:: Developer Documentation Request Request Type: Correction Gecko Version: Trunk Technical Contact: bzbarsky@mit.edu :: Details "display: -moz-box" is mentioned several places, e.g. • https://developer.mozilla.org/en-US/docs/Web/CSS/Mozilla_Extensions under "Values: display" • https://developer.mozilla.org/en-US/docs/Web/CSS/-moz-box-pack under "Applies to" • etc. It is also often used in chrome, as can be seen by means of the DOM Inspector But guess what? It is not mentioned at all in the description of the display property, where only the (many) values known at W3C are mentioned.

There isn't much to document there. It exists. We would like to remove it. If you're not writing Firefox chrome code, you shouldn't use it. If you're writing Firefox chrome code, you should try not to use it. Its behavior is whatever it is. Not quite sure why I'm the technical contact here. ;)

(In reply to Boris Zbarsky [:bz] from comment #1) > There isn't much to document there. It exists. We would like to remove it. > If you're not writing Firefox chrome code, you shouldn't use it. If you're > writing Firefox chrome code, you should try not to use it. Its behavior is > whatever it is. > > Not quite sure why I'm the technical contact here. ;) I'm writing userChrome.css for Firefox, Thunderbird and SeaMonkey, so at times I wonder how to make the chrome do what I want. "display: -moz-box" appears here and there in the existing chrome, and sometimes I put it in, and sometimes I took it out, not really knowing what I was doing. You'll agree that "it's behaviour is whatever it is" isn't a very good reference when I'm hunting about, trying to familiarize myself with Firefox, Thunderbird and SeaMonkey chrome in order to tweak its look and feel to my liking. For instance, http://users.skynet.be/antoine.mechelynck/other/userChrome-firefox.css and http://users.skynet.be/antoine.mechelynck/other/userChrome-seamonkey.css (the latter is newer) are some of the results of my "trials and errors", but there are a few rulesets therein which simply don't work. Others I'm proud of, like the scrollbars (instead of scroll buttons) on long (sometimes very long) menus, or the "flowing tabs" (putting the tabs on several rows rather than scrolling them sideways, if there are too many for the width of the screen). I put you in as technical contact because I hesitated about which code module was most relevant, but you were owner or peer of all those which seemed they might be. If you think that someone else is a better technical contact than you are, by all means write his name in instead (or hers, as the case may be). Maybe I should ask Neil Rashbrook or Philip Chee? Or David Baron or Blake Kaplan or…? You know, I don't really know whom to ask about what hereabouts…

P.S. If you (y'all) want to remove it, add it to the documentation with a banner saying that this is a deprecated value which will go away "in some future release". IMHO as long as Trunk knows about it this would be better than leaving it out of the docs and answering questions about it by — please excuse me Boris — brush-offs like comment #1, which left me in the dark and made me want to ask someone — not someone more competent, I believe you are competent, but someone more helpful.

> You'll agree that "it's behaviour is whatever it is" isn't a very good reference While true, it's the only one that will give you an actual description of the behavior. There's some documentation for simple cases at https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XUL/Tutorial/The_Box_Model and the following pages if that's what you're looking for, but I'm not aware of any comprehensive documentation for the XUL box model other than the implementation code. We really don't want this value to appear in web developer facing documentation because we very much don't want web developers using it (e.g. see bug 879275), so I'm strongly opposed to adding it to https://developer.mozilla.org/en-US/docs/Web/CSS/display but in the end that's a call for the devmo owners to make, of course. And comment 1 wasn't intended as a brush-off except to the extent that if you were asking me personally to write actual documentation for this display value and the XUL box model in general (which is what I interpreted comment 0 to mean) then you were asking me to invest several weeks of my time and I'm just not willing to do that in this case. The value's behavior is really just defined by whatever the XUL code does. There is no particular rhyme to reason to it, necessarily. Simple cases are easy to explain and are explained in the tutorial I link to above. Complicated cases more often than not come down to "that's just what the code does"....

Not invest weeks of your time, no, that wasn't what I was asking for. I thought it would have been possible to mention that value on the CSS/display page with a one-line summary of its meaning and a link to another page (which I thought already existed but had escaped my search) describing it in more detail, but if that other page doesn't (yet) exist, it will have to be written by someone who feels that it is missing. Maybe me some years from now, if by then I understand it better and it (or XUL altogether) hasn't yet been removed by then. Also maybe a warning that it applies only to XUL and (obviously, for a -moz-something) to the Gecko engine (i.e. not Webkit, not Presto, etc.). Thanks for the XUL tutorial link and the bug number, I'll go see what is written there; and I'm still looking for someone willing to explain the fine points to me — if there is any explanation (and any explainer) to be found.

Please feel free to ask in #firefox or #developers with specific questions, of course. In general, though -moz-box kind acts like CSS flexbox except the names of the properties that actually control its behavior are sometimes different....

I’ve now added a table of all XUL display values to https://developer.mozilla.org/docs/Web/CSS/display#XUL_values, and I have https://github.com/mdn/browser-compat-data/pull/1955 in flight to update the browser compatibility table.

The XUL display values are now documented at https://developer.mozilla.org/docs/Mozilla/Gecko/Chrome/CSS/display-xul and were hidden from web content in bug 1288572 and bug 879275.