GLFX – a framework for OpenGL-based 2D graphics

Basic idea: create an OpenGL rectangle that covers the drawing surface and use a user-supplied GLSL fragment shader to render it.

Two independent modules, 'XDL' and 'glfx' provide the necessary functionality:

• XDL is an event-driven framework for OpenGL applications.
• glfx is a set of functions for doing 2D drawing with GLSL.

XDL

XDL provides one function, XDL_Main(), that sets up the XDL application. XDL_Main() takes a pointer to an XDL_Options struct that contains the following fields:

• char *title: a string used for the window title.
• int width, int height: the dimensions of the drawing surface.
• int frameRate: the number of times per second to update the drawing surface. May be -1, in which case there is no delay between updates.

The remaining fields are pointers to functions that are called when certain events occur. Any of these may be NULL.

• void (*init)(void): a function to be called once when the application starts.
• void (*update)(unsigned int timestamp): a function to be called on each frame update.
• void (*redraw)(unsigned int timestamp): a function to be called each time the drawing surface is redrawn.
• void (*exit)(void): a function to be called once when the application finishes.

XDL requires SDL.

glfx

Provides the following functions:

• void glfxSetup(const char *fragShaderStr): sets up the drawing surface with the provided GLSL fragment shader.
• GLint glfxGetUniformLocation(const GLchar *name): returns the location of the named uniform within the shader program. This location is used to update the uniform via the glUniform*() functions.
• void glfxRedraw(void): re-render the drawing surface.

Example program

The main.c and frag.glsl files in this directory make up an example program demonstrating how the XDL and glfx modules can be used. Run make to build the demo (requires OpenGL and SDL).