htui 0.2.0

//! Box content-shape classification.
//!
//! [`BoxKind`] distinguishes a box's *content shape* — what it carries —
//! independently of the box's outer / inner display roles. A flex container
//! is still [`BoxKind::Normal`]; only its
//! [`crate::layout::LayoutBox::inner_formatting_context`] switches to
//! [`crate::layout::FormattingContext::Flex`].
//!
//! ## Variants
//!
//! - [`BoxKind::Normal`] — Regular block container.
//! - [`BoxKind::Replaced`] — Leaf whose content is supplied outside the DOM
//!   (an `<img>` rasterisation today; room for `<video>` / `<input>` later).
//! - [`BoxKind::Anonymous`] — Synthetic wrapper emitted by the layout engine
//!   itself.

/// Content payload of a [`BoxKind::Replaced`] box.
///
/// Browsers treat `<img>` as a *replaced element*: the box's content is
/// supplied by an external source (the image file) rather than by the box's
/// own subtree. The engine extends that model to the form controls, which
/// own their terminal chrome and interactive value instead of rendering a
/// subtree.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum ReplacedContent {
    /// `<img>` rasterized into a fixed-size grid of `cols` × `rows` cells.
    Image {
        path: String,
        cols: usize,
        rows: usize,
    },
    /// `<input>` — a single-line text field.
    ///
    /// Focused editing state lives in
    /// [`TermLayout::input_states`](crate::graphics::TermLayout::input_states);
    /// unfocused fields render from the DOM `value` attribute. The box only
    /// marks this as an input leaf so the paint phase knows to draw a field.
    Input,
    /// `<select>` — a single-line dropdown field. The options are read from
    /// the node's `<option>` children (see `select_options`); the currently
    /// selected value lives in the `value` attribute.
    Select,
    /// `<textarea>` — a multi-line editable field sized from its `cols` /
    /// `rows` attributes. The value is the node's text content (edited state
    /// lives in [`TermLayout::input_states`](crate::graphics::TermLayout::input_states));
    /// the paint phase draws the framed box with a caret.
    Textarea,
    /// `<button>` — a push-button: the node's text content painted inside a
    /// frame, with `disabled` dimming. Clicks dispatch to the button and
    /// `type=submit` / `reset` also fire on the containing form.
    Button,
}

/// Distinguishes the rendering shape of a layout box.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum BoxKind {
    /// Regular block container — has its own inline runs and a tree of nested
    /// block children. The vast majority of boxes (every block element that
    /// is not a replaced leaf) fall into this category.
    Normal,
    /// Replaced element: leaf whose content is not in the DOM. Currently only
    /// `<img>`. Carries its own [`ReplacedContent`] payload.
    Replaced(ReplacedContent),
    /// Anonymous wrapper produced by the layout engine itself, e.g. to
    /// surround text children for a flex container or to hold an inline
    /// formatting context. The current engine doesn't emit these yet, but
    /// the variant exists so the type stays exhaustive.
    Anonymous,
}