aetna_core/tree/

node.rs

//! Core [`El`] node data shape.

use crate::anim::Timing;
use crate::image::{Image, ImageFit};
use crate::layout::{LayoutFn, VirtualItems};
use crate::metrics::{ComponentSize, MetricsRole};
use crate::shader::ShaderBinding;
use crate::style::StyleProfile;

use super::color::Color;
use super::geometry::Sides;
use super::identity::HoverAlpha;
use super::layout_types::{Align, Axis, Justify, Size};
use super::semantics::{Kind, Source, SurfaceRole};
use super::text_types::{FontFamily, FontWeight, TextAlign, TextOverflow, TextRole, TextWrap};

/// The core tree node.
///
/// Construct via the component builders (`text`, `button`, `card`,
/// `column`, …) and chain modifiers (`.padding`, `.gap`, `.fill`, …).
/// Avoid building `El` directly — the builders set polished defaults.
///
/// `#[non_exhaustive]` — `El` is meant to be built through the
/// component constructors, not by struct-literal syntax. Direct
/// construction from outside this crate is intentionally disabled
/// so adding new layout/style fields stays a non-breaking change.
#[derive(Clone, Debug)]
#[non_exhaustive]
pub struct El {
    pub kind: Kind,
    pub style_profile: StyleProfile,
    pub key: Option<String>,
    pub block_pointer: bool,
    pub focusable: bool,
    /// Show the focus ring on this node even when focus arrived via
    /// pointer (i.e. the runtime's `focus_visible` is `false`). Default
    /// behavior matches the web platform's `:focus-visible` heuristic
    /// — ring on Tab, no ring on click. Widgets like text inputs and
    /// text areas opt in here because the ring is a meaningful
    /// "this surface is now the active editing target" affordance even
    /// when activated by mouse, beyond what the caret alone shows.
    pub always_show_focus_ring: bool,
    /// When true, this node is a pointer target for the library's
    /// text-selection manager: pointer-down inside its rect starts (or
    /// extends) the global [`crate::selection::Selection`] anchored at
    /// this node's `key`. The leaf must also carry an explicit
    /// `.key(...)` — same convention as focusable widgets — so the
    /// selection survives tree rebuilds.
    ///
    /// Set via [`Self::selectable`]. Coordinates with focus on a
    /// per-pointer-event basis: pointer-down on a focusable widget
    /// transfers focus and clears selection; pointer-down on a
    /// selectable-only leaf moves selection without disturbing focus.
    pub selectable: bool,
    /// When true, all key events (other than registered hotkeys) route
    /// to this node as raw `KeyDown` instead of being interpreted by
    /// the library's defaults (Tab traversal, Enter/Space activation,
    /// Escape escape). Used by text-input widgets that need to consume
    /// Tab/Enter/etc. as text or editing actions. Implies `focusable`
    /// at the runner — the flag only takes effect when the node is
    /// also the focused target.
    pub capture_keys: bool,
    /// When true, this node's paint opacity is multiplied by the
    /// nearest focusable ancestor's focus envelope (0..1). The library
    /// already animates that envelope on focus / blur; flagged nodes
    /// fade in and out with the same easing without any app-side
    /// focus tracking.
    ///
    /// Used by `text_input`'s caret bar — the caret only paints when
    /// the input is focused, fading via the standard focus animation.
    /// Documented in `widget_kit.md` as part of the public surface.
    pub alpha_follows_focused_ancestor: bool,
    /// When true, this node's paint opacity is also multiplied by the
    /// runtime's caret blink alpha. Combine with
    /// `alpha_follows_focused_ancestor` (the caret should blink only
    /// while the input is focused) — the two compose multiplicatively.
    /// Used by `text_input` / `text_area`'s caret bar.
    pub blink_when_focused: bool,
    /// When true, this node's hover and press visual envelopes are
    /// borrowed from its nearest focusable ancestor instead of being
    /// driven by its own (always-zero) envelope.
    ///
    /// The hit-test only ever resolves to a focusable target, so a
    /// child of an interactive container — a slider thumb, a select
    /// trigger's chevron, the dot inside a radio — never receives
    /// hover or press envelopes of its own. Flagged children pick up
    /// the ancestor's envelopes so they can lighten / darken / ring
    /// out alongside the surface that captured the input.
    ///
    /// Used by `slider`'s thumb so grabbing the slider visibly
    /// reacts on the thumb itself, mirroring shadcn's
    /// `hover:ring-4 hover:ring-ring/50`.
    pub state_follows_interactive_ancestor: bool,
    /// When `Some`, this node's paint opacity is bound to the
    /// **subtree interaction envelope** — `max` of the hover, focus,
    /// and press envelopes for the subtree rooted here. The drawn
    /// alpha interpolates from `rest` (no interaction anywhere in the
    /// subtree) to `peak` (full interaction), then composes
    /// multiplicatively with the existing [`Self::opacity`] /
    /// inherited opacity stack.
    ///
    /// "Interaction" includes hovering, pressing, or keyboard-focusing
    /// any descendant — so a hover-revealed close icon stays visible
    /// when its tab is keyboard-focused, and an action pill stays
    /// visible when the cursor moves to one of its focusable buttons.
    /// Mirrors CSS's "this element OR any descendant is hot."
    ///
    /// Layout-neutral — the element's geometry stays fixed regardless
    /// of interaction state. Use for hover-revealed close buttons,
    /// secondary actions on list rows, hover-only validation icons,
    /// and other "show on interaction" patterns whose visibility
    /// shouldn't shift the surrounding layout.
    pub hover_alpha: Option<HoverAlpha>,
    pub source: Source,

    // Layout
    pub axis: Axis,
    pub gap: f32,
    pub padding: Sides,
    pub align: Align,
    pub justify: Justify,
    pub width: Size,
    pub height: Size,
    /// Optional t-shirt size for stock widgets. `None` means the active
    /// theme supplies the component-class default.
    pub component_size: Option<ComponentSize>,
    /// Optional theme-facing metrics role. Stock widgets set this so
    /// the theme can resolve default height/padding/radius before
    /// layout; app-defined widgets can set the same role to opt into
    /// identical sizing behavior.
    pub metrics_role: Option<MetricsRole>,
    /// Author-overrode layout metrics. Stock constructors set defaults
    /// without these flags; public modifiers flip them so theme metrics
    /// do not clobber explicit app choices.
    pub explicit_width: bool,
    pub explicit_height: bool,
    pub explicit_padding: bool,
    pub explicit_gap: bool,
    pub explicit_radius: bool,
    pub explicit_font_family: bool,
    /// Author overrode the monospace font face for this node — theme
    /// application leaves [`Self::mono_font_family`] alone when set.
    pub explicit_mono_font_family: bool,
    /// Author opted this node into the monospace family via
    /// [`Self::mono`]. Role modifiers ([`Self::caption`], [`Self::label`],
    /// [`Self::body`], [`Self::title`], [`Self::heading`],
    /// [`Self::display`]) leave [`Self::font_mono`] alone when this flag
    /// is set, so the natural reading order `text(s).mono().caption()`
    /// keeps the mono family. Without this guard, role application
    /// silently resets `font_mono = false`. The [`Self::code`] role
    /// always forces `font_mono = true` regardless.
    pub explicit_mono: bool,

    // Visual style — these still live on `El` because the modifier API
    // (`.fill(c)`, `.radius(r)`, `.shadow(s)`) is what users type. The
    // renderer translates them into a [`ShaderBinding`] for
    // `stock::rounded_rect` (or whatever `shader_override` specifies)
    // when emitting [`crate::ir::DrawOp`]s.
    pub fill: Option<Color>,
    /// Alternate fill used when the nearest focusable ancestor's focus
    /// envelope is below 1.0; the painter linearly interpolates from
    /// `dim_fill` toward `fill` as the envelope approaches 1.0. Used by
    /// `text_input` / `text_area` selection bands so the highlight
    /// remains visible (in a muted color) even when the input loses
    /// focus, matching the macOS convention.
    pub dim_fill: Option<Color>,
    pub stroke: Option<Color>,
    pub stroke_width: f32,
    /// Corner radii in logical pixels. Authored as a scalar in the
    /// common case (`.radius(tokens::RADIUS_MD)` works via
    /// [`Corners::from`]); per-corner shapes use [`Corners::top`],
    /// [`Corners::bottom`], etc. The painter clamps each corner to
    /// half the shorter side.
    pub radius: super::geometry::Corners,
    pub shadow: f32,
    pub surface_role: SurfaceRole,
    /// Permit this element to paint outside its layout bounds. The
    /// outset enlarges the quad geometry handed to the shader (and
    /// any focus / shadow / glow visuals are positioned in the
    /// overflow band) while leaving the layout rect — and therefore
    /// sibling positions and hit-testing — unchanged. Subject to
    /// ancestor clip rects: a focused widget inside a `clip()`ped
    /// parent has its overflow clipped, same as any other paint.
    pub paint_overflow: Sides,
    /// Clip this element's own paint and descendants to its computed rect.
    /// Used by scroll panes, host-painted regions, overlays, and any region
    /// where overflow should not leak visually or receive events.
    pub clip: bool,
    /// This element is a vertical scroll viewport. The layout pass reads
    /// the offset from `UiState`'s scroll-offset side map keyed by
    /// `computed_id`, clamps it to `[0, content_h - viewport_h]`, and
    /// writes the clamped value back. Set automatically by [`crate::scroll`].
    pub scrollable: bool,
    /// When set on a [`Kind::Scroll`] container, the runtime tracks the
    /// "stick to bottom" pin used by chat logs and activity feeds: the
    /// scroll offset stays glued to the tail across content growth, the
    /// user can scroll up to break the pin, and scrolling back to the
    /// bottom re-engages it. No effect on non-scrollable nodes. Defaults
    /// to `false`; opt in with [`Self::pin_end`].
    ///
    /// Mirrors egui's `ScrollArea::stick_to_bottom(true)`. The "is the
    /// pin currently engaged" bit lives in
    /// [`crate::state::UiState`]'s scroll subsystem, keyed by
    /// `computed_id`; layout reads it each frame to decide whether to
    /// snap the stored offset to `max_offset` before clamping.
    pub pin_end: bool,
    /// Treat this element's focusable children as a single arrow-navigable
    /// group: while a focused element is one of the direct children,
    /// `Up` / `Down` / `Home` / `End` move focus among the group's
    /// focusable siblings instead of being routed as a `KeyDown`. Tab
    /// traversal is unchanged.
    ///
    /// Used by `popover_panel` so menu items in a dropdown are
    /// keyboard-navigable; available to any user widget that wants the
    /// same semantics.
    pub arrow_nav_siblings: bool,
    /// Tooltip text. When set, the runtime synthesizes a hover-driven
    /// tooltip layer anchored to this node — appearing after the
    /// hover delay elapses, fading in with the standard envelope, and
    /// dismissed when the pointer leaves or presses the node. The
    /// trigger doesn't have to be focusable or keyed; the runtime
    /// anchors the tooltip via the trigger's `computed_id`.
    pub tooltip: Option<String>,
    /// Pointer cursor declared for this element. `None` falls through
    /// to whatever an ancestor declared, else [`crate::cursor::Cursor::Default`].
    /// Resolution lives in [`crate::state::UiState::cursor`]: if a
    /// press is captured, the cursor follows the press target;
    /// otherwise the hovered node is walked root-ward for the first
    /// explicit declaration. Disabled state is *not* auto-mapped —
    /// widgets that want [`crate::cursor::Cursor::NotAllowed`] when disabled set it
    /// explicitly in their build closure.
    pub cursor: Option<crate::cursor::Cursor>,
    /// Cursor to show *only while a press is captured at this exact
    /// node*. Powers the natural Grab → Grabbing transition: the
    /// slider sets `cursor=Grab` + `cursor_pressed=Grabbing`, and the
    /// resolver picks the latter while the press anchors here. Unlike
    /// [`Self::cursor`], this does **not** walk up: an ancestor's
    /// `cursor_pressed` doesn't apply to a descendant press target.
    /// The press target's own `cursor` is the fallback when this is
    /// `None`.
    pub cursor_pressed: Option<crate::cursor::Cursor>,
    /// Override the implicit `stock::rounded_rect` binding for this
    /// node's surface. The escape hatch a user crate uses to bind a
    /// custom shader (e.g. `liquid_glass`).
    pub shader_override: Option<ShaderBinding>,
    /// Second escape hatch: author-supplied layout function that
    /// positions this node's direct children. When set, the layout
    /// pass calls the function instead of running its column/row/
    /// overlay distribution. The library still recurses into each
    /// child and still drives hit-test / focus / animation / scroll
    /// off the rects the function returns. See [`LayoutFn`] for the
    /// contract.
    pub layout_override: Option<LayoutFn>,
    /// Virtualized list state. Set by [`crate::virtual_list`] (and only
    /// on `Kind::VirtualList` nodes). The layout pass uses this to
    /// realize only the rows whose rect intersects the viewport. The
    /// node is automatically `scrollable` + `clip`.
    pub virtual_items: Option<VirtualItems>,
    /// Show a draggable vertical scrollbar thumb when this node is
    /// scrollable and its content overflows the viewport. The thumb
    /// overlays the right edge of the viewport — it does not reflow
    /// children. No effect on non-scrollable nodes. Defaults to
    /// `false`; the [`crate::scroll`] and [`crate::virtual_list`]
    /// constructors flip it on by default. Authors disable with
    /// [`Self::no_scrollbar`].
    pub scrollbar: bool,

    // Text
    pub text: Option<String>,
    pub text_color: Option<Color>,
    pub text_align: TextAlign,
    pub text_wrap: TextWrap,
    pub text_overflow: TextOverflow,
    pub text_role: TextRole,
    pub text_max_lines: Option<usize>,
    pub font_size: f32,
    pub line_height: f32,
    pub font_family: FontFamily,
    /// Monospace face used when [`Self::font_mono`] is set (or when the
    /// node carries [`TextRole::Code`]). Stamped by theme application
    /// from [`crate::Theme::mono_font_family`] unless the author set it
    /// explicitly via [`Self::mono_font_family`].
    pub mono_font_family: FontFamily,
    pub font_weight: FontWeight,
    pub font_mono: bool,
    /// Italic styling. Author-set via [`Self::italic`]; honoured when
    /// this El is a styled text leaf inside an [`Kind::Inlines`] parent
    /// and (best-effort) on standalone text Els.
    pub text_italic: bool,
    /// Underline styling. Author-set via [`Self::underline`].
    pub text_underline: bool,
    /// Strikethrough styling. Author-set via [`Self::strikethrough`].
    pub text_strikethrough: bool,
    /// Link target URL. When set on a text leaf inside [`Kind::Inlines`],
    /// the run renders as a link (themed) and runs sharing a URL group
    /// together for hit-test. Author-set via [`Self::link`].
    pub text_link: Option<String>,
    /// Inline-run background. When set on a text leaf inside
    /// [`Kind::Inlines`], the shaped span paints a solid quad behind
    /// its glyphs (one rect per line if the span wraps). No effect on
    /// standalone text Els — author wraps in a styled `row()` for
    /// chip-shaped surfaces. Author-set via [`Self::background`].
    pub text_bg: Option<Color>,

    // Icon
    pub icon: Option<crate::svg_icon::IconSource>,
    pub icon_stroke_width: f32,

    /// Raster image. When set together with [`Kind::Image`] (or any
    /// kind, though [`crate::image`] is the idiomatic builder) the
    /// `draw_ops` pass emits a [`crate::ir::DrawOp::Image`] projected
    /// per [`Self::image_fit`] and tinted by [`Self::image_tint`].
    /// Layout intrinsic is the image's natural pixel size when both
    /// `width` and `height` are `Hug`.
    pub image: Option<Image>,
    /// Multiply each sampled pixel by this colour (RGBA `[0..1]`). Most
    /// raster art wants `None` (no tint); set it for monochrome assets
    /// (icon-style PNGs) the app wants to recolour.
    pub image_tint: Option<Color>,
    /// How the image projects into the resolved rect. Defaults to
    /// `ImageFit::Contain` — preserves aspect ratio and letterboxes.
    pub image_fit: ImageFit,

    /// App-owned GPU texture source for [`Kind::Surface`] elements.
    /// Set via [`Self::surface_source`] (typically through the
    /// [`crate::tree::surface`] builder).
    pub surface_source: Option<crate::surface::SurfaceSource>,
    /// How the surface texture composes with widgets painted below it.
    /// Defaults to [`crate::surface::SurfaceAlpha::Premultiplied`].
    pub surface_alpha: crate::surface::SurfaceAlpha,
    /// How the surface texture projects into the resolved rect.
    /// Defaults to [`ImageFit::Fill`] — stretch to the rect, ignoring
    /// aspect ratio. `Contain` / `Cover` / `None` mirror the
    /// corresponding modes on [`crate::tree::image`].
    pub surface_fit: ImageFit,
    /// Affine applied to the texture quad in destination space, around
    /// the centre of the post-fit rect. Defaults to identity.
    /// Composes after [`Self::surface_fit`]: the fit projection picks
    /// the destination rect, then this matrix transforms it (rotate,
    /// scale, translate, shear). The auto-clip scissor still clamps
    /// to the El's content rect, so transforms that move the texture
    /// outside that rect are cropped.
    pub surface_transform: crate::affine::Affine2,

    /// Vector asset for [`Kind::Vector`] elements. Set via
    /// [`Self::vector_source`] (typically through the
    /// [`crate::tree::vector`] builder). The asset's view box determines
    /// the natural aspect ratio.
    pub vector_source: Option<std::sync::Arc<crate::vector::VectorAsset>>,
    /// Render policy for [`Self::vector_source`]. Defaults to
    /// [`crate::vector::VectorRenderMode::Painted`] so authored vector
    /// paint is preserved unless the caller explicitly opts into mask
    /// rendering.
    pub vector_render_mode: crate::vector::VectorRenderMode,

    pub children: Vec<El>,

    /// Paint-time alpha multiplier in `[0, 1]`. Default `1.0`. Multiplies
    /// the alpha channel of `fill`, `stroke`, and text colour at draw
    /// time. Layout-neutral. App-driven changes are eased when
    /// [`Self::animate`] is set.
    pub opacity: f32,
    /// Paint-time offset in logical pixels. Default `(0.0, 0.0)`.
    /// **Subtree-inheriting**: descendants paint at their computed rect
    /// plus all ancestor `translate` accumulated through the paint
    /// recursion. Use this to slide a sidebar / drawer / list-item
    /// without re-running layout. App-driven changes are eased when
    /// [`Self::animate`] is set.
    pub translate: (f32, f32),
    /// Per-node uniform scale around the computed-rect centre. Default
    /// `1.0`. Scales this node's surface quad and (if it carries text)
    /// its glyph run together. **Not** subtree-inheriting — descendants
    /// keep their own scale. Use this for tap-bounce on a button. App-
    /// driven changes are eased when [`Self::animate`] is set.
    pub scale: f32,
    /// Opt-in app-driven prop interpolation. When `Some(timing)`, the
    /// animation tracker eases `fill` / `text_color` / `stroke` /
    /// `opacity` / `translate` / `scale` between rebuilds — the value
    /// the build closure produces becomes the spring/tween target;
    /// `current` carries over from last frame. State visuals (hover /
    /// press / focus ring) keep their own library defaults regardless.
    pub animate: Option<Timing>,

    /// Inside-out redraw deadline: when `Some(d)` and this El is
    /// visible (rect intersects the viewport), Aetna asks the host to
    /// schedule the next frame within `d`. Aggregated across the tree
    /// via `min` and surfaced as
    /// [`crate::runtime::PrepareResult::next_redraw_in`]; the host
    /// drives the loop, Aetna mediates by visibility.
    ///
    /// Use this for any widget whose paint depends on time (animated
    /// images, video frames written via `surface()`, custom shaders
    /// that don't go through the `samples_time` registration path,
    /// hover-and-fade effects implemented outside the built-in
    /// animation tracker). `Duration::ZERO` means "next frame ASAP";
    /// non-zero values let the host pace at lower-than-display
    /// cadence.
    pub redraw_within: Option<std::time::Duration>,

    /// Stable path-based ID, filled by the layout pass. Used as the
    /// key for every side map that holds per-node bookkeeping in
    /// [`crate::state::UiState`] — computed rects, interaction state,
    /// state-envelope amounts, scroll offsets, in-flight animations.
    pub computed_id: String,
}