Uderzo v0.5.2 Uderzo.GenRenderer behaviour View Source
Generic rendering code. This will start a process that will render a frame at a regular rate in a window of the indicated size. Rendering the frame is done by calling a callback with the current window size and height and the current mouse pointer position.
GenRenderer
is using GenServer
internally and is thus OTP compatible.
Usually, if you want to use Uderzo, this is the module you want to build around. See also the examples and demos in the repository.
The basic usage of GenRenderer is the same as GenServer: you use
the
module, supply a render_frame/5
callback and an optional init_renderer/1
callback. There
are just more arguments than with GenServer ;-). Short skeleton:
defmodule MyRenderer do
use Uderzo.GenRenderer
def start_link(...) do
Uderzo.GenRenderer.start_link(__MODULE__, "My Demo", 800, 600, 60, [], name: __MODULE__)
end
def init_renderer([]) do
{:ok, %{some: :state}}
end
def render_frame(window_width, window_height, mouse_x, mouse_y, state) do
... Paint your frame here ...
{:ok, state}
end
One important difference with GenServer is that the init_renderer/1
callback isn’t
called during start time but rather as soon as Uderzo is initialized. This means
that you can call functions to load fonts, etcetera, at initialization time.
Note that once calls, GenRenderer just goes off and does rendering. There’s little interaction possible with it, so there’s usually no need to keep the PID around or name it.
Link to this section Summary
Functions
Returns a specification to start this module under a supervisor
Invoked when the server is started. start_link/3
or start/3
will
block until it returns
Start a GenRenderer with the indicated window height, width and title and the target FPS
Callbacks
The (optional) init callback. It either returns :ok
and the initial state, or
an error which will cause the GenRenderer to bail out
The rendering function. This is called fps
times per second. It should try to
complete quickly so that frames aren’t skipped
Link to this section Functions
Returns a specification to start this module under a supervisor.
See Supervisor
.
Invoked when the server is started. start_link/3
or start/3
will
block until it returns.
args
is the argument term (second argument) passed to start_link/3
.
Returning {:ok, state}
will cause start_link/3
to return
{:ok, pid}
and the process to enter its loop.
Returning {:ok, state, timeout}
is similar to {:ok, state}
except handle_info(:timeout, state)
will be called after timeout
milliseconds if no messages are received within the timeout.
Returning {:ok, state, :hibernate}
is similar to
{:ok, state}
except the process is hibernated before entering the loop. See
c:handle_call/3
for more information on hibernation.
Returning :ignore
will cause start_link/3
to return :ignore
and the
process will exit normally without entering the loop or calling c:terminate/2
.
If used when part of a supervision tree the parent supervisor will not fail
to start nor immediately try to restart the GenServer
. The remainder of the
supervision tree will be (re)started and so the GenServer
should not be
required by other processes. It can be started later with
Supervisor.restart_child/2
as the child specification is saved in the parent
supervisor. The main use cases for this are:
- The
GenServer
is disabled by configuration but might be enabled later. - An error occurred and it will be handled by a different mechanism than the
Supervisor
. Likely this approach involves callingSupervisor.restart_child/2
after a delay to attempt a restart.
Returning {:stop, reason}
will cause start_link/3
to return
{:error, reason}
and the process to exit with reason reason
without
entering the loop or calling c:terminate/2
.
Callback implementation for GenServer.init/1
.
Start a GenRenderer with the indicated window height, width and title and the target FPS.
The target_fps is a target, much rests on the speed of the rendering function for the real fps.
The final argument, genserver_opts
, is just passed on to GenServer.start_link/3
.
Returns GenServer.on_start
.
Link to this section Callbacks
The (optional) init callback. It either returns :ok
and the initial state, or
an error which will cause the GenRenderer to bail out.
The rendering function. This is called fps
times per second. It should try to
complete quickly so that frames aren’t skipped.