Add streaming digitizing mode

[nyalldawson]

When active, points are automatically added following the mouse cursor movement. You can quickly toggle between normal (or circular string) digitizing and streaming by hitting the "R" key mid-digitize operation.

Works with all the map tools you'd expect: digitize line/polygon, add ring, add part, reshape, split features/parts, ...!

Refs Natural resources Canada Contract: 3000720707

[Saijin-Naib]

This is going to make digitizing with my drawing tablet so much nicer!
Thanks so much, Nyall!

[nyalldawson]

~~Oops. forget that I need a new icon for this tool 😆 ~~

[github-actions]

@nyalldawson
This pull request has been tagged as requiring documentation.

A documentation ticket will be opened at https://github.com/qgis/QGIS-Documentation when this PR is merged.

Please update the description (not the comments) with helpful description and screenshot to help the work from documentors.
Also, any commit having [needs-doc] or [Needs Documentation] in will see its message pushed to the issue, so please be as verbose as you can.

Thank you!

[uclaros]

Nice!
How does it play along with snapping and tracing?
Also, can it be used in conjunction with Digitize with curve? If not, some kind of a tri-state selector between StraightSegments, CircularString and Streaming would make sense.

[gioman]

How does it play along with snapping and tracing?

as also with "avoid overlaps".

[uclaros]

Avoid overlaps is handled later on each tool, after digitizing is completed so it should not be affected.

[nyalldawson]

@uclaros

How does it play along with snapping and tracing?

Snapping works as you'd expect, but tracing is bypassed whenever streaming mode is enabled. I don't really see how these two options could work together, because tracing implies a click somewhere and then a click somewhere distant from that first point to trace between.

Also, can it be used in conjunction with Digitize with curve? If not, some kind of a tri-state selector between StraightSegments, CircularString and Streaming would make sense.

I've moved the circular string toggle into the newly introduced drop down group:

[nirvn]

@nyalldawson , really nice stuff (this PR and the prep PRs that preceded it).

[nyalldawson]

Thanks @nirvn!

[github-actions]

@nyalldawson
A documentation ticket has been opened at qgis/QGIS-Documentation#6582
It is your responsibility to visit this ticket and add as much detail as possible for the documentation team to correctly document this change.
Thank you!

[albertolozada]

Hi, I have a question. ¿How you can end the trace without right clicking and open the attributes table? Thank you so much!