Loop the append queue has been proved to be very inefficient, and
some times lead to N^2 time complexity.
Especially when some abnormal data could not be appended into the
real DOM, will make a dead loop.
Previously we use a 5000ms time out to handle this, which is not
user-friendly and not explicitly.
In this patch, we transform the queue into a tree data structure,
which reflects the layout of real DOM. With the tree data structure,
we can find whether there are dangling nodes that need to be dropped.
Also, the iteration will be much more efficient.
There is still a 500ms time out to avoid a dead loop, but should not
be called in expected scenarios.
* The `processMutations` function needed to be bound to the `mutationBuffer` object, as otherwise `this` referred to the `MutationObserver` object itself
* Enable external pausing of mutation buffer emissions
- no automatic pausing based on e.g. pageVisibility yet, assuming such a thing is desirable
https://developer.mozilla.org/en-US/docs/Web/API/Page_Visibility_API
- user code has to call new API method `freezePage` e.g. when page is hidden or after a timeout
- automatically unpauses when the next user initiated event occurs
(am assuming everything that isn't a mutation event counts as 'user initiated'
either way think this is the correct thing to do until I see a counterexample
of an event that shouldn't cause the mutations to be unbufferred)
* Avoid a build up of duplicate `adds` by delaying pushing to adds until emission time
* Need to export freezePage in order to use it from rrweb.min.js
* Add a test to check if mutations can be turned off with the `freezePage` method
* I noticed out of order ids (in terms of a DOM walk) in a FullSnapshot. A DOM mutation was executed against the mirror asynchronously before it could be fully processed. This would lead to a situation in replay where a mutation is executed against a DOM tree that already has the mutation applied. This changeset fixes that by freezing any mutations until the snapshot is completed.
* Remove attribute modifications from a mutation event that were incorrect in that they were repeating the attributes of those nodes present in the 'adds' array of the same mutation
* I've manually verified that this empty text node is actually removed when the dropdown is opened:
document.getElementById('select2-results-1').childNodes
NodeList(2) [li.select2-results-dept-0.select2-result.select2-result-selectable.select2-highlighted, li.select2-results-dept-0.select2-result.select2-result-selectable]
and also that it is not reinstated after the second `await page.click('.select2-container');`
* Rearrange when removal happens in order to satisfy tests. I'm also reverting a recent test change (2600fe7) so that tests pass after this rearrangement; I believe that test change to still be the correct way of doing it, but maybe it is not strictly important that there are extra mutations on attributes of just added nodes
* As mutations are now paused during FullSnapshots, we shouldn't be counting this as a 'user emission'. We automatically emit mutations after unpause anyway ('emit anything queued up now')
* Ensure that we clear arrays before emitting, as the mutation could have the side effect of triggering a FullSnapshot (checkoutEveryNth), which would otherwise re-trigger emission of same mutation (through the new pause/fullsnapshot/mutationemit/unpause process)
* Don't let the programattic pausing during TakeFullSnapshot accidentally unpause a manual call to the API method `freezePage`
* Rename paused -> frozen for consistency and change to use getter/setter access methods
