When != 0, this property will express the W:H ratio of the desired
output area (be it one monitor or the span of all monitors). At
the time of translating coordinates, coordinates will be skewed so
that the input area of the tablet is a rectangle of the given ratio.
Events happening in the input areas that fall outside the output
aspect ratio will be clamped to the nearest coordinate in the rect.
If the ratio is 0, the whole input area of the tablet will be used
and no coordinate skewing will happen.
https://bugzilla.gnome.org/show_bug.cgi?id=774115
And transform absolute events using this matrix. This property is
akin to the "Coordinate Transformation Matrix" property in X11,
and will be used to map tablets/touchscreens to outputs, favoured
over the libinput matrix which is meant for calibration.
https://bugzilla.gnome.org/show_bug.cgi?id=774115
