Restore OpenGL 1.1 support (GL_CLAMP)

GL_CLAMP (clamp to border) was changed to GL_CLAMP_TO_EDGE in 2008
(f2baf35). In 2018 (ce1d540) I made OpenGL 1.2 be required since
GL_CLAMP_TO_EDGE is used.

Restore support for GL_CLAMP in order to support OpenGL 1.1 like vanilla
Quake 3 does. This should allow using the default Microsoft Windows
GDI Generic OpenGL 1.1 driver (untested but it won't fail the version
check at least).

From gpuinfo.org, it looks like drivers stopped advertising support for
GL_SGIS_texture_edge_clamp so use a version check in addition to the
extension check.

r_allowExtensions 0 disables using GL_CLAMP_TO_EDGE in the opengl1
renderer. GL_CLAMP support wasn't added to the opengl2 renderer.

code/renderercommon/tr_common.h

@@ -80,6 +80,7 @@ extern glconfig_t	glConfig;		// outside of TR since it shouldn't be cleared duri
 extern qboolean  textureFilterAnisotropic;
 extern int       maxAnisotropy;
 extern float     displayAspect;
+extern qboolean  haveClampToEdge;
 
 //
 // cvars

code/renderergl1/tr_backend.c

@@ -794,8 +794,8 @@ void RE_UploadCinematic (int w, int h, int cols, int rows, const byte *data, int
 		qglTexImage2D( GL_TEXTURE_2D, 0, GL_RGB8, cols, rows, 0, GL_RGBA, GL_UNSIGNED_BYTE, data );
 		qglTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
 		qglTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
-		qglTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE );
-		qglTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE );	
+		qglTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, haveClampToEdge ? GL_CLAMP_TO_EDGE : GL_CLAMP );
+		qglTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, haveClampToEdge ? GL_CLAMP_TO_EDGE : GL_CLAMP );
 	} else {
 		if (dirty) {
 			// otherwise, just subimage upload it so that drivers can tell we are going to be changing

code/renderergl1/tr_image.c

@@ -866,7 +866,7 @@ image_t *R_CreateImage( const char *name, byte *pic, int width, int height,
 	image->width = width;
 	image->height = height;
 	if (flags & IMGFLAG_CLAMPTOEDGE)
-		glWrapClampMode = GL_CLAMP_TO_EDGE;
+		glWrapClampMode = haveClampToEdge ? GL_CLAMP_TO_EDGE : GL_CLAMP;
 	else
 		glWrapClampMode = GL_REPEAT;
 

code/renderergl1/tr_init.c

@@ -27,6 +27,7 @@ glconfig_t  glConfig;
 qboolean    textureFilterAnisotropic = qfalse;
 int         maxAnisotropy = 0;
 float       displayAspect = 0.0f;
+qboolean    haveClampToEdge = qfalse;
 
 glstate_t	glState;
 
@@ -1294,6 +1295,7 @@ void RE_Shutdown( qboolean destroyWindow ) {
 		textureFilterAnisotropic = qfalse;
 		maxAnisotropy = 0;
 		displayAspect = 0.0f;
+		haveClampToEdge = qfalse;
 
 		Com_Memset( &glState, 0, sizeof( glState ) );
 	}

code/renderergl2/tr_init.c

@@ -30,6 +30,7 @@ glRefConfig_t glRefConfig;
 qboolean    textureFilterAnisotropic = qfalse;
 int         maxAnisotropy = 0;
 float       displayAspect = 0.0f;
+qboolean    haveClampToEdge = qfalse;
 
 glstate_t	glState;
 
@@ -1552,6 +1553,7 @@ void RE_Shutdown( qboolean destroyWindow ) {
 		textureFilterAnisotropic = qfalse;
 		maxAnisotropy = 0;
 		displayAspect = 0.0f;
+		haveClampToEdge = qfalse;
 
 		Com_Memset( &glState, 0, sizeof( glState ) );
 	}

code/sdl/sdl_glimp.c

@@ -277,7 +277,7 @@ static qboolean GLimp_GetProcAddresses( qboolean fixedFunction ) {
 	}
 
 	if ( fixedFunction ) {
-		if ( QGL_VERSION_ATLEAST( 1, 2 ) ) {
+		if ( QGL_VERSION_ATLEAST( 1, 1 ) ) {
 			QGL_1_1_PROCS;
 			QGL_1_1_FIXED_FUNCTION_PROCS;
 			QGL_DESKTOP_1_1_PROCS;
@@ -291,7 +291,7 @@ static qboolean GLimp_GetProcAddresses( qboolean fixedFunction ) {
 			// error so this doesn't segfault due to NULL desktop GL functions being used
 			Com_Error( ERR_FATAL, "Unsupported OpenGL Version: %s", version );
 		} else {
-			Com_Error( ERR_FATAL, "Unsupported OpenGL Version (%s), OpenGL 1.2 is required", version );
+			Com_Error( ERR_FATAL, "Unsupported OpenGL Version (%s), OpenGL 1.1 is required", version );
 		}
 	} else {
 		if ( QGL_VERSION_ATLEAST( 2, 0 ) ) {
@@ -965,6 +965,17 @@ static void GLimp_InitExtensions( qboolean fixedFunction )
 	{
 		ri.Printf( PRINT_ALL, "...GL_EXT_texture_filter_anisotropic not found\n" );
 	}
+
+	haveClampToEdge = qfalse;
+	if ( QGL_VERSION_ATLEAST( 1, 2 ) || QGLES_VERSION_ATLEAST( 1, 0 ) || SDL_GL_ExtensionSupported( "GL_SGIS_texture_edge_clamp" ) )
+	{
+		ri.Printf( PRINT_ALL, "...using GL_SGIS_texture_edge_clamp\n" );
+		haveClampToEdge = qtrue;
+	}
+	else
+	{
+		ri.Printf( PRINT_ALL, "...GL_SGIS_texture_edge_clamp not found\n" );
+	}
 }
 
 #define R_MODE_FALLBACK 3 // 640 * 480