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+.. default-domain:: c
+.. highlight:: c
+
+######################
+Driving the Event Loop
+######################
+
+Pugl does not contain any threads or other event loop "magic".
+For flexibility, the event loop is driven explicitly by repeatedly calling :func:`puglUpdate`,
+which processes events from the window system and dispatches them to views when necessary.
+
+The exact use of :func:`puglUpdate` depends on the application.
+Plugins should call it with a ``timeout`` of 0 in a callback driven by the host.
+This avoids blocking the main loop,
+since other plugins and the host itself need to run as well.
+
+A program can use whatever timeout is appropriate:
+event-driven applications may wait forever by using a ``timeout`` of -1,
+while those that draw continuously may use a significant fraction of the frame period
+(with enough time left over to render).
+
+*********
+Redrawing
+*********
+
+Occasional redrawing can be requested by calling :func:`puglPostRedisplay` or :func:`puglPostRedisplayRect`.
+After these are called,
+a :struct:`PuglEventExpose` will be dispatched on the next call to :func:`puglUpdate`.
+
+For continuous redrawing,
+call :func:`puglPostRedisplay` while handling a :struct:`PuglEventUpdate` event.
+This event is sent just before views are redrawn,
+so it can be used as a hook to expand the update region right before the view is exposed.
+Anything else that needs to be done every frame can be handled similarly.
+
+*****************
+Event Dispatching
+*****************
+
+Ideally, pending events are dispatched during a call to :func:`puglUpdate`,
+directly within the scope of that call.
+
+Unfortunately, this is not universally true due to differences between platforms.
+
+MacOS
+=====
+
+On MacOS, drawing is handled specially and not by the normal event queue mechanism.
+This means that configure and expose events,
+and possibly others,
+may be dispatched to a view outside the scope of a :func:`puglUpdate` call.
+In general, you can not rely on coherent event dispatching semantics on MacOS:
+the operating system can call into application code at "random" times,
+and these calls may result in Pugl events being dispatched.
+
+An application that follows the Pugl guidelines should work fine,
+but there is one significant inconsistency you may encounter on MacOS:
+posting a redisplay will not wake up a blocked :func:`puglUpdate` call.
+
+Windows
+=======
+
+On Windows, the application has relatively tight control over the event loop,
+so events are typically dispatched explicitly by :func:`puglUpdate`.
+Drawing is handled by events,
+so posting a redisplay will wake up a blocked :func:`puglUpdate` call.
+
+However, it is possible for the system to dispatch events at other times.
+So,
+it is possible for events to be dispatched outside the scope of a :func:`puglUpdate` call,
+but this does not happen in normal circumstances and can largely be ignored.
+
+X11
+===
+
+On X11, the application strictly controls event dispatching,
+and there is no way for the system to call into application code at surprising times.
+So, all events are dispatched in the scope of a :func:`puglUpdate` call.
+
+*********************
+Recursive Event Loops
+*********************
+
+On Windows and MacOS,
+the event loop is stalled while the user is resizing the window or,
+on Windows,
+has displayed the window menu.
+This means that :func:`puglUpdate` will block until the resize is finished,
+or the menu is closed.
+
+Pugl dispatches :struct:`PuglEventLoopEnter` and :struct:`PuglEventLoopLeave` events to notify the application of this situation.
+If you want to continuously redraw during resizing on these platforms,
+you can schedule a timer with :func:`puglStartTimer` when the recursive loop is entered,
+and post redisplays when handling the :struct:`PuglEventTimer`.
+Be sure to remove the timer with :func:`puglStopTimer` when the recursive loop is finished.
+
+On X11, there are no recursive event loops,
+and everything works as usual while the user is resizing the window.
+There is nothing special about a "live resize" on X11,
+and the above loop events will never be dispatched.
+