So many problems here. One is that we can't do the quadrant handling
for all the channels at the same time, so we call the float(y, x)
version multiple times. I'd also left out the x == 0 handling. Also,
the quadrant handling was broken for y == 0, so there was a funny
discontinuity on the +x side if you plugged in obvious values to test.
I generated the atan(float y, float x) code from a short segment of
GLSL and pasted it in by hand. It would be nice to automate that
somehow.
Fixes:
glsl-fs-atan-1
glsl-fs-atan-2
This is an invasive set of changes. Each user shader tracks a set of other
shaders that contain built-in functions. During compilation, function
prototypes are imported from these shaders. During linking, the
shaders are linked with these built-in-function shaders just like with
any other shader.
I'd flipped around the order of two operations in paren-balancing
adventures, and left out the multiply by sign(x) required for negative x.
Fixes:
glsl1-acos(vec4) function
glsl1-asin(vec4) function
glsl1-atan(vec4) function
