Screen rotates despite phone being held flat because of previously detected rotation

[Matthew Exon]

The phone should only rotate the screen if it detects that the current position and the currently displayed app are inconsistent. If the phone is being held flat, do not rotate the app.

Test procedure:

* Open, say, the browser
* Hold the phone with the short side perpendicular to the ground, long enough for the browser to switch to landscape mode
* Move the phone flat to the ground (by putting flat on a table)
* Swipe from the right and select another app (say settings)
* Hold the phone with the long side perpendicular to the ground, long enough to switch to portrait mode
* Move the phone flat to the ground again
* Swipe from the right and select the first app (browser)
* Browser immediately rotates - even though the phone is flat

Part of the reason this is bad is that much of the user interface still doesn't rotate, particularly the parts you first see when you switch on the phone. So it comes as a surprise when you finally navigate to your app and it rotates to the wrong mode for no apparent reason.

Even so, however, if the phone is flat and you're rotating the orientation, you're saying you somehow know which side of the phone is pointing away from me. You don't. So do nothing.

One of the effects of doing what I suggest is that when the phone is flat different apps will be in different rotation states. If the phone is being held flat I'd say that's correct. But if that is considered bad UX, then the logic should be to just stay in the same state as the previous thing that was on the screen. If that was another app, rotate to that app's orientation. If that was the lock screen or something, rotate to portrait.

Also: a rotation animation should only be displayed when the orientation of the phone changes. It's disconcerting to see it switch when the phone hasn't moved. It also wastes my time. It's true that this will cause a jump with the blurry screenshot, but that shouldn't be displayed for long, right?

[Pat McGowan (pat-mcgowan)]

await design input

[Vesa Rautiainen (vesar)]

One very important thing that is not considered in this bug description is that the Shell orientation and the app orientations need to be in sync. Always. This is due to the bottom edge swipe that is a gesture that belongs to the application. So what is bottom for the app, needs to be bottom for the Shell as well. Otherwise different gestures would collide.

Orientation UX specification states basic rules for application and shell orientations:
1. Application orientation follows the device orientation as long as that orientation is supported by the application
2. Shell orientation follows always current application’s orientation

Consider this use case:
- Open Browser and turn the device to landscape. Device in landscape -> Browser in Landscape -> Shell in Landscape.
- Open System settings app in landscape and turn the device to portrait. Device in portrait -> System settings in portrait -> Shell in portrait. (Browser still in landscape)
- Lay device flat on the table.
- Use right edge switcher to focus to Browser.

Now the shell is in portrait and the focused Browser application in landscape. Something needs to be done as the app and the Shell are in different orientations. Either the app needs to rotate (which might be unwanted behaviour for some users) or the shell needs to rotate and change for example the edge through which to access the switcher. I'm sure some users find this also unwanted behaviour.

There is already a bug open about this issue: https://bugs.launchpad.net/ubuntu-ux/+bug/1500633
Whether the current behaviour is correct or needs fixing will be discussed in that report and this is marked as a duplicate.