Add sdl_gl:create_context/1 and sdl_gl:swap_window/1

These functions are the bare minimum needed to experiment
with OpenGL.

My experiments so far rule out reusing the gl and glu modules
found in the wx application. It seems that any OpenGL call
from a different thread than the window's thread won't work,
at least on Linux.

I'm afraid that implementing OpenGL in the future will require
duplicating the work done in the wx application. OpenGL support
is not a priority however, so it's not a big deal just yet.

5 files changed, 115 insertions, 3 deletions

diff --git a/README.md b/README.md
index 324a7e9..2717c4f 100644
--- a/README.md
+++ b/README.md
@@ -87,15 +87,12 @@ The following tasks remain to be done:
 	* SDL_GL_ResetAttributes()
 	* SDL_GL_SetAttribute()
 	* SDL_GL_GetAttribute()
-	* SDL_GL_CreateContext()
 	* SDL_GL_MakeCurrent()
 	* SDL_GL_GetCurrentWindow()
 	* SDL_GL_GetCurrentContext()
 	* SDL_GL_GetDrawableSize()
 	* SDL_GL_SetSwapInterval()
 	* SDL_GL_GetSwapInterval()
-	* SDL_GL_SwapWindow()
-	* SDL_GL_DeleteContext()
   * We do not support any of the video driver related functions:
     * SDL_GetNumVideoDrivers()
 	* SDL_GetVideoDriver()
diff --git a/c_src/esdl2.h b/c_src/esdl2.h
index 6e69cff..ac479b4 100644
--- a/c_src/esdl2.h
+++ b/c_src/esdl2.h
@@ -123,6 +123,7 @@
 
 #define NIF_RES_TYPE(r) SDL_ ## r
 #define NIF_RESOURCES(R) \
+	R(GLContext) \
 	R(Renderer) \
 	R(Surface) \
 	R(Texture) \
@@ -162,6 +163,9 @@
 	/* sdl_filesystem */ \
 	F(get_base_path, 0) \
 	F(get_pref_path, 2) \
+	/* sdl_gl */ \
+	F(gl_create_context, 1) \
+	F(gl_swap_window, 1) \
 	/* sdl_power */ \
 	F(get_power_info, 0) \
 	/* sdl_renderer */ \
diff --git a/c_src/sdl_gl.c b/c_src/sdl_gl.c
new file mode 100644
index 0000000..febd49f
--- /dev/null
+++ b/c_src/sdl_gl.c
@@ -0,0 +1,69 @@
+// 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.
+
+#include "esdl2.h"
+
+void dtor_GLContext(ErlNifEnv* env, void* obj)
+{
+	SDL_GL_DeleteContext(NIF_RES_GET(GLContext, obj));
+	enif_release_resource(NIF_RES_DEP(GLContext, obj));
+}
+
+// gl_create_context
+
+NIF_CALL_HANDLER(thread_gl_create_context)
+{
+	SDL_GLContext context;
+	ERL_NIF_TERM term;
+
+	context = SDL_GL_CreateContext(args[0]);
+	if (!context)
+		return sdl_error_tuple(env);
+
+	enif_keep_resource(args[0]);
+
+	NIF_RES_TO_TERM_WITH_DEP(GLContext, context, term, args[0]);
+
+	return enif_make_tuple2(env,
+		atom_ok,
+		term
+	);
+}
+
+NIF_FUNCTION(gl_create_context)
+{
+	void* window_res;
+
+	BADARG_IF(!enif_get_resource(env, argv[0], res_Window, &window_res));
+
+	return nif_thread_call(env, thread_gl_create_context, 1,
+		NIF_RES_GET(Window, window_res));
+}
+
+// gl_swap_window
+
+NIF_CAST_HANDLER(thread_gl_swap_window)
+{
+	SDL_GL_SwapWindow(args[0]);
+}
+
+NIF_FUNCTION(gl_swap_window)
+{
+	void* window_res;
+
+	BADARG_IF(!enif_get_resource(env, argv[0], res_Window, &window_res));
+
+	return nif_thread_cast(env, thread_gl_swap_window, 1,
+		NIF_RES_GET(Window, window_res));
+}
diff --git a/src/esdl2.erl b/src/esdl2.erl
index ec07b2c..af8f322 100644
--- a/src/esdl2.erl
+++ b/src/esdl2.erl
@@ -49,6 +49,10 @@
 -export([get_base_path/0]).
 -export([get_pref_path/2]).
 
+%% sdl_gl
+-export([gl_create_context/1]).
+-export([gl_swap_window/1]).
+
 %% sdl_power
 -export([get_power_info/0]).
 
@@ -225,6 +229,14 @@ get_base_path() ->
 get_pref_path(_, _) ->
 	erlang:nif_error({not_loaded, ?MODULE}).
 
+%% sdl_gl
+
+gl_create_context(_) ->
+	erlang:nif_error({not_loaded, ?MODULE}).
+
+gl_swap_window(_) ->
+	erlang:nif_error({not_loaded, ?MODULE}).
+
 %% sdl_power
 
 get_power_info() ->
diff --git a/src/sdl_gl.erl b/src/sdl_gl.erl
new file mode 100644
index 0000000..457994a
--- /dev/null
+++ b/src/sdl_gl.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_gl).
+
+-export([create_context/1]).
+-export([swap_window/1]).
+
+-opaque context() :: <<>>.
+-export_type([context/0]).
+
+-spec create_context(sdl_window:window()) -> {ok, context()} | sdl:error().
+create_context(Window) ->
+	esdl2:gl_create_context(Window),
+	receive {'_nif_thread_ret_', Ret} -> Ret end.
+
+-spec swap_window(sdl_window:window()) -> ok.
+swap_window(Window) ->
+	esdl2:gl_swap_window(Window).