Set force_s3tc_enable automatically for greater chance of compressed texture support on Linux (see #575).

This was SVN commit r8356.

binaries/data/config/default.cfg

@@ -36,6 +36,10 @@ noautomipmap = true
 novbo = false
 noframebufferobject = false
 
+; Linux only: Set the driconf force_s3tc_enable option at startup,
+; for compressed texture support
+force_s3tc_enable = true
+
 ; Specify the render path. This can be one of:
 ;   default       Automatically select one of the below, depending on system capabilities
 ;   fixed         Only use OpenGL fixed function pipeline

source/ps/GameSetup/GameSetup.cpp

@@ -496,8 +496,8 @@ static void InitPs(bool setup_gui, const CStrW& gui_page)
 		g_GUI->DisplayMessageBox(600, 270, L"Warning",
 			L"Your graphics drivers do not support S3TC compressed textures. This may reduce performance.\n\n"
 #if !(OS_WIN || OS_MACOSX)
-			L"To fix this, run the program \"driconf\" and enable the force_s3tc_enable option (\"Enable S3TC texture compression\"). "
-			L"(If this causes rendering errors, you may have to disable the option again.)"
+			L"To fix this, you may have to install the \"libtxc_dxtn\" library. "
+			L"See http://dri.freedesktop.org/wiki/S3TC for more information."
 #else
 			L"Please try updating your graphics drivers to ensure you have full hardware acceleration."
 #endif

source/ps/VideoMode.cpp

@@ -43,7 +43,7 @@ CVideoMode g_VideoMode;
 CVideoMode::CVideoMode() :
 	m_IsInitialised(false),
 	m_PreferredW(0), m_PreferredH(0), m_PreferredBPP(0), m_PreferredFreq(0),
-	m_ConfigW(0), m_ConfigH(0), m_ConfigBPP(0), m_ConfigFullscreen(false),
+	m_ConfigW(0), m_ConfigH(0), m_ConfigBPP(0), m_ConfigFullscreen(false), m_ConfigForceS3TCEnable(true),
 	m_WindowedW(DEFAULT_WINDOW_W), m_WindowedH(DEFAULT_WINDOW_H)
 {
 	// (m_ConfigFullscreen defaults to false, so users don't get stuck if
@@ -59,6 +59,7 @@ void CVideoMode::ReadConfig()
 	CFG_GET_USER_VAL("xres", Int, m_ConfigW);
 	CFG_GET_USER_VAL("yres", Int, m_ConfigH);
 	CFG_GET_USER_VAL("bpp", Int, m_ConfigBPP);
+	CFG_GET_USER_VAL("force_s3tc_enable", Bool, m_ConfigForceS3TCEnable);
 }
 
 bool CVideoMode::SetVideoMode(int w, int h, int bpp, bool fullscreen)
@@ -115,6 +116,25 @@ bool CVideoMode::InitSDL()
 
 	ReadConfig();
 
+	// On Linux we have to try hard to get S3TC compressed texture support.
+	// If the extension is already provided by default, that's fine.
+	// Otherwise we should enable the 'force_s3tc_enable' environment variable
+	// and (re)initialise the video system, so that Mesa provides the extension
+	// (if the driver at least supports decompression).
+	// (This overrides the force_s3tc_enable specified via driconf files.)
+	// Otherwise we should complain to the user, and stop using compressed textures.
+	//
+	// Setting the environment variable causes Mesa to print an ugly message to stderr
+	// ("ATTENTION: default value of option force_s3tc_enable overridden by environment."),
+	// so it'd be nicer to skip that if S3TC will be supported by default,
+	// but reinitialising video is a pain (and it might do weird things when fullscreen)
+	// so we just unconditionally set it (unless our config file explicitly disables it).
+
+#if !(OS_WIN || OS_MACOSX) // (assume Mesa is used for all non-Windows non-Mac platforms)
+	if (m_ConfigForceS3TCEnable)
+		setenv("force_s3tc_enable", "true", 0);
+#endif
+
 	// preferred video mode = current desktop settings
 	// (command line params may override these)
 	gfx_get_video_mode(&m_PreferredW, &m_PreferredH, &m_PreferredBPP, &m_PreferredFreq);

source/ps/VideoMode.h

@@ -72,6 +72,7 @@ private:
 	int m_ConfigH;
 	int m_ConfigBPP;
 	bool m_ConfigFullscreen;
+	bool m_ConfigForceS3TCEnable;
 
 	// If we're fullscreen, size of window when we were last windowed (or the default window size
 	// if we started fullscreen), to support switching back to the old window size