[Libreoffice-ux-advise] [Bug 105618] Weaknesses in creating Bézier curve

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=105618

--- Comment #4 from Regina Henschel <rb.henschel at t-online.de> ---
(In reply to Heiko Tietze from comment #3)
> Created attachment 131387 [details]
> Sequential steps to create a curve with Inkscape
> 
> (In reply to Regina Henschel from comment #0)
> > Show all control points and all help lines while creating a Bézier curve.
> That requires an assumption of the curve. You can draw a straight line with
> the curve today by double-clicking the second point.

Yes, that is one of the automatic reductions. But it is not the usual way to
use Bézier tool, because the more suitable tool for such a task is the Polyline
tool.

> 
> > Always show different line styles for help lines and parts of the curve.
> Yes, but isn't that how it works today? Control points are connected with
> dashed lines in Draw 5.3 at least.

Not at the beginning.  When you start with click-mouse-button-down, and then
drag, and then do a mouse-button-up, then a control point is set. So in first
place this line is a help line from anchor point to control point and should be
dashed, so that the user knows, that he is going to set a control point by
mouse-button-up. Later on it is correct.

> 
> > Create the second and following segments the same way as the first segment.
> You mean to connect another Bezier curve after the first rather than adding
> a line? Alternatively we could just end after the second click - and allow
> to add segments/points later. One could also argue that right click to
> delete the last point is not obvious, but users can easily try it out.

Currently you add a Bézier segment (hold mouse button down as in the
beginning). The next mouse-button-up generates a control point for the first
segment at the position where you do the mouse-button-up, and it turns the
second anchor point to a symmetric transition and therefore generates the first
control point of the second segment automatically in addition. But the user
does not know this, because he doesn't get the associated help line to this
control point. So the user is surprised, that he cannot set a control point,
but has do set the end-anchor-point of the second segment.

It would already be an improvement, if this automatically inserted, associated
control point and its help line is shown too, as Inkscape and Corel Draw do it.
Another improvement would be to allow edge transition as Inkscape does.

You can add and delete points always later. That does not solve the problem.

Continuing a first segment with a straight line is only one way to use this
tool.

"Right click to delete" is indeed not obvious. Right click for reverting last
step is new to me and not mentioned in the help. Another thing to improve, not
this function, but the help.  

> 
> > Add help text for use of Alt-key to the text "Drawing Curves".
> Don't get this.

If you hold the Alt-key down, when you click for an anchor point, then the
curve up to there is closed and your mouse is "free" and you can draw a next,
closed curve, but you stay _inside the same object_. The result is the same as
if you first draw two objects and then combine them.

> 
> > Please have a look at Inkscape or Corel Draw to see other UI concepts.
> Inkscape works very similar. You start with a straight line and have to
> click once in order to see a curve and a second time to finish it. But
> unless you double-clicked, segments will be added. Inkscape supports the
> user with coloring and keeps the first helpline active, however. Good idea.

Corel Draw keeps showing all anchor points while creating the curve.
Inkscape allows to switch from symmetric transition to edge transition by
holding shift key. Inkscape shows possible modifiers in the status bar. All
further nice ideas.

> 
> What also would be really helpful is when the coordinates would be shown at
> the control (not only for curves). The statusbar is way too far away to
> attract the attention when a curve is being drawn or modified. And when we
> could edit the end points as well as the control points we'd have a perfect
> tool.
Yes, better numeric control of point positions, is really desired, not only for
Bézier curves but for polylines and legacy arc and segment too.

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