Expose the TabBar of a TabContainer

[raulsntos]

Add TabContainer::get_tab_bar method to retrieve the TabBar of a TabContainer.

• Implements point 2 of Make the TabContainer node use Tabs internally, instead of its own implementation godot-proposals#2514 (comment).

[YeldhamDev]

In my original PR, where I made TabContainer use TabBar internally, I decided to not have this function because of how the former depended on the latter to be in sync with what was happening. If it's decided to expose it anyways, it should be stated in its doc description (which appears that there isn't even one yet) how fragile it is.

[raulsntos]

I'm not totally sure I need this to be exposed, my goal is just to add buttons to the right of the TabBar of a TabContainer. Do you think this functionality should be exposed in a different way?

[YeldhamDev]

Funnily enough, there's a theme constant that does something similar, side_margin. However, the margin affected depends of the tab orientation.

[raulsntos]

I'm not sure how I can use side_margin to achieve what I want.

For context, I'm using TabBar in #80260 to make the MSBuild panel more consistent with the rest of the editor. I'm trying to follow the same design as the scene tabs which also has buttons on the right side:

To achieve this I'm using this code¹:

var tabs = TabContainer.new()

var tab_actions = HBoxContainer.new()
tab_actions.size_flags_vertical = Control.SIZE_EXPAND_FILL
tab_actions.size_flags_horizontal = Control.SIZE_EXPAND_FILL
tab_actions.alignment = BoxContainer.AlignmentMode.ALIGNMENT_END
tab_actions.set_anchors_and_offsets_preset(Control.LayoutPreset.PRESET_FULL_RECT)

tabs.get_tab_bar().add_child(tab_actions)

Footnotes

1. The PR does this in C# but I translated it to GDScript here because it'd be easier to understand for other contributors. ↩

[YeldhamDev]

I'm not sure how I can use side_margin to achieve what I want.

I was just pointing out one of the node's features that could be modified to achieve that.

Considering that currently TabContainer also has the set/get_popup() methods, which adds a button to open a given popup, maybe this should be expanded further, adding an add_button() method as well?

[raulsntos]

I've opened #80301 to implement your suggestion. Either way works for me, let me know which you prefer or if you want me to change it further.

[YuriSizov]

Generally speaking, I don't see any harm in this. We expose methods to get inner nodes all the time, and this one is pretty important to the affected container. That said, if for the particular problem we don't need this solution specifically, then perhaps we should wait for some demand.

[akien-mga]

Thanks!