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chore: comments

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This commit is contained in:
Evan You 2019-05-27 15:59:02 +08:00
parent 73df1fa192
commit a4d116e3f7
1 changed files with 20 additions and 6 deletions
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26
packages/runtime-core/src/createRenderer.ts
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@ -484,9 +484,12 @@ export function createRenderer(options: RendererOptions) {
} }
// 5. unknown sequence // 5. unknown sequence
// [i ... e1 + 1]: a b [c d e] f g
// [i ... e2 + 1]: a b [e d c h] f g
// i = 2, e1 = 4, e2 = 5
else { else {
let s1 = i // prev starting index const s1 = i // prev starting index
let s2 = i // next starting index const s2 = i // next starting index
// 5.1 build key:index map for newChildren // 5.1 build key:index map for newChildren
const keyToNewIndexMap: Map<any, number> = new Map() const keyToNewIndexMap: Map<any, number> = new Map()
@ -504,13 +507,20 @@ export function createRenderer(options: RendererOptions) {
let patched = 0 let patched = 0
const toBePatched = e2 - s2 + 1 const toBePatched = e2 - s2 + 1
let moved = false let moved = false
// used to track whether any node has moved
let maxNewIndexSoFar = 0 let maxNewIndexSoFar = 0
const newIndexToOldIndexMap = [] // works as Map<newIndex, oldIndex> // works as Map<newIndex, oldIndex>
// Note that oldIndex is offset by +1
// and oldIndex = 0 is a special value indicating the new node has
// no corresponding old node.
// used for determining longest stable subsequence
const newIndexToOldIndexMap = []
for (i = 0; i < toBePatched; i++) newIndexToOldIndexMap.push(0) for (i = 0; i < toBePatched; i++) newIndexToOldIndexMap.push(0)
for (i = s1; i <= e1; i++) { for (i = s1; i <= e1; i++) {
const prevChild = c1[i] const prevChild = c1[i]
if (patched >= toBePatched) { if (patched >= toBePatched) {
// all new children have been patched so this can only be a removal
unmount(prevChild, true) unmount(prevChild, true)
continue continue
} }
@ -519,7 +529,7 @@ export function createRenderer(options: RendererOptions) {
newIndex = keyToNewIndexMap.get(prevChild.key) newIndex = keyToNewIndexMap.get(prevChild.key)
} else { } else {
// key-less node, try to locate a key-less node of the same type // key-less node, try to locate a key-less node of the same type
for (j = s2; j < e2; j++) { for (j = s2; j <= e2; j++) {
if (isSameType(prevChild, c2[j] as VNode)) { if (isSameType(prevChild, c2[j] as VNode)) {
newIndex = j newIndex = j
break break
@ -540,11 +550,13 @@ export function createRenderer(options: RendererOptions) {
} }
} }
// 5.3 apply minimal move w/ longest increasing subsequence // 5.3 move and mount
// generate longest stable subsequence only when nodes have moved
const increasingNewIndexSequence = moved const increasingNewIndexSequence = moved
? getSequence(newIndexToOldIndexMap) ? getSequence(newIndexToOldIndexMap)
: emptyArr : emptyArr
j = increasingNewIndexSequence.length - 1 j = increasingNewIndexSequence.length - 1
// looping backwards so that we can use last patched node as anchor
for (i = toBePatched - 1; i >= 0; i--) { for (i = toBePatched - 1; i >= 0; i--) {
const nextIndex = s2 + i const nextIndex = s2 + i
const nextChild = c2[nextIndex] as VNode const nextChild = c2[nextIndex] as VNode
@ -554,7 +566,9 @@ export function createRenderer(options: RendererOptions) {
// mount new // mount new
patch(null, nextChild, container, anchor) patch(null, nextChild, container, anchor)
} else if (moved) { } else if (moved) {
// move // move if:
// There is no stable subsequence (e.g. a reverse)
// OR current node is not among the stable sequence
if (j < 0 || i !== increasingNewIndexSequence[j]) { if (j < 0 || i !== increasingNewIndexSequence[j]) {
move(nextChild, container, anchor) move(nextChild, container, anchor)
} else { } else {