Fix closing of viewports (#3591)

This ensures the closed viewport gets a close-event, and that it and the
parent viewport gets repainting, allowing the event to be registered.

crates/egui/src/context.rs

@@ -2563,8 +2563,13 @@ impl Context {
     ///
     /// This lets you affect another viewport, e.g. resizing its window.
     pub fn send_viewport_cmd_to(&self, id: ViewportId, command: ViewportCommand) {
-        self.write(|ctx| ctx.viewport_for(id).commands.push(command));
         self.request_repaint_of(id);
+
+        if command.requires_parent_repaint() {
+            self.request_repaint_of(self.parent_viewport_id());
+        }
+
+        self.write(|ctx| ctx.viewport_for(id).commands.push(command));
     }
 
     /// Show a deferred viewport, creating a new native window, if possible.

crates/egui/src/data/input.rs

@@ -163,6 +163,18 @@ impl RawInput {
     }
 }
 
+/// An input event from the backend into egui, about a specific [viewport](crate::viewport).
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+pub enum ViewportEvent {
+    /// The user clicked the close-button on the window, or similar.
+    ///
+    /// It is up to the user to react to this by _not_ showing the viewport in the next frame in the parent viewport.
+    ///
+    /// This even will wake up both the child and parent viewport.
+    Close,
+}
+
 /// Information about the current viewport,
 /// given as input each frame.
 ///
@@ -176,9 +188,7 @@ pub struct ViewportInfo {
     /// Name of the viewport, if known.
     pub title: Option<String>,
 
-    /// The user requested the viewport should close,
-    /// e.g. by pressing the close button in the window decoration.
-    pub close_requested: bool,
+    pub events: Vec<ViewportEvent>,
 
     /// Number of physical pixels per ui point.
     pub pixels_per_point: f32,
@@ -212,15 +222,17 @@ pub struct ViewportInfo {
 }
 
 impl ViewportInfo {
-    pub fn take(&mut self) -> Self {
-        core::mem::take(self)
+    pub fn close_requested(&self) -> bool {
+        self.events
+            .iter()
+            .any(|&event| event == ViewportEvent::Close)
     }
 
     pub fn ui(&self, ui: &mut crate::Ui) {
         let Self {
             parent,
             title,
-            close_requested,
+            events,
             pixels_per_point,
             monitor_size,
             inner_rect,
@@ -240,8 +252,8 @@ impl ViewportInfo {
             ui.label(opt_as_str(title));
             ui.end_row();
 
-            ui.label("Close requested:");
-            ui.label(close_requested.to_string());
+            ui.label("Events:");
+            ui.label(format!("{events:?}"));
             ui.end_row();
 
             ui.label("Pixels per point:");

crates/egui/src/viewport.rs

@@ -369,7 +369,7 @@ impl ViewportBuilder {
     /// The default icon is a white `e` on a black background (for "egui" or "eframe").
     /// If you prefer the OS default, set this to `None`.
     #[inline]
-    pub fn with_window_icon(mut self, icon: impl Into<Arc<IconData>>) -> Self {
+    pub fn with_icon(mut self, icon: impl Into<Arc<IconData>>) -> Self {
         self.icon = Some(icon.into());
         self
     }
@@ -641,7 +641,7 @@ impl ViewportBuilder {
             };
 
             if is_new {
-                commands.push(ViewportCommand::WindowIcon(Some(new_icon.clone())));
+                commands.push(ViewportCommand::Icon(Some(new_icon.clone())));
                 self.icon = Some(new_icon.clone());
             }
         }
@@ -765,7 +765,9 @@ pub enum ResizeDirection {
     SouthWest,
 }
 
-/// You can send a [`ViewportCommand`] to the viewport with [`Context::send_viewport_cmd`].
+/// An output [viewport](crate::viewport)-command from egui to the backend, e.g. to change the window title or size.
+///
+///  You can send a [`ViewportCommand`] to the viewport with [`Context::send_viewport_cmd`].
 ///
 /// See [`crate::viewport`] for how to build new viewports (native windows).
 ///
@@ -842,7 +844,7 @@ pub enum ViewportCommand {
     WindowLevel(WindowLevel),
 
     /// The the window icon.
-    WindowIcon(Option<Arc<IconData>>),
+    Icon(Option<Arc<IconData>>),
 
     IMEPosition(Pos2),
     IMEAllowed(bool),
@@ -903,6 +905,11 @@ impl ViewportCommand {
             }
         })
     }
+
+    /// This command requires the parent viewport to repaint.
+    pub fn requires_parent_repaint(&self) -> bool {
+        self == &Self::Close
+    }
 }
 
 /// Describes a viewport, i.e. a native window.