use std::cmp::Ordering; use gpui::{AnyElement, IntoElement, Stateful};use smallvec::SmallVec; use crate::{prelude::*, BASE_REM_SIZE_IN_PX}; /// The position of a [`Tab`] within a list of tabs.#[derive(Debug, PartialEq, Eq, Clone, Copy)]pub enum TabPosition {    /// The tab is first in the list.    First,     /// The tab is in the middle of the list (i.e., it is not the first or last tab).    ///    /// The [`Ordering`] is where this tab is positioned with respect to the selected tab.    Middle(Ordering),     /// The tab is last in the list.    Last,} #[derive(Debug, PartialEq, Eq, Clone, Copy)]pub enum TabCloseSide {    Start,    End,} #[derive(IntoElement)]pub struct Tab {    div: Stateful<Div>,    selected: bool,    position: TabPosition,    close_side: TabCloseSide,    start_slot: Option<AnyElement>,    end_slot: Option<AnyElement>,    children: SmallVec<[AnyElement; 2]>,} impl Tab {    pub fn new(id: impl Into<ElementId>) -> Self {        let id = id.into();        Self {            div: div()                .id(id.clone())                .debug_selector(|| format!("TAB-{}", id)),            selected: false,            position: TabPosition::First,            close_side: TabCloseSide::End,            start_slot: None,            end_slot: None,            children: SmallVec::new(),        }    }     pub const CONTAINER_HEIGHT_IN_REMS: f32 = 29. / BASE_REM_SIZE_IN_PX;     const CONTENT_HEIGHT_IN_REMS: f32 = 28. / BASE_REM_SIZE_IN_PX;     pub fn position(mut self, position: TabPosition) -> Self {        self.position = position;        self    }     pub fn close_side(mut self, close_side: TabCloseSide) -> Self {        self.close_side = close_side;        self    }     pub fn start_slot<E: IntoElement>(mut self, element: impl Into<Option<E>>) -> Self {        self.start_slot = element.into().map(IntoElement::into_any_element);        self    }     pub fn end_slot<E: IntoElement>(mut self, element: impl Into<Option<E>>) -> Self {        self.end_slot = element.into().map(IntoElement::into_any_element);        self    }} impl InteractiveElement for Tab {    fn interactivity(&mut self) -> &mut gpui::Interactivity {        self.div.interactivity()    }} impl StatefulInteractiveElement for Tab {} impl Selectable for Tab {    fn selected(mut self, selected: bool) -> Self {        self.selected = selected;        self    }} impl ParentElement for Tab {    fn extend(&mut self, elements: impl IntoIterator<Item = AnyElement>) {        self.children.extend(elements)    }} impl RenderOnce for Tab {    #[allow(refining_impl_trait)]    fn render(self, cx: &mut WindowContext) -> Stateful<Div> {        let (text_color, tab_bg, _tab_hover_bg, _tab_active_bg) = match self.selected {            false => (                cx.theme().colors().text_muted,                cx.theme().colors().tab_inactive_background,                cx.theme().colors().ghost_element_hover,                cx.theme().colors().ghost_element_active,            ),            true => (                cx.theme().colors().text,                cx.theme().colors().tab_active_background,                cx.theme().colors().element_hover,                cx.theme().colors().element_active,            ),        };         let (start_slot, end_slot) = {            let start_slot = h_flex().size_3().justify_center().children(self.start_slot);             let end_slot = h_flex().size_3().justify_center().children(self.end_slot);             match self.close_side {                TabCloseSide::End => (start_slot, end_slot),                TabCloseSide::Start => (end_slot, start_slot),            }        };         self.div            .h(rems(Self::CONTAINER_HEIGHT_IN_REMS))            .bg(tab_bg)            .border_color(cx.theme().colors().border)            .map(|this| match self.position {                TabPosition::First => {                    if self.selected {                        this.pl_px().border_r_1().pb_px()                    } else {                        this.pl_px().pr_px().border_b_1()                    }                }                TabPosition::Last => {                    if self.selected {                        this.border_l_1().border_r_1().pb_px()                    } else {                        this.pr_px().pl_px().border_b_1().border_r_1()                    }                }                TabPosition::Middle(Ordering::Equal) => this.border_l_1().border_r_1().pb_px(),                TabPosition::Middle(Ordering::Less) => this.border_l_1().pr_px().border_b_1(),                TabPosition::Middle(Ordering::Greater) => this.border_r_1().pl_px().border_b_1(),            })            .cursor_pointer()            .child(                h_flex()                    .group("")                    .relative()                    .h(rems(Self::CONTENT_HEIGHT_IN_REMS))                    .px(crate::custom_spacing(cx, 4.))                    .gap(Spacing::Small.rems(cx))                    .text_color(text_color)                    .child(start_slot)                    .children(self.children)                    .child(end_slot),            )    }}