I'm becoming more and more convinced that the application should never use XRandR, and it's the window manager's responsibility to track and manage display modes for fullscreen windows.

Because it's so broken, I'm going to disable XRandR by default.  You can still enable it via environment variable or application hint (SDL_HINT_VIDEO_X11_XRANDR)

include/SDL_hints.h

@@ -148,7 +148,7 @@ extern "C" {
  *    "0"       - Disable XRandR
  *    "1"       - Enable XRandR
  *
- *  By default SDL will use XRandR if it is available.
+ *  By default SDL will not use XRandR because of window manager issues.
  */
 #define SDL_HINT_VIDEO_X11_XRANDR           "SDL_VIDEO_X11_XRANDR"
 

src/video/x11/SDL_x11modes.c

@@ -25,7 +25,17 @@
 #include "SDL_hints.h"
 #include "SDL_x11video.h"
 
-/*#define X11MODES_DEBUG*/
+#define X11MODES_DEBUG
+
+/* I'm becoming more and more convinced that the application should never use XRandR,
+ * and it's the window manager's responsibility to track and manage display modes for
+ * fullscreen windows.  Right now XRandR is completely broken with respect to window
+ * manager behavior on every window manager that I can find.  For example, on Unity 3D
+ * if you show a fullscreen window while the resolution is changing (within ~250 ms)
+ * your window will retain the fullscreen state hint but be decorated and windowed.
+*/
+#define XRANDR_DISABLED_BY_DEFAULT
+
 
 static int
 get_visualinfo(Display * display, int screen, XVisualInfo * vinfo)
@@ -190,12 +200,21 @@ CheckXRandR(Display * display, int *major, int *minor)
 
     /* Allow environment override */
     env = SDL_GetHint(SDL_HINT_VIDEO_X11_XRANDR);
+#ifdef XRANDR_DISABLED_BY_DEFAULT
+    if (!env || !SDL_atoi(env)) {
+#ifdef X11MODES_DEBUG
+        printf("XRandR disabled by default due to window manager issues\n");
+#endif
+        return SDL_FALSE;
+    }
+#else
     if (env && !SDL_atoi(env)) {
 #ifdef X11MODES_DEBUG
         printf("XRandR disabled due to hint\n");
 #endif
         return SDL_FALSE;
     }
+#endif /* XRANDR_ENABLED_BY_DEFAULT */
 
     if (!SDL_X11_HAVE_XRANDR) {
 #ifdef X11MODES_DEBUG