Fixed original video mode being overwritten.

README.md

@@ -124,6 +124,8 @@ See the [GLFW documentation](http://www.glfw.org/docs/latest/).
                  race condition
  - [X11] Bugfix: The reported window position did not account for the size of
                  the window frame on some WMs
+ - [X11] Bugfix: The original video mode of a monitor was overwritten by calls
+                 to glfwSetWindowSize
 
 
 ## Contact

src/x11_monitor.c

@@ -111,6 +111,7 @@ void _glfwSetVideoMode(_GLFWmonitor* monitor, const GLFWvidmode* desired)
             }
         }
 
+        if (monitor->x11.oldMode == None)
             monitor->x11.oldMode = ci->mode;
 
         XRRSetCrtcConfig(_glfw.x11.display,
@@ -137,6 +138,9 @@ void _glfwRestoreVideoMode(_GLFWmonitor* monitor)
         XRRScreenResources* sr;
         XRRCrtcInfo* ci;
 
+        if (monitor->x11.oldMode == None)
+            return;
+
         sr = XRRGetScreenResources(_glfw.x11.display, _glfw.x11.root);
         ci = XRRGetCrtcInfo(_glfw.x11.display, sr, monitor->x11.crtc);
 
@@ -151,6 +155,8 @@ void _glfwRestoreVideoMode(_GLFWmonitor* monitor)
 
         XRRFreeCrtcInfo(ci);
         XRRFreeScreenResources(sr);
+
+        monitor->x11.oldMode = None;
     }
 }