Unity panel shadow should not draw over unfocussed windows

Do you mean full screen windows or maximized windows? Full screen windows should not have a panel drawn over them at all.

maximized windows

Workaround to remove the shadow completely:
 cd /usr/share/unity/5/
 sudo mv panel-shadow.png panel-no-shadow.png
and then logout and back in.

Yeah I'm sorry - I meant maximized, not fullscreened.

If I use that shadow removal hack, will those get put back when the bug is fixed in a later package?

If you want to get the shadow back just do:
 cd /usr/share/unity/5/
 sudo mv panel-no-shadow.png panel-shadow.png
and then logout and back in.

This bug is particularly bad when showing a LibreOffice presentation on two screens in extended mode. The Unity panel shadow obscures the top of the presentation, which looks really ugly. See the attached screenshot for an example.

I doubt this is intentional, so I'm changing the status from Opinion; apologies if this is incorrect.

Shane, your screenshots of LibreOffice seem to show full screen windows. Please subscribe to bug 858378 which is more relevant to you.

This is a regression in Precise. I definitely do not think this qualifies as an opinion.

Whether the change was intentional I'm not yet sure. I have not yet asked Design or looked at the relevant code history. However if there is anyone (such as myself) who prefers the new behaviour, then the bug is a matter of opinion. This can be overridden by the design team of course.

I am subscribing Ayatana Design for a verdict.

awaiting design feedback ==> incomplete.

Is this still being looked into?

The offending code is fairly easy to change from what I've seen. It's just a matter of whether the panel shadow gets drawn before or after certain windows.

We are still waiting on feedback from the design team regarding what their preferred behaviour is.

the change was intended. bug 871760 is where it actually took place.

Confirmed by bug 871760. Drawing the panel shadow over other windows was a design decision. The change was intentionally introduced in Unity 5.4.

Here is a better fix, which won't be undone when unity next updates.

dpkg-divert --local --rename --divert /usr/share/unity/5/panel-shadow.png_disabled --add /usr/share/unity/5/panel-shadow.png

IMO the new behavior is better. The old behavior where the panel would not cast a shadow on maximized windows, even if they loose focus, has usability problems:

For example, if you maximize a window and then open a unmaximized window on top of it that window will now be controlled by a menu bar that's a part of another application window. By adding a shadow there is a clear distinction between the menu bar, that now controls another application, and the maximized window.

This problem becomes even worse if you do the same with some application that has it's own menu bar, such as libreoffice. The libreoffice window now has two menu bars with no distinction which controls what application.

The new behaviour tells "this menu now, isnt of the maximized window. but of something else".

IMO, even if it is necessary to convey this message, it should be done by a (black?) line [border] of 3-5px width. Definitely not a shadow 15 px long with gradient which is about 10px more obtrusive for the underlying maximized app.

In my use, I often keep one window maximized and one not-maximized for a reason: to be able to see the maximized content not overlapped by the unmaximized window. If at all overlap exists in a portion I want to see, I can move the un maximized window.
The 15 px height shadow cannot be moved, and will obstruct no matter what.
Whether or not those 15 px on top will hold any information which is important is a different issue, but the obstruction should be minimum, and flat. Gradients for borders are painful to look at, and gives me a feeling the composting manager has caused the issue, rather than an intended behaviour.

I have to agree with Bhaavan here. That information should be conveyed in a way that is more visually consistent. For example, an unfocused, maximization window always casts a shadow and gets darker when focused. This is backwards for the menu bar. It has no shadow when focused and part of a maximized window and a dark shadow when part of another window. Frankly, it just looks like a bug, even if it isn't. It's distracting.

This looks really bad on dual monitors where there might be a maximized window on each monitor.

I'd suggest changing the heuristic of not drawing the shadow from "focused window" to "topmost window on the current monitor". This way it would still work as intended, but not look as distracting on the second monitor.

It could be kind of confusing to not being able to do anything with the global menu though since it's only available for the currently focused window. I think you should allow multiple global menus at the same time - one for each monitor, for the topmost window.