Allow ScrollContainer's ScrollBar to always claim space

[Arecher]

Describe the project you are working on

Attempting to use a ScrollContainer, to show it's limitations, in my opinion. As I said I would do in (#2119)

Describe the problem or limitation you are having in your project

The pop-in of the scrollbar, which rescales/moves content inside the scrollbar can be quite jarring. (This mostly happens whenever a scrollbar is used on a piece of UI that can be resized). I want to reserve a place for the scrollbar, so it doesn't need to adjust the content whenever it spawns. If the scrollbar isn't currently necessary, it will leave a blank space.

The issue: Whenever the scrollbar pops in, the content is moved/rescaled. I show this in editor, because I was too lazy to make the panelcontainer resizable in-game, but it works the same.

Essentially, allow me to give the Scrollbar inside a ScrollContainer a rect_min_size.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

An additional setting for ScrollContainers, which allows the space required for the scrollbar to be shown is always claimed for the scrollbar.
This can either be a manual x,y input, or a boolean which automatically takes the minimum size that the scrollbar can be, and claims that.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

Doing this with a custom built Scrollbar/ScrollContainer is very easy, as you can just set a rect_min_size and make the scrollbar invisible.

The scrollbar on the right doesn't move the content of the "ScrollContainer". It is assigned its own space, which isn't taken by the content when the scrollbar becomes invisible

If this enhancement will not be used often, can it be worked around with a few lines of script?

Not that I know of.

Is there a reason why this should be core and not an add-on in the asset library?

Core: Addition to functionality of ScrollContainers

[AndersonDeMatos]

That's the enhancement that I need in ScrollbarContainer for my project.

The Itens name area will have vertical scrolling enabled (but the VScrollbar will be 100% transparent), the numbers area will have horizontal scrolling enabled (but the HScrollbar will be 100% transparent), and the area where the itens are (bottom right) will have both vertical and horizontal scrolling enabled.
When I scroll any VScrollbar it will send a signal to scroll the other VScrollbar, and when I scroll any HScrollbar it will send a signal to scroll the other HScrollbar. The Idea is that the lines of itens stay always aligned with the itens names and the rows are always aligned with the numbers. When I press any Item Name button all the itens of that line are select and when I press any number button all the itens of that row are selected.
The problem is that when I reach the end of any scrollbar they are not aligned anymore because the contents of the bottom right area are moved a little more to compensate the space used by the scrollbars, but the contents of the top right and bottom left areas don't have that extra space, so they can't keep the alignment with the bottom right area.

With this enhancement I could do what I want to keep the itens always aligned with the names and numbers.

[Razoric480]

The workaround is to put your scroll container's first child as a margin container, then put whatever your stuff as a child of that. You then use/extend the following script:

tool
extends ScrollContainer

onready var _v_scroll := get_v_scrollbar()
onready var margin := $MarginContainer

func _ready() -> void:
	_v_scroll.connect("visibility_changed", self, "_on_scroll_bar_visibility_changed")

func _on_scroll_bar_visibility_changed() -> void:
	if _v_scroll.visible:
		margin.set("custom_constants/margin_right", 0)
	else:
		margin.set("custom_constants/margin_right", _v_scroll.rect_size.x)

(optionally add the same for h_scroll but on y)

But yes, it's kind of a drag and forcing the scroll bar (or at least forcing it to take up its size) would be a nice feature to have be part of scroll container.

[Calinou]

A built-in way to implement this (albeit hacky) would be to set the VScrollBar's modulate to Color(1, 1, 1, 0) (which does not free space for other Controls) and set its mouse mode to Ignore. This would be toggleable using a property in ScrollContainer (or an additional enum value).

[L4Vo5]

After godotengine/godot#48008 and godotengine/godot#55694, setting vertical_scroll_mode or horizontal_scroll_mode to ScrollContainer.SCROLL_MODE_AUTO or ScrollContainer.SCROLL_MODE_SHOW_ALWAYS achieves the desired effect.
I actually wish the old behaviour was available too 😅

[KoBeWi]

ScrollContainer.SCROLL_MODE_AUTO achieves the desired effect.

It doesn't

godot_459xJKFfdX.mp4

SHOW_ALWAYS is probably the closest to the requested feature.
Actually, it's better than having an empty space in place of the scrollbar, so I think this proposal is resolved?

[Arecher]

Personally I'd never want to show a scrollbar when it cannot be scrolled. It can only confuse users in my opinion, so I would still suggest adding an option to the default ScrollContainer that achieves this. And if anything, I'd probably want to show only the scrollbar background, without the grabber, when it's full size.

However with the SCROLL_MODE_SHOW_ALWAYS it makes it significantly easier to write a script to make it invisible/change the textures when it's unnecessary, so it's not vital. But since ScrollContainer is a single node, accessing the @VScrollbar and @HScrollbar children to make such custom logic can be confusing to new users. Definitely took me a long time back in the day to realise they were just nodes that got added to the tree, rather than built-in, inaccessible parts of the Container.

[KoBeWi]

I think we could add SCROLL_MODE_RESERVED, which is like SCROLL_MODE_ALWAYS, but hides ScrollBar when it can't be scrolled.