Fibers - a small technical change in AutoCAD 2015

You have probably NOT noticed a small technical change in the latest AutoCAD 2015. This change is more important for programmers but it has also some consequences for normal AutoCAD users.

AutoCAD (at least its Windows versions) has traditionally used so called "fibers", an old Windows multitasking technology for switching contexts and threads. This allowed AutoCAD to switch drawings (documents in Windows terms) transparently in a middle of a command, without interrupting it. You could start a polyline in one drawing, switch to a different drawing opened in the same AutoCAD session, draw something there, and then return back to the original drawing to continue with the original polyline.

This is maybe a nice feature but it was not used much. And first of all it created major technical obstacles in debugging add-on applications, especially modern .NET and ObjectARX plugins, as Windows do not fully support this fibers technology anymore. See programming details on ADN DevBlog. Our programmers do like this change.

So since AutoCAD 2015, switching MDI context (switching to another opened drawing tab) now effectively means interrupting the active command - like pressing ESC. Do not confuse this with switching viewports in layouts - you can still use this type of "in-DWG" context switching in AutoCAD 2015.

There won't be many mourners at this funeral...