101 lines
4.0 KiB
TypeScript
101 lines
4.0 KiB
TypeScript
// Patch flags are optimization hints generated by the compiler.
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// when a block with dynamicChildren is encountered during diff, the algorithm
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// enters "optimized mode". In this mode, we know that the vdom is produced by
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// a render function generated by the compiler, so the algorithm only needs to
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// handle updates explicitly marked by these patch flags.
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// Patch flags can be combined using the | bitwise operator and can be checked
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// using the & operator, e.g.
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//
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// const flag = TEXT | CLASS
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// if (flag & TEXT) { ... }
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//
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// Check the `patchElement` function in './renderer.ts' to see how the
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// flags are handled during diff.
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export const enum PatchFlags {
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// Indicates an element with dynamic textContent (children fast path)
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TEXT = 1,
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// Indicates an element with dynamic class binding.
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CLASS = 1 << 1,
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// Indicates an element with dynamic style
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// The compiler pre-compiles static string styles into static objects
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// + detects and hoists inline static objects
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// e.g. style="color: red" and :style="{ color: 'red' }" both get hoisted as
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// const style = { color: 'red' }
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// render() { return e('div', { style }) }
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STYLE = 1 << 2,
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// Indicates an element that has non-class/style dynamic props.
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// Can also be on a component that has any dynamic props (includes
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// class/style). when this flag is present, the vnode also has a dynamicProps
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// array that contains the keys of the props that may change so the runtime
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// can diff them faster (without having to worry about removed props)
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PROPS = 1 << 3,
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// Indicates an element with props with dynamic keys. When keys change, a full
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// diff is always needed to remove the old key. This flag is mutually
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// exclusive with CLASS, STYLE and PROPS.
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FULL_PROPS = 1 << 4,
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// Indicates an element with event listeners (which need to be attached
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// during hydration)
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HYDRATE_EVENTS = 1 << 5,
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// Indicates a fragment whose children order doesn't change.
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STABLE_FRAGMENT = 1 << 6,
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// Indicates a fragment with keyed or partially keyed children
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KEYED_FRAGMENT = 1 << 7,
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// Indicates a fragment with unkeyed children.
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UNKEYED_FRAGMENT = 1 << 8,
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// Indicates an element that only needs non-props patching, e.g. ref or
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// directives (onVnodeXXX hooks). since every patched vnode checks for refs
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// and onVnodeXXX hooks, it simply marks the vnode so that a parent block
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// will track it.
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NEED_PATCH = 1 << 9,
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// Indicates a component with dynamic slots (e.g. slot that references a v-for
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// iterated value, or dynamic slot names).
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// Components with this flag are always force updated.
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DYNAMIC_SLOTS = 1 << 10,
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// SPECIAL FLAGS -------------------------------------------------------------
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// Special flags are negative integers. They are never matched against using
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// bitwise operators (bitwise matching should only happen in branches where
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// patchFlag > 0), and are mutually exclusive. When checking for a speical
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// flag, simply check patchFlag === FLAG.
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// Indicates a hoisted static vnode. This is a hint for hydration to skip
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// the entire sub tree since static content never needs to be updated.
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HOISTED = -1,
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// A special flag that indicates that the diffing algorithm should bail out
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// of optimized mode. This is only on block fragments created by renderSlot()
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// when encountering non-compiler generated slots (i.e. manually written
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// render functions, which should always be fully diffed)
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BAIL = -2
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}
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// dev only flag -> name mapping
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export const PatchFlagNames = {
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[PatchFlags.TEXT]: `TEXT`,
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[PatchFlags.CLASS]: `CLASS`,
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[PatchFlags.STYLE]: `STYLE`,
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[PatchFlags.PROPS]: `PROPS`,
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[PatchFlags.FULL_PROPS]: `FULL_PROPS`,
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[PatchFlags.HYDRATE_EVENTS]: `HYDRATE_EVENTS`,
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[PatchFlags.STABLE_FRAGMENT]: `STABLE_FRAGMENT`,
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[PatchFlags.KEYED_FRAGMENT]: `KEYED_FRAGMENT`,
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[PatchFlags.UNKEYED_FRAGMENT]: `UNKEYED_FRAGMENT`,
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[PatchFlags.DYNAMIC_SLOTS]: `DYNAMIC_SLOTS`,
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[PatchFlags.NEED_PATCH]: `NEED_PATCH`,
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[PatchFlags.HOISTED]: `HOISTED`,
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[PatchFlags.BAIL]: `BAIL`
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}
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