Programmatically open / closing windows

crates/egui/src/containers/collapsing_header.rs

@@ -6,8 +6,10 @@ use epaint::Shape;
 #[derive(Clone, Copy, Debug)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub(crate) struct InnerState {
-    open: bool,   // Expand / collapse
-    hidden: bool, // Show / Hide
+    /// Expand / collapse
+    open: bool,
+    /// Show / Hide (only on windows)
+    hidden: bool,
 
     /// Height of the region when open. Used for animations
     #[cfg_attr(feature = "serde", serde(default))]
@@ -66,14 +68,17 @@ impl CollapsingState {
         ui.ctx().request_repaint();
     }
 
+    /// Only on windows
     pub fn is_hidden(&self) -> bool {
         self.state.hidden
     }
 
+    /// Only on windows
     pub fn toggle_hidden(&mut self) {
         self.state.hidden = !self.state.hidden;
     }
 
+    /// Only on windows
     pub fn set_hidden(&mut self, hidden: bool) {
         self.state.hidden = hidden;
     }
@@ -345,6 +350,16 @@ pub fn paint_default_icon(ui: &mut Ui, openness: f32, response: &Response) {
     ));
 }
 
+/// A event to expand / collapse the widget automatically
+#[derive(PartialEq, Default, Clone, Copy, Debug)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+pub enum CollapsingHeaderEvent {
+    #[default]
+    Expand,
+    Collapse,
+    ToggleCollapse,
+}
+
 /// A function that paints an icon indicating if the region is open or not
 pub type IconPainter = Box<dyn FnOnce(&mut Ui, f32, &Response)>;
 
@@ -368,6 +383,7 @@ pub struct CollapsingHeader {
     text: WidgetText,
     default_open: bool,
     open: Option<bool>,
+    display_event: Option<CollapsingHeaderEvent>,
     id_source: Id,
     enabled: bool,
     selectable: bool,
@@ -396,6 +412,7 @@ impl CollapsingHeader {
             selected: false,
             show_background: false,
             icon: None,
+            display_event: None,
         }
     }
 
@@ -416,6 +433,11 @@ impl CollapsingHeader {
         self
     }
 
+    pub fn display(mut self, new_event: &mut Option<CollapsingHeaderEvent>) -> Self {
+        self.display_event = new_event.take();
+        self
+    }
+
     /// Explicitly set the source of the [`Id`] of this widget, instead of using title label.
     /// This is useful if the title label is dynamic or not unique.
     pub fn id_source(mut self, id_source: impl Hash) -> Self {
@@ -517,8 +539,8 @@ impl CollapsingHeader {
             selectable,
             selected,
             show_background,
+            display_event,
         } = self;
-
         // TODO(emilk): horizontal layout, with icon and text as labels. Insert background behind using Frame.
 
         let id = ui.make_persistent_id(id_source);
@@ -548,7 +570,18 @@ impl CollapsingHeader {
 
         let mut state = CollapsingState::load(ui.ctx(), id, default_open);
 
-        if let Some(open) = open {
+        let request_repaint = display_event.is_some();
+
+        match display_event {
+            Some(CollapsingHeaderEvent::Expand) => state.set_open(true),
+            Some(CollapsingHeaderEvent::Collapse) => state.set_open(false),
+            Some(CollapsingHeaderEvent::ToggleCollapse) => state.set_open(!state.is_open()),
+            None => {}
+        }
+
+        if request_repaint {
+            ui.ctx().request_repaint();
+        } else if let Some(open) = open {
             if open != state.is_open() {
                 state.toggle_open(ui);
                 header_response.mark_changed();

crates/egui/src/containers/mod.rs

@@ -21,5 +21,5 @@ pub use {
     popup::*,
     resize::Resize,
     scroll_area::ScrollArea,
-    window::{DisplayEvent, SetEvent, Window},
+    window::{SetEvent, Window, WindowEvent},
 };

crates/egui/src/containers/window.rs

@@ -35,13 +35,13 @@ pub struct Window<'open> {
     default_open: bool,
     with_title_bar: bool,
     with_closing_btn: bool,
-    display_event: Option<DisplayEvent>,
+    display_event: Option<WindowEvent>,
     open: Option<&'open mut bool>,
 }
 
 #[derive(PartialEq, Default, Clone, Copy, Debug)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
-pub enum DisplayEvent {
+pub enum WindowEvent {
     #[default]
     Expand,
     Collapse,
@@ -52,12 +52,12 @@ pub enum DisplayEvent {
 
 // Helper function for user space
 pub trait SetEvent {
-    fn set(&mut self, display_event: DisplayEvent);
+    fn set(&mut self, display_event: WindowEvent);
 }
 
-impl SetEvent for Option<DisplayEvent> {
-    fn set(&mut self, display_event: DisplayEvent) {
-        let _ = self.insert(display_event);
+impl SetEvent for Option<WindowEvent> {
+    fn set(&mut self, display_event: WindowEvent) {
+        *self = Some(display_event);
     }
 }
 
@@ -239,7 +239,7 @@ impl<'open> Window<'open> {
         self
     }
 
-    pub fn display_event(mut self, new_event: &mut Option<DisplayEvent>) -> Self {
+    pub fn display_event(mut self, new_event: &mut Option<WindowEvent>) -> Self {
         self.display_event = new_event.take();
         self
     }
@@ -385,11 +385,11 @@ impl<'open> Window<'open> {
         }
 
         match display_event {
-            Some(DisplayEvent::Hide) => collapsing.set_hidden(true),
-            Some(DisplayEvent::Expand) => collapsing.set_open(true),
-            Some(DisplayEvent::Collapse) => collapsing.set_open(false),
-            Some(DisplayEvent::ToggleHidden) => collapsing.toggle_hidden(),
-            Some(DisplayEvent::ToggleCollapse) => collapsing.set_open(!collapsing.is_open()),
+            Some(WindowEvent::Hide) => collapsing.set_hidden(true),
+            Some(WindowEvent::Expand) => collapsing.set_open(true),
+            Some(WindowEvent::Collapse) => collapsing.set_open(false),
+            Some(WindowEvent::ToggleHidden) => collapsing.toggle_hidden(),
+            Some(WindowEvent::ToggleCollapse) => collapsing.set_open(!collapsing.is_open()),
             None => collapsing.set_hidden(matches!(open, Some(false))),
         }
 

crates/egui_demo_lib/src/demo/about.rs

@@ -1,10 +1,10 @@
-use egui::DisplayEvent;
+use egui::{SetEvent, WindowEvent};
 
 #[derive(Default)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[cfg_attr(feature = "serde", serde(default))]
 pub struct About {
-    display_event: Option<DisplayEvent>,
+    display_event: Option<WindowEvent>,
 }
 
 impl super::Demo for About {
@@ -27,11 +27,11 @@ impl super::Demo for About {
 
 impl About {
     pub fn toggle_collapse(&mut self) {
-        self.display_event = Some(DisplayEvent::ToggleCollapse);
+        self.display_event.set(WindowEvent::ToggleCollapse);
     }
 
     pub fn toggle_hidden(&mut self) {
-        self.display_event = Some(DisplayEvent::ToggleHidden);
+        self.display_event.set(WindowEvent::ToggleHidden);
     }
 }