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fix: Backtracking now doesn't create dots at end of lines #54

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merged 1 commit into from
Aug 22, 2022
Merged

fix: Backtracking now doesn't create dots at end of lines #54

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38 changes: 25 additions & 13 deletions packages/perfect-freehand/src/getStrokeOutlinePoints.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -127,6 +127,10 @@ export function getStrokeOutlinePoints(
let tl = pl
let tr = pr

// Keep track of whether the previous point is a sharp corner
// ... so that we don't detect the same corner twice
let isPrevPointSharpCorner = false

// let short = true

/*
Expand Down Expand Up @@ -197,18 +201,6 @@ export function getStrokeOutlinePoints(

/* Add points to left and right */

// Handle the last point
if (i === points.length - 1) {
const offset = mul(per(vector), radius)
leftPts.push(sub(point, offset))
rightPts.push(add(point, offset))
continue
}

const nextVector = points[i + 1].vector

const nextDpr = dpr(vector, nextVector)

/*
Handle sharp corners

Expand All @@ -217,7 +209,14 @@ export function getStrokeOutlinePoints(
draw a cap at the current point.
*/

if (nextDpr < 0) {
const nextVector = (i < points.length - 1? points[i + 1] : points[i]).vector
const nextDpr = (i < points.length - 1? dpr(vector, nextVector) : 1.0)
const prevDpr = dpr(vector, prevVector)
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Is prevDpr always equal to last iteration's nextDpr?

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Maybe! I'll check. Definitely a cleaner fix in here somewhere

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@TodePond TodePond Aug 22, 2022 •
edited
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Ok so yes, they are usually the same (apart from some occasional float imprecision)
image

Except for very rare cases:
image

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Here's another example that's not from the final two iterations:

image


const isPointSharpCorner = prevDpr < 0 && !isPrevPointSharpCorner
const isNextPointSharpCorner = nextDpr !== null && nextDpr < 0

if (isPointSharpCorner || isNextPointSharpCorner) {
// It's a sharp corner. Draw a rounded cap and move on to the next point
// Considering saving these and drawing them later? So that we can avoid
// crossing future points.
Expand All @@ -235,6 +234,19 @@ export function getStrokeOutlinePoints(
pl = tl
pr = tr

if (isNextPointSharpCorner) {
isPrevPointSharpCorner = true
}
continue
}

isPrevPointSharpCorner = false

// Handle the last point
if (i === points.length - 1) {
const offset = mul(per(vector), radius)
leftPts.push(sub(point, offset))
rightPts.push(add(point, offset))
continue
}

Expand Down
112 changes: 108 additions & 4 deletions packages/perfect-freehand/src/test/__snapshots__/getStroke.spec.ts.snap
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1976,8 +1976,60 @@ Array [
266.2468669394994,
],
Array [
957.6602662835733,
259.49321610477915,
942.0612244920976,
259.33589413407526,
],
Array [
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],
Array [
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],
Array [
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Array [
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],
Array [
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],
Array [
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],
Array [
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Array [
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],
Array [
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Array [
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Array [
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],
Array [
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],
Array [
957.2533438954803,
Expand Down Expand Up @@ -2096,8 +2148,60 @@ Array [
259.4998168076582,
],
Array [
942.0595476718931,
259.502156915616,
942.0612083518535,
259.33667400313146,
],
Array [
942.3263727347852,
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],
Array [
943.0293864818785,
255.73077596700165,
],
Array [
944.1293904011217,
254.20554091035703,
],
Array [
945.5624522130447,
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],
Array [
947.2452822978064,
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Array [
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Array [
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],
Array [
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],
Array [
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],
Array [
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],
Array [
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],
Array [
957.4706802254859,
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Array [
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],
Array [
957.4176762060673,
Expand Down