is there a GLSL editor for the mac? I need it for iOS OpenGLES2 shader.
How do you best debug shader?
There are two supported GLSL editors for OS X. The first, known as Shader Builder, comes with the Graphics Tools available from the Apple developer website. The second is the open source Shader Maker. Neither of these tools are strictly for OpenGL ES 2.0, but the best workflow would probably be to get the look you want before you determine how to get the look you can have.
In terms of debugging shaders, it is very difficult to send debugging information back to the CPU. The only strategy that I have ever used is to use conditionals to output a specific color to the screen and look at the output. Tools such as glslDevil also exist, but not for OS X.