Initial implementation of Expander widget

src/widget/expander.rs

@@ -0,0 +1,81 @@
+use std::vec;
+
+use apply::Apply;
+use iced::{
+    Element,
+    Length,
+    widget::{
+        row, 
+        horizontal_space, button, container, text, Column
+    }, alignment::{Vertical, Horizontal}, theme 
+};
+use iced_native::widget::column;
+
+#[derive(Default)]
+pub struct Expander
+{
+    pub expanded: bool
+}
+
+#[derive(Clone, Copy, Debug)]
+pub enum ExpanderMsg {
+    Expand,
+}
+
+impl Expander {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn render<'a, T>(&self, children: Vec<Element<'a, T>>) -> Element<'a, T> 
+        where T: Clone + From<ExpanderMsg> + 'static
+    {
+        let title = text("Title")
+            .size(18)
+            .vertical_alignment(Vertical::Center)
+            .horizontal_alignment(Horizontal::Center)
+            .into();
+        let subtitle = iced::widget::text("Subtitle")
+            .size(14)
+            .vertical_alignment(Vertical::Center)
+            .horizontal_alignment(Horizontal::Center)
+            .into();
+        let header = column(
+            vec![title, subtitle]
+        ).into();
+        let space = horizontal_space(Length::Fill).into();
+        let icon = super::icon(
+            if self.expanded {
+                "go-down-symbolic"
+            } else {
+                "go-next-symbolic"
+            },
+            16
+        )
+        .apply(button)
+        .on_press(T::from(ExpanderMsg::Expand))
+        .width(Length::Units(25))
+        .into();
+    
+        container(
+            column(
+                if self.expanded {
+                    vec![
+                        row(vec![header, space, icon]).into(),
+                        container(
+                            Column::with_children(children)
+                        )
+                        .style(theme::Container::Transparent)
+                        .padding(5)
+                        .into()
+                    ]
+                } else {
+                    vec![row(vec![header, space, icon]).into()]
+                }
+            )
+            .padding(5)
+        )
+        .style(theme::Container::Box)
+        .into()
+    }
+}