Can you qualify your reasoning please? I don't remember seeing anything that suggests this behaviour in the HIG.

I've no idea whether it's in the HIG. If it isn't, I think it should be added.
Maximizing a window is far easier with a maximize button then with manual resizing. So, I think every resizable window should have a maximize button.
I also think this should be done in the framework and not in every individual application or window.

The theme preferences window is a dialog window, so I can't see that anyone should ever be maximising it.

Why should it be resizable but not easily maximizable?

It shouldn't be maximizable because it is not the "main window" of an application. It is a preference dialog, and so therefore you should never need to be maximised. I think if you need to maximize it, then there is a different problem altogether.

Perhaps we need some input from a usability expert!

It might be the case that the window should not be resizable in the first place. I think the only reason it is resizable is for convenience if you have items wider than the width of the window, or if you have only a very short list and can resize it so you do not have to use the scroll bars.

> It shouldn't be maximizable because it is not the "main window" of an
application. 

Why sould only main windows be maximizable?

> It might be the case that the window should not be resizable in the first
place.

In my opinion, when a window shows scrollbars, it should be resizable. And when it's resizable, it should be maximizable.

After all, the user can already maximize the window by manually resizing it to fill the entire screen.

Calum, any thoughts on this?

I am not certain that a maximize button is needed or wanted, as it would break consistency, amongst other reaons. Olav, do you have a use case for such a need?

> I am not certain that a maximize button is needed or wanted, 

I want it.

> as it would break consistency, 

What consistency?
With what?

> amongst other reaons.

Such as?

> Olav, do you have a use case for such a need?

Sure. I wish to reduce the need to scroll by maximizing the window. Without maximize option, this requires a lot of effort. With maximize option, it's a simple click, doubleclick or keypress.

olaf, danger of avalanches on this bug ;-)

I agree the dialog should be maximizable, and the keys according to this should work properly. Its because of the list with dynamic amounts of content, the same with gdmphotosetup and gnome-session-properties.
The gnome-session-properties is a good example for a dialog that would profit of a maximize button. But it would profit too, if metacity would memorize the size and position you had last time.

A question to think of, should it be minimizable too? Probably not, thats a attribute of dialogs. 

I think Olaf has a point; suggesting that all resizable windows should be maximizable is probably reasonable.

It would be nice if "maximized" meant different things in different contexts-- e.g. in this case, "vertically maximized" would probably be more useful than "fill the whole screen"[1]-- but since we don't have that sort of subtlety in our window manager, I don't see any harm in just adding a regular maximize button.

[1]  Does the keybinding for "vertically maximize" work even if the dialog doesn't have a maximize button?  I guess not...

> I don't see any harm in just adding a regular maximize button.

What's the reason for doing this in the dialog instead of doing it in the framework / window manager?

This is somewhat related to bug 315910.

This is a metacity bug at the moment, because it is not possible to add maximise (or minimize for that matter) buttons to a dialog window. However, I think there is a case here to say that the theme manager should have a "normal" window type, rather than dialog.

I changed the window type to "Normal", so it now has both Minimize and Maximise buttons.

I'm glad it has been fixed in this case, but it's a shame it hasn't been fixed at the framework level.

You ought to file a bug against Metacity to this effect. The problem was that Dialog window types could be resizable, but could not have a maximise button. I would suggest that dialog windows probably ought not be allowed to be resizable, so that they have an obvious distinction between Normal type windows.

> I would suggest that dialog windows probably ought not be allowed to be
resizable, so that they have an obvious distinction between Normal type
windows.

Eh, why?
In my opinion every window that contains a scrollbar should be resizable and have a maximize button.

Well, you better keep filing bugs then ;-)