config: add just-mapped window criteria

jay-config/src/_private.rs

@@ -116,6 +116,7 @@ pub enum WindowCriterionIpc {
     Urgent,
     SeatFocus(Seat),
     Fullscreen,
+    JustMapped,
 }
 
 #[derive(Serialize, Deserialize, Clone, Debug, Hash, Eq, PartialEq)]

jay-config/src/_private/client.rs

@@ -1662,6 +1662,7 @@ impl ConfigClient {
             WindowCriterion::Urgent => WindowCriterionIpc::Urgent,
             WindowCriterion::Focus(seat) => WindowCriterionIpc::SeatFocus(seat),
             WindowCriterion::Fullscreen => WindowCriterionIpc::Fullscreen,
+            WindowCriterion::JustMapped => WindowCriterionIpc::JustMapped,
         };
         let res = self.send_with_response(&ClientMessage::CreateWindowMatcher { criterion });
         get_response!(

jay-config/src/window.rs

@@ -255,6 +255,11 @@ pub enum WindowCriterion<'a> {
     Focus(Seat),
     /// Matches if the window is fullscreen.
     Fullscreen,
+    /// Matches if the window has/hasn't just been mapped.
+    ///
+    /// This is true for one iteration of the compositor's main loop immediately after the
+    /// window has been mapped.
+    JustMapped,
 }
 
 impl WindowCriterion<'_> {