Which issues need to be reopened then?

I have reopened #20882.

@Roy-043 should we merge this onto only the 1.1 branch? Or do you want it on main as well?

I'm in two minds about this one. Having extensively used the SillHeight property during the 1.1dev cycle, I'll sorely miss it, as it makes the window positioning workflow so much effective.

I agree with the statement made on #26233 to potentially simplify the SillHeight calculation:

the sill height should be measured from the placement of the window, which should normally match the floor level the window belongs to. So: if Placement.Base.z=3000 and SillHeight=850, the bottom of the window is at 3850.

I can see it introduces a regression (which I reported myself), but I do wonder whether there is an easy way to implement the above without removing the feature.

I understand that reverting the work of others in a FOSS project is by definition controversial. But in this case I see no other option.

There are scenarios where the solution will fail. For one thing, the sketch the window is based on should never be moved in the Z-direction. But a window does have a Move Base property, which instructs Draft_Move to move the sketch instead of the window. After moving the sketch in the Z-direction the Sill Height is not updated and no longer makes sense.

More importantly perhaps is that a window is an Arch Component. We cannot look at windows in isolation. Whatever we decide about the way windows interact with their base sketches has an impact on all other BIM objects. We are talking about major changes that will require a lot of work and care.

@chennes This should also be merged on main.

I also don't like undoing work, but in this case this seems appropriate as the implementation is indeed wrong. The sill property in the current form is a "dummy" property that in fact hackishly changes the placement. It is annoying and very error-prone.

I agree with the proposal, the final positioning of the window should be position.z + sill, and those two properties should not modify each other. But, simply changing the code to this would cause problems to existing files (the windows will suddenly "jump" to a new location if they have a non-zero sill value). So I think it's best to do as @Roy-043 suggests, first step remove the stuff (and existing files stay as they are), second step re-implement and then we can take more care

I hope this setting won't be forgotten and will be implemented again in a more correct manner.

My thoughts on this topic, briefly.
The Z coordinate is the origin coordinate.
The window sill height is a local offset (similar to offset in other tools) that doesn't affect the Z coordinate of the origin.

Successfully created backport PR for releases/FreeCAD-1-1:

• [Backport releases/FreeCAD-1-1] BIM: remove v1.1 Sill Height code #26682