Docs: Timers

Author: einarf

docs/source/performance.rst

@@ -9,7 +9,7 @@ This is ignoring delays or blocks caused by OpenGL calls.
 
 .. Note::
 
-    How important performance is will of course depends on the project.
+    How important performance is will of course depend on the project.
     Visualization for a scientific application doing some heavy
     calculations would probably not need to run at 60 fps.
     It's also not illegal to not care about performance and just have fun.

docs/source/timers.rst

@@ -2,4 +2,33 @@
 Timers
 ======
 
-Write stuff
+Timers are classes keeping track of time passing these time values
+to the effect's ``draw`` methods. We should assume that time can move
+in any direction at any speed. Time is always reported as a float in
+seconds.
+
+The default timer if not specified in settings:
+
+.. code-block:: shell
+
+    TIMER = 'demosys.timers.Timer'
+
+This is a simple timer starting at 0 when effects start drawing.
+All timers should respond correctly to pause ``SPACE``.
+
+
+Standard Timers
+^^^^^^^^^^^^^^^
+
+- ``demosys.timers.Timer``: Default timer just tracking time in seconds
+- ``demosys.timers.Music``: Timer playing music reporting duration in the song
+- ``demosys.timers.RocketTimer``: Timer using the rocket sync system
+- ``demosys.timers.RocketMusicTimer``: Timer using the rocket sync system with music playback
+
+Custom Timer
+^^^^^^^^^^^^
+
+You create a custom timer by extending ``demosys.timers.base.BaseTimer``.
+
+.. autoclass:: demosys.timers.base.BaseTimer
+   :members: