teksilo-widgets 0.9.0

// SPDX-License-Identifier: MPL-2.0
// SPDX-FileCopyrightText: 2026 FernTech

//! GroupBox — titled cluster of controls in Int UI / Jewel style.
//!
//! A bold title (optionally preceded by a checkbox) sits above an indented
//! content area. No border, no frame — pure composition. The standard use
//! is grouping related settings controls on a preferences sheet or
//! form — the IntelliJ "group" pattern.
//!
//! In checkable mode, unchecking disables event dispatch to every descendant
//! of the content area (via `ctx.enabled_when` with ancestor propagation) AND
//! paints a translucent surface overlay over the content so it reads as
//! greyed-out. The title checkbox itself stays interactive.
//!
//! ## When to use
//!
//! - **GroupBox** — logical cluster with a title; optional enable/disable
//!   toggle for the whole cluster. Use for settings sections.
//! - [`GroupHeader`](crate::GroupHeader) — lighter-weight "soft divider +
//!   caption" without a content slot; use to label regions that are not
//!   collapsed or disabled as a unit.
//!
//! ## Accessibility
//!
//! The box node carries `Role::Group` and its `name` is set to the title
//! string. When checkable and unchecked, `set_disabled()` is set on the
//! group node so assistive technology announces the cluster as unavailable.
//!
//! ```rust
//! # use teksilo_widgets::GroupBox;
//! # use teksilo_widgets::primitives::TextWidget;
//! # use teksilo_i18n::lit;
//! let _w = GroupBox::new(lit!("Indentation"))
//!     .child(TextWidget::new(lit!("Tab width: 4")));
//! ```

use teksilo_canvas::{Rect, Size, SizeProposal};
use teksilo_core::accessibility::AccessNodeBuilder;
use teksilo_core::binding::BindingLevel;
use teksilo_core::build_context::BuildContext;
use teksilo_core::signal::Signal;
use teksilo_core::widget::{LayoutContext, Widget, WidgetPlacement};
use teksilo_core::widget_id::WidgetId;

use crate::Checkbox;
use crate::primitives::{HStack, Padding, RectWidget, TextWidget, VStack, ZStack};
use teksilo_i18n::LocalizedString;
use teksilo_tokens::{TextRole, TextStyleRole};

/// Horizontal indent of the content area below the title (dp).
pub const GROUP_BOX_CONTENT_INDENT: f32 = 24.0;
/// Vertical gap between the title row and the content area (dp).
pub const GROUP_BOX_TITLE_CONTENT_SPACING: f32 = 8.0;
/// Gap between the checkbox and the adjacent title label in checkable mode (dp).
pub const GROUP_BOX_CHECKBOX_GAP: f32 = 6.0;

/// A titled cluster of controls with optional enable/disable toggle.
///
/// See the [module documentation](self) for the checkable-mode details and
/// the [`GroupHeader`](crate::GroupHeader) sibling.
pub struct GroupBox {
    title: LocalizedString,
    checked: Option<Signal<bool>>,
    pending_content: Option<Box<dyn Widget>>,
    content_id: Option<WidgetId>,
    root_child_id: Option<WidgetId>,
}

impl GroupBox {
    /// Create a non-checkable group box with the given `title`.
    pub fn new(title: impl Into<LocalizedString>) -> Self {
        let ls: LocalizedString = title.into();
        Self {
            title: ls,
            checked: None,
            pending_content: None,
            content_id: None,
            root_child_id: None,
        }
    }

    /// Turn this into a checkable GroupBox. When the signal is `false`, events
    /// to descendants of the content area are blocked via effective-enabled
    /// ancestor propagation. The title checkbox itself stays interactive.
    pub fn checkable(mut self, checked: Signal<bool>) -> Self {
        self.checked = Some(checked);
        self
    }

    /// Set the content widget inline (deferred insertion).
    pub fn child(mut self, widget: impl Widget + 'static) -> Self {
        self.pending_content = Some(Box::new(widget));
        self
    }

    /// Set the content widget by pre-registered ID.
    pub fn child_id(mut self, id: WidgetId) -> Self {
        self.content_id = Some(id);
        self
    }
}

impl std::fmt::Debug for GroupBox {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("GroupBox")
            .field("title", &self.title)
            .field("checkable", &self.checked.is_some())
            .finish()
    }
}

impl Widget for GroupBox {
    fn build(&mut self, ctx: &mut BuildContext) -> Vec<WidgetId> {
        if let Some(pending) = self.pending_content.take() {
            self.content_id = Some(ctx.add_boxed(pending));
        }

        // When checkable, refresh the group's own a11y node (set_disabled
        // tracks the unchecked state) without triggering a relayout.
        if let Some(ref checked) = self.checked {
            let self_id = ctx.self_id();
            checked.bind_to(
                self_id,
                ctx.binding_registry(),
                BindingLevel::AccessibilityOnly,
            );
        }

        let theme_signal = ctx.theme_signal();
        let _ = theme_signal.get();

        let title_label = TextWidget::new(self.title.clone())
            .style(TextStyleRole::BodyBold)
            .color(TextRole::Primary)
            .single_line()
            .a11y_hidden();

        let title_row_id = if let Some(ref checked) = self.checked {
            // The adjacent title text is `a11y_hidden`, so the checkbox must
            // carry the accessible name for the group's on/off state.
            let checkbox = Checkbox::new(checked.clone()).label(self.title.clone());
            ctx.add(
                HStack::new()
                    .spacing(GROUP_BOX_CHECKBOX_GAP)
                    .child(checkbox)
                    .child(title_label),
            )
        } else {
            ctx.add(title_label)
        };

        let padded_content_id = if let Some(content_id) = self.content_id {
            ctx.add(Padding::new(0.0, 0.0, 0.0, GROUP_BOX_CONTENT_INDENT).child_id(content_id))
        } else {
            ctx.add(Padding::new(0.0, 0.0, 0.0, GROUP_BOX_CONTENT_INDENT))
        };

        // When checkable and unchecked, lay a translucent surface tint over
        // the padded content so it reads as greyed-out. The dispatcher-level
        // ancestor-enabled check already blocks interaction; this overlay is
        // purely a visual cue.
        let content_wrapper_id = if let Some(ref checked) = self.checked {
            let dim_color = theme_signal.map(|t| t.colors.surface_main.with_alpha(0.6));
            let dim_overlay_id = ctx.add(RectWidget::new().background(dim_color));
            ctx.visible_when(dim_overlay_id, checked.map(|v| !*v));
            ctx.enabled_when(padded_content_id, checked.clone());
            ctx.add(
                ZStack::new()
                    .add_child(padded_content_id)
                    .add_child(dim_overlay_id),
            )
        } else {
            padded_content_id
        };

        let root = ctx.add(
            VStack::new()
                .spacing(GROUP_BOX_TITLE_CONTENT_SPACING)
                .add_child(title_row_id)
                .add_child(content_wrapper_id),
        );
        self.root_child_id = Some(root);

        vec![root]
    }

    fn layout_response(
        &self,
        proposal: SizeProposal,
        ctx: &LayoutContext,
    ) -> teksilo_core::widget::LayoutResponse {
        if let Some(root) = self.root_child_id
            && let Some(size) = ctx.child_size(root, proposal)
        {
            return (size).into();
        }
        proposal.resolve(0.0, 0.0).into()
    }

    fn place_children(
        &self,
        bounds: Rect,
        _proposal: SizeProposal,
        children: &mut [WidgetPlacement],
        _ctx: &LayoutContext,
    ) {
        for child in children.iter_mut() {
            child.origin = teksilo_canvas::Point::new(bounds.x, bounds.y);
            child.size = Size::new(bounds.width, bounds.height);
        }
    }

    fn accessibility(&self, builder: &mut AccessNodeBuilder) {
        builder.set_role(teksilo_core::accesskit::Role::Group);
        builder.set_name(self.title.resolve_now());
        if let Some(ref checked) = self.checked
            && !checked.get()
        {
            builder.set_disabled();
        }
    }

    fn children(&self) -> Vec<WidgetId> {
        self.root_child_id.into_iter().collect()
    }
}