FocusZoom

A camera over 2D content that pushes in on each burst of pointer clicks (or on given shots) and eases back out, clamped to the content.

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theme

graphitepapersignal

content

set in code

What the camera films, laid out at full size in the view's coordinates.

shots

Manual shots: from at until the next shot (or hold frames).

set in code

Follow a pointer: push in around each burst of clicks.

zoom

Zoom for a shot without its own.

maxZoom

lead

Frames the push starts before a click (it always lands before the click). Default: about a second.

idle

Frames without a click before easing back out.

smoothing

0 = quick camera moves, 1 = slow, soft ones.

padding

Space kept around click points / targets.

clamp

Never show past the content's edges.

bounds

set in code

When zoomed, keep the view inside this region (e.g. the app window).

smear

Motion blur while the camera moves.

length

Frames to solve. Default: through the last shot plus its return.

Usage, as set above

Install

Copies the source into your project. It's yours from then on: edit it like any other file.

$ npx framefields add focus-zoom

Writes 2 files (focus-zoom/index.ts, focus-zoom/plan.ts) into your components folder. Then:

import { FocusZoom } from "./components/focus-zoom/index.js";

FocusZoom({ content: [frame, pointer], follow: pointer })

Props

Plus the props every component takes: at, duration, hold,enter, exit, x, y, width, height,theme, seed and customize.

Prop	Type	Default
`content`required	`unknown`
What the camera films, laid out at full size in the view's coordinates.
`shots`	`Array<{ at, target, zoom, hold }>`
Manual shots: from `at` until the next shot (or `hold` frames).
`follow`	`unknown`
Follow a pointer: push in around each burst of clicks.
`zoom`	`number`	`1.8`
Zoom for a shot without its own.
`maxZoom`	`number`	`2.5`
`lead`	`number`
Frames the push starts before a click (it always lands before the click). Default: about a second.
`idle`	`number`	`40`
Frames without a click before easing back out.
`smoothing`	`number`	`0.5`
0 = quick camera moves, 1 = slow, soft ones.
`padding`	`number`	`160`
Space kept around click points / targets.
`clamp`	`boolean`	`true`
Never show past the content's edges.
`bounds`	`"full" \| unknown`
When zoomed, keep the view inside this region (e.g. the app window).
`smear`	`false \| "subtle" \| "standard" \| "heavy"`	`"subtle"`
Motion blur while the camera moves.
`length`	`number`
Frames to solve. Default: through the last shot plus its return.

Cues

Frames other layers can key off, on the returned node: node.cues.shots[0].frame. Change the props and everything keyed to a cue moves with it.

shots

Parts

The layers customize receives by name, to restyle or animate one piece without forking the component.

clipcamera

Source

What framefields add focus-zoom writes for focus-zoom/index.ts.

Show 276 lines

/**
 * FocusZoom: a camera over 2D content that pushes in on what matters and
 * eases back out — the auto-zoom of polished product demos. Give it shots,
 * or let it follow a MousePointer and frame each burst of clicks.
 */
import { LayerAnimation, type LayoutNode } from "framefields";
import {
  bakeSamples,
  bindComponent,
  boundsOf,
  defineComponent,
  resolveTarget,
  targetPoint,
  targetSchema,
  type Vec2,
  z,
} from "framefields/components";
import {
  type ClickEvent,
  type ShotWindow,
  shotsFromClicks,
  solveCamera,
} from "./plan.js";

/** What `follow` needs from a pointer (a MousePointer node has it). */
export interface Followable {
  positionAt(frame: number): Vec2;
  cues: { clicks: ReadonlyArray<{ frame: number; point: Vec2 }> };
}

/** A target, or "full" for the whole view. */
function shotTargetSchema() {
  return z.union([z.literal("full"), targetSchema()]);
}

export interface FocusZoomCues {
  [name: string]: ReadonlyArray<{ frame: number }>;
  /** One per shot: push starts (`frame`), lands (`settled`), lets go (`end`). */
  shots: ReadonlyArray<{
    frame: number;
    settled: number;
    end: number;
    zoom: number;
    center: Vec2;
  }>;
}

export interface FocusZoomApi {
  /** A content point → where it shows on screen (parent coordinates) at a parent frame. */
  toScreen(point: Vec2, frame: number): Vec2;
  /** Camera at a parent frame: the content point at the centre, and the zoom. */
  cameraAt(frame: number): { center: Vec2; zoom: number };
}

// Shutter angles. Camera moves scale everything at once, so even a little
// blur reads strongly: keep the default restrained.
const SMEAR = { subtle: 24, standard: 60, heavy: 140 } as const;

export const focusZoom = /* @__PURE__ */ defineComponent({
  name: "FocusZoom",
  props: () => ({
    /** What the camera films, laid out at full size in the view's coordinates. */
    content: z.custom<LayoutNode | LayoutNode[]>(
      (v) => typeof v === "object" && v !== null,
    ),
    /** Manual shots: from `at` until the next shot (or `hold` frames). */
    shots: z
      .array(
        z
          .object({
            at: z.number().int().min(0),
            target: shotTargetSchema(),
            zoom: z.number().min(1).optional(),
            hold: z.number().int().positive().optional(),
          })
          .strict(),
      )
      .optional(),
    /** Follow a pointer: push in around each burst of clicks. */
    follow: z
      .custom<Followable>(
        (v) =>
          typeof v === "object" &&
          v !== null &&
          typeof (v as Followable).positionAt === "function",
        {
          message:
            "Expected a MousePointer (anything with positionAt and cues.clicks)",
        },
      )
      .optional(),
    /** Zoom for a shot without its own. */
    zoom: z.number().min(1).default(1.8),
    maxZoom: z.number().min(1).default(2.5),
    /** Frames the push starts before a click (it always lands before the click). Default: about a second. */
    lead: z.number().int().min(0).optional(),
    /** Frames without a click before easing back out. */
    idle: z.number().int().min(0).default(40),
    /** 0 = quick camera moves, 1 = slow, soft ones. */
    smoothing: z.number().min(0).max(1).default(0.5),
    /** Space kept around click points / targets. */
    padding: z.number().min(0).default(160),
    /** Never show past the content's edges. */
    clamp: z.boolean().default(true),
    /** When zoomed, keep the view inside this region (e.g. the app window). */
    bounds: shotTargetSchema().optional(),
    /** Motion blur while the camera moves. */
    smear: z
      .union([z.literal(false), z.enum(["subtle", "standard", "heavy"])])
      .default("subtle"),
    /** Frames to solve. Default: through the last shot plus its return. */
    length: z.number().int().positive().optional(),
  }),
  defaults: { enter: false, exit: false },
  build(ctx, props) {
    const { host, fps } = ctx;
    const W = ctx.requested.width ?? ctx.canvas.width;
    const H = ctx.requested.height ?? ctx.canvas.height;
    // By default the push starts early enough to run at its natural pace.
    const lead =
      props.lead ?? Math.round((0.55 + 0.75 * props.smoothing) * fps) + 2;

    const shots: ShotWindow[] = [];
    if (props.follow) {
      const pointer = props.follow;
      // Click frames are in the pointer's parent timeline — the content —
      // which starts with this component.
      const clicks: ClickEvent[] = pointer.cues.clicks.map((c) => ({
        frame: c.frame,
        point: c.point,
      }));
      shots.push(
        ...shotsFromClicks(clicks, {
          width: W,
          height: H,
          lead,
          idle: props.idle,
          zoom: props.zoom,
          maxZoom: props.maxZoom,
          padding: props.padding,
        }),
      );
    }
    const manual = [...(props.shots ?? [])].sort((a, b) => a.at - b.at);
    manual.forEach((shot, i) => {
      const next = manual[i + 1];
      const end =
        shot.hold !== undefined
          ? shot.at + shot.hold
          : (next?.at ?? shot.at + Math.round(fps * 3));
      if (shot.target === "full") {
        shots.push({ start: shot.at, end, zoom: 1, center: [W / 2, H / 2] });
        return;
      }
      const resolved = resolveTarget(shot.target, {
        measure: host.measure,
        fps,
      });
      if (resolved.kind === "dynamic") {
        shots.push({
          start: shot.at,
          end,
          zoom: shot.zoom ?? props.zoom,
          center: (f) => targetPoint(resolved, f),
        });
        return;
      }
      const r = boundsOf(resolved.rects);
      const fit = Math.min(
        W / (r.width + props.padding * 2),
        H / (r.height + props.padding * 2),
      );
      const zoom = Math.min(
        props.maxZoom,
        shot.zoom ?? Math.max(1, Math.min(props.zoom, fit)),
      );
      shots.push({
        start: shot.at,
        end,
        zoom,
        center: [r.x + r.width / 2, r.y + r.height / 2],
      });
    });
    shots.sort((a, b) => a.start - b.start);

    const lastEnd = Math.max(0, ...shots.map((s) => s.end));
    const length = props.length ?? lastEnd + Math.round(fps * 1.5) + 1;
    let bounds:
      | { x: number; y: number; width: number; height: number }
      | undefined;
    if (props.bounds !== undefined && props.bounds !== "full") {
      const resolved = resolveTarget(props.bounds, {
        measure: host.measure,
        fps,
      });
      if (resolved.kind !== "static")
        throw new Error("FocusZoom: `bounds` must be a static target.");
      bounds = boundsOf(resolved.rects);
    }
    const plan = solveCamera({
      width: W,
      height: H,
      length,
      fps,
      shots,
      smoothing: props.smoothing,
      clamp: props.clamp,
      bounds,
    });

    const camera = host.box({
      id: ctx.partId("camera"),
      position: "absolute",
      x: 0,
      y: 0,
      width: W,
      height: H,
      anchorX: 0,
      anchorY: 0,
      ...(props.smear !== false && { motionBlurShutter: SMEAR[props.smear] }),
      children: Array.isArray(props.content) ? props.content : [props.content],
    });
    camera.animate(
      LayerAnimation.keys("x", bakeSamples(plan.x, 0, { tolerance: 0.15 })),
      LayerAnimation.keys("y", bakeSamples(plan.y, 0, { tolerance: 0.15 })),
      LayerAnimation.keys(
        "scale",
        bakeSamples(plan.scale, 0, { tolerance: 0.0004 }),
      ),
    );
    const clip = host.box({
      id: ctx.partId("clip"),
      position: "absolute",
      x: 0,
      y: 0,
      width: W,
      height: H,
      overflow: "hidden",
      children: [camera],
    });

    const stateAt = (local: number) =>
      plan.states[
        Math.max(0, Math.min(plan.states.length - 1, Math.round(local)))
      ] ?? { cx: W / 2, cy: H / 2, zoom: 1 };
    return {
      children: [clip],
      width: W,
      height: H,
      duration: null,
      origin: [0, 0],
      cues: { shots: plan.shots } as FocusZoomCues,
      parts: { camera, clip },
      api: (placement): FocusZoomApi => ({
        toScreen(point, frame) {
          const s = stateAt(frame - placement.start);
          return [
            placement.x + W / 2 + (point[0] - s.cx) * s.zoom,
            placement.y + H / 2 + (point[1] - s.cy) * s.zoom,
          ];
        },
        cameraAt(frame) {
          const s = stateAt(frame - placement.start);
          return { center: [s.cx, s.cy], zoom: s.zoom };
        },
      }),
    };
  },
});

/**
 * A camera over 2D content that pushes in on each burst of pointer clicks (or
 * on given shots) and eases back out, clamped to the content.
 */
export const FocusZoom = /* @__PURE__ */ bindComponent(focusZoom);