Prepare to manage multiple windows

crates/fj-viewer/src/display.rs

@@ -1,7 +1,4 @@
-use std::{
+use std::{collections::BTreeMap, sync::mpsc::Receiver};
-    collections::BTreeMap,
-    sync::mpsc::{Receiver, sync_channel},
-};
 
 use fj_interop::TriMesh;
 use futures::executor::block_on;
@@ -28,24 +25,18 @@ pub struct Viewer {}
 
 impl Viewer {
     /// # Construct a new model viewer
-    pub fn new(tri_mesh: TriMesh, invert_zoom: bool) -> Result<Viewer, Error> {
+    pub fn new(
+        tri_mesh: Receiver<TriMesh>,
+        invert_zoom: bool,
+    ) -> Result<Viewer, Error> {
         let event_loop = EventLoop::new()?;
 
-        let (tri_mesh_tx, tri_mesh_rx) = sync_channel(1);
-
         let mut display_state = DisplayState {
-            next_tri_mesh: tri_mesh_rx,
+            next_tri_mesh: tri_mesh,
             invert_zoom,
             windows: BTreeMap::new(),
         };
 
-        let Ok(()) = tri_mesh_tx.send(tri_mesh) else {
-            unreachable!(
-                "Receiver has not been dropped, so it's not possible for the \
-                send to fail."
-            );
-        };
-
         event_loop.run_app(&mut display_state)?;
 
         Ok(Viewer {})

crates/fj/src/instance.rs

@@ -1,4 +1,4 @@
-use std::{error::Error as _, fmt};
+use std::{error::Error as _, fmt, sync::mpsc::sync_channel};
 
 use fj_core::{
     Core,
@@ -90,7 +90,15 @@ impl Instance {
             return Ok(());
         }
 
-        Viewer::new(mesh, false)?;
+        let (tri_mesh_tx, tri_mesh_rx) = sync_channel(1);
+        let Ok(()) = tri_mesh_tx.send(mesh) else {
+            unreachable!(
+                "Receiver has not been dropped, so it's not possible for the \
+                send to fail."
+            );
+        };
+
+        Viewer::new(tri_mesh_rx, false)?;
 
         Ok(())
     }