Enum percy_vdom::Patch

pub enum Patch<'a> {
    AppendChildren(usize, Vec<&'a VirtualNode>),
    TruncateChildren(usize, usize),
    Replace(usize, &'a VirtualNode),
    AddAttributes(usize, HashMap<&'a str, &'a str>),
    RemoveAttributes(usize, Vec<&'a str>),
    ChangeText(usize, &'a VText),
}

A Patch encodes an operation that modifies a real DOM element.

To update the real DOM that a user sees you’ll want to first diff your old virtual dom and new virtual dom.

This diff operation will generate Vec<Patch> with zero or more patches that, when applied to your real DOM, will make your real DOM look like your new virtual dom.

Each Patch has a u32 node index that helps us identify the real DOM node that it applies to.

Our old virtual dom’s nodes are indexed depth first, as shown in this illustration (0 being the root node, 1 being it’s first child, 2 being it’s first child’s first child).

            .─.
           ( 0 )
            `┬'
        ┌────┴──────┐
        │           │
        ▼           ▼
       .─.         .─.
      ( 1 )       ( 4 )
       `┬'         `─'
   ┌────┴───┐       │
   │        │       ├─────┬─────┐
   ▼        ▼       │     │     │
  .─.      .─.      ▼     ▼     ▼
 ( 2 )    ( 3 )    .─.   .─.   .─.
  `─'      `─'    ( 5 ) ( 6 ) ( 7 )
                   `─'   `─'   `─'

The patching process is tested in a real browser in crates/percy-vdom/tests/diff_patch.rs

Variants

AppendChildren(usize, Vec<&'a VirtualNode>)

Append a vector of child nodes to a parent node id.

TruncateChildren(usize, usize)

For a node_i32, remove all children besides the first len

Replace(usize, &'a VirtualNode)

Replace a node with another node. This typically happens when a node’s tag changes. ex:

becomes

AddAttributes(usize, HashMap<&'a str, &'a str>)

Add attributes that the new node has that the old node does not

RemoveAttributes(usize, Vec<&'a str>)

Remove attributes that the old node had that the new node doesn’t

ChangeText(usize, &'a VText)

Change the text of a Text node.

Implementations

impl<'a> Patch<'a>

pub fn node_idx(&self) -> usize

Every Patch is meant to be applied to a specific node within the DOM. Get the index of the DOM node that this patch should apply to. DOM nodes are indexed depth first with the root node in the tree having index 0.

Trait Implementations

impl<'a> Debug for Patch<'a>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a> PartialEq<Patch<'a>> for Patch<'a>

fn eq(&self, other: &Patch<'a>) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Patch<'a>) -> bool

This method tests for !=.

impl<'a> StructuralPartialEq for Patch<'a>