I must first establish that I LOVE AFFINITY DESIGNER AND PHOTO !!!!
BUT ...... CANVAS-X by ACD Systems was the best program I had ever used as a graphic artist and a construction tradesman.
1) I could design LAYOUTS in 2-D, Then set my own Scale, In ANY Unit of Measure,
2) and then by merely drawing or selecting a vector object, it would give me the AREA in Square Feet
(or whatever the unit was that I designated) in a Dialog Box within the Menu Bar.
3) I could import a Blue Print and SET MY SCALE using any known DISTANCE. I would outline the floor plan with the vector drawing pen to determine the AREA and PERIMETER of the space.
4) It had built-in Dimensioning tools.
5) and it was a photo editor, publishing program and scientific design software as well.
If AFFINITY DESIGNER would incorporate this into it's UI, It would be powerful and complete!! I keep my old Mac G5 Computer Tower set up in my garage for the sole purpose of doing "TAKE-OFFS" of blue prints and to transpose my layouts that I create in Affinity, just so it can calculate the AREAS in Square Feet, and to get the PERIMETER Distance. Because Canvas-X will calculate any complex shape, its indispensable and I will never dump this computer until Affinity or Adobe get their act together.