[whatwg] Fixing undo on the Web - UndoManager and Transaction

Ryosuke Niwa rniwa at webkit.org
Tue Aug 30 12:30:48 PDT 2011

On Tue, Aug 30, 2011 at 12:21 PM, Ehsan Akhgari <ehsan at mozilla.com> wrote:

> On 11-08-30 3:15 PM, Ryosuke Niwa wrote:
>>    1. Should Transaction have reapply property or not?  It appears that
>> some
>>    of us (e.g. me, Annie, Alex) want it for semantical clarity while
>> others
>>    (e.g. Jonas and Ehsan) doesn't wait to avoid code duplication and to
>> simply
>>    the API.
> I still think that if we can design an API which discourages code
> duplication, we probably should.

(I feel like we're bikesheding here but) authors can do that by omitting
reapply as in {'apply': ..., 'unapply': ...}.

>     2. "Transaction" seems to be too generic.  Need more domain-specific
>> name
>>    such as UndoTransaction.
> I don't have a lot of ideas on what a better name would be.  I don't like
> any of the suggested ones.  UndoTransaction makes it seem like the
> transaction can only be undone.  EditingTransaction makes it seem like the
> transaction is somehow tied to editing commands...

I had used the name DOMTransaction in earlier drafts of my document.

>     3. "Managed transaction" seems to be confusing as to whether it's
>> managed
>>    by the UA or the author.
>>    4. Jonas requested that we have manualTransact and managedTransact
>>    instead of single transact on undoManager for clarity.  I think this is
>> a
>>    good idea but I'd rather settle the naming issue first.
> I agree that this is a good idea.

Alternatively, we can make separate the idea of managed/manual transaction
and undoManager and add a function like createAutomaticTransaction() that
takes a callback.  It'll then create a Transaction object with apply,
unapply reapply properties.  Authors can then add it to UndoManager just
like manual transactions.

This will make the responsibility of undoManager and transactions clear;
undoManager is solely responsible for managing undo transaction history and
won't be concerned with DOM changes at all.  With this interface, there is
exactly one type of Transaction.  And the difference between manual
transaction and managed transaction is just that whether it's created
manually by the author or via some special function
(e.g. createAutomaticTransaction).

- Ryosuke

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