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| 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 | 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x 1x | import type { NumberLineState, RenderConstant } from '../types'
import { numberToScreenX } from '../numberLineTicks'
import type { MathConstant } from './constantsData'
export interface ConstantVisibility {
constant: MathConstant
screenX: number
isOnScreen: boolean
opacity: number
}
/**
* Compute visibility for a single constant.
*
* A constant is visible when:
* 1. It's on screen (within canvas bounds + margin)
* 2. The zoom level is adequate to distinguish it (pxPerPrecisionUnit >= 20)
*
* Unlike FindTheNumber, there's no position proximity factor —
* constants appear whenever on screen AND zoomed enough.
*/
export function computeConstantVisibility(
constant: MathConstant,
state: NumberLineState,
canvasWidth: number
): ConstantVisibility {
const screenX = numberToScreenX(constant.value, state.center, state.pixelsPerUnit, canvasWidth)
// Margin so constants don't pop in right at the edge
const margin = 40
const isOnScreen = screenX >= -margin && screenX <= canvasWidth + margin
if (!isOnScreen) {
return { constant, screenX, isOnScreen, opacity: 0 }
}
// Zoom adequacy: one unit at the constant's precision should be >= 20px
const unitAtPrecision = 10 ** -constant.revealPrecision
const pxPerPrecisionUnit = unitAtPrecision * state.pixelsPerUnit
const opacity = Math.min(1, pxPerPrecisionUnit / 20)
return { constant, screenX, isOnScreen, opacity }
}
/**
* Compute visibility for all constants at once.
* Returns only those with opacity > 0.
*/
export function computeAllConstantVisibilities(
constants: MathConstant[],
state: NumberLineState,
canvasWidth: number,
discoveredSet: Set<string>
): RenderConstant[] {
const result: RenderConstant[] = []
for (const constant of constants) {
const vis = computeConstantVisibility(constant, state, canvasWidth)
if (vis.opacity > 0) {
result.push({
id: constant.id,
symbol: constant.symbol,
screenX: vis.screenX,
opacity: vis.opacity,
discovered: discoveredSet.has(constant.id),
})
}
}
return result
}
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