mir::scene::Surface::input_area_contains is reset when surface moved onto a new display

I'm changing ubuntu-keyboard to fill out its input shape/region.

qtmir/unity8 then calls mir::scene::Surface::input_area_contains on a surface that is hit by an input event in unity8 QML scene before deciding whether that Qt input event is gonna be transformed into a MirEvent and consumed/sent-to that mir::scene::Surface or whether it will pass through.

It all works as expected until I connect my mako to an external display. Once that happens, mir::scene::Surface::input_area_contains returns false on any point on any surface. Meaning that no surface gets input.

At the present moment, that code hasn't landed yet. It's in https://requests.ci-train.ubuntu.com/#/ticket/1525.

The qtmir patch is https://code.launchpad.net/~dandrader/qtmir/mirSurfaceInputBounds/+merge/296986

In the meantime I've added a workaround in this branch that makes qtmir store locally the input rect and use it to decide whether a point hits the surface's input area instead of querying mir::scene::Surface::input_area_contains