Yet more header file comments.

util.h

@@ -1,6 +1,8 @@
 #ifndef _UTIL_H
 #define _UTIL_H 1
 
+// Various utilities.
+
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -10,16 +12,27 @@
 
 #define BUFFER_OFFSET(i) ((char *)NULL + (i))
 
-// assumes h in [0, 2pi> or [-pi, pi>
+// Converts a HSV color to RGB. Assumes h in [0, 2pi> or [-pi, pi>
 void hsv2rgb(float h, float s, float v, float *r, float *g, float *b);
 
 // Column major (same as OpenGL).
 typedef double Matrix3x3[9];
 
+// Read a file from disk and return its contents.
+// Dies if the file does not exist.
 std::string read_file(const std::string &filename);
+
+// Compile the given GLSL shader (typically a vertex or fragment shader)
+// and return the object number.
 GLuint compile_shader(const std::string &shader_src, GLenum type);
+
+// Compute a * b.
 void multiply_3x3_matrices(const Matrix3x3 a, const Matrix3x3 b, Matrix3x3 result);
+
+// Compute m^-1. Result is undefined if the matrix is singular or near-singular.
 void invert_3x3_matrix(const Matrix3x3 m, Matrix3x3 result);
+
+// Print a 3x3 matrix to standard output. Useful for debugging.
 void print_3x3_matrix(const Matrix3x3 m);
 
 #ifdef NDEBUG

widgets.h

@@ -1,6 +1,8 @@
 #ifndef _WIDGETS_H
 #define _WIDGETS_H 1
 
+// Some simple UI widgets for test use.
+
 void draw_hsv_wheel(float y, float rad, float theta, float value);
 void draw_saturation_bar(float y, float saturation);
 void make_hsv_wheel_texture();