Move windows to their monitors

When we create Firefox windows for each monitor, we need to move them to
their respective screens.  The Marionette protocol provides a
`SetWindowRect` command that *should* move the active window (it doesn't
work for all window managers, notably *i3*).

src/marionette/message.rs

@@ -98,6 +98,16 @@ pub struct SwitchToWindowParams {
     pub focus: bool,
 }
 
+#[derive(Debug, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+#[allow(dead_code)]
+pub struct WindowRect {
+    pub x: Option<i32>,
+    pub y: Option<i32>,
+    pub height: Option<u32>,
+    pub width: Option<u32>,
+}
+
 #[derive(Debug, Serialize)]
 #[serde(tag = "command", content = "params")]
 pub enum Command {
@@ -119,4 +129,6 @@ pub enum Command {
     SwitchToWindow(SwitchToWindowParams),
     #[serde(rename = "WebDriver:FullscreenWindow")]
     FullscreenWindow,
+    #[serde(rename = "WebDriver:SetWindowRect")]
+    SetWindowRect(WindowRect),
 }

src/marionette/mod.rs

@@ -20,7 +20,7 @@ pub use error::{CommandError, ConnectionError, ErrorResponse, MessageError};
 use message::{
     CloseWindowParams, Command, GetCurrentUrlResponse, GetTitleResponse,
     Hello, NavigateParams, NewSessionParams, NewSessionResponse,
-    SwitchToWindowParams,
+    SwitchToWindowParams, WindowRect,
 };
 
 #[derive(Debug, Deserialize, Serialize)]
@@ -251,6 +251,27 @@ impl Marionette {
         let res: String =
             self.conn.send_message(Command::NewWindow).await?.unwrap();
         debug!("Received message: {:?}", res);
+        Ok(res.handle)
+    }
+
+    pub async fn set_window_rect(
+        &mut self,
+        x: Option<i32>,
+        y: Option<i32>,
+        height: Option<u32>,
+        width: Option<u32>,
+    ) -> Result<WindowRect, CommandError> {
+        let res: WindowRect = self
+            .conn
+            .send_message(Command::SetWindowRect(WindowRect {
+                x,
+                y,
+                height,
+                width,
+            }))
+            .await?
+            .unwrap();
+        debug!("Received message: {:?}", res);
         Ok(res)
     }
 

src/monitor.rs

@@ -3,5 +3,6 @@ pub struct Monitor {
     pub name: String,
     pub width: u32,
     pub height: u32,
+    pub x: i32,
+    pub y: i32,
 }
-

src/session.rs

@@ -140,11 +140,22 @@ impl Session {
         let mut windowmap = HashMap::new();
         let mut window = Some(handles.remove(handles.len() - 1));
         for monitor in monitors {
+            debug!(
+                "Creating window for monitor {}: {}x{} ({}, {})",
+                monitor.name,
+                monitor.width,
+                monitor.height,
+                monitor.x,
+                monitor.y
+            );
             if window.is_none() {
                 window = Some(self.marionette.new_window().await?);
             }
             let w = window.take().unwrap();
             self.marionette.switch_to_window(w.clone(), false).await?;
+            self.marionette
+                .set_window_rect(Some(monitor.x), Some(monitor.y), None, None)
+                .await?;
             self.marionette.fullscreen().await?;
             windowmap.insert(monitor.name, w);
         }
@@ -218,6 +229,8 @@ fn get_monitors() -> Vec<Monitor> {
             name: m.name().unwrap().to_string(),
             width: m.width(),
             height: m.height(),
+            x: m.x(),
+            y: m.y(),
         })
         .collect()
 }

src/x11/xrandr.rs

@@ -29,6 +29,14 @@ impl XMonitor {
     pub fn name(&self) -> Option<&str> {
         Some(&self.name)
     }
+
+    pub fn x(&self) -> i32 {
+        self.monitor.x as i32
+    }
+
+    pub fn y(&self) -> i32 {
+        self.monitor.y as i32
+    }
 }
 
 /// Return information about the monitors attached to an X display