Add support for MSAA.

MSAA was a long wanted and often requested feature. Just set set the
desired number of samples with gl_msaa_samples and do a vid_restart.
This code is based upon work done in Hecatomb.

CHANGELOG

@@ -1,6 +1,8 @@
 Quake II 5.21 to 5.22:
 - Provide a fallback if SDL2s relative mouse mode
   cannot be activated.
+- Add support for MSAA through the gl_msaa_samples
+  cvar.
 
 Quake II 5.20 to 5.21:
 - Fix a bug regaring mouse key handling (reported 

LICENSE

@@ -9,11 +9,12 @@ copys for each license:
 Parts of other Quake II Clients were included into the source. They
 covered by the same GPLv2 license as Quake II itself:
 
+- Hecatomb
 - Icculus Quake 2
-- r1q2
-- QuDoS
 - KMQuake2
 - Q2Pro
+- QuDoS
+- r1q2
 - zeq2
 
 The following code is used in library form and thus not part of Yamagi

src/backends/sdl/refresh.c

@@ -505,10 +505,11 @@ GLimp_InitGraphics(qboolean fullscreen)
 {
 	int counter = 0;
 	int flags;
+	int msaa_samples;
 	int stencil_bits;
+	int width, height;
 	char title[24];
 
-	int width, height;
 
 	if (GetWindowSize(&width, &height) && (width == vid.width) && (height == vid.height))
 	{
@@ -546,6 +547,22 @@ GLimp_InitGraphics(qboolean fullscreen)
 	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
 	SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
 
+	if (gl_msaa_samples->value)
+	{
+		msaa_samples = gl_msaa_samples->value;
+
+		if (SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1) == -1)
+		{
+			Com_Printf("MSAA is unsupported: %s\n", SDL_GetError());
+			Cvar_SetValue ("gl_msaa_samples", 0);
+		}
+		else if (SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, msaa_samples) == -1)
+		{
+			Com_Printf("%i MSAA are unsupported: %s\n", msaa_samples, SDL_GetError());
+			Cvar_SetValue("gl_msaa_samples", 0);
+		}
+	}
+
 	/* Initiate the flags */
 	flags = SDL_OPENGL;
 

src/client/refresh/header/local.h

@@ -242,6 +242,7 @@ extern cvar_t *gl_texturealphamode;
 extern cvar_t *gl_texturesolidmode;
 extern cvar_t *gl_saturatelighting;
 extern cvar_t *gl_lockpvs;
+extern cvar_t *gl_msaa_samples;
 
 extern cvar_t *vid_fullscreen;
 extern cvar_t *vid_gamma;

src/client/refresh/r_main.c

@@ -139,6 +139,7 @@ cvar_t *gl_texturesolidmode;
 cvar_t *gl_anisotropic;
 cvar_t *gl_anisotropic_avail;
 cvar_t *gl_lockpvs;
+cvar_t *gl_msaa_samples;
 
 cvar_t *vid_fullscreen;
 cvar_t *vid_gamma;
@@ -1015,6 +1016,7 @@ R_Register(void)
 
 	gl_customwidth = Cvar_Get("gl_customwidth", "1024", CVAR_ARCHIVE);
 	gl_customheight = Cvar_Get("gl_customheight", "768", CVAR_ARCHIVE);
+	gl_msaa_samples = Cvar_Get ( "gl_msaa_samples", "0", CVAR_ARCHIVE );
 
 #ifdef RETEXTURE
 	gl_retexturing = Cvar_Get("gl_retexturing", "1", CVAR_ARCHIVE);

src/client/refresh/r_misc.c

@@ -164,6 +164,7 @@ void
 R_SetDefaultState(void)
 {
 	glClearColor(1, 0, 0.5, 0.5);
+	glDisable(GL_MULTISAMPLE);
 	glCullFace(GL_FRONT);
 	glEnable(GL_TEXTURE_2D);
 
@@ -216,8 +217,13 @@ R_SetDefaultState(void)
 	if (qglColorTableEXT && gl_ext_palettedtexture->value)
 	{
 		glEnable(GL_SHARED_TEXTURE_PALETTE_EXT);
-
 		R_SetTexturePalette(d_8to24table);
 	}
+
+	if (gl_msaa_samples->value)
+	{
+		glEnable(GL_MULTISAMPLE);
+		glHint(GL_MULTISAMPLE_FILTER_HINT_NV, GL_NICEST);
+	}
 }