X11: Improve hint support (#529)

Fixes #257

src/platform/linux/x11/util/hint.rs

@@ -18,3 +18,51 @@ impl From<bool> for StateOperation {
         }
     }
 }
+
+/// X window type. Maps directly to
+/// [`_NET_WM_WINDOW_TYPE`](https://specifications.freedesktop.org/wm-spec/1.3/ar01s05.html).
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub enum WindowType {
+    /// A desktop feature. This can include a single window containing desktop icons with the same dimensions as the
+    /// screen, allowing the desktop environment to have full control of the desktop, without the need for proxying
+    /// root window clicks.
+    Desktop,
+    /// A dock or panel feature. Typically a Window Manager would keep such windows on top of all other windows.
+    Dock,
+    /// Toolbar windows. "Torn off" from the main application.
+    Toolbar,
+    /// Pinnable menu windows. "Torn off" from the main application.
+    Menu,
+    /// A small persistent utility window, such as a palette or toolbox.
+    Utility,
+    /// The window is a splash screen displayed as an application is starting up.
+    Splash,
+    /// This is a dialog window.
+    Dialog,
+    /// This is a normal, top-level window.
+    Normal,
+}
+
+impl Default for WindowType {
+    fn default() -> Self {
+        WindowType::Normal
+    }
+}
+
+impl WindowType {
+    pub(crate) fn as_atom(&self, xconn: &Arc<XConnection>) -> ffi::Atom {
+        use self::WindowType::*;
+        let atom_name: &[u8] = match self {
+            Desktop => b"_NET_WM_WINDOW_TYPE_DESKTOP\0",
+            Dock => b"_NET_WM_WINDOW_TYPE_DOCK\0",
+            Toolbar => b"_NET_WM_WINDOW_TYPE_TOOLBAR\0",
+            Menu => b"_NET_WM_WINDOW_TYPE_MENU\0",
+            Utility => b"_NET_WM_WINDOW_TYPE_UTILITY\0",
+            Splash => b"_NET_WM_WINDOW_TYPE_SPLASH\0",
+            Dialog => b"_NET_WM_WINDOW_TYPE_DIALOG\0",
+            Normal => b"_NET_WM_WINDOW_TYPE_NORMAL\0",
+        };
+        unsafe { get_atom(xconn, atom_name) }
+            .expect("Failed to get atom for `WindowType`")
+    }
+}