Hi Abdullah, in your second screen grab it looks like you've solved it!
abdullah wrote:What do you think? If we decide to apply some offset
After looking at your screen grabs I think it is more helpful to the user if the Symmetry Constraint is not offset. With no offset the Symmetry Constraint symbol is directly aligned with the two outer points and lies on the line, and this direct orientation is another visual indication to the FreeCAD user of where these outer points are located. This visual cue can be very helpful in more complicated sketches having multiple symmetry constraints.
In your most recent screen grab, the two outer line segments both have their endpoints constrained symmetrically about the construction line, and the Symmetry Constraint symbol lies directly on the other lines. I think that is a better visual representation than the longer segment towards the middle of the construction line (where the constraint symbol is offset).
abdullah wrote:modify the symbol so that it is something like >|<,... or not, what do you think?
The Symmetry Constraint can also be used to constrain two outer points symmetrical to a middle point, so my initial thought is to keep the Symmetry Constraint symbol as it is now and not change it. Screen grabs are in this thread
if you'd like to have a look.
If you look at the rectangles in that posting, the endpoints of the construction line are constrained coincident to the two corners of the larger rectangle, and these points are constrained symmetrically to the middle point on the construction line. Two corners of the smaller rectangle are constrained the same way. When two sets of endpoints are constrained symmetrically to another point in the middle (kind of a unique situation) I think the symmetry constraint symbol only needs to appear to be a single symbol because clicking on either Constraint 21 or 22 in the constraints list causes the symbol to display in the 3D view as green.
abdullah wrote:It is me, or those icons are tiny?
I don't think it's just you, sometimes for me the constraint icons look small too.
abdullah wrote:Now I am rather satisfied with the result. Let me know your impressions.
Other than the offset I think they look great - it's much more helpful for the user if the constraint symbol isn't always displayed horizontally.
I'd still like to compile your branch and try your changes but that won't be for another 8 hours or so because I'm getting sleepy.