X11 client hints to make a window top-most. Depends on the window manager being cooperative to work.

Urgent window hint

Setting a client hint to make the window manager bring attention to a window, kind of like my IRC client does when somebody mentions my handle. Depends on the window manager being cooperative to work, and depends on the window manager what actually happens.