X11: Fix get_current_monitor (#515)

* X11: Fix get_current_monitor

Fixes #64

* impl Debug for MonitorId on all platforms

src/platform/linux/wayland/event_loop.rs

@@ -1,5 +1,6 @@
 use std::cell::RefCell;
 use std::collections::VecDeque;
+use std::fmt;
 use std::sync::{Arc, Mutex, Weak};
 use std::sync::atomic::{AtomicBool, Ordering};
 
@@ -427,6 +428,29 @@ impl Clone for MonitorId {
     }
 }
 
+impl fmt::Debug for MonitorId {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        #[derive(Debug)]
+        struct MonitorId {
+            name: Option<String>,
+            native_identifier: u32,
+            dimensions: (u32, u32),
+            position: (i32, i32),
+            hidpi_factor: f32,
+        }
+
+        let monitor_id_proxy = MonitorId {
+            name: self.get_name(),
+            native_identifier: self.get_native_identifier(),
+            dimensions: self.get_dimensions(),
+            position: self.get_position(),
+            hidpi_factor: self.get_hidpi_factor(),
+        };
+
+        monitor_id_proxy.fmt(f)
+    }
+}
+
 impl MonitorId {
     pub fn get_name(&self) -> Option<String> {
         self.mgr.with_info(&self.proxy, |_, info| {