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

packages/perfect-freehand/src/getStrokeOutlinePoints.ts

@@ -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
 
   /*
@@ -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
 
@@ -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)
+
+    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.
@@ -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
     }
 

packages/perfect-freehand/src/test/__snapshots__/getStroke.spec.ts.snap

@@ -1976,8 +1976,60 @@ Array [
     266.2468669394994,
   ],
   Array [
-    957.6602662835733,
-    259.49321610477915,
+    942.0612244920976,
+    259.33589413407526,
+  ],
+  Array [
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+    257.4741906980951,
+  ],
+  Array [
+    943.0297632070849,
+    255.73009293378777,
+  ],
+  Array [
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+    254.20496788516107,
+  ],
+  Array [
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+    251.73632731981203,
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+  Array [
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+  Array [
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+    252.26334358658096,
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+  Array [
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+    253.17172113101702,
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+  Array [
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+    254.4477640805153,
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+    256.01730875889626,
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+  Array [
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+    257.78913315570776,
+  ],
+  Array [
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+    259.66025875375817,
   ],
   Array [
     957.2533438954803,
@@ -2096,8 +2148,60 @@ Array [
     259.4998168076582,
   ],
   Array [
-    942.0595476718931,
-    259.502156915616,
+    942.0612083518535,
+    259.33667400313146,
+  ],
+  Array [
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+    257.47494404140434,
+  ],
+  Array [
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+    255.73077596700165,
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+  Array [
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+    254.20554091035703,
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+  Array [
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+    252.98788560462555,
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+  Array [
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+    252.14858023338758,
+  ],
+  Array [
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+    251.73640526425407,
+  ],
+  Array [
+    950.9601905865417,
+    251.77531632579706,
+  ],
+  Array [
+    952.7763581462298,
+    252.2630519052914,
+  ],
+  Array [
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+    253.17126478794077,
+  ],
+  Array [
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+    254.44716959833332,
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+  Array [
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+    256.01661068894094,
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+  Array [
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+    257.7883720698377,
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+  Array [
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+    259.6594788863199,
   ],
   Array [
     957.4176762060673,