Add sdl_hints:add_callback/3 function

This also sets up esdl2 to start accepting callbacks.
The module/process esdl2_callbacks must always be running
for that purpose, so esdl2 was made an OTP application
instead of a simple library.

Implementation of the rest of SDL_hints will follow in
subsequent commits.

1 files changed, 30 insertions, 0 deletions

diff --git a/src/sdl_hints.erl b/src/sdl_hints.erl
new file mode 100644
index 0000000..a6921b0
--- /dev/null
+++ b/src/sdl_hints.erl
@@ -0,0 +1,30 @@
+%% Copyright (c) 2015, Loïc Hoguin <[email protected]>
+%%
+%% Permission to use, copy, modify, and/or distribute this software for any
+%% purpose with or without fee is hereby granted, provided that the above
+%% copyright notice and this permission notice appear in all copies.
+%%
+%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+-module(sdl_hints).
+
+-export([add_callback/3]).
+-export([test_callback/3]).
+
+%% The hint names are the same as the environment variable names
+%% that SDL2 accepts.
+
+-spec add_callback(string(), module(), atom()) -> ok.
+add_callback(Hint, Module, Function) ->
+	esdl2:add_hint_callback(Hint, Module, Function).
+
+%% This callback can be used to test hints.
+-spec test_callback(string(), undefined | string(), undefined | string()) -> ok.
+test_callback(Hint, OldValue, NewValue) ->
+	io:format("Hint ~p has value changed from ~p to ~p~n", [Hint, OldValue, NewValue]).