[Core] Reformat structure string operators

[aaronfranke]

Implements and closes godotengine/godot-proposals#1819

Explanation in bullets below each set of outputs. Test code:

func _ready():
	print("Vector2")
	print(Vector2())
	print("Vector2i")
	print(Vector2i())
	print("Vector3")
	print(Vector3())
	print("Vector3i")
	print(Vector3i())
	print("Color")
	print(Color())
	print("Quaternion")
	print(Quaternion())
	print("Plane")
	print(Plane())
	print("AABB")
	print(AABB())
	print("Rect2")
	print(Rect2())
	print("Rect2i")
	print(Rect2i())
	var t = Transform2D()
	t.x = Vector2(1, 5)
	print("Transform2D")
	print(t)
	var b = Basis()
	b.x = Vector3(1, 5, 0)
	print("Basis")
	print(b)
	print("Transform3D")
	print(Transform(b))

Output with current master:

Vector2
(0, 0)
Vector2i
(0, 0)
Vector3
(0, 0, 0)
Vector3i
(0, 0, 0)
Color
0,0,0,1
Quaternion
(0, 0, 0, 1)
Plane
0, 0, 0, 0
AABB
0, 0, 0 - 0, 0, 0
Rect2
(0, 0, 0, 0)
Rect2i
(0, 0, 0, 0)
Transform2D
((1, 5), (0, 1), (0, 0))
Basis
((1, 0, 0), (5, 1, 0), (0, 0, 1))
Transform3D
1, 5, 0, 0, 1, 0, 0, 0, 1 - 0, 0, 0

The current output is a bit confusing and inconsistent:

• Color is lacking spaces after the commas.

• AABB and Transform both contain a dash, which can be mistaken for a minus sign.

• Some things have parenthesis, some don't, and Basis/Transform2D have nested parenthesis.

• Transform2D prints out column-major, while Basis prints out row-major, and Transform is row major except the origin is last.

• The current internal code is a bit strange, with some of the string logic being inside of Variant and some being in the class.

Output with this PR:

Vector2
(0, 0)
Vector2i
(0, 0)
Vector3
(0, 0, 0)
Vector3i
(0, 0, 0)
Color
(0, 0, 0, 1)
Quaternion
(0, 0, 0, 1)
Plane
[N: (0, 0, 0), D: 0]
AABB
[P: (0, 0, 0), S: (0, 0, 0)]
Rect2
[P: (0, 0), S: (0, 0)]
Rect2i
[P: (0, 0), S: (0, 0)]
Transform2D
[X: (1, 5), Y: (0, 1), O: (0, 0)]
Basis
[X: (1, 5, 0), Y: (0, 1, 0), Z: (0, 0, 1)]
Transform3D
[X: (1, 5, 0), Y: (0, 1, 0), Z: (0, 0, 1), O: (0, 0, 0)]

• I've moved all the code to the classes and out of Variant.

• No dashes anywhere, parenthesis used for grouping with commas for separation.

• Transforms and Basis are now printed consistently and with explicit labels to avoid any confusion.

• Since they store real_t, I decided to use String::num_real, but normally this adds a trailing .0 to whole numbers, so I added a new bool to include it or not called p_trailing, which defaults to true so its current uses are the same.

• Color is an exception to the above, it uses String::num with a fixed amount of decimals (4 seems like a good value, but maybe 5, 3 or 2 would be better).

[aaronfranke]

I updated this PR with C# changes that match the behavior above.

This should be good to merge any time, the sooner the better.

[akien-mga]

Do we really want to make this optional though? IMO it would be just as well to enforce it, so that it's always clear that it's a real and not an integer.

Edit: I'm not asking to change it for now, just putting this up for debate.

[aaronfranke]

Either is fine to me. I made it this way because it's the existing behavior for floats, but maybe it's better to always show it to make it clear that it's a float.

P.S. In C#, the default behavior of converting numbers to string does not include the trailing decimals, so if we want them I'd add a format specifier ("0.0#############").

EDIT: Actually, the C# bindings generator currently depends on it not having trailing decimals. This could be fixed in the bindings generator, though.

[jonbonazza]

@akien-mga @aaronfranke i put this in the accompanying proposal already, but this is important so im leaving it here too. This can't be merged as-is

Printing mtiple lines is npt an option. Often times, you want to coalesce the string representation into another string. Most importantly though, it makes it unusable in log lines (for instance in server logs that are consumed by a log consumer such as fluentd)

[akien-mga]

Thanks!

[RolandMarchand]

Legendary PR.