SOLVESPACE -- parametric 2d/3d CAD

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"tangent arc" (by DIV)
Is there any special reason that tangent arcs are not allowed to be construction lines? Everything else on a 2D sketch seems to be able to be set as "construction line", (including Bezier curves), other than text (which is as expected).

BTW, there are a couple of other odd things about this.

(1) If I create a tangent arc in a 2D sketch, then parts of the original two lines that neighboured the selected (vertex) point are apparently converted into construction lines. If I select the entire sketch and press "G", then those lines which define the shape of the arc are toggled to white, but the arc itself doesn't get toggled. That behaviour seems inconsistent to me: if the arc itself can't be toggled, then I don't think the bounding lines should be toggle-able either.

(2) Depending upon precisely where I click on one of the neighbouring lines, with a single left-click I might either select the entire line (if clicking midway along?), or else just part of the line (if clicking far from the arc?). This was not what I expected, and I'm not sure whether it's intended (design behaviour) or not.

Example file attached.

Tue Oct 15 2019, 10:12:27, download attachment test_tangent-arc.slvs
(no subject) (by Paul)
The tangent arc tool asks that the point selected be at the end of two non-construction lines (I tried using it on construction lines). I don't know why. Not sure why one would want a construction line for the arc, but you can toggle all the lines and curves - select the arc and press G. Not sure why groups of selected elements work the way they do.

When the arc is created, 3 sketch entites are created and two are modified. I believe the original lines are changed to construction lines. Then two shorter (non-construction) lines are added, along with the arc and two parallel constraints. The tool seems to be designed for the specific use-case of rounding a non-construction corner (draw a rectangle and then round the corners for example). This leaves a line directly on top of a construction line and it can be tricky to select the one you want.

One might argue that it would be better to break the line segments into two. One construction and one non-construction, with a parallel constraint between them. You can manually create that. That would prevent the overlapping lines. However, any points already constrained to the line might have problems of some sort.

Unless the corner point is important to you (it is often useful to define a distance for example) I find it better to draw two lines, one arc, and apply the parallel constraints manually to avoid the construction lines entirely.
Tue Oct 15 2019, 15:00:34
Avoid the construction lines entirely for tangent arc creation. (by DIV)
Hi, Paul.

I agree that it's confusing having two overlapping lines. Maybe it was just a fluke that moving my mouse slightly I sometimes selected one line, and sometimes the other line.

In one sense, it could be good for the tangent arc tool to itself "avoid construction lines entirely". Maybe the bounding lines are necessary to be shown: it could be sufficient just to retain the external control point. (The original lines would be trimmed back appropriately, as already happens now.) If any user wants/needs construction lines between an end of the arc and the control point, then they could add them in manually.

It is possible even now to delete the bounding lines after a tangent arc is created.

Upon a little reflection, I can see the logic of including those bounding lines, which is that they are enforcing the condition of tangency.
BUT when I manually delete the bounding lines, and then drag one end of the arc, tangency persists even without any bounding lines nor the external control point! (In fact, separate arc-line-tangent constraints are explicitly shown in the Property Browser.) So it seems those bounding lines aren't really necessary at all.
Tue Oct 15 2019, 19:34:00
BUG: unable to toggle construction line status with lasso selection (by DIV)
I have just discovered that I CAN toggle the tangent arc as a construction line when I manually select that arc by clicking on it with the mouse.

Therefore it seems to be a BUG that when I select all elements, by dragging the mouse to create a selection-rectangle/lasso, it fails to toggle the construction line status of a tangent arc.

The same (buggy) behaviour occurs with regular arcs (non-tangent) and also circles.
Their construction line status can be toggled by manually clicking those sketch elements, but not by selecting with a 'lasso' of the relevant drawing region.
Tue Oct 15 2019, 19:38:00
Selecting overlapping lines (by DIV)
Here are some other forum posts about selecting a line when overlapping occurs:;parent=2641&tt=1553676286;parent=960&tt=1443734038
Wed Oct 16 2019, 08:13:30
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