This issue was originally reported in #280 but may also relate
to #167 and other potential performance issues in the recording.
In #206 I implemented the new mutation observer which will defer
the serialization of DOM, which helps us to have a consistent DOM
order for the replay.
In this implementation, we use an array to represent the `addQueue`.
Whenever we need to consume the queue, we will iterate it to make
sure there is no dead loop, and then shift the first item to see
whether it can be serialized at the new timing.
But this implementation may be very slow when there are a lot of newly
added DOM since it will do an O(n^2) iteration.
For example, if we have three newly added DOM `n1`, `n2`, `n3`,
the iteration looks like this:
```
[n1, n2, n3]
n1 -> n2 -> n3, consume n3
[n1, n2]
n1 -> n2, consume n2
[n1]
n1, consume n1
```
We should have a better performance if te iteration looks like this:
```
[n1, n2, n3]
n3, consume n3
[n1, n2]
n2, consume n2
[n1]
n1, consume n1
```
Simply reverse the mutation payload does not work, because it does
not always as same as the DOM order.
So in this patch, we replace the `addQueue` with a double linked list,
which can:
1. represent the DOM order in its data structure
2. has an O(1) time complexity when looking up the sibling of a list item
3. has an O(1) time complexity when removing a list item
* part of #80, support mask input options
* close#188 enhance sampling options
Use a more general sampling strategy interface to describe the
configuration of sampling events collection.
Implemented mousmove, mouse interaction, scroll and input sampling
strategy.
There are some long-term issues in rrweb's mutation observer.
A scenario cause problem:
A list of DOM node: n1, n2, n3, n4, n5
Steps of modifying the nodes:
1. remove n1, n2, n3, n4 sequentially
2. append n4, n3, n2, n1 after n5 sequentially
Then we got the added node data like this:
(id: n4, prev: null, next: n3 )
(id: n3, prev: n4, next: n2 )
(id: n2, prev: n3, next: n1 )
(id: n1, prev: n2, next: null)
The problem comes when we try to replay the first add node datum.
Since its prev node is null, we rely on its next sibling n3. But
n3 was not present at this moment, and in previous code, we fallback
to append n4 to the last of its parent node.
The solution is to defer the append of elements that missing
siblings. But it is also hard to tell which node is the first one
that needs to be appended.
Take a step back and rethink the design of the mutation observer,
we've found there are two implementations make things complicated.
1. We set the id to -1 when we seeing some nodes are not serialized yet.
2. We record both previous sibling and next sibling to determine the
position of the node.
But we can do better!
First, we can put nodes with un-serialized siblings
to a queue, and try to add it again later. Then we can just record the next
sibling as 'the single truth' so we can be sure which node is the last
one of its parent.
This patch has implemented the new observer strategy. Data recorded with
the new observer should no longer have any node with id -1. But for
compatibility consideration, we still keep some replayer code that helps
solve legacy data.
* hack together stylesheet observer
* Add test coverage for insertRule/deleteRule on stylesheets
* Add new observers
* update patch based on changes to master
* Functioning event recording
* Remove print statements
* Fix ID usage and mark add vs remove
* Correct type
Co-authored-by: Jon Perl <perl.jonathan@gmail.com>
This is an important patch contains some crtical bug fixes for
the DOM mutation observer.
Previously the observer did not handle complex DOM movement very
well. So in this patch we optimized this by distinguishing moved
node better and added a resolving queue to avoid the error caused
by ordering.
If an element was blocked, its child nodes should also be blocked.
The interactions and mutations on the element and its child nodes
also need to be blocked.
