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#2021 change log and docs

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Pierre-Yves Gérardy 2017-11-24 00:29:15 +01:00 • committed by Pierre-Yves Gérardy
parent 02aab654f0
commit 3f37d3d7c0
2 changed files with 125 additions and 1 deletions
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docs/change-log.md
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@ -42,6 +42,7 @@
- core: `xlink:href` attributes are now correctly removed
- render: fixed an ommission that caused `oninit` to be called unnecessarily in some cases [#1992](https://github.com/MithrilJS/mithril.js/issues/1992)
- render: Render state correctly on select change event [#1916](https://github.com/MithrilJS/mithril.js/issues/1916)
- render: fix various updateNodes/removeNodes issues when the pool and fragments are involved [#1990](https://github.com/MithrilJS/mithril.js/issues/1990), [#1991](https://github.com/MithrilJS/mithril.js/issues/1991), [#2003](https://github.com/MithrilJS/mithril.js/issues/2003), [#2021](https://github.com/MithrilJS/mithril.js/pull/2021)
---

125
render/render.js
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@ -161,6 +161,124 @@ module.exports = function($window) {
}
//update
/**
* @param {Element|Fragment} parent - the parent element
* @param {Vnode[] | null} old - the list of vnodes of the last `render()` call for
* this part of the tree
* @param {Vnode[] | null} vnodes - as above, but for the current `render()` call.
* @param {boolean} recyclingParent - was the parent vnode or one of its ancestor
* fetched from the recycling pool?
* @param {Function[]} hooks - an accumulator of post-render hooks (oncreate/onupdate)
* @param {Element | null} nextSibling - the next DOM node if we're dealing with a
* fragment that is not the last item in its
* parent
* @param {'svg' | 'math' | String | null} ns) - the current XML namespace, if any
* @returns void
*/
// This function diffs and patches lists of vnodes, both keyed and unkeyed.
//
// We will:
//
// 1. describe its general structure
// 2. focus on the diff algorithm optimizations
// 3. describe how the recycling pool meshes into this
// 4. discuss DOM node operations.
// ## Overview:
//
// The updateNodes() function:
// - deals with trivial cases
// - determines whether the lists are keyed or unkeyed
// (we take advantage of the fact that mixed diff is not supported and settle on the
// keyedness of the first vnode we find)
// - diffs them and patches the DOM if needed (that's the brunt of the code)
// - manages the leftovers: after diffing, are there:
// - old nodes left to remove?
// - new nodes to insert?
// - nodes left in the recycling pool?
// deal with them!
//
// The lists are only iterated over once, with an exception for the nodes in `old` that
// are visited in the fourth part of the diff and in the `removeNodes` loop.
// ## Diffing
//
// There's first a simple diff for unkeyed lists of equal length that eschews the pool.
//
// It is followed by a small section that activates the recycling pool if present, we'll
// ignore it for now.
//
// Then comes the main diff algorithm that is split in four parts (simplifying a bit).
//
// The first part goes through both lists top-down as long as the nodes at each level have
// the same key. This is always true for unkeyed lists that are entirely processed by this
// step.
//
// The second part deals with lists reversals, and traverses one list top-down and the other
// bottom-up (as long as the keys match).
//
// The third part goes through both lists bottom up as long as the keys match.
//
// The first and third sections allow us to deal efficiently with situations where one or
// more contiguous nodes were either inserted into, removed from or re-ordered in an otherwise
// sorted list. They may reduce the number of nodes to be processed in the fourth section.
//
// The fourth section does keyed diff for the situations not covered by the other three. It
// builds a {key: oldIndex} dictionary and uses it to find old nodes that match the keys of
// new ones.
// The nodes from the `old` array that have a match in the new `vnodes` one are marked as
// `vnode.skip: true`.
//
// If there are still nodes in the new `vnodes` array that haven't been matched to old ones,
// they are created.
// The range of old nodes that wasn't covered by the first three sections is passed to
// `removeNodes()`. Those nodes are removed unless marked as `.skip: true`.
//
// Then some pool business happens.
//
// It should be noted that the description of the four sections above is not perfect, because those
// parts are actually implemented as only two loops, one for the first two parts, and one for
// the other two. I'm not sure it wins us anything except maybe a few bytes of file size.
// ## The pool
//
// `old.pool` is an optional array that holds the vnodes that have been previously removed
// from the DOM at this level (provided they met the pool eligibility criteria).
//
// If the `old`, `old.pool` and `vnodes` meet some criteria described in `isRecyclable`, the
// elements of the pool are appended to the `old` array, which enables the reconciler to find
// them.
//
// While this is optimal for unkeyed diff and map-based keyed diff (the fourth diff part),
// that strategy clashes with the second and third parts of the main diff algo, because
// the end of the old list is now filled with the nodes of the pool.
//
// To determine if a vnode was brought back from the pool, we look at its position in the
// `old` array (see the various `oFromPool` definitions). That information is important
// in three circumstances:
// - If the old and the new vnodes are the same object (`===`), diff is not performed unless
// the old node comes from the pool (since it must be recycled/re-created).
// - The value of `oFromPool` is passed as the `recycling` parameter of `upateNode()` (whether
// the parent is being recycled is also factred in here)
// - It is used in the DOM node insertion logic (see below)
//
// At the very end of `updateNodes()`, the nodes in the pool that haven't been picked back
// are put in the new pool for the next render phase.
//
// The pool eligibility and `isRecyclable()` criteria are to be updated as part of #1675.
// ## DOM node operations
//
// In most cases `updateNode()` and `createNode()` perform the DOM operations. However,
// this is not the case if the node moved (second and fourth part of the diff algo), or
// if the node was brough back from the pool and both the old and new nodes have the same
// `.tag` value (when the `.tag` differ, `updateNode()` does the insertion).
//
// The fourth part of the diff currently inserts nodes unconditionally, leading to issues
// like #1791 and #1999. We need to be smarter about those situations where adjascent old
// nodes remain together in the new list in a way that isn't covered by parts one and
// three of the diff algo.
function updateNodes(parent, old, vnodes, recyclingParent, hooks, nextSibling, ns) {
if (old === vnodes && !recyclingParent || old == null && vnodes == null) return
else if (old == null) createNodes(parent, vnodes, 0, vnodes.length, hooks, nextSibling, ns)
@ -178,7 +296,6 @@ module.exports = function($window) {
}
}
if (isUnkeyed && originalOldLength === vnodes.length) {
// treat it as a tuple, no pool here
for (; start < originalOldLength; start++) {
if (old[start] === vnodes[start] && !recyclingParent || old[start] == null && vnodes[start] == null) continue
else if (old[start] == null) createNode(parent, vnodes[start], hooks, ns, getNextSibling(old, start + 1, originalOldLength, nextSibling))
@ -272,6 +389,8 @@ module.exports = function($window) {
}
}
}
// when recycling, we're re-using an old DOM node, but firing the oninit/oncreate hooks
// instead of onbeforeupdate/onupdate.
function updateNode(parent, old, vnode, hooks, nextSibling, recycling, ns) {
var oldTag = old.tag, tag = vnode.tag
if (oldTag === tag) {
@ -412,6 +531,8 @@ module.exports = function($window) {
}
else return vnode.dom
}
// the vnodes array may hold items that come from the pool (after `limit`) they should
// be ignored
function getNextSibling(vnodes, i, limit, nextSibling) {
for (; i < limit; i++) {
if (vnodes[i] != null && vnodes[i].dom != null) return vnodes[i].dom
@ -443,6 +564,8 @@ module.exports = function($window) {
}
}
}
// when a node is removed from a parent that's brought back from the pool, its hooks should
// not fire.
function removeNode(vnode, context, recycling) {
var expected = 1, called = 0
var original = vnode.state