New windows have incorrect dimensions on launch (not the dimensions the app specifies)

Status changed to 'Confirmed' because the bug affects multiple users.

Actually this bug occurs with all toolkits, not just Xmir.

Unity8 chooses an incorrect window size.

This also does not require design input as the apps themselves are providing sane default dimensions and Unity8 is just ignoring them. It works in other Mir shells though.

When I say "sane" default dimensions I mean Unity8 is ignoring the initial window size specified by apps and always resizing them to something incorrect on launch.

This seems closely related to bug 1543467 too. Possibly a duplicate as in both cases the problem is Unity8 failing to honor the dimensions specified by the app.

Can we have a specific example of the bug?

The size of the window requested is a hint to the window manager, not a requirement. The requested size may legitimately be overridden (e.g. for layout reasons).

I.e. There is no guarantee that size created matches the requested size.

Unity8 is overriding the client-requested window size in phone/tablet mode, but this shouldn't be happening for desktop mode.

We also need to save the client-requested window geometry in case shell later wishes to apply that.

Agreed I'd like a specific example

Specific examples:
(1) Open a drop-down menu in a GTK app and verify it looks the right size.
(2) Hover over some elements that will pop up a tooltip and to verify the tooltip is a sane size.
(3) xclock -geometry 100x100
(4) Run 'zenity --scale' and verify the default window size fits neatly around the widgets like in X.

I think you've probably fixed all this recently but it's mostly been discussed in bug 1543467 as mentioned above.