(ml5717) Compressed erase intervals representation, fixed singular point erasing

src/canvas.js

@@ -200,9 +200,13 @@ const applyErasureIntervals = (pathID, points, erasureIntervals) => {
       pathID,
       i,
     )
-    if (!eraseIntervals || nextPoint === undefined) {
+
+    if (!eraseIntervals) {
       subpath.push(point)
       continue
+    } else if (nextPoint === undefined) {
+      if (JSON.stringify(eraseIntervals) != "[[0,0]]") subpath.push(point)
+      continue
     }
 
     if (!pointWasErased(eraseIntervals) || subpath.length) {

src/erasure.js

@@ -45,14 +45,19 @@ function project([x1, y1], [x2, y2], [x3, y3]) {
 }
 
 function erasureInterval(lineStart, lineEnd, erasureCenter, erasureRadius) {
-  if (!(lineStart && lineEnd && erasureCenter)) return
+  if (!(lineStart && erasureCenter)) return undefined
+
+  if (!lineEnd) {
+    const dist2ToSingularity = distanceSquared(erasureCenter, lineStart)
+    return dist2ToSingularity <= erasureRadius ** 2 ? [0, 0] : undefined
+  }
 
   const distToSegment2 = distToSegmentSquared(lineStart, lineEnd, erasureCenter)
-  if (erasureRadius ** 2 < distToSegment2) return
+  if (erasureRadius ** 2 < distToSegment2) return undefined
 
   const lineLength = distance(lineStart, lineEnd)
   if (lineLength === 0) {
-    return distToSegment2 <= erasureRadius ** 2 ? [0, 1] : [0, 0]
+    return distToSegment2 <= erasureRadius ** 2 ? [0, 1] : undefined
   }
 
   const projT = project(lineStart, lineEnd, erasureCenter)
@@ -98,7 +103,6 @@ function overlaps([s1, e1], [, e2]) {
 
 function mergeIntervals(...intervals) {
   if (!intervals.length) return []
-
   const sorted = intervals.sort(([a], [b]) => a > b)
   const stack = [sorted[0]]
   sorted.forEach((x) => {
@@ -121,3 +125,38 @@ export function combineErasureIntervals(i1, i2) {
   })
   return { ...i2, ..._i1 }
 }
+
+export function spreadErasureIntervals(intervals) {
+  const spread = []
+
+  intervals.forEach(([l, u]) => {
+    if (u > l) {
+      for (let li = Math.floor(l); li < u; li++) {
+        const list = spread[li] || []
+
+        const [il, iu] = [Math.max(li, l), Math.min(li + 1, u)]
+
+        list.push([il % 1, iu == li + 1 ? 1 : iu % 1])
+
+        spread[li] = list
+      }
+    } else {
+      spread[Math.floor(l)] = [[l % 1, u % 1]]
+    }
+  })
+
+  return spread
+}
+
+export function flattenErasureIntervals(intervals) {
+  const flatten = []
+
+  for (const idx in intervals) {
+    if (intervals[idx])
+      flatten.push(
+        intervals[idx].map(([l, u]) => [parseInt(idx) + l, parseInt(idx) + u]),
+      )
+  }
+
+  return flatten.flat()
+}

src/room.js

@@ -11,6 +11,12 @@ yMap(Y)
 yArray(Y)
 yWebrtc(Y)
 
+import {
+  combineErasureIntervals,
+  spreadErasureIntervals,
+  flattenErasureIntervals,
+} from "./erasure.js"
+
 class Room extends EventTarget {
   constructor(name) {
     super()
@@ -37,23 +43,22 @@ class Room extends EventTarget {
   extendErasureIntervals(pathID, pointID, newIntervals) {
     const self = this
 
-    const afterJSON = JSON.stringify(newIntervals)
-
+    // eslint-disable-next-line require-yield
     this._y.db.requestTransaction(function* requestTransaction() {
-      const pathIntervals = yield* JSON.parse(
-        self.sharedMergeIntervals.get(pathID) || "{}",
-      )
+      const prevJSON = self.sharedMergeIntervals.get(pathID) || "[]"
+      const pathIntervals = JSON.parse(prevJSON)
+
+      const combinedIntervals = combineErasureIntervals(
+        [pathIntervals],
+        [flattenErasureIntervals({ [pointID]: newIntervals })],
+      )[0]
+      const postJSON = JSON.stringify(combinedIntervals)
 
-      if (afterJSON == JSON.stringify(pathIntervals[pointID])) {
+      if (prevJSON == postJSON) {
         return
       }
 
-      pathIntervals[pointID] = newIntervals
-
-      yield* self.sharedMergeIntervals.set(
-        pathID,
-        JSON.stringify(pathIntervals),
-      )
+      self.sharedMergeIntervals.set(pathID, postJSON)
     })
   }
 
@@ -88,8 +93,10 @@ class Room extends EventTarget {
 
   _generateRemovedIntervals(id) {
     const intervals = this.sharedMergeIntervals.get(id)
+
     if (!intervals) return []
-    return JSON.parse(intervals)
+
+    return spreadErasureIntervals(JSON.parse(intervals))
   }
 
   inviteUser(id) {