Add some documentation to egui_flex

crates/egui_flex/src/flex_widget.rs

@@ -1,15 +1,57 @@
 use crate::{FlexContainerResponse, FlexContainerUi};
-use egui::{Ui, Widget};
+use egui::Ui;
 
+/// Implement this trait for a widget to make it usable in a flex container.
+///
+/// The reason there is a separate trait is that we need to measure the content size independently
+/// of the frame size. (The content will stay at it's intrinsic size while the frame will be
+/// stretched according to the flex layout.)
+///
+/// If your widget has no frmae you don't need to implement this trait and can use
+/// [`crate::FlexInstance::add_widget`] to add any [`egui::Widget`].
 pub trait FlexWidget {
     type Response;
-    fn ui(self, ui: &mut Ui, container: FlexContainerUi) -> FlexContainerResponse<Self::Response>;
+    /// Show your widget here. Use the provided [`Ui`] to draw the container (e.g. using a [`egui::Frame`])
+    /// and in the frame ui use [`FlexContainerUi::content`] to draw your widget.
+    /// The frame will grow according to the flex layout while the content will be centered / positioned
+    /// based on [`crate::FlexItem::align_self_content`].
+    fn flex_ui(
+        self,
+        ui: &mut Ui,
+        container: FlexContainerUi,
+    ) -> FlexContainerResponse<Self::Response>;
 }
 
-impl<T: Widget> FlexWidget for T {
-    type Response = egui::Response;
+mod egui_widgets {
+    use super::*;
+    use egui::widgets::*;
+    macro_rules! impl_widget {
+        ($($widget:ty),*) => {
+            $(
+                impl FlexWidget for $widget {
+                    type Response = egui::Response;
 
-    fn ui(self, ui: &mut Ui, container: FlexContainerUi) -> FlexContainerResponse<Self::Response> {
-        container.content_widget(ui, self)
+                    fn flex_ui(self, ui: &mut Ui, container: FlexContainerUi) -> FlexContainerResponse<Self::Response> {
+                        container.content_widget(ui, self)
+                    }
+                }
+            )*
+        };
     }
+    impl_widget!(
+        Button<'_>,
+        Label,
+        Checkbox<'_>,
+        Image<'_>,
+        DragValue<'_>,
+        Hyperlink,
+        ImageButton<'_>,
+        ProgressBar,
+        RadioButton,
+        Link,
+        SelectableLabel,
+        Slider<'_>,
+        TextEdit<'_>,
+        Spinner
+    );
 }

crates/egui_flex/src/lib.rs

@@ -688,8 +688,19 @@ impl<'a> FlexInstance<'a> {
         self.add_container(item, |ui, container| container.content(ui, content))
     }
 
+    /// Add a [`FlexWidget`] to the flex container.
+    /// [`FlexWidget`] is implemented for all default egui widgets.
+    /// If you use a custom third party widget you can use [`Self::add_widget`] instead.
     pub fn add<W: FlexWidget>(&mut self, item: FlexItem, widget: W) -> InnerResponse<W::Response> {
-        self.add_container(item, |ui, container| widget.ui(ui, container))
+        self.add_container(item, |ui, container| widget.flex_ui(ui, container))
+    }
+
+    /// Add a [`egui::Widget`] to the flex container.
+    /// The default egui widgets implement [`FlexWidget`] Aso you can just use [`Self::add`] instead.
+    /// If the widget reports it's intrinsic size via the [`egui::Response`] it will be able to
+    /// grow it's frame according to the flex layout.
+    pub fn add_widget<W: Widget>(&mut self, item: FlexItem, widget: W) -> InnerResponse<Response> {
+        self.add_container(item, |ui, container| container.content_widget(ui, widget))
     }
 
     pub fn add_frame<R>(