44 lines
1.4 KiB
Diff
44 lines
1.4 KiB
Diff
diff --git a/vtree/diff.js b/vtree/diff.js
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index b5bccbd..058d6b3 100644
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--- a/vtree/diff.js
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+++ b/vtree/diff.js
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@@ -311,6 +311,38 @@ function reorder(aChildren, bChildren) {
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var inserts = []
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var simulateItem
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+ // handle prepends without reordering old elements
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+ var shift = bChildren.length - aChildren.length
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+ if (shift > 0 && simulate.length === bChildren.length) {
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+ var prepend = true
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+ for (var i = 0; prepend && i < simulate.length; i++) {
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+ prepend = simulate[i] && simulate[i].key
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+ }
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+ for (var i = 0; prepend && i < aChildren.length; i++) {
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+ prepend = aChildren[i].key === bChildren[i + shift].key
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+ }
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+
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+ if (prepend) {
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+ for (var i = 0; i < shift; i++) {
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+ removes.push({
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+ from: aChildren.length,
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+ key: bChildren[i].key
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+ })
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+ inserts.push({
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+ to: i,
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+ key: bChildren[i].key
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+ })
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+ }
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+ return {
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+ children: newChildren,
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+ moves: {
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+ removes: removes,
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+ inserts: inserts
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+ }
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+ }
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+ }
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+ }
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+
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for (var k = 0; k < bChildren.length;) {
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var wantedItem = bChildren[k]
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simulateItem = simulate[simulateIndex]
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