Do you mean dimension like on a proper technical drawing that can be printed? Like this:
If so I think it is a brilliant idea, I have used the measure tool in Blender 2.8, but it doesn’t work as I would like and is a bit “weird” in operation to a draughtsman. See below:
They also disappear when you select another tool. However, the basic building blocks of code must be there for someone to develop into perhaps a new type of object (a “Dimensions” object) that consists of lines and text and will print… On that subject it would be nice if we could print line drawings, without using grease pencil, has that ever been looked at? Edge loops not made into faces do not render AFAIK.
I had considered adding a set of measure tools to my CAD functions, so you could measure the length between two vertices and set this as the “Delta” distance for example. It is very useful to be able to look at an object and say, “How far apart are these points” and use that to extrude another point the same amount. Even taking two points that are not on the X-Z plane but use their length on the X-Z plane to extrude another vertex - I may have to make a picture to explain that! This is a very necessary feature, my routines already do this to measure apparent angles of edges sloped in all axes on a global plane, like X-Z.
This line at the back is not planar to X-Z, but its angle in the front view relative to the X axis was used to draw the highlighted edge, which is planar to X-Z, making a flat face:
It is definitely feasible to have these tools, using Numpy routines to measure lengths and angles is quite straightforward, very powerful and very efficient in terms of computing time.
What is the level of support within BF for these developments, it would be a bit disappointing to do a shed load of work only for it to be “lost”.
Cheers, Clock.