gamma transform in webGLSL: when already done or yet to be done? Color spaces issues are such a pain, especially when you create color data at the middle of the chain, and a pile of libs and apps separate this to the display... Here I only worry about gamma transform.

Shadertoy addicts are coding in this web site webGLSL shaders, which in my case are rendered through google chrome on linux ubuntu and displayed on a calibrated monitor. 

Is one layer already doing the gamma transform, or should I do pow(color,1./2.2) at the end of my rendering ?
For me (linux,etc), it seems I must do it. Is it also true on windows, mac OS, whether Angle or Native OpenGL is used (windows), whatever the browser ?
The point is that often shaders look ok on windows and very dark on linux, for instance, both people being sure of their settings and qualibration.
This is a hard problem since the systems do not in fact tell you how it should operate. The problem is that there are several ways to address this issue:


Apply a LUT to all output
Let the system color manage
Let each application color manage


Nearly all of our color management systems are borderline braindead. There is really no sane way to ensure that you are doing the proper thing without extensively testing the system. You can not ask or specify your intent. In case of multi operating system situations. If there is reason for me to color manage something myself im at the mercy of each operating system peculiarities.

For a alternate discussion on this see this stackoverflow post. But its not really a robust enough talk to cover all cases.