gpui_component/dock/

tab_panel.rs

use std::sync::Arc;

use gpui::{
    div, prelude::FluentBuilder, px, relative, rems, App, AppContext, Context, Corner,
    DismissEvent, Div, DragMoveEvent, Empty, Entity, EventEmitter, FocusHandle, Focusable,
    InteractiveElement as _, IntoElement, ParentElement, Pixels, Render, ScrollHandle,
    SharedString, StatefulInteractiveElement, StyleRefinement, Styled, WeakEntity, Window,
};
use rust_i18n::t;

use crate::{
    button::{Button, ButtonVariants as _},
    dock::PanelInfo,
    h_flex,
    menu::{DropdownMenu, PopupMenu},
    tab::{Tab, TabBar},
    v_flex, ActiveTheme, AxisExt, IconName, Placement, Selectable, Sizable,
};

use super::{
    ClosePanel, DockArea, DockPlacement, Panel, PanelControl, PanelEvent, PanelState, PanelStyle,
    PanelView, StackPanel, ToggleZoom,
};

#[derive(Clone)]
struct TabState {
    closable: bool,
    zoomable: Option<PanelControl>,
    draggable: bool,
    droppable: bool,
    active_panel: Option<Arc<dyn PanelView>>,
}

#[derive(Clone)]
pub(crate) struct DragPanel {
    pub(crate) panel: Arc<dyn PanelView>,
    pub(crate) tab_panel: Entity<TabPanel>,
}

impl DragPanel {
    pub(crate) fn new(panel: Arc<dyn PanelView>, tab_panel: Entity<TabPanel>) -> Self {
        Self { panel, tab_panel }
    }
}

impl Render for DragPanel {
    fn render(&mut self, window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
        div()
            .id("drag-panel")
            .cursor_grab()
            .py_1()
            .px_3()
            .w_24()
            .overflow_hidden()
            .whitespace_nowrap()
            .border_1()
            .border_color(cx.theme().border)
            .rounded(cx.theme().radius)
            .text_color(cx.theme().tab_foreground)
            .bg(cx.theme().tab_active)
            .opacity(0.75)
            .child(self.panel.title(window, cx))
    }
}

pub struct TabPanel {
    focus_handle: FocusHandle,
    dock_area: WeakEntity<DockArea>,
    /// The stock_panel can be None, if is None, that means the panels can't be split or move
    stack_panel: Option<WeakEntity<StackPanel>>,
    pub(crate) panels: Vec<Arc<dyn PanelView>>,
    pub(crate) active_ix: usize,
    /// If this is true, the Panel closable will follow the active panel's closable,
    /// otherwise this TabPanel will not able to close
    ///
    /// This is used for Dock to limit the last TabPanel not able to close, see [`super::Dock::new`].
    pub(crate) closable: bool,

    tab_bar_scroll_handle: ScrollHandle,
    zoomed: bool,
    collapsed: bool,
    /// When drag move, will get the placement of the panel to be split
    will_split_placement: Option<Placement>,
    /// Is TabPanel used in Tiles.
    in_tiles: bool,
}

impl Panel for TabPanel {
    fn panel_name(&self) -> &'static str {
        "TabPanel"
    }

    fn title(&self, window: &Window, cx: &App) -> gpui::AnyElement {
        self.active_panel(cx)
            .map(|panel| panel.title(window, cx))
            .unwrap_or("Empty Tab".into_any_element())
    }

    fn closable(&self, cx: &App) -> bool {
        if !self.closable {
            return false;
        }

        self.active_panel(cx)
            .map(|panel| panel.closable(cx))
            .unwrap_or(false)
    }

    fn zoomable(&self, cx: &App) -> Option<PanelControl> {
        self.active_panel(cx).and_then(|panel| panel.zoomable(cx))
    }

    fn visible(&self, cx: &App) -> bool {
        self.visible_panels(cx).next().is_some()
    }

    fn dropdown_menu(&self, menu: PopupMenu, window: &Window, cx: &App) -> PopupMenu {
        if let Some(panel) = self.active_panel(cx) {
            panel.dropdown_menu(menu, window, cx)
        } else {
            menu
        }
    }

    fn toolbar_buttons(&self, window: &mut Window, cx: &mut App) -> Option<Vec<Button>> {
        self.active_panel(cx)
            .and_then(|panel| panel.toolbar_buttons(window, cx))
    }

    fn dump(&self, cx: &App) -> PanelState {
        let mut state = PanelState::new(self);
        for panel in self.panels.iter() {
            state.add_child(panel.dump(cx));
            state.info = PanelInfo::tabs(self.active_ix);
        }
        state
    }

    fn inner_padding(&self, cx: &App) -> bool {
        self.active_panel(cx)
            .map_or(true, |panel| panel.inner_padding(cx))
    }
}

impl TabPanel {
    pub fn new(
        stack_panel: Option<WeakEntity<StackPanel>>,
        dock_area: WeakEntity<DockArea>,
        _: &mut Window,
        cx: &mut Context<Self>,
    ) -> Self {
        Self {
            focus_handle: cx.focus_handle(),
            dock_area,
            stack_panel,
            panels: Vec::new(),
            active_ix: 0,
            tab_bar_scroll_handle: ScrollHandle::new(),
            will_split_placement: None,
            zoomed: false,
            collapsed: false,
            closable: true,
            in_tiles: false,
        }
    }

    /// Mark the TabPanel as being used in Tiles.
    pub(super) fn set_in_tiles(&mut self, in_tiles: bool) {
        self.in_tiles = in_tiles;
    }

    pub(super) fn set_parent(&mut self, view: WeakEntity<StackPanel>) {
        self.stack_panel = Some(view);
    }

    /// Return current active_panel View
    pub fn active_panel(&self, cx: &App) -> Option<Arc<dyn PanelView>> {
        let panel = self.panels.get(self.active_ix);

        if let Some(panel) = panel {
            if panel.visible(cx) {
                Some(panel.clone())
            } else {
                // Return the first visible panel
                self.visible_panels(cx).next()
            }
        } else {
            None
        }
    }

    fn set_active_ix(&mut self, ix: usize, window: &mut Window, cx: &mut Context<Self>) {
        if ix == self.active_ix {
            return;
        }

        let last_active_ix = self.active_ix;

        self.active_ix = ix;
        self.tab_bar_scroll_handle.scroll_to_item(ix);
        self.focus_active_panel(window, cx);

        // Sync the active state to all panels
        cx.spawn_in(window, async move |view, cx| {
            _ = cx.update(|window, cx| {
                _ = view.update(cx, |view, cx| {
                    if let Some(last_active) = view.panels.get(last_active_ix) {
                        last_active.set_active(false, window, cx);
                    }
                    if let Some(active) = view.panels.get(view.active_ix) {
                        active.set_active(true, window, cx);
                    }
                });
            });
        })
        .detach();

        cx.emit(PanelEvent::LayoutChanged);
        cx.notify();
    }

    /// Add a panel to the end of the tabs
    pub fn add_panel(
        &mut self,
        panel: Arc<dyn PanelView>,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        self.add_panel_with_active(panel, true, window, cx);
    }

    fn add_panel_with_active(
        &mut self,
        panel: Arc<dyn PanelView>,
        active: bool,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        assert_ne!(
            panel.panel_name(cx),
            "StackPanel",
            "can not allows add `StackPanel` to `TabPanel`"
        );

        if self
            .panels
            .iter()
            .any(|p| p.view().entity_id() == panel.view().entity_id())
        {
            return;
        }

        self.panels.push(panel);
        // set the active panel to the new panel
        if active {
            self.set_active_ix(self.panels.len() - 1, window, cx);
        }
        cx.emit(PanelEvent::LayoutChanged);
        cx.notify();
    }

    /// Add panel to try to split
    pub fn add_panel_at(
        &mut self,
        panel: Arc<dyn PanelView>,
        placement: Placement,
        size: Option<Pixels>,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        cx.spawn_in(window, async move |view, cx| {
            cx.update(|window, cx| {
                view.update(cx, |view, cx| {
                    view.will_split_placement = Some(placement);
                    view.split_panel(panel, placement, size, window, cx)
                })
                .ok()
            })
            .ok()
        })
        .detach();
        cx.emit(PanelEvent::LayoutChanged);
        cx.notify();
    }

    fn insert_panel_at(
        &mut self,
        panel: Arc<dyn PanelView>,
        ix: usize,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        if self
            .panels
            .iter()
            .any(|p| p.view().entity_id() == panel.view().entity_id())
        {
            return;
        }

        self.panels.insert(ix, panel);
        self.set_active_ix(ix, window, cx);
        cx.emit(PanelEvent::LayoutChanged);
        cx.notify();
    }

    /// Remove a panel from the tab panel
    pub fn remove_panel(
        &mut self,
        panel: Arc<dyn PanelView>,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        self.detach_panel(panel, window, cx);
        self.remove_self_if_empty(window, cx);
        cx.emit(PanelEvent::ZoomOut);
        cx.emit(PanelEvent::LayoutChanged);
    }

    fn detach_panel(
        &mut self,
        panel: Arc<dyn PanelView>,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        let panel_view = panel.view();
        self.panels.retain(|p| p.view() != panel_view);
        if self.active_ix >= self.panels.len() {
            self.set_active_ix(self.panels.len().saturating_sub(1), window, cx)
        }
    }

    /// Check to remove self from the parent StackPanel, if there is no panel left
    fn remove_self_if_empty(&self, window: &mut Window, cx: &mut Context<Self>) {
        if !self.panels.is_empty() {
            return;
        }

        let tab_view = cx.entity().clone();
        if let Some(stack_panel) = self.stack_panel.as_ref() {
            _ = stack_panel.update(cx, |view, cx| {
                view.remove_panel(Arc::new(tab_view), window, cx);
            });
        }
    }

    pub(super) fn set_collapsed(
        &mut self,
        collapsed: bool,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        self.collapsed = collapsed;
        if let Some(panel) = self.panels.get(self.active_ix) {
            panel.set_active(!collapsed, window, cx);
        }
        cx.notify();
    }

    fn is_locked(&self, cx: &App) -> bool {
        let Some(dock_area) = self.dock_area.upgrade() else {
            return true;
        };

        if dock_area.read(cx).is_locked() {
            return true;
        }

        if self.zoomed {
            return true;
        }

        self.stack_panel.is_none()
    }

    /// Return true if self or parent only have last panel.
    fn is_last_panel(&self, cx: &App) -> bool {
        if let Some(parent) = &self.stack_panel {
            if let Some(stack_panel) = parent.upgrade() {
                if !stack_panel.read(cx).is_last_panel(cx) {
                    return false;
                }
            }
        }

        self.panels.len() <= 1
    }

    /// Return all visible panels
    fn visible_panels<'a>(&'a self, cx: &'a App) -> impl Iterator<Item = Arc<dyn PanelView>> + 'a {
        self.panels.iter().filter_map(|panel| {
            if panel.visible(cx) {
                Some(panel.clone())
            } else {
                None
            }
        })
    }

    /// Return true if the tab panel is draggable.
    ///
    /// E.g. if the parent and self only have one panel, it is not draggable.
    fn draggable(&self, cx: &App) -> bool {
        !self.is_locked(cx) && !self.is_last_panel(cx)
    }

    /// Return true if the tab panel is droppable.
    ///
    /// E.g. if the tab panel is locked, it is not droppable.
    fn droppable(&self, cx: &App) -> bool {
        !self.is_locked(cx)
    }

    fn render_toolbar(
        &self,
        state: &TabState,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) -> impl IntoElement {
        if self.collapsed {
            return div();
        }

        let zoomed = self.zoomed;
        let view = cx.entity().clone();
        let zoomable_toolbar_visible = state.zoomable.map_or(false, |v| v.toolbar_visible());

        h_flex()
            .gap_1()
            .occlude()
            .when_some(self.toolbar_buttons(window, cx), |this, buttons| {
                this.children(
                    buttons
                        .into_iter()
                        .map(|btn| btn.xsmall().ghost().tab_stop(false)),
                )
            })
            .map(|this| {
                let value = if zoomed {
                    Some(("zoom-out", IconName::Minimize, t!("Dock.Zoom Out")))
                } else if zoomable_toolbar_visible {
                    Some(("zoom-in", IconName::Maximize, t!("Dock.Zoom In")))
                } else {
                    None
                };

                if let Some((id, icon, tooltip)) = value {
                    this.child(
                        Button::new(id)
                            .icon(icon)
                            .xsmall()
                            .ghost()
                            .tab_stop(false)
                            .tooltip_with_action(tooltip, &ToggleZoom, None)
                            .when(zoomed, |this| this.selected(true))
                            .on_click(cx.listener(|view, _, window, cx| {
                                view.on_action_toggle_zoom(&ToggleZoom, window, cx)
                            })),
                    )
                } else {
                    this
                }
            })
            .child(
                Button::new("menu")
                    .icon(IconName::Ellipsis)
                    .xsmall()
                    .ghost()
                    .tab_stop(false)
                    .dropdown_menu({
                        let zoomable = state.zoomable.map_or(false, |v| v.menu_visible());
                        let closable = state.closable;

                        move |this, window, cx| {
                            view.read(cx)
                                .dropdown_menu(this, window, cx)
                                .separator()
                                .menu_with_disabled(
                                    if zoomed {
                                        t!("Dock.Zoom Out")
                                    } else {
                                        t!("Dock.Zoom In")
                                    },
                                    Box::new(ToggleZoom),
                                    !zoomable,
                                )
                                .when(closable, |this| {
                                    this.separator()
                                        .menu(t!("Dock.Close"), Box::new(ClosePanel))
                                })
                        }
                    })
                    .anchor(Corner::TopRight),
            )
    }

    fn render_dock_toggle_button(
        &self,
        placement: DockPlacement,
        _: &mut Window,
        cx: &mut Context<Self>,
    ) -> Option<impl IntoElement> {
        if self.zoomed {
            return None;
        }

        let dock_area = self.dock_area.upgrade()?.read(cx);
        if !dock_area.toggle_button_visible {
            return None;
        }
        if !dock_area.is_dock_collapsible(placement, cx) {
            return None;
        }

        let view_entity_id = cx.entity().entity_id();
        let toggle_button_panels = dock_area.toggle_button_panels;

        // Check if current TabPanel's entity_id matches the one stored in DockArea for this placement
        if !match placement {
            DockPlacement::Left => {
                dock_area.left_dock.is_some() && toggle_button_panels.left == Some(view_entity_id)
            }
            DockPlacement::Right => {
                dock_area.right_dock.is_some() && toggle_button_panels.right == Some(view_entity_id)
            }
            DockPlacement::Bottom => {
                dock_area.bottom_dock.is_some()
                    && toggle_button_panels.bottom == Some(view_entity_id)
            }
            DockPlacement::Center => unreachable!(),
        } {
            return None;
        }

        let is_open = dock_area.is_dock_open(placement, cx);

        let icon = match placement {
            DockPlacement::Left => {
                if is_open {
                    IconName::PanelLeft
                } else {
                    IconName::PanelLeftOpen
                }
            }
            DockPlacement::Right => {
                if is_open {
                    IconName::PanelRight
                } else {
                    IconName::PanelRightOpen
                }
            }
            DockPlacement::Bottom => {
                if is_open {
                    IconName::PanelBottom
                } else {
                    IconName::PanelBottomOpen
                }
            }
            DockPlacement::Center => unreachable!(),
        };

        Some(
            Button::new(SharedString::from(format!("toggle-dock:{:?}", placement)))
                .icon(icon)
                .xsmall()
                .ghost()
                .tab_stop(false)
                .tooltip(match is_open {
                    true => t!("Dock.Collapse"),
                    false => t!("Dock.Expand"),
                })
                .on_click(cx.listener({
                    let dock_area = self.dock_area.clone();
                    move |_, _, window, cx| {
                        _ = dock_area.update(cx, |dock_area, cx| {
                            dock_area.toggle_dock(placement, window, cx);
                        });
                    }
                })),
        )
    }

    fn render_title_bar(
        &self,
        state: &TabState,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) -> impl IntoElement {
        let view = cx.entity().clone();

        let Some(dock_area) = self.dock_area.upgrade() else {
            return div().into_any_element();
        };
        let panel_style = dock_area.read(cx).panel_style;

        let left_dock_button = self.render_dock_toggle_button(DockPlacement::Left, window, cx);
        let bottom_dock_button = self.render_dock_toggle_button(DockPlacement::Bottom, window, cx);
        let right_dock_button = self.render_dock_toggle_button(DockPlacement::Right, window, cx);

        let is_bottom_dock = bottom_dock_button.is_some();

        if self.panels.len() == 1 && panel_style == PanelStyle::Default {
            let panel = self.panels.get(0).unwrap();

            if !panel.visible(cx) {
                return div().into_any_element();
            }

            let title_style = panel.title_style(cx);

            return h_flex()
                .justify_between()
                .line_height(rems(1.0))
                .h(px(30.))
                .py_2()
                .pl_3()
                .pr_2()
                .when(left_dock_button.is_some(), |this| this.pl_2())
                .when(right_dock_button.is_some(), |this| this.pr_2())
                .when_some(title_style, |this, theme| {
                    this.bg(theme.background).text_color(theme.foreground)
                })
                .when(
                    left_dock_button.is_some() || bottom_dock_button.is_some(),
                    |this| {
                        this.child(
                            h_flex()
                                .flex_shrink_0()
                                .mr_1()
                                .gap_1()
                                .children(left_dock_button)
                                .children(bottom_dock_button),
                        )
                    },
                )
                .child(
                    div()
                        .id("tab")
                        .flex_1()
                        .min_w_16()
                        .overflow_hidden()
                        .text_ellipsis()
                        .whitespace_nowrap()
                        .child(panel.title(window, cx))
                        .when(state.draggable, |this| {
                            this.on_drag(
                                DragPanel {
                                    panel: panel.clone(),
                                    tab_panel: view,
                                },
                                |drag, _, _, cx| {
                                    cx.stop_propagation();
                                    cx.new(|_| drag.clone())
                                },
                            )
                        }),
                )
                .children(panel.title_suffix(window, cx))
                .child(
                    h_flex()
                        .flex_shrink_0()
                        .ml_1()
                        .gap_1()
                        .child(self.render_toolbar(&state, window, cx))
                        .children(right_dock_button),
                )
                .into_any_element();
        }

        let tabs_count = self.panels.len();

        TabBar::new("tab-bar")
            .tab_item_top_offset(-px(1.))
            .track_scroll(&self.tab_bar_scroll_handle)
            .when(
                left_dock_button.is_some() || bottom_dock_button.is_some(),
                |this| {
                    this.prefix(
                        h_flex()
                            .items_center()
                            .top_0()
                            // Right -1 for avoid border overlap with the first tab
                            .right(-px(1.))
                            .border_r_1()
                            .border_b_1()
                            .h_full()
                            .border_color(cx.theme().border)
                            .bg(cx.theme().tab_bar)
                            .px_2()
                            .children(left_dock_button)
                            .children(bottom_dock_button),
                    )
                },
            )
            .children(self.panels.iter().enumerate().filter_map(|(ix, panel)| {
                let mut active = state.active_panel.as_ref() == Some(panel);
                let droppable = self.collapsed;

                if !panel.visible(cx) {
                    return None;
                }

                // Always not show active tab style, if the panel is collapsed
                if self.collapsed {
                    active = false;
                }

                Some(
                    Tab::default()
                        .map(|this| {
                            if let Some(tab_name) = panel.tab_name(cx) {
                                this.child(tab_name)
                            } else {
                                this.child(panel.title(window, cx))
                            }
                        })
                        .selected(active)
                        .on_click(cx.listener({
                            let is_collapsed = self.collapsed;
                            let dock_area = self.dock_area.clone();
                            move |view, _, window, cx| {
                                view.set_active_ix(ix, window, cx);

                                // Open dock if clicked on the collapsed bottom dock
                                if is_bottom_dock && is_collapsed {
                                    _ = dock_area.update(cx, |dock_area, cx| {
                                        dock_area.toggle_dock(DockPlacement::Bottom, window, cx);
                                    });
                                }
                            }
                        }))
                        .when(!droppable, |this| {
                            this.when(state.draggable, |this| {
                                this.on_drag(
                                    DragPanel::new(panel.clone(), view.clone()),
                                    |drag, _, _, cx| {
                                        cx.stop_propagation();
                                        cx.new(|_| drag.clone())
                                    },
                                )
                            })
                            .when(state.droppable, |this| {
                                this.drag_over::<DragPanel>(|this, _, _, cx| {
                                    this.rounded_l_none()
                                        .border_l_2()
                                        .border_r_0()
                                        .border_color(cx.theme().drag_border)
                                })
                                .on_drop(cx.listener(
                                    move |this, drag: &DragPanel, window, cx| {
                                        this.will_split_placement = None;
                                        this.on_drop(drag, Some(ix), true, window, cx)
                                    },
                                ))
                            })
                        }),
                )
            }))
            .last_empty_space(
                // empty space to allow move to last tab right
                div()
                    .id("tab-bar-empty-space")
                    .h_full()
                    .flex_grow()
                    .min_w_16()
                    .when(state.droppable, |this| {
                        this.drag_over::<DragPanel>(|this, _, _, cx| {
                            this.bg(cx.theme().drop_target)
                        })
                        .on_drop(cx.listener(
                            move |this, drag: &DragPanel, window, cx| {
                                this.will_split_placement = None;

                                let ix = if drag.tab_panel == view {
                                    Some(tabs_count - 1)
                                } else {
                                    None
                                };

                                this.on_drop(drag, ix, false, window, cx)
                            },
                        ))
                    }),
            )
            .when(!self.collapsed, |this| {
                this.suffix(
                    h_flex()
                        .items_center()
                        .top_0()
                        .right_0()
                        .border_l_1()
                        .border_b_1()
                        .h_full()
                        .border_color(cx.theme().border)
                        .bg(cx.theme().tab_bar)
                        .px_2()
                        .gap_1()
                        .children(
                            self.active_panel(cx)
                                .and_then(|panel| panel.title_suffix(window, cx)),
                        )
                        .child(self.render_toolbar(state, window, cx))
                        .when_some(right_dock_button, |this, btn| this.child(btn)),
                )
            })
            .into_any_element()
    }

    fn render_active_panel(
        &self,
        state: &TabState,
        _: &mut Window,
        cx: &mut Context<Self>,
    ) -> impl IntoElement {
        if self.collapsed {
            return Empty {}.into_any_element();
        }

        let Some(active_panel) = state.active_panel.as_ref() else {
            return Empty {}.into_any_element();
        };

        let is_render_in_tabs = self.panels.len() > 1 && self.inner_padding(cx);

        v_flex()
            .id("active-panel")
            .group("")
            .flex_1()
            .when(is_render_in_tabs, |this| this.pt_2())
            .child(
                div()
                    .id("tab-content")
                    .overflow_y_scroll()
                    .overflow_x_hidden()
                    .flex_1()
                    .child(
                        active_panel
                            .view()
                            .cached(StyleRefinement::default().absolute().size_full()),
                    ),
            )
            .when(state.droppable, |this| {
                this.on_drag_move(cx.listener(Self::on_panel_drag_move))
                    .child(
                        div()
                            .invisible()
                            .absolute()
                            .bg(cx.theme().drop_target)
                            .map(|this| match self.will_split_placement {
                                Some(placement) => {
                                    let size = relative(0.5);
                                    match placement {
                                        Placement::Left => this.left_0().top_0().bottom_0().w(size),
                                        Placement::Right => {
                                            this.right_0().top_0().bottom_0().w(size)
                                        }
                                        Placement::Top => this.top_0().left_0().right_0().h(size),
                                        Placement::Bottom => {
                                            this.bottom_0().left_0().right_0().h(size)
                                        }
                                    }
                                }
                                None => this.top_0().left_0().size_full(),
                            })
                            .group_drag_over::<DragPanel>("", |this| this.visible())
                            .on_drop(cx.listener(|this, drag: &DragPanel, window, cx| {
                                this.on_drop(drag, None, true, window, cx)
                            })),
                    )
            })
            .into_any_element()
    }

    /// Calculate the split direction based on the current mouse position
    fn on_panel_drag_move(
        &mut self,
        drag: &DragMoveEvent<DragPanel>,
        _: &mut Window,
        cx: &mut Context<Self>,
    ) {
        let bounds = drag.bounds;
        let position = drag.event.position;

        // Check the mouse position to determine the split direction
        if position.x < bounds.left() + bounds.size.width * 0.35 {
            self.will_split_placement = Some(Placement::Left);
        } else if position.x > bounds.left() + bounds.size.width * 0.65 {
            self.will_split_placement = Some(Placement::Right);
        } else if position.y < bounds.top() + bounds.size.height * 0.35 {
            self.will_split_placement = Some(Placement::Top);
        } else if position.y > bounds.top() + bounds.size.height * 0.65 {
            self.will_split_placement = Some(Placement::Bottom);
        } else {
            // center to merge into the current tab
            self.will_split_placement = None;
        }
        cx.notify()
    }

    /// Handle the drop event when dragging a panel
    ///
    /// - `active` - When true, the panel will be active after the drop
    fn on_drop(
        &mut self,
        drag: &DragPanel,
        ix: Option<usize>,
        active: bool,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        let panel = drag.panel.clone();
        let is_same_tab = drag.tab_panel == cx.entity();

        // If target is same tab, and it is only one panel, do nothing.
        if is_same_tab && ix.is_none() {
            if self.will_split_placement.is_none() {
                return;
            } else {
                if self.panels.len() == 1 {
                    return;
                }
            }
        }

        // Here is looks like remove_panel on a same item, but it difference.
        //
        // We must to split it to remove_panel, unless it will be crash by error:
        // Cannot update ui::dock::tab_panel::TabPanel while it is already being updated
        if is_same_tab {
            self.detach_panel(panel.clone(), window, cx);
        } else {
            let _ = drag.tab_panel.update(cx, |view, cx| {
                view.detach_panel(panel.clone(), window, cx);
                view.remove_self_if_empty(window, cx);
            });
        }

        // Insert into new tabs
        if let Some(placement) = self.will_split_placement {
            self.split_panel(panel, placement, None, window, cx);
        } else {
            if let Some(ix) = ix {
                self.insert_panel_at(panel, ix, window, cx)
            } else {
                self.add_panel_with_active(panel, active, window, cx)
            }
        }

        self.remove_self_if_empty(window, cx);
        cx.emit(PanelEvent::LayoutChanged);
    }

    /// Add panel with split placement
    fn split_panel(
        &self,
        panel: Arc<dyn PanelView>,
        placement: Placement,
        size: Option<Pixels>,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        let dock_area = self.dock_area.clone();
        // wrap the panel in a TabPanel
        let new_tab_panel = cx.new(|cx| Self::new(None, dock_area.clone(), window, cx));
        new_tab_panel.update(cx, |view, cx| {
            view.add_panel(panel, window, cx);
        });

        let stack_panel = match self.stack_panel.as_ref().and_then(|panel| panel.upgrade()) {
            Some(panel) => panel,
            None => return,
        };

        let parent_axis = stack_panel.read(cx).axis;

        let ix = stack_panel
            .read(cx)
            .index_of_panel(Arc::new(cx.entity().clone()))
            .unwrap_or_default();

        if parent_axis.is_vertical() && placement.is_vertical() {
            stack_panel.update(cx, |view, cx| {
                view.insert_panel_at(
                    Arc::new(new_tab_panel),
                    ix,
                    placement,
                    size,
                    dock_area.clone(),
                    window,
                    cx,
                );
            });
        } else if parent_axis.is_horizontal() && placement.is_horizontal() {
            stack_panel.update(cx, |view, cx| {
                view.insert_panel_at(
                    Arc::new(new_tab_panel),
                    ix,
                    placement,
                    size,
                    dock_area.clone(),
                    window,
                    cx,
                );
            });
        } else {
            // 1. Create new StackPanel with new axis
            // 2. Move cx.entity() from parent StackPanel to the new StackPanel
            // 3. Add the new TabPanel to the new StackPanel at the correct index
            // 4. Add new StackPanel to the parent StackPanel at the correct index
            let tab_panel = cx.entity().clone();

            // Try to use the old stack panel, not just create a new one, to avoid too many nested stack panels
            let new_stack_panel = if stack_panel.read(cx).panels_len() <= 1 {
                stack_panel.update(cx, |view, cx| {
                    view.remove_all_panels(window, cx);
                    view.set_axis(placement.axis(), window, cx);
                });
                stack_panel.clone()
            } else {
                cx.new(|cx| {
                    let mut panel = StackPanel::new(placement.axis(), window, cx);
                    panel.parent = Some(stack_panel.downgrade());
                    panel
                })
            };

            new_stack_panel.update(cx, |view, cx| match placement {
                Placement::Left | Placement::Top => {
                    view.add_panel(Arc::new(new_tab_panel), size, dock_area.clone(), window, cx);
                    view.add_panel(
                        Arc::new(tab_panel.clone()),
                        None,
                        dock_area.clone(),
                        window,
                        cx,
                    );
                }
                Placement::Right | Placement::Bottom => {
                    view.add_panel(
                        Arc::new(tab_panel.clone()),
                        None,
                        dock_area.clone(),
                        window,
                        cx,
                    );
                    view.add_panel(Arc::new(new_tab_panel), size, dock_area.clone(), window, cx);
                }
            });

            if stack_panel != new_stack_panel {
                stack_panel.update(cx, |view, cx| {
                    view.replace_panel(
                        Arc::new(tab_panel.clone()),
                        new_stack_panel.clone(),
                        window,
                        cx,
                    );
                });
            }

            cx.spawn_in(window, async move |_, cx| {
                cx.update(|window, cx| {
                    tab_panel.update(cx, |view, cx| view.remove_self_if_empty(window, cx))
                })
            })
            .detach()
        }

        cx.emit(PanelEvent::LayoutChanged);
    }

    fn focus_active_panel(&self, window: &mut Window, cx: &mut Context<Self>) {
        if let Some(active_panel) = self.active_panel(cx) {
            active_panel.focus_handle(cx).focus(window);
        }
    }

    fn on_action_toggle_zoom(
        &mut self,
        _: &ToggleZoom,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        if self.zoomable(cx).is_none() {
            return;
        }

        if !self.zoomed {
            cx.emit(PanelEvent::ZoomIn)
        } else {
            cx.emit(PanelEvent::ZoomOut)
        }
        self.zoomed = !self.zoomed;

        cx.spawn_in(window, {
            let zoomed = self.zoomed;
            async move |view, cx| {
                _ = cx.update(|window, cx| {
                    _ = view.update(cx, |view, cx| {
                        view.set_zoomed(zoomed, window, cx);
                    });
                });
            }
        })
        .detach();
    }

    fn on_action_close_panel(
        &mut self,
        _: &ClosePanel,
        window: &mut Window,
        cx: &mut Context<Self>,
    ) {
        if let Some(panel) = self.active_panel(cx) {
            self.remove_panel(panel, window, cx);
        }

        // Remove self from the parent DockArea.
        // This is ensure to remove from Tiles
        if self.panels.is_empty() && self.in_tiles {
            let tab_panel = Arc::new(cx.entity());
            window.defer(cx, {
                let dock_area = self.dock_area.clone();
                move |window, cx| {
                    _ = dock_area.update(cx, |this, cx| {
                        this.remove_panel_from_all_docks(tab_panel, window, cx);
                    });
                }
            });
        }
    }

    // Bind actions to the tab panel, only when the tab panel is not collapsed.
    fn bind_actions(&self, cx: &mut Context<Self>) -> Div {
        v_flex().when(!self.collapsed, |this| {
            this.on_action(cx.listener(Self::on_action_toggle_zoom))
                .on_action(cx.listener(Self::on_action_close_panel))
        })
    }
}

impl Focusable for TabPanel {
    fn focus_handle(&self, cx: &App) -> gpui::FocusHandle {
        if let Some(active_panel) = self.active_panel(cx) {
            active_panel.focus_handle(cx)
        } else {
            self.focus_handle.clone()
        }
    }
}
impl EventEmitter<DismissEvent> for TabPanel {}
impl EventEmitter<PanelEvent> for TabPanel {}
impl Render for TabPanel {
    fn render(&mut self, window: &mut Window, cx: &mut Context<Self>) -> impl gpui::IntoElement {
        let focus_handle = self.focus_handle(cx);
        let active_panel = self.active_panel(cx);
        let mut state = TabState {
            closable: self.closable(cx),
            draggable: self.draggable(cx),
            droppable: self.droppable(cx),
            zoomable: self.zoomable(cx),
            active_panel,
        };

        // 1. When is the final panel in the dock, it will not able to close.
        // 2. When is in the Tiles, it will always able to close (by active panel state).
        if !state.draggable && !self.in_tiles {
            state.closable = false;
        }

        self.bind_actions(cx)
            .id("tab-panel")
            .track_focus(&focus_handle)
            .tab_group()
            .size_full()
            .overflow_hidden()
            .bg(cx.theme().background)
            .child(self.render_title_bar(&state, window, cx))
            .child(self.render_active_panel(&state, window, cx))
    }
}