This PR has a smaller scope, and this are some reverts

Will no longer change egui::Window!

crates/egui_demo_lib/src/demo/demo_app_windows.rs

@@ -81,7 +81,7 @@ impl Demos {
 #[cfg_attr(feature = "serde", serde(default))]
 struct Tests {
     #[cfg_attr(feature = "serde", serde(skip))]
-    demos: Vec<Box<dyn Demo + Sync + Send>>,
+    demos: Vec<Box<dyn Demo>>,
 
     open: BTreeSet<String>,
 }
@@ -101,7 +101,7 @@ impl Default for Tests {
 }
 
 impl Tests {
-    pub fn from_demos(demos: Vec<Box<dyn Demo + Sync + Send>>) -> Self {
+    pub fn from_demos(demos: Vec<Box<dyn Demo>>) -> Self {
         let mut open = BTreeSet::new();
         open.insert(
             super::widget_gallery::WidgetGallery::default()
@@ -146,7 +146,6 @@ fn set_open(open: &mut BTreeSet<String>, key: &'static str, is_open: bool) {
 // ----------------------------------------------------------------------------
 
 /// A menu bar in which you can select different demo windows to show.
-
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[cfg_attr(feature = "serde", serde(default))]
 pub struct DemoWindows {

crates/egui_demo_lib/src/demo/drag_and_drop.rs

@@ -70,6 +70,7 @@ pub fn drop_target<R>(
     InnerResponse::new(ret, response)
 }
 
+#[derive(Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 pub struct DragAndDropDemo {
     /// columns with items

crates/egui_demo_lib/src/demo/tests.rs

@@ -94,7 +94,7 @@ enum WidgetType {
     TextEdit,
 }
 
-#[derive(Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq)]
 pub struct ManualLayoutTest {
     widget_offset: egui::Vec2,
     widget_size: egui::Vec2,
@@ -133,7 +133,7 @@ impl super::View for ManualLayoutTest {
     fn ui(&mut self, ui: &mut egui::Ui) {
         egui::reset_button(ui, self);
 
-        let ManualLayoutTest {
+        let Self {
             widget_offset,
             widget_size,
             widget_type,

crates/egui_demo_lib/src/demo/text_edit.rs

@@ -1,4 +1,5 @@
 /// Showcase [`TextEdit`].
+#[derive(PartialEq, Eq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[cfg_attr(feature = "serde", serde(default))]
 pub struct TextEdit {

crates/egui_demo_lib/src/demo/widget_gallery.rs

@@ -74,6 +74,7 @@ impl super::View for WidgetGallery {
                     self.gallery_grid_contents(ui);
                 });
         });
+
         ui.separator();
 
         ui.horizontal(|ui| {