Improve the placement logic for slabs, etc

[Oblomov]

When placing stairs+ nodes with the special / fast key (E), an alternative placement strategy similar to the one from MTG (and actually batter, IMO) is used. The new / alternative strategy is as follows:

• items in the same category clone the param2 of the node they're being placed next to; this allows putting adjacent slabs/stairs all with the same orientation without worrying too much;
• otherwise, the orientation for the placement is chosen according to the area of the node clicked: this allows placement of “high” slabs by clicking on the upper half of a side face of another node, and similar to orient the vertically-placed slabs according to the close/far position.

[Oblomov]

I'm putting it out here for testing, but it's possible may need some more tuning, especially for the “from the bottom” placement.

[Oblomov]

OK this definitely needs more work. (I wanted to change the title to [WIP] but apparently I cannot.)

[Oblomov]

Revised all the placement computations, now they seem correct. I have tested predominantly with the inner staircase (slap + raised corner): the slab corner corresponding to the raise now always goes to the face quarter that was clicked on. So for me this is now ready for merge, although of course further testing is welcome.

[Oblomov]

OK, maybe not yet, I am still having second thoughts about the modifier to use. I want to move to sneak+placement, but this requires some thought about handling of param2 copy.

[Oblomov]

New revision of the PR, with further revised, simplified placement rules. These are direct extensions of the standard placement rules, so they do not use a special key. Instead, top/bottom or left/right side of the face, where appropriate, is checked to determine the placement orientation. The aux / special / fast key can still be used to place same-category nodes with the same orientation, or to place nodes as if the placer was on the opposite side otherwise.

[BuckarooBanzay]

@Oblomov maybe i'm using that wrong, but if i now try to place slopes onto a flat surface (without special/E key) the slope gets placed weirdly with the slope part facing the ground (in some extreme cases) :confused: Building with slopes like this really is a nightmare now, sorry...

Was that your intention or am i using that wrong?

Illustrations

Before your PR:

After your PR:

Every slope was placed while standing on the center trunk

[OgelGames]

It's the snow that is causing this. I tested without snow, and they were placed correctly (as in image 1), but when I placed them in snow, they got placed sideways (like image 2).

I also found that placing nodes next to each other was much easier, just like it was intended to be.

[Oblomov]

Can you please open an issue describing the problem? I'll try to debug this when I can. I've also seen some odd issues on Android, so there's definitely some quirk that needs to be resolved in the new logic.