Err when a X connection cannot be created instead of panicking

src/api/x11/mod.rs

@@ -2,7 +2,7 @@
 
 pub use self::monitor::{MonitorID, get_available_monitors, get_primary_monitor};
 pub use self::window::{Window, XWindow, PollEventsIterator, WaitEventsIterator, Context, WindowProxy};
-pub use self::xdisplay::XConnection;
+pub use self::xdisplay::{XConnection, XNotSupported};
 
 pub mod ffi;
 

src/api/x11/xdisplay.rs

@@ -1,4 +1,6 @@
 use std::ptr;
+use std::fmt;
+use std::error::Error;
 use std::ffi::CString;
 
 use libc;
@@ -21,10 +23,6 @@ pub struct XConnection {
 unsafe impl Send for XConnection {}
 unsafe impl Sync for XConnection {}
 
-/// Error returned if this system doesn't have XLib or can't create an X connection.
-#[derive(Copy, Clone, Debug)]
-pub struct XNotSupported;
-
 impl XConnection {
     pub fn new() -> Result<XConnection, XNotSupported> {
         // opening the libraries
@@ -104,3 +102,19 @@ impl Drop for XConnection {
         unsafe { (self.xlib.XCloseDisplay)(self.display) };
     }
 }
+
+/// Error returned if this system doesn't have XLib or can't create an X connection.
+#[derive(Copy, Clone, Debug)]
+pub struct XNotSupported;
+
+impl Error for XNotSupported {
+    fn description(&self) -> &str {
+        "The X windowing system could not be initialized"
+    }
+}
+
+impl fmt::Display for XNotSupported {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        formatter.write_str(self.description())
+    }
+}