[whatwg] Authoring Re: several messages about HTML5
news at terrainformatica.com
Sun Feb 25 18:18:27 PST 2007
----- Original Message -----
From: "Adrian Sutton" <adrian.sutton at ephox.com>
To: "Andrew Fedoniouk" <news at terrainformatica.com>; "Dave Raggett"
<dsr at w3.org>
Cc: "Karl Dubost" <karl at w3.org>; <whatwg at lists.whatwg.org>
Sent: Sunday, February 25, 2007 2:26 PM
Subject: RE: [whatwg] Authoring Re: several messages about HTML5
>> | > I agree that HTML DOM is not suitable for WYSIWYG editing.
>> | I beg to differ. It is true that an editing style sheet may be
>> | needed to avoid problems with delivery style sheets that use the
>> | display and visibility properties to hide content, or which use CSS
>> | positioning to layer things in complex ways. But apart from that,
>> | The HTML DOM is just fine as it is.
>> So this means relaxation of requirements - strictly speaking
>> it will not be WYSIWYG anymore. If "editing style sheet may be
>> needed" then what you will see is not what you will get.
> There are a couple of problems here. Firstly as far as I know there is
> not and has never been an editor that does What You See Is *Precisely*
> What You Get, they all have various ways to help the user understand the
> structure of the document or visualize physical elements such as page
> boundaries which don't exist on screen. Furthermore, users don't want to
> see precisely what they'll get, what they want and what WYSIWYG is
> really about, is that they can see and work with the document in visual
> form instead of having to learn a mark-up language and for the rendering
> to be close enough that they don't need to use preview (or don't have to
> use it more than as a final check). HTML editors in particular don't
> provide a precise rendering of the document because no two browsers
> render a document precisely the same and even the same browser on
> different machines will render it differently depending on user
> settings, screen resolution etc.
> Secondly, HTML DOM is not suitable for WYSIWYG editing because it is an
> inefficient and difficult representation to use for editing operations.
> It is perfectly possible to use it to write an editor - it's just not
> the best representation. For instance, if you have content like:
> <p><em>This is <strong>my content</strong></em></p>
> If the user then selects "is my" and applies an inline style (<span
> class='stuff'>), with a DOM representation you have a couple of tree
> operations to perform, plus you probably should do some normalization to
> ensure that the generated tree structure is consistent regardless of how
> the content got to this point. However, if you represent the text as an
> attributed string, you simply add "span class='stuff'" to the attribute
> set for "is my" and it's done. When you serialize the model you have to
> construct a valid DOM out of it, but it's fairly trivial to make the DOM
> come out in a consistent form and speed is a lot less of an issue at
> that point. The attributed string model also has the benefit of better
> matching the way the user thinks about the document - they rarely think
> of a tree structure, they think of text with formatting. A good example
> of the problems caused by the backend model not matching the user's
> model is http://www.codinghorror.com/blog/archives/000583.html also see
> my response
> em/ - there's a whole series of back and forth responses if you have
> nothing better to do, I seem to write about this far too much.
>> | Manipulating the DOM is a straightforward matter of tree walking
>> | algorithms. The really difficulty is understanding what the users
>> | would like to do. For example, you might type some text and click on
>> | the list bullet button. The enter key then starts a new paragraph
>> | within that list item, whilst enter followed immediately by another
>> | enter starts a new list item. Pressing enter on an empty list item
>> | closes the list. When it comes to the markup produced, you can
>> | conceptualize this in terms of a collection of critics that look for
>> | and fix particular problems, e.g. merging adjacent ul elements, or
>> | for moving leading and trailing whitespace out of inline elements.
> True, the challenge is always to 1) find out what the user meant and 2)
> do it. The model you choose can make that task easier or more difficult
> - in fact it generally does both because no single model is ideal for
> every editing operation. In our editor, we have a specific list model
> which is different to both the attributed string model and the DOM model
> - it simply has a list of LIs that are indented at different levels and
> have attributes like list type (OL/UL), style attributes etc. There are
> then a relatively small number of atomic changes users can make to lists
> (change indent level, change list type or attributes or merge items) and
> the model knows how to perform them on itself. The model also knows how
> to serialize itself in terms of a valid HTML document structure. The
> challenge is then simply mapping user actions to list operations in a
> way that is intuitive and consistent for users. By picking an
> appropriate model you can save a lot of effort in terms of keeping the
> model sane and correct. Lists and tables are excellent examples of where
> the HTML DOM is not ideal for editing because there are too many extra
> elements around that the user doesn't want to think about. Reconciling
> this difference in HTML DOM to user expectations is one of the reasons
> why lists and tables are so hard to get right.
>> HTML and its DOM has logical/semantic elements that
>> have no visual representation at all. Think about DIVs that
>> are used for wrapping portions of textual data and has no
>> visual representation. Your style sheet may rely
>> on some containment in some DIV - so the same
>> sequence of editing actions made by the user produces
>> dramatically different (for the user) visual results.
> This is why it's so useful to have a visual representation - the user
> can *see* that with the DIV there it renders one way and without it, it
> renders a different way. Of course, getting the user to understand the
> inherent tree structure that DIVs work with is difficult, so is the
> rules for how CSS applies. I don't have a good solution for this, but
> we're continuing to try to find one.
>> Let's take a look on example you've provided:
>> "The enter key then starts a new paragraph within that list item"
>> So after enter you will have:
>> Case #1:
>> <li>First paragraph.
>> <p>Second paragraph.</p>
>> *or* Case #2:
>> <p>First paragraph.</p>
>> <p>Second paragraph.</p>
>> So even in this "simple" case you have two options how to make
>> mapping of "action -> dom structure".
>> And now imagine that you will get following markup:
>> Case #3:
>> <li>First paragraph.</li>
>> <p>Second paragraph.</p>
> All three of these are completely wrong. When the user presses enter in
> a list item, the editor should insert another <li>. There is simply no
> excuse for doing anything else. A startling number of editors get this
> completely wrong though. Another very popular error is indenting a list
> item and generating:
>> Visually and by default this is indistinguishable from the Case #1.
>> So looking on these two list items user has no clue of
>> what he/she just did by pressing "Enter". Enter press is the most
>> unpredictable action in all WYSIWYG editors in the wild.
>> For the simple reason: there is no single unambiguous way
>> of changing DOM for such an action. Again tree-alike
>> DOM is simply not suitable for that.
> The DOM isn't ideal for this, but it's still quite possible to get it
> right, it just takes a lot more effort. It also helps if you run the
> HTML you start with through something like Tidy so that it starts out
> sane and you don't have to deal with the infinite range of completely
> broken HTML as a starting point. I suspect, but don't know for sure,
> editor has thankfully managed to avoid this particular set of problems.
>> | p.s. one missing feature in CSS that would really help would be a
>> | means to add a forced line break symbol to the rendering of <br>
>> | elements. It is already easy to add a paragraph symbol, but CSS
>> | balks at <br> elements for inappropriate reasons.
> We just changed the renderer to put it there without CSS, but I guess
> that's cheating.
> Adrian Sutton
> PS: My apologies, I've lost track of who actually said what above.
My statement "HTML DOM model is not suitable for
WYSIWYG editing" meant not physical limitation but
logical one. I agree with you - theoretically it is possible
to create some WYSIWYG HTML editor that will be
asymptotically close to some ideal.
But somewhere on the way to it system will hit
a point when it will become a "determenistic chaos"
where each line of code is a perfect finite state automata
but the whole system is not manageable.
Yes, practical solution for this is to simplify DOM
structure ( you use "attributed strings" and I am using
"flat DOM" in my http://blocknote.net and couple
of other editors)
I think that HTML WYSIWYG editing solution to be used
as <htmlarea> engine in HTML should not use HTML, at
least it should not use HTML DOM "as is" but something
more human visualy comprehensible.
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