[panel] The main panel is not on the leftmost monitor in a dual-head setup

By 'The button for the spread' do you mean the Ubuntu button? The button which opens up the Dash?

Moreover it would be good if you made a screenshot of this so that developers can understand the situation. Thanks.

Also affects me, I have an old Radeon that displays garbage with Unity 3D so am running the official Unity 2D from the Repo's

I Think this could be related to monitor 1(on the card) being on the right hand side of monitor 2

Thank you samo_nz. That screenshot reflects my problem as well.

Perhaps a clearer description of this would be: The Ubuntu Button and the Dash are always on different monitors.

Clearly this is undesirable behavior.

is this also an issue on Unity(3d) you seem to be using unity-2d. If so can you please attach a screenshot of the problem in unity too.

Quick guess: the code that determines where to position which panels relies on the screen numbers only instead of testing which screen is the primary monitor.

In addition to the Ubuntu button being on the panel on the other monitor, the window control buttons (close, min, max) appear on that panel too. So the current window has a pair of control buttons on both monitors.
This I did not see on the screenshot attached in comment #2.

A correction: the extra set of buttons appear only for maximized windows. Once I toggle maximization they go away from the second panel.

@Jani, you may want to file that as a separate bug, as it seems to do with unintended mirroring in the two displays. (Does anyone want the taskbar at all on the secondary monitor? Not me.)

@Joel, you mean the control buttons issue as a separate bug? Indeed there is some overlap in the two panels - I think I should just do a clean install, as configs from gnome-panel / unity may be picked up?
Right now both panels have sound/empathy/time/shutdown, but only second panel has ubuntu button network-manager and me-menu.

@Joel, Jani: let me try to summarize what the expected behaviour is (by design): there should be one panel per monitor. The panel that is on the same monitor as the launcher has additional "features" compared to the panels on the other monitors: it has the ubuntu button that invokes the dash, and it hosts the legacy systray icons. All panels can display the window controls and title, as well as application/system indicators (like sound/datetime/me menu…). The window controls and application title for the active window will appear only in the panel that is on the same screen as the active window.

Now, considering that the launcher must always be on the leftmost monitor (because space for panels, aka struts, can only be reserved at the edges of the virtual desktop), as a consequence the "main" panel (the one that has the ubuntu button and that hosts the systray) should also always be on the leftmost monitor. IIRC the code that handles this tests on the primary monitor rather than the leftmost one, which is probably the cause of the issue.

I can reproduce with a dual-head setup where the primary monitor is the rightmost one.

The screen index used to identify screens cannot be used to determine the leftmost monitor.

@Olivier, that is a very good summary of the issue. I would argue that there are two bugs at play here.

1) Exactly as you have stated, main panel should be on leftmost monitor instead of primary, and

2) Each monitor's panel should only have controls and title for windows maximized in that particular monitor, instead of on both monitors.

Your analysis is correct Joel. Those are technically two separate issues, but they can be fixed in the same bundle as they are very related one with another.

On second thought I filed a separate bug report for the window controls present on all panels for maximized windows. See bug #771306. I am about to submit a merge request that fixes both issues.

This applies to Unity 3D on my triple head setup.

As you can see in the attached image, Catalyst Control Center shows that the first output is the leftmost display and second is the rightmost.

seems like bug 742544 is on the same issue and have a few duplicates too.

@Omer: the two bugs are indeed related, even though bug #742544 is about the position of the launcher whereas this one is about the positions of the top panels.

@Gaz: as pointed out by Omer, I think the issue you are experiencing is bug #742544.