Allow the user to override the relative mouse mode.

They almost never want to do this, as it seriously affects
applications that rely on continuous relative mouse motion.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%4080

src/video/x11/SDL_x11mouse.c

@@ -229,11 +229,23 @@ static void SetMouseAccel(_THIS, const char *accel_param)
 /* Check to see if we need to enter or leave mouse relative mode */
 void X11_CheckMouseModeNoLock(_THIS)
 {
+	char *env_override;
+	int enable_relative = 1;
+
+	/* Allow the user to override the relative mouse mode.
+	   They almost never want to do this, as it seriously affects
+	   applications that rely on continuous relative mouse motion.
+	*/
+	env_override = getenv("SDL_MOUSE_NORELATIVE");
+	if ( env_override ) {
+		enable_relative = atoi(env_override);
+	}
+
 	/* If the mouse is hidden and input is grabbed, we use relative mode */
-	if ( !(SDL_cursorstate & CURSOR_VISIBLE) &&
+	if ( enable_relative &&
+	     !(SDL_cursorstate & CURSOR_VISIBLE) &&
 	     (this->input_grab != SDL_GRAB_OFF) &&
-             (SDL_GetAppState() & SDL_APPACTIVE) &&
-	     !getenv("SDL_MOUSE_NORELATIVE") ) {
+             (SDL_GetAppState() & SDL_APPACTIVE) ) {
 		if ( ! mouse_relative ) {
 			X11_EnableDGAMouse(this);
 			if ( ! (using_dga & DGA_MOUSE) ) {