Implemented "level terrain" feature, fix #28

[DanielMowitz]

This is an overall naïve implementation, in the sense that it copies the height of the initial selected node and applies it to the whole area.

The main factors for code complexity stem from:

• my assumption that we want to level an arbitrary area and not always a rectangular area, which prevents some checks
• my personal requirements for levelling behavior on sloped nodes (see below)

The first point might be mitigated though by deciding on only having rectangular selection for levelling (see #1016).

Sloped node behavior

Slopes should lower the terrain when the selection is pulled from the lower side:

levels to

They should raise the terrain when the selection goes the other way:

levels to

Edged slopes should behave the same:

levels to

In all screenshots the rectangle was dragged up from the lowest edge (I couldn't more meaningful screenshots, sorry).

[lizzyd710]

Oh wow, this is awesome, thank you! I don't know why sonarcloud is throwing a fit, but all the checks pass so that's the key part. I'll play around with it and give a review.

[DanielMowitz]

As an aside, the format-files.sh script changed 16 additional files that I haven't touched at all. Maybe the Shell script/clang handles formatting a bit differently to the windows/js one?

[DanielMowitz]

… and with this commit it even compiles :+1:

[sonarcloud[bot]]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
8 Code Smells

1.2% Coverage
0.0% Duplication

[lizzyd710]

As an aside, the format-files.sh script changed 16 additional files that I haven't touched at all. Maybe the Shell script/clang handles formatting a bit differently to the windows/js one?

Maybe. It's also possible that those files were formatted wrong. (As you saw in some other files you changed in this PR someone was doing weird formatting so that's entirely possible.)