display.get_driver() test and fix

[gabsmoreira]

Add unit test: display.get_driver() and closes #1744

[MyreMylar]

Two things:

1. I suspect the list of SDL video drivers is out of date. I believe the SDL wiki & the pygame docs are not keeping pace with the current state of the SDL codebase, the SDL wiki only claims to have a 'partial' list.
   For example, I suspect there is a driver called 'wayland' on linux that is becoming fairly popular. The folders visible here are probably a decent guide to the video drivers that actually exist right now:

https://github.com/spurious/SDL-mirror/tree/6b6170caf69b4189c9a9d14fca96e97f09bbcc41/src/video

though those will be for SDL 2 and I suppose their driver names might not correspond exactly with the folder names, so you may profit best from a set union with your current list and those ones above for a better chance to catch-them-all.

2. You should perhaps try calling pygame.display.quit() and seeing if a call to get_driver() then returns None. It looks like the code does something like that.

[gabsmoreira]

Thanks for your quick reply @MyreMylar, I added more drivers and tested get_driver() after display.quit() as requested.

[MyreMylar]

The CI tests on Travis are failing on that one specific build because that is our SDL 1 build and this function has a slightly different definition for SDL 1 and SDL 2.

Right now on SDL 1 the function calls the VIDEO_INIT_CHECK() macro before doing anything:

pygame/src_c/_pygame.h

Lines 170 to 172 in c10a68e

	#define VIDEO_INIT_CHECK() \
	if (!SDL_WasInit(SDL_INIT_VIDEO)) \
	return RAISE(pgExc_SDLError, "video system not initialized")

which as you can see raises an assert if the display is not initialised.

I think the best fix for this would likely be to add the VIDEO_INIT_CHECK() to the sdl2 version of this function here (after line 701):

pygame/src_c/display.c

Lines 697 to 706 in 9e8fedc

	#if IS_SDLv2
	static PyObject *
	pg_get_driver(PyObject *self, PyObject *args)
	{
	const char *name = NULL;
	name = SDL_GetCurrentVideoDriver();
	if (!name)
	Py_RETURN_NONE;
	return Text_FromUTF8(name);
	}

In basically the same place as it is in the sdl1 version seen here:

pygame/src_c/display.c

Lines 741 to 749 in 9e8fedc

	static PyObject *
	pg_get_driver(PyObject *self, PyObject *args)
	{
	char buf[256];
	VIDEO_INIT_CHECK();
	if (!SDL_VideoDriverName(buf, sizeof(buf)))
	Py_RETURN_NONE;
	return Text_FromUTF8(buf);
	}

And then change the test to check this assert is being being raised using something like:

display.quit()
with self.assertRaises(errorTypeHere):
     driver = display.get_driver()

That should make the function's behaviour consistent on both SDL 1 and SDL 2.

[illume]

Thank you :)
It looks like @MyreMylar's requests were addressed, so I'll merge it.

[MyreMylar]

👍