OptionButton 'fit to longest' does not match dropdown menu size

[Aisoipheo]

Tested versions

Engine Version: v4.5.1.stable.fedora.f62fdbde1
Using editor

System information

Fedora 43 - Godot Engine v4.5.1.stable.fedora.f62fdbde1 - Vulkan 1.4.318 - Forward Mobile - AMD Radeon RX 7800 XT (RADV NAVI32)

Issue description

When creating a OptionButton with a few items and checking 'Fit To Longest Item' option dropdown menu of component does not match the size of button and overextends to right for approx 8 pixels. The only way to fix this is to set minsize that is larger than longest item. (Yes i checked options for trimming whitespace and checked that item has no whitespace in the end)

As it is shown above longest item has some space in the end in dropdown menu and it causes dropdown menu to overextend

Steps to reproduce

1. Scene > New Scene > Add Child Node > Option Button
2. Set 'Fit to Longest Item' true
3. Add a few items
4. Run Current Scene
5. Open dropdown menu

Minimal reproduction project (MRP)

option-button-bug.zip

[Aisoipheo]

Desired state is when button and menu sizes are matched when checking 'Fit to Longest' option

[rsubtil]

Can reproduce in v4.6.beta3 and v.4.3.stable, but not on v4.2.2.stable. Seems to be a regression from quite some time.

[rsubtil]

⚙️ Bisecting...

[rsubtil]

Bisected to f29a7d3 (#64351)
cc @Rindbee

[Rindbee]

This is not a regression issue.

Bisected to f29a7d3 (#64351)

Its parent commit can still reproduce the issue.

Furthermore, #64351 only modifies the calculation order during drawing (NOTIFICATION_DRAW). It fills the elements within the space defined by the size. The issue of inconsistent sizes should be addressed in *Button::get_minimum_size().

This is essentially a calculation issue, not only a drawing issue.