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import {
getDefaultLeftHandle,
getDefaultRightHandle,
} from "@/animation/bezier";
import type {
CurveHandle,
NormalizedCubicBezier,
ScalarAnimationKey,
} from "@/animation/types";
const VALUE_EPSILON = 1e-6;
function clamp01({ value }: { value: number }): number {
return Math.max(0, Math.min(1, value));
}
export function getNormalizedCubicBezierForScalarSegment({
leftKey,
rightKey,
referenceSpanValue,
}: {
leftKey: ScalarAnimationKey;
rightKey: ScalarAnimationKey;
/** Fallback Y-axis scale used when the segment is flat (spanValue ≈ 0). */
referenceSpanValue?: number;
}): NormalizedCubicBezier | null {
const spanTime = rightKey.time - leftKey.time;
const spanValue = rightKey.value - leftKey.value;
const effectiveSpanValue =
Math.abs(spanValue) > VALUE_EPSILON
? spanValue
: referenceSpanValue !== undefined && Math.abs(referenceSpanValue) > VALUE_EPSILON
? referenceSpanValue
: null;
if (spanTime === 0 || effectiveSpanValue === null) {
return null;
}
const rightHandle =
leftKey.rightHandle ?? getDefaultRightHandle({ leftKey, rightKey });
const leftHandle =
rightKey.leftHandle ?? getDefaultLeftHandle({ leftKey, rightKey });
return [
clamp01({ value: rightHandle.dt / spanTime }),
rightHandle.dv / effectiveSpanValue,
clamp01({ value: 1 + leftHandle.dt / spanTime }),
1 + leftHandle.dv / effectiveSpanValue,
];
}
export function getCurveHandlesForNormalizedCubicBezier({
leftKey,
rightKey,
cubicBezier,
referenceSpanValue,
}: {
leftKey: ScalarAnimationKey;
rightKey: ScalarAnimationKey;
cubicBezier: NormalizedCubicBezier;
/** Fallback Y-axis scale used when the segment is flat (spanValue ≈ 0). */
referenceSpanValue?: number;
}): {
rightHandle: CurveHandle;
leftHandle: CurveHandle;
} | null {
const spanTime = rightKey.time - leftKey.time;
const spanValue = rightKey.value - leftKey.value;
const effectiveSpanValue =
Math.abs(spanValue) > VALUE_EPSILON
? spanValue
: referenceSpanValue !== undefined && Math.abs(referenceSpanValue) > VALUE_EPSILON
? referenceSpanValue
: null;
if (spanTime === 0 || effectiveSpanValue === null) {
return null;
}
const [rawX1, y1, rawX2, y2] = cubicBezier;
const x1 = clamp01({ value: rawX1 });
const x2 = clamp01({ value: rawX2 });
return {
rightHandle: {
dt: spanTime * x1,
dv: effectiveSpanValue * y1,
},
leftHandle: {
dt: spanTime * (x2 - 1),
dv: effectiveSpanValue * (y2 - 1),
},
};
}
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