[Regular Shape] Allow to finish regular shapes with left mouse click

[qgib]

Author Name: Harrissou Santanna (@DelazJ)
Original Redmine Issue: 17701

Redmine category:digitising

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I was about sending a bug report entitled "Unable to use the Add Circle from 2 tangents and a point" (will also concern the 3 tangents one) when I realized that the dozen of minutes I spent trying to figure out what was going wrong is due to me clicking the third point with the left mouse button instead of the right one.
I know that right-click is used to finish the feature shape in QGIS but until now, shape was undefined; QGIS was unable to know whether the user is willing to add a new vertex or not, so a dedicated button is required.
With Regular shape tools, QGIS knows how many clicks are expected and what the shape would look like. However, in the current implementation, clicking more than required does nothing; QGIS just ignores (afaics) the left mouse clicks when he expects the final click (ie a right click) is expected. And with no hints shown to the user, this doesn't seem to be a nice UX imho.

Couldn't we accept the left click as an equivalent of the right click when enough clicks have been done? Or accept the left-click and draw a preview of the shape and then wait from a right-click to confirm and finish/open (if required) the feature form?

[qgib]

Author Name: Loïc BARTOLETTI (@lbartoletti)

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Hi Harrissou,

To tell you the truth, in my tests (and the old plugin), I finished digitizing with a left click.
As on QGis we finish the digitization of the geometries (except the simple point) by a right click, I followed this way.

I thought about adding messages to a bar to indicate where the user is in their digitization.

[qgib]

Author Name: Harrissou Santanna (@DelazJ)

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I would find allowing left-click to finish or "about-to-finish" features digitizing a better UX than a message popping on the status bar (not sure people really pay attention to this place) or the message bar (in the long run, can be boring)