Box reference to shared memory

@@ -36,7 +36,7 @@ pub struct XcbCanvas<'a> { conn   :Arc<xcb::Connection>
                          , window :u32
                          , pixmap :u32
                          , gc     :u32
-                         , shm    :&'a mut [u32] }
+                         , shm    :Box<&'a mut [u32]> }
 
 impl XcbEasel {
     pub fn new() -> Result<XcbEasel, xcb::ConnError> {
@@ -55,7 +55,7 @@ impl XcbEasel {
         self.setup().roots().nth(*num as usize)
     }
 
-    pub fn canvas(&self, width :u16, height :u16) -> Option<XcbCanvas> {
+    pub fn canvas<'a>(&self, width :u16, height :u16) -> Option<XcbCanvas<'a>> {
         let Self(conn, _) = self;
         let conn          = conn.clone();
         let screen        = match self.screen() {
@@ -63,6 +63,8 @@ impl XcbEasel {
             Some(screen) => screen,
         };
 
+        println!("root depth: {}", screen.root_depth());
+
         let shmseg = conn.generate_id();
         let gc     = conn.generate_id();
         let pixmap = conn.generate_id();
@@ -94,7 +96,7 @@ impl XcbEasel {
                       , window: window
                       , pixmap: pixmap
                       , gc:     gc
-                      , shm:    shm } )
+                      , shm:    Box::new(shm) } )
     }
 }