285005 - need scrollbox with scrollbars (like overflow: auto)

Status: RESOLVED FIXED

(Core :: XUL, enhancement)

Description

[Chris Spencer]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.5) Gecko/20041107 Firefox/1.0
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.5) Gecko/20041107 Firefox/1.0

Setting the style of a scrollbox to overflow: auto; does not produce a
scrollbar. This is extremely inconvenient since the scrollbox is apparently the
only element whose scroll position is programmatically accessible via
javascript. In other words, with any other scrollable element, the user can
control the scroll position, but not a script, and with the scrollbox, the
script can control the scroll position, but not the user. The following XUL code
will create a textbox which will capture the enter key and paste text into a
vertically-oriented scrollbox. Notice that when the text begins to overflow, the
scroll box is scrolled, but no scrollbars appear even though the scrollbox style
is explicitly set to overflow: auto;

<?xml version="1.0"?>
<?xml-stylesheet href="chrome://global/skin" type="text/css"?>
	
<window title="Console"
        xmlns:html="http://www.w3.org/1999/xhtml"
        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">

<html:script>
//<![CDATA[

function enter_text(e){
    // Takes text from input and displays in output.
    inp = document.getElementById('input_text');
    if (inp.value.length && e.keyCode == 13){
        outp = document.getElementById('output_text');
        text =
document.createElementNS('http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul',
'description');
        text.appendChild(document.createTextNode(inp.value));
        outp.appendChild(text);
        inp.value = '';
        repos('output_text')
    }
}

function repos(baseid)
{
  var scrollBoxObject =
document.getElementById(baseid).boxObject.QueryInterface(Components.interfaces.nsIScrollBoxObject);
  scrollBoxObject.scrollByIndex(9999999);
}

//]]>
</html:script>

<groupbox flex="1" >
    <scrollbox id="output_text" flex="1" orient="vertical" style='overflow: auto;'>
    </scrollbox>
    <textbox id="input_text" flex="0" />
</groupbox>

<html:script>
//<![CDATA[

// setup event handlers
inp = document.getElementById('input_text');
inp.addEventListener("keypress", enter_text, false);
inp.focus();

//]]>
</html:script>

</window>


Reproducible: Always

Comment 1

[Nickolay_Ponomarev]

no duplicates found -> NEW

See also:
http://groups-beta.google.com/group/netscape.public.dev.xul/browse_frm/thread/d319e7bbfa6d908/c560067ebe6a76d1?tvc=1#c560067ebe6a76d1

As Neil pointed out, this is by design for <scrollbox>, so I'm changing the bug
to ask for a widget that has nsIScrollBoxObject methods *and* automatic
scrollbars. This can easily be done by changing overflow value for that widget
from hidden to something else.

I think it should be something like <scrollbox scrollbars="true"/> with the
following implementation in xul.css:

scrollbox {
  -moz-binding: url("chrome://global/content/bindings/scrollbox.xml#scrollbox");
}
scrollbox:not([scrollbars="true"]) {
  overflow: hidden !important;
}
scrollbox[scrollbars="true"] {
  overflow:auto; /* This should not be !important */
  -moz-box-flex: 1; /* this is needed so that the scrollbox doesn't grow larger
than containing element */
}

As far as I can tell, it may help fixing bug 235203 (but I can't be sure there
isn't an easier way).

Comment 2

[[e-mail]]

roc, this could be popular, would you be ok with this change?

Comment 3

[Neil Deakin]

I think providing a scrolling API for all elements would be better in the long
run. Or at least just for those with an overflow set.

How feasible would it be to make element.boxObject return a scrollBoxObject for
those things with a scrolling view? Hmmm. nsIScrollBoxObject isn't a
subinterface of nsIBoxObject though.

Comment 4

[Robert O'Callahan (:roc) (email my personal email if necessary)]

(In reply to comment #2)
> roc, this could be popular, would you be ok with this change?

I've said several times that I'd be fine with making scrollbox be just
'overflow:hidden' so that can be overridden by authors.

(In reply to comment #3)
> I think providing a scrolling API for all elements would be better in the long
> run. Or at least just for those with an overflow set.
> 
> How feasible would it be to make element.boxObject return a scrollBoxObject
> for those things with a scrolling view? Hmmm. nsIScrollBoxObject isn't a
> subinterface of nsIBoxObject though.

That won't work as soon as you want to use scrollBoxObject properties on any
element which has its own special boxObject. It's probably easier to leave
things as they are. For now anyway.

Comment 5

[[e-mail]]

Attachment: Proposed patch

I'm not disputing that you've mentioned it before I just haven't known of
anywhere to point at before.

Comment 6

[[e-mail]]

Fix checked in.