Add inner_item_margin_* Theme constants to the Tree control

[joao-pedro-braz]

Description

This PR adds the "inner_item_margin" Theme constant to the Tree Control.
It behaves like a horizontal padding (in CSS), but only in the active
writing direction (So on LTR it'll apply a left padding and on RTL right
padding).

This PR also makes use of this newly added feature to adjust the Editor Theme.
Previously, icons, like the ones in the FileSystemDock or even in the SceneTree, didn't have proper spacing between borders and would therefore appear too close to them, which was specially noticeable with large Corner Radius values, such as 6.

Comparisons

Currently (pre-PR)

File System Dock

File System Dock in RTL

With PR

File System Dock

File System Dock in RTL

Note 2: This superseeds my first PR and also my second PR

[joao-pedro-braz]

Basically #74321, but with different branches

[KoBeWi]

The StyleBox does not work well if it draws anything:

godot.windows.editor.dev.x86_64_rzRLAYLYKz.mp4

It overrides any other style.

If your aim is only to increase spacing, maybe it should be a theme constant instead?

[joao-pedro-braz]

@KoBeWi

Interesting... In a way that's kinda expected, given that the "item" StyleBox is only for the item itself, so everything in red doesn't really "belong" to the item and is more akin to an outer padding:

But I do see how that might be confusing and counter-intuitive!
I'll have a look at implementing it as a theme constant.

[KoBeWi]

What I meant is that selected and focused style no longer shows, because item overrides it, which is wrong.
But yeah, constant would be better for this use-case anyway.

[joao-pedro-braz]

@KoBeWi

Do you rather I force-push to this branch or create another PR altogether?

[KoBeWi]

Force-push this one, but you'll need to update commit message and title.

[joao-pedro-braz]

Sure thing!

[joao-pedro-braz]

@KoBeWi

Done!

Thank you for the suggestion, this new approach is not only simpler, but also stabler when on RTL, given that the text no longer "moves" around when resizing the item.

[joao-pedro-braz]

Force-pushed again to update the default value for the editor theme.
Seems to be good to go.

[joao-pedro-braz]

Github apparently had a stroke and force-closed my issue :/
Reopened and fixed a conflict in tree.cpp

[KoBeWi]

The feature itself works correctly and implementation looks ok.
There is no linked proposal though.

[joao-pedro-braz]

There is now: godotengine/godot-proposals#6902
😄

[YuriSizov]

The StyleBox does not work well if it draws anything:

I think we should start accepting cases where only StyleBoxEmpty makes sense. We have pleeeeenty of controls that need 4 numeric definitions for each side. Using 4 constants or arbitrary using only one constant doesn't seem practical. Like, why we only add one constant here? And with such vague name too.

If we don't want to go the StyleBoxEmpty route, then this PR needs to be updated to introduce 4 constants, like we did in #70901.

• item_margin_top
• item_margin_bottom
• item_margin_left
• item_margin_right

[joao-pedro-braz]

Interesting, if we were to add the StyleBoxEmpty back I guess it could just act as a container for the margin values (ie, without actually being drawn)?
Also, about the name, I got the inspiration from the "item_margin", which does virtually the same thing, but applied to the outside of the item (From the docs: The horizontal margin at the start of an item. This is used when folding is enabled for the item.).

[joao-pedro-braz]

@YuriSizov Went with the 4 constants route, as per #70901.

[YuriSizov]

Also, about the name, I got the inspiration from the "item_margin"

Ah, right. That existing property is some weird hack, but I guess we have to work around it now.

[kleonc]

Currently (pre-PR)

With PR

Not sure if it's just me but I do like the "before" look more. The "after" seems like wasting horizontal space for no reason/gain.
What I'm saying is maybe the default editor Theme should be made to look like before (or have a smaller left mergin)? 🤔
(given nobody mentioned it yet it's likely just me 😄)

[joao-pedro-braz]

I think the "wasted space" is an illusion because of that icon in particular (the teardrop rainbow).
With other (specially squared) icons, the issue seems more prominent, not to mention with rounded themes, which was originally my inspiration for this.

[YuriSizov]

What I'm saying is maybe the default editor Theme should be made to look like before (or have a smaller left mergin)?

I definitely don't like how it looks now, and it bothered me for years at this point, but I agree that we can use a smaller extra margin by default (and we can perhaps respect the additional spacing editor setting here for a bit of extra space for those who need it).

[joao-pedro-braz]

Great idea!
I'll work on it rn

[joao-pedro-braz]

Done!

Without additional spacing:

With additional spacing (value of 3):

[YuriSizov]

Thanks!