Element refinement passing on ui2

crates/ui2/src/components/checkbox.rs

@@ -1,4 +1,4 @@
-use gpui::{div, prelude::*, Component, Element, ElementId, Styled, ViewContext};
+use gpui::{div, prelude::*, Div, Element, ElementId, RenderOnce, Stateful, Styled, ViewContext};
 use std::sync::Arc;
 use theme2::ActiveTheme;
 
@@ -11,7 +11,7 @@ pub type CheckHandler<V> = Arc<dyn Fn(Selection, &mut V, &mut ViewContext<V>) +
 /// Checkboxes are used for multiple choices, not for mutually exclusive choices.
 /// Each checkbox works independently from other checkboxes in the list,
 /// therefore checking an additional box does not affect any other selections.
-#[derive(Component)]
+#[derive(RenderOnce)]
 pub struct Checkbox<V: 'static> {
     id: ElementId,
     checked: Selection,
@@ -19,6 +19,130 @@ pub struct Checkbox<V: 'static> {
     on_click: Option<CheckHandler<V>>,
 }
 
+impl<V: 'static> Component<V> for Checkbox<V> {
+    type Rendered = Stateful<V, Div<V>>;
+
+    fn render(self, view: &mut V, cx: &mut ViewContext<V>) -> Self::Rendered {
+        let group_id = format!("checkbox_group_{:?}", self.id);
+
+        let icon = match self.checked {
+            // When selected, we show a checkmark.
+            Selection::Selected => {
+                Some(
+                    IconElement::new(Icon::Check)
+                        .size(crate::IconSize::Small)
+                        .color(
+                            // If the checkbox is disabled we change the color of the icon.
+                            if self.disabled {
+                                TextColor::Disabled
+                            } else {
+                                TextColor::Selected
+                            },
+                        ),
+                )
+            }
+            // In an indeterminate state, we show a dash.
+            Selection::Indeterminate => {
+                Some(
+                    IconElement::new(Icon::Dash)
+                        .size(crate::IconSize::Small)
+                        .color(
+                            // If the checkbox is disabled we change the color of the icon.
+                            if self.disabled {
+                                TextColor::Disabled
+                            } else {
+                                TextColor::Selected
+                            },
+                        ),
+                )
+            }
+            // When unselected, we show nothing.
+            Selection::Unselected => None,
+        };
+
+        // A checkbox could be in an indeterminate state,
+        // for example the indeterminate state could represent:
+        //  - a group of options of which only some are selected
+        //  - an enabled option that is no longer available
+        //  - a previously agreed to license that has been updated
+        //
+        // For the sake of styles we treat the indeterminate state as selected,
+        // but it's icon will be different.
+        let selected =
+            self.checked == Selection::Selected || self.checked == Selection::Indeterminate;
+
+        // We could use something like this to make the checkbox background when selected:
+        //
+        // ~~~rust
+        // ...
+        // .when(selected, |this| {
+        //     this.bg(cx.theme().colors().element_selected)
+        // })
+        // ~~~
+        //
+        // But we use a match instead here because the checkbox might be disabled,
+        // and it could be disabled _while_ it is selected, as well as while it is not selected.
+        let (bg_color, border_color) = match (self.disabled, selected) {
+            (true, _) => (
+                cx.theme().colors().ghost_element_disabled,
+                cx.theme().colors().border_disabled,
+            ),
+            (false, true) => (
+                cx.theme().colors().element_selected,
+                cx.theme().colors().border,
+            ),
+            (false, false) => (
+                cx.theme().colors().element_background,
+                cx.theme().colors().border,
+            ),
+        };
+
+        div()
+            .id(self.id)
+            // Rather than adding `px_1()` to add some space around the checkbox,
+            // we use a larger parent element to create a slightly larger
+            // click area for the checkbox.
+            .size_5()
+            // Because we've enlarged the click area, we need to create a
+            // `group` to pass down interactivity events to the checkbox.
+            .group(group_id.clone())
+            .child(
+                div()
+                    .flex()
+                    // This prevent the flex element from growing
+                    // or shrinking in response to any size changes
+                    .flex_none()
+                    // The combo of `justify_center()` and `items_center()`
+                    // is used frequently to center elements in a flex container.
+                    //
+                    // We use this to center the icon in the checkbox.
+                    .justify_center()
+                    .items_center()
+                    .m_1()
+                    .size_4()
+                    .rounded_sm()
+                    .bg(bg_color)
+                    .border()
+                    .border_color(border_color)
+                    // We only want the interactivity states to fire when we
+                    // are in a checkbox that isn't disabled.
+                    .when(!self.disabled, |this| {
+                        // Here instead of `hover()` we use `group_hover()`
+                        // to pass it the group id.
+                        this.group_hover(group_id.clone(), |el| {
+                            el.bg(cx.theme().colors().element_hover)
+                        })
+                    })
+                    .children(icon),
+            )
+            .when_some(
+                self.on_click.filter(|_| !self.disabled),
+                |this, on_click| {
+                    this.on_click(move |view, _, cx| on_click(self.checked.inverse(), view, cx))
+                },
+            )
+    }
+}
 impl<V: 'static> Checkbox<V> {
     pub fn new(id: impl Into<ElementId>, checked: Selection) -> Self {
         Self {
@@ -175,7 +299,7 @@ mod stories {
 
     pub struct CheckboxStory;
 
-    impl Render for CheckboxStory {
+    impl Render<Self> for CheckboxStory {
         type Element = Div<Self>;
 
         fn render(&mut self, cx: &mut ViewContext<Self>) -> Self::Element {