[demo] Alwyas start with widget gallery

egui_demo_lib/src/apps/demo/dancing_strings.rs

@@ -11,7 +11,7 @@ impl Default for DancingStrings {
 }
 
 impl super::Demo for DancingStrings {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "♫ Dancing Strings"
     }
 

egui_demo_lib/src/apps/demo/demo_window.rs

@@ -27,7 +27,7 @@ impl Default for DemoWindow {
 }
 
 impl Demo for DemoWindow {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "✨ Misc Demos"
     }
 

egui_demo_lib/src/apps/demo/demo_windows.rs

@@ -1,14 +1,15 @@
 use egui::{CtxRef, ScrollArea, Ui, Window};
+use std::collections::BTreeSet;
 
 // ----------------------------------------------------------------------------
 
 #[cfg_attr(feature = "persistence", derive(serde::Deserialize, serde::Serialize))]
 #[cfg_attr(feature = "persistence", serde(default))]
 struct Demos {
-    open: Vec<bool>,
-
     #[cfg_attr(feature = "persistence", serde(skip))]
     demos: Vec<Box<dyn super::Demo>>,
+
+    open: BTreeSet<String>,
 }
 impl Default for Demos {
     fn default() -> Self {
@@ -31,29 +32,48 @@ impl Default for Demos {
             Box::new(super::tests::ManualLayoutTest::default()),
             Box::new(super::tests::TableTest::default()),
         ];
-        Self {
-            open: vec![false; demos.len()],
-            demos,
-        }
+
+        use crate::apps::demo::Demo;
+        let mut open = BTreeSet::new();
+        open.insert(
+            super::widget_gallery::WidgetGallery::default()
+                .name()
+                .to_owned(),
+        );
+
+        Self { open, demos }
     }
 }
 impl Demos {
     pub fn checkboxes(&mut self, ui: &mut Ui) {
         let Self { open, demos } = self;
-        for (ref mut open, demo) in open.iter_mut().zip(demos.iter()) {
-            ui.checkbox(open, demo.name());
+        for demo in demos {
+            let mut is_open = open.contains(demo.name());
+            ui.checkbox(&mut is_open, demo.name());
+            set_open(open, demo.name(), is_open);
         }
     }
 
     pub fn show(&mut self, ctx: &CtxRef) {
         let Self { open, demos } = self;
-        open.resize(demos.len(), false); // Handle deserialization of old data.
-        for (ref mut open, demo) in open.iter_mut().zip(demos.iter_mut()) {
-            demo.show(ctx, open);
+        for demo in demos {
+            let mut is_open = open.contains(demo.name());
+            demo.show(ctx, &mut is_open);
+            set_open(open, demo.name(), is_open);
         }
     }
 }
 
+fn set_open(open: &mut BTreeSet<String>, key: &'static str, is_open: bool) {
+    if is_open {
+        if !open.contains(key) {
+            open.insert(key.to_owned());
+        }
+    } else {
+        open.remove(key);
+    }
+}
+
 // ----------------------------------------------------------------------------
 
 /// A menu bar in which you can select different demo windows to show.

egui_demo_lib/src/apps/demo/drag_and_drop.rs

@@ -94,7 +94,7 @@ impl Default for DragAndDropDemo {
 }
 
 impl super::Demo for DragAndDropDemo {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "✋ Drag and Drop"
     }
 

egui_demo_lib/src/apps/demo/font_book.rs

@@ -40,7 +40,7 @@ impl FontBook {
 }
 
 impl super::Demo for FontBook {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "🔤 Font Book"
     }
 

egui_demo_lib/src/apps/demo/layout_test.rs

@@ -28,7 +28,7 @@ impl Default for LayoutTest {
 }
 
 impl super::Demo for LayoutTest {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "Layout Test"
     }
 

egui_demo_lib/src/apps/demo/mod.rs

@@ -34,7 +34,8 @@ pub trait View {
 
 /// Something to view
 pub trait Demo {
-    fn name(&self) -> &str;
+    /// `&'static` so we can also use it as a key to store open/close state.
+    fn name(&self) -> &'static str;
 
     /// Show windows, etc
     fn show(&mut self, ctx: &egui::CtxRef, open: &mut bool);

egui_demo_lib/src/apps/demo/painting.rs

@@ -64,7 +64,7 @@ impl Painting {
 }
 
 impl super::Demo for Painting {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "🖊 Painting"
     }
 

egui_demo_lib/src/apps/demo/plot_demo.rs

@@ -26,7 +26,7 @@ impl Default for PlotDemo {
 }
 
 impl super::Demo for PlotDemo {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "🗠 Plot"
     }
 

egui_demo_lib/src/apps/demo/scrolling.rs

@@ -20,7 +20,7 @@ impl Default for Scrolling {
 }
 
 impl super::Demo for Scrolling {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "↕ Scrolling"
     }
 

egui_demo_lib/src/apps/demo/sliders.rs

@@ -30,7 +30,7 @@ impl Default for Sliders {
 }
 
 impl super::Demo for Sliders {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "⬌ Sliders"
     }
 

egui_demo_lib/src/apps/demo/tests.rs

@@ -2,7 +2,7 @@
 pub struct IdTest {}
 
 impl super::Demo for IdTest {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "ID Test"
     }
 
@@ -79,7 +79,7 @@ impl Default for ManualLayoutTest {
 }
 
 impl super::Demo for ManualLayoutTest {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "Manual Layout Test"
     }
 
@@ -156,7 +156,7 @@ impl Default for TableTest {
 }
 
 impl super::Demo for TableTest {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "Table Test"
     }
 
@@ -221,7 +221,7 @@ pub struct InputTest {
 }
 
 impl super::Demo for InputTest {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "Input Test"
     }
 
@@ -273,7 +273,7 @@ impl super::View for InputTest {
 pub struct WindowResizeTest {}
 
 impl super::Demo for WindowResizeTest {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "↔ Window Resize"
     }
 

egui_demo_lib/src/apps/demo/widget_gallery.rs

@@ -30,7 +30,7 @@ impl Default for WidgetGallery {
 }
 
 impl super::Demo for WidgetGallery {
-    fn name(&self) -> &str {
+    fn name(&self) -> &'static str {
         "🗄 Widget Gallery"
     }
 

egui_demo_lib/src/apps/demo/window_options.rs

@@ -25,9 +25,8 @@ impl Default for WindowOptions {
 }
 
 impl super::Demo for WindowOptions {
-    fn name(&self) -> &str {
-        // "🗖 Window Options"
-        &self.title
+    fn name(&self) -> &'static str {
+        "🗖 Window Options"
     }
 
     fn show(&mut self, ctx: &egui::CtxRef, open: &mut bool) {