Slide DownATM

/* -- Motion component -------------------------------------------------

   The shared entrance-animation vocabulary: CSS @keyframes are the single

   source of truth (geometry, easing, defaults, reduced-motion), driven either

   declaratively via [data-df-entrance] or imperatively through the JS

   controller `ddf$.entrance(el, effect, opts)` (src/shared/motion.ts - same

   functions under df$.shadcn.entrance). The JS never defines keyframes; it

   only triggers/retriggers, overrides timing vars and owns the

   finished/cancel lifecycle via the platform's CSSAnimation objects.

   Why animations (not transitions): they run deterministically when the

   attribute first applies - including on freshly inserted DOM - and they

   replay cleanly (cancel → play). Transitions need a rendered "from" state

   and never fire on initial application (the reason the first vocabulary

   demo showed a static grid).

   Why animation-composition: add - transform/filter keyframes COMPOSE with

   any pre-existing transform/filter on the element instead of replacing it,

   so entrances are safe on arbitrarily styled DOM (no transform inspection

   or reconstruction). The paired fade runs with `replace`.

   Limits: non-replaced inline boxes (display:inline spans) are not

   transformable per CSS - this is deliberate and NOT worked around (silent

   display changes would alter text wrapping). Wrap inline content or let the

   caller promote it. */

@layer components {

  /* timing tunables - :root defaults so ANY ancestor (deck mount, container,

     inline style) can override by ordinary cascade; inline styles win last */

  :root {

    --df-motion-duration: 1500ms;

    --df-motion-delay: 0ms;

    --df-motion-ease: cubic-bezier(0.16, 1, 0.3, 1);

    --df-motion-distance: 24px;

    --df-motion-scale-in: 0.9;

    --df-motion-scale-out: 1.1;

    --df-motion-blur: 12px;

    --df-motion-angle: 12deg;

    --df-motion-spin: -0.5turn;

    /* JS writes the element's CURRENT computed opacity here, so fading an

       opacity:.6 element ends at .6 - never brightens content it doesn't own */

    --df-motion-base-opacity: 1;

  }

  /* one animation declaration, parameterized entirely by the vars above */

  [data-df-entrance] {

    animation-duration: var(--df-motion-duration);

    animation-delay: var(--df-motion-delay);

    animation-timing-function: var(--df-motion-ease);

    animation-fill-mode: both;

    /* transform-channel entrances pair with the fade (composition: add keeps

       the element's own transform underneath); clip-path entrances need no

       fade - the clip alone reveals the content */

    &[data-df-entrance="up"] { animation-name: df-enter-up, df-enter-fade; animation-composition: add, replace; }

    &[data-df-entrance="down"] { animation-name: df-enter-down, df-enter-fade; animation-composition: add, replace; }

    &[data-df-entrance="left"] { animation-name: df-enter-left, df-enter-fade; animation-composition: add, replace; }

    &[data-df-entrance="right"] { animation-name: df-enter-right, df-enter-fade; animation-composition: add, replace; }

    &[data-df-entrance="zoom"] { animation-name: df-enter-zoom, df-enter-fade; animation-composition: add, replace; }

    &[data-df-entrance="zoom-out"] { animation-name: df-enter-zoom-out, df-enter-fade; animation-composition: add, replace; }

    &[data-df-entrance="pop"] { animation-name: df-enter-pop, df-enter-fade; animation-composition: add, replace; }

    &[data-df-entrance="spin"] { animation-name: df-enter-spin, df-enter-fade; animation-composition: add, replace; }

    &[data-df-entrance="flip"] { animation-name: df-enter-flip, df-enter-fade; animation-composition: add, replace; }

    &[data-df-entrance="skew"] { animation-name: df-enter-skew, df-enter-fade; animation-composition: add, replace; }

    &[data-df-entrance="blur"] { animation-name: df-enter-blur, df-enter-fade; animation-composition: add, replace; }

    &[data-df-entrance="wipe"] { animation-name: df-enter-wipe; }

    &[data-df-entrance="wipe-up"] { animation-name: df-enter-wipe-up; }

    &[data-df-entrance="iris"] { animation-name: df-enter-iris; }

    &[data-df-entrance="fade"] { animation-name: df-enter-fade; }

  }

  /* stagger: children of a [data-df-stagger] container get graded delays

     (--df-motion-stagger-step per container) while keeping their own

     direction. ponytail: beyond the 8th child the delay caps at *7 - long

     lists should chunk into columns. An inline --df-motion-delay on a child

     still wins (inline beats any stylesheet rule). */

  [data-df-stagger] {

    --df-motion-stagger-step: 120ms;

    & > :nth-child(1) { --df-motion-delay: calc(var(--df-motion-stagger-step) * 0); }

    & > :nth-child(2) { --df-motion-delay: calc(var(--df-motion-stagger-step) * 1); }

    & > :nth-child(3) { --df-motion-delay: calc(var(--df-motion-stagger-step) * 2); }

    & > :nth-child(4) { --df-motion-delay: calc(var(--df-motion-stagger-step) * 3); }

    & > :nth-child(5) { --df-motion-delay: calc(var(--df-motion-stagger-step) * 4); }

    & > :nth-child(6) { --df-motion-delay: calc(var(--df-motion-stagger-step) * 5); }

    & > :nth-child(7) { --df-motion-delay: calc(var(--df-motion-stagger-step) * 6); }

    & > :nth-child(n + 8) { --df-motion-delay: calc(var(--df-motion-stagger-step) * 7); }

  }

  /* SVG draw-in - a distinct primitive, not a DOM entrance: pathLength="1"

     calibrates distance-along-path so ONE dash rule (1 → 0) fits every

     geometry regardless of actual path length. (The CSS `path-length`

     property stays experimental - the SVG attribute is the portable form.) */

  [data-df-draw][pathLength="1"] {

    stroke-dasharray: 1;

    stroke-dashoffset: 1;

    animation:

      df-draw

      var(--df-motion-duration)

      var(--df-motion-ease)

      var(--df-motion-delay)

      both;

  }

  /* vocabulary - every direction is exactly one keyframes rule */

  @keyframes df-enter-fade {

    from { opacity: 0; }

    to { opacity: var(--df-motion-base-opacity); }

  }

  /* "up" travels upward into its final position (from below) */

  @keyframes df-enter-up {

    from { transform: translateY(var(--df-motion-distance)); }

    to { transform: translateY(0); }

  }

  @keyframes df-enter-down {

    from { transform: translateY(calc(-1 * var(--df-motion-distance))); }

    to { transform: translateY(0); }

  }

  @keyframes df-enter-left {

    from { transform: translateX(var(--df-motion-distance)); }

    to { transform: translateX(0); }

  }

  @keyframes df-enter-right {

    from { transform: translateX(calc(-1 * var(--df-motion-distance))); }

    to { transform: translateX(0); }

  }

  @keyframes df-enter-zoom {

    from { transform: scale(var(--df-motion-scale-in)); }

    to { transform: scale(1); }

  }

  @keyframes df-enter-zoom-out {

    from { transform: scale(var(--df-motion-scale-out)); }

    to { transform: scale(1); }

  }

  @keyframes df-enter-pop {

    0% { transform: scale(0.65); }

    65% { transform: scale(1.07); }

    100% { transform: scale(1); }

  }

  @keyframes df-enter-spin {

    from { transform: rotate(var(--df-motion-spin)); }

    to { transform: rotate(0deg); }

  }

  @keyframes df-enter-flip {

    from { transform: perspective(900px) rotateY(-70deg); }

    to { transform: perspective(900px) rotateY(0deg); }

  }

  @keyframes df-enter-skew {

    from { transform: skewX(var(--df-motion-angle)); }

    to { transform: skewX(0deg); }

  }

  @keyframes df-enter-blur {

    from { filter: blur(var(--df-motion-blur)); }

    to { filter: blur(0); }

  }

  @keyframes df-enter-wipe {

    from { clip-path: inset(0 100% 0 0); }

    to { clip-path: inset(0); }

  }

  @keyframes df-enter-wipe-up {

    from { clip-path: inset(100% 0 0 0); }

    to { clip-path: inset(0); }

  }

  @keyframes df-enter-iris {

    from { clip-path: circle(0% at 50% 50%); }

    to { clip-path: circle(150% at 50% 50%); }

  }

  @keyframes df-draw {

    from { stroke-dashoffset: 1; }

    to { stroke-dashoffset: 0; }

  }

  /* accessibility: near-instant instead of none - the JS finished/cancel

     contract behaves identically (a finished 1ms animation still resolves),

     while nothing visibly moves. REQUIRED for every animation. */

  @media (prefers-reduced-motion: reduce) {

    [data-df-entrance],

    [data-df-draw] {

      --df-motion-duration: 1ms !important;

      --df-motion-delay: 0ms !important;

    }

  }

}