123075 - Allow scrolling of textarea with JavaScript

Status: RESOLVED WORKSFORME

(Core :: DOM: Core & HTML, enhancement, P4)

Description

[Jonathan Watt [:jwatt]]

IE allows textareas to be scrolled by using: 

textareaObj.scrollTop = <length>;

where <length> is the distance to scroll down. If the length exceeds the
distance then the textarea is simply scrolled to the end. This can alternatively
be done using: 

textareaObj.scrollTop = textareaObj.scrollHeight; // scroll to end 

There is also scrollLeft and scrollWidth to allow this to be done in horizontally. 

Several of my scripts (including a multiline calculator and a CAD script)
repeatedly add textual results to the end of a textarea and naturally need to
scroll to the end to show the last result (while allowing the user to scroll up
manualy if they want to see previous results). 

I am sure that there are other applications and other people who would find the
means to scroll a textarea useful. Perhaps the scrollTo() and scrollBy() methods
could be added to textareas as a means to allow this in Mozilla. 

Other things to consider would be if the page is ltr or rtl, and providing a
means of determining the possible amount of scroll (both horizontally and
vertically).

Comment 1

[Boris Zbarsky [:bzbarsky]]

To DOM.

Comment 2

[Johnny Stenback (:jst)]

Mass-reassigning bugs to [e-mail]

Comment 3

[Roman Ivanov]

Please, make this "bug" alive.

I'm making shorcuts for fast text formatting in my WikiEdit -
http://wiki.oversite.ru/WikiEdit (based on simple textarea with autoindent (made
through the JavaScript)).

But nasty behaviour of Mozilla browser that scrolls up on every change in
textarea content made by script, makes my work absolutely seemless.

Please!

Comment 4

[Martijn Wargers (dead)]

The scrolltop,scrollleft, scrollheight and scrollwidth properties are working at
least in the latest versions of Mozilla (Moz 1.4b). See:
http://home.hccnet.nl/m.wargers/test/mozilla/scrolltobottom.htm

I would say this bug has been fixed somehow.

Determining the amount of scroll, you could do with some scripting yourself.
You could experiment with textarea offsetheight property rows property
scrollheight and the amount of returns in the textarea value property.
The amount of soft returns (the returns added by Mozilla in order to wrap text
in textareas) you would need also, but I can't think of a way to get these.

Comment 5

[Roman Ivanov]

Thanks for fixed scrollTop and friends.

But there's one more question.

Let's imagine that we have some (selected) text. But we have no ideas where is
it located in textarea. It can be out of the visible part. MSIE has this method
for scrolling to this text:
tr = document.selection.createRange();
tr.scrollIntoView(false); //for end of selection aligned to end of scrolled area
or
tr.scrollIntoView(true); //for beginning of selection aligned to top of scrolled
area

Are there any methods to do this task in Mozilla? Are there any plans to
implement it if not? 

Comment 6

[Martijn Wargers (dead)]

There is no scrollIntoView method for the range object. For HTML elements there
is a scrollIntoView method.
I've sort of made a simple and not complete (no scrolling to the right, no
arguments, extra scrolling inside element only for textareas') scrollIntoView
method for the range object.
http://home.hccnet.nl/m.wargers/test/mozilla/scrollintoviewrange.htm

I already said it is not complete, and although I could it make more complete,
it would be extremly difficult (or a lot of work, which is the same) to let it
behave correctly. 
In textarea's I can count the hard returns, so I can see where the
scrollposition of the selection is. But I can't count the 'soft' returns (the
returns when Mozilla wraps the text), so with a lot of soft returns, it doesn't
work anymore.
In other elements I get other problems, but basically I could solve it, except 
again the 'soft' returns problem.

So I think this method is quite necessary. That's why I've file a bug for this one:
Bug 220262
http://bugzilla.mozilla.org/show_bug.cgi?id=220262

This bug can still be closed by the way.

Comment 7

[Fabian Guisset]

Thanks for the comments, Martijn. According to last comment, marking WORKSFORME
because scrolling of a textarea with JavaScript seems to work now (please reopen
if you disagree, if so, please attach a testcase, thanks!)