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Re: [UndoManager] Disallowing live UndoManager on detached nodes

From: Maciej Stachowiak <mjs@apple.com>
Date: Wed, 22 Aug 2012 23:16:37 -0700
Cc: Ojan Vafai <ojan@chromium.org>, Ryosuke Niwa <rniwa@webkit.org>, Glenn Maynard <glenn@zewt.org>, public-webapps <public-webapps@w3.org>, Kentaro Hara <haraken@chromium.org>, Sukolsak Sakshuwong <sukolsak@google.com>, Adam Barth <abarth@webkit.org>, Ehsan Akhgari <ehsan@mozilla.com>, Jonas Sicking <jonas@sicking.cc>, Olli Pettay <Olli.Pettay@helsinki.fi>, Dimitri Glazkov <dglazkov@chromium.org>
Message-id: <49778B2B-06DC-4985-8C37-848E25FDFD62@apple.com>
To: olli@pettay.fi

On Aug 22, 2012, at 11:08 PM, Olli Pettay <Olli.Pettay@helsinki.fi> wrote:

> On 08/22/2012 10:44 PM, Maciej Stachowiak wrote:
>> On Aug 22, 2012, at 6:53 PM, Ojan Vafai <ojan@chromium.org <mailto:ojan@chromium.org>> wrote:
>>> On Wed, Aug 22, 2012 at 6:49 PM, Ryosuke Niwa <rniwa@webkit.org <mailto:rniwa@webkit.org>> wrote:
>>>    On Wed, Aug 22, 2012 at 5:55 PM, Glenn Maynard <glenn@zewt.org <mailto:glenn@zewt.org>> wrote:
>>>        On Wed, Aug 22, 2012 at 7:36 PM, Maciej Stachowiak <mjs@apple.com <mailto:mjs@apple.com>> wrote:
>>>            Ryosuke also raised the possibility of multiple text fields having separate UndoManagers. On Mac, most apps wipe they undo queue when
>>>            you change text field focus. WebKit preserves a single undo queue across text fields, so that tabbing out does not kill your ability to
>>>            undo. I don't know of any app where you get separate switchable persistent undo queues. Thins are similar on iOS.
>>> Think of the use-case of a threaded email client where you can reply to any message in the thread. If it shows your composing mails inline (e.g. as
>>> gmail does), the most common user expectation IMO is that each email gets it's own undo stack. If you undo the whole stack in one email you wouldn't
>>> expect the next undo to start undo stuff in another composing mail. In either case, since there's a simple workaround (seamless iframes), I don't
>>> think we need the added complexity of the attribute.
>> Depends on the user and their platform of choice. On the Mac I think it's pretty much never the case that changing focus within a window changes your
>> undo stack, it either has a shared one or wipes undo history on focus switch. So if GMail forced that, users would probably be surprised. I can
>> imagine a use case for having an API that allows multiple undo stacks on platforms where they are appropriate, but merges to a single undo stack on
>> platforms where they are not. However, I suspect an API that could handle this automatically would be pretty hairy. So maybe we should handle the
>> basic single-undo-stack use case first and then think about complexifying it.
> I think the undo-stack per editing context (like <input>) is pretty basics, and certainly something I wouldn't remove from Gecko.
> (Largely because using the same undo for separate <input> elements is just very weird, and forcing web apps to use iframes to achieve
> Gecko's current behavior would be horribly complicated.)

It might be ok to let Web pages conditionally get Gecko-like separate undo stack behavior inside Firefox, at least on Windows. (Firefox even seems to do per-field undo on Mac, so I'm starting to think that it's more of a Gecko quirk than a Windows platform thing.)

But, again, letting webpages force that behavior in Safari seems wrong to me. I don't think we should allow violating the platform conventions for undo so freely. You seem to feel strongly that webpages should be able to align with the Gecko behavior, but wouldn't it be even worse to let them forcibly violate the WebKit behavior?

So if there is an API for separate undo stacks, it has to handle the case where there's really a single undo stack. And that would potentially be hard to program with.

On the other hand, there are certainly use cases where a single global undo stack is right (such as a page with a single rich text editor). And it's easy to handle those cases without adding a lot of complexity. And if we get that right, we could try to add on something for conditional multiple undo stacks.


Received on Thursday, 23 August 2012 06:17:05 UTC

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