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Re: [UndoManager] Disallowing live UndoManager on detached nodes

From: Jonas Sicking <jonas@sicking.cc>
Date: Mon, 20 Aug 2012 23:47:12 -0700
Message-ID: <CA+c2ei9B0geNuNNnEX26Zv7RuFe=vMc_TdeeV8shgwyCFmHbjQ@mail.gmail.com>
To: Ryosuke Niwa <rniwa@webkit.org>
Cc: public-webapps <public-webapps@w3.org>, Kentaro Hara <haraken@chromium.org>, Sukolsak Sakshuwong <sukolsak@google.com>, Adam Barth <abarth@webkit.org>, Maciej Stachowiak <mjs@apple.com>, Ehsan Akhgari <ehsan@mozilla.com>, Olli Pettay <Olli.Pettay@helsinki.fi>, Ojan Vafai <ojan@chromium.org>
Will this still allow a node which has an undo manager to be moved
from one part of the document to another part of the document, without
losing all transactions attached to the undo manager?

That seems like an important use case.

/ Jonas

On Mon, Aug 20, 2012 at 9:52 PM, Ryosuke Niwa <rniwa@webkit.org> wrote:
> Greetings all,
>
> We've been implementing undo manager in WebKit, and we've found out that
> allowing live undo manager on a detached undo scope host is a terrible idea.
>
> e.g. say you have a subtree like follows:
>
> A
>
> B
>
> D
>
> C
>
> where A is the undo scope host. If we then detach B from A, and then insert
> A under D, all automatic transactions in A's undo manager are broken and may
> create a cyclic reference graph because nodes touched in automatic
> transactions need to be kept alive for undo/redo.
>
> If there is no objection, I'm changing the spec to disallow live undo
> manager on detached nodes so that scripts can't move the host around inside
> a document or between documents; i.e. when a undo scope host is removed from
> its parent, its undo manager must be disconnected and a new undo manager be
> created for the node.
>
> Alternatively, we can turn all automatic transactions in the undo manager
> into no-ops but I'd prefer disconnecting the undo manager altogether to make
> the behavior simple.
>
> Best,
> Ryosuke Niwa
> Software Engineer
> Google Inc.
>
>
Received on Tuesday, 21 August 2012 06:48:09 GMT

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