Add UpdateCtx::submit_command

That this was missing was an oversight.

druid/src/contexts.rs

@@ -72,6 +72,7 @@ pub struct UpdateCtx<'a> {
     // invalidations, which would mean a structure very much like
     // `EventCtx` (and possibly using the same structure). But for
     // now keep it super-simple.
+    pub(crate) command_queue: &'a mut CommandQueue,
     pub(crate) window_id: WindowId,
     pub(crate) base_state: &'a mut BaseState,
 }
@@ -503,6 +504,23 @@ impl<'a> UpdateCtx<'a> {
         self.base_state.needs_inval = true;
     }
 
+    /// Submit a [`Command`] to be run after layout and paint finish.
+    ///
+    /// **Note:**
+    ///
+    /// Commands submited during an `update` call are handled *after* update,
+    /// layout, and paint have completed; this will trigger a new event cycle.
+    ///
+    /// [`Command`]: struct.Command.html
+    pub fn submit_command(
+        &mut self,
+        command: impl Into<Command>,
+        target: impl Into<Option<Target>>,
+    ) {
+        let target = target.into().unwrap_or_else(|| self.window_id.into());
+        self.command_queue.push_back((target, command.into()))
+    }
+
     /// Get an object which can create text layouts.
     pub fn text(&mut self) -> Text {
         self.window.text()

druid/src/core.rs

@@ -714,6 +714,7 @@ impl<T: Data, W: Widget<T>> WidgetPod<T, W> {
             window: ctx.window,
             base_state: &mut self.state,
             window_id: ctx.window_id,
+            command_queue: ctx.command_queue,
         };
 
         self.inner

druid/src/window.rs

@@ -264,6 +264,7 @@ impl<T: Data> Window<T> {
         let mut base_state = BaseState::new(self.root.id());
         let mut update_ctx = UpdateCtx {
             base_state: &mut base_state,
+            command_queue: queue,
             window: &self.handle,
             window_id: self.id,
         };