summaryrefslogtreecommitdiffstats
path: root/packages/excalidraw/animation-frame-handler.ts
blob: b1a9844669758ff7339e3ea371b6518899ccb4e8 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
export type AnimationCallback = (timestamp: number) => void | boolean;

export type AnimationTarget = {
  callback: AnimationCallback;
  stopped: boolean;
};

export class AnimationFrameHandler {
  private targets = new WeakMap<object, AnimationTarget>();
  private rafIds = new WeakMap<object, number>();

  register(key: object, callback: AnimationCallback) {
    this.targets.set(key, { callback, stopped: true });
  }

  start(key: object) {
    const target = this.targets.get(key);

    if (!target) {
      return;
    }

    if (this.rafIds.has(key)) {
      return;
    }

    this.targets.set(key, { ...target, stopped: false });
    this.scheduleFrame(key);
  }

  stop(key: object) {
    const target = this.targets.get(key);
    if (target && !target.stopped) {
      this.targets.set(key, { ...target, stopped: true });
    }

    this.cancelFrame(key);
  }

  private constructFrame(key: object): FrameRequestCallback {
    return (timestamp: number) => {
      const target = this.targets.get(key);

      if (!target) {
        return;
      }

      const shouldAbort = this.onFrame(target, timestamp);

      if (!target.stopped && !shouldAbort) {
        this.scheduleFrame(key);
      } else {
        this.cancelFrame(key);
      }
    };
  }

  private scheduleFrame(key: object) {
    const rafId = requestAnimationFrame(this.constructFrame(key));

    this.rafIds.set(key, rafId);
  }

  private cancelFrame(key: object) {
    if (this.rafIds.has(key)) {
      const rafId = this.rafIds.get(key)!;

      cancelAnimationFrame(rafId);
    }

    this.rafIds.delete(key);
  }

  private onFrame(target: AnimationTarget, timestamp: number): boolean {
    const shouldAbort = target.callback(timestamp);

    return shouldAbort ?? false;
  }
}