60 lines
1.7 KiB
TypeScript
60 lines
1.7 KiB
TypeScript
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import {
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clampNumber,
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roundToStepPrecision,
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} from '$shared/lib/utils';
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/**
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* Geometry/range options shared by the math helpers.
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*/
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type SliderMathOpts = {
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/**
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* Minimum value (inclusive)
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*/
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min: number;
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/**
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* Maximum value (inclusive)
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*/
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max: number;
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/**
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* Step increment
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*/
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step: number;
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};
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/**
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* Snap a raw value onto the step grid, then clamp to [min, max].
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*
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* Snapping is anchored to `min` so non-zero ranges land on valid stops.
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* `roundToStepPrecision` removes IEEE-754 drift from fractional steps.
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*/
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export function snapToStep(raw: number, { min, max, step }: SliderMathOpts): number {
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if (step <= 0) {
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return clampNumber(raw, min, max);
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}
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const snapped = min + Math.round((raw - min) / step) * step;
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return clampNumber(roundToStepPrecision(snapped, step), min, max);
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}
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/**
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* Convert a pointer coordinate into a slider value.
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*
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* Horizontal maps left→min, right→max. Vertical is inverted so that
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* up→max, matching natural slider expectations. The DOMRect is passed in
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* to keep this pure and unit-testable without layout.
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*/
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export function pointerToValue(
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point: { clientX: number; clientY: number },
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rect: DOMRect,
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opts: SliderMathOpts & { orientation: 'horizontal' | 'vertical' },
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): number {
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const { min, max, orientation } = opts;
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const size = orientation === 'vertical' ? rect.height : rect.width;
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if (size <= 0) {
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return snapToStep(min, opts);
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}
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const ratio = orientation === 'vertical'
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? (rect.bottom - point.clientY) / size
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: (point.clientX - rect.left) / size;
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return snapToStep(min + clampNumber(ratio, 0, 1) * (max - min), opts);
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}
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