prepare

Prepares to poll sources within a main loop.

The resulting information for polling is determined by calling [method@GLib.MainContext.query].

You must have successfully acquired the context with [method@GLib.MainContext.acquire] before you may call this function.

Parameters:

this	a main context (if `NULL`, the global-default main context will be used)
priority	location to store priority of highest priority source already ready

Returns:

true if some source is ready to be dispatched prior to polling, false otherwise