ramarren / opengl-text

Common Lisp library for texture mapped fonts.

Overview

This is a Common Lisp library for texture mapped fonts in OpenGL.

Dependencies

• cl-opengl
• iterate
• alexandria
• cl-vectors
• zpb-ttf
• ffa
• trivial-garbage

Usage

Font and other information is stored in an instance of opengl-text class. Important initargs are:

• :font a zpb-ttf font loader
• :emsquare somewhat misnamed, more or less the side of a square containing a single glyph.
• :length length of string there are preallocated vertex buffers for. Default is 20.

Their respective accessors are font-loader-of, emsquare-of and length-of, which are all setfable.

Only the characters actually used are drawn on the texture. It might be useful to use ensure-characters (sequence opengl-text-object) function to avoid pauses when characters are first used.

Dynamic variable *auto-extend-buffers* controls whether vertex/texture coordinates buffers are automatically extended when string is drawn longer that length. Setting it to nil might be useful if a longer string is only rarely drawn.

The function draw-gl-string (string opengl-text-object &key kerning) renders a series of rectangles textured with proper letters in the current RGBA color. No newlines are allowed. The size is normalized so that a font em square (~font size) is one unit in OpenGL coordinate system.

Note

There is an experimental branch using other ways to store the texture, inluding mipmaps, polygon and outline font. The code there is even less tested and in desperate need of refactoring though, which may or may not happen in the future.