====== Renderer detection ======

===== Introduction =====

You can detect whether the client is currently using the software renderer or the OpenGL renderer by calling the ''IsOpenGL'' function provided by ACSUtils.

<note warning>
**Things not to do:**
  * don't just check ''GetCVar("vid_renderer")'' -- the user may also have ''gl_nogl'' set to true.
  * don't just check for ''vid_renderer'' and ''gl_nogl'' -- the user may be playing in ZDoom, which doesn't have the OpenGL renderer. 
  * don't just use [[source_port_identification|IsGZDoom]] and assume that if the engine is GZDoom, the user is playing in OpenGL renderer.
  * don't check the renderer serverside -- the server has no renderer.

Nonetheless, many badly coded mods do a lot of the above and get incorrect results.
</note>

===== IsOpenGL =====

''bool IsOpenGL()'' -- returns true if the mod is being played in the OpenGL renederer, false if in software renderer.

If called serverside, ''IsOpenGL'' logs an [[error]] and returns true, because the server can't identify a client's renderer remotely. The renderer is assumed to be OpenGL when called serverside because the OpenGL renderer has less restrictions.

<note important>
This function will return an incorrect value if ''vid_renderer'' or ''gl_nogl'' is changed mid-game because the renderer only actually switches after restart, but the values of the cvars change immediately. 
</note>


===== How it works =====

This functions first calls [[client_server_detection|IsClient]] to see if it's running on a client (see above).

If it's running on a client, it calls [[port_detection|IsGZDoom]] to check if the port is GZDoom or a derivative like Zandronum. If the port is not a GZDoom derivative, it can't have the OpenGL renderer, and this function returns false. This is to prevent detecting the OpenGL renderer when ZDoom is run with a config from GZDoom which has ''vid_renderer=1''.

If the port is confirmed to be a GZDoom derivative, this function checks for two CVars: ''vid_renderer'' and ''gl_nogl''. This function only returns true if ''vid_renderer'' is true and ''gl_nogl'' is false.