Fix OptionButton PopupMenu not shrinking after item changes

[Clubhouse1661]

Fixes #114786.

Updates OptionButton::show_popup() to correctly handle PopupMenu resizing when content changes from larger to smaller items.

• Calls popup->set_min_size(Size2(0, 0)) before opening. This is crucial because Window::popup(rect) clamps the size to the current min_size. Without resetting it, the window refuses to shrink to the new smaller content size because it's still constrained by the previous items' minimum size.
• Explicitly enables popup->set_shrink_height(true) to ensure the height is recalculated to fit the new content.

Verified with the MRP from the issue. The PopupMenu now immediately shrinks to the correct size when switching from long items to short items.

Before_bug.mp4

After_bug.mp4

[AThousandShips]

Please turn off the copilot feature for contributing to Godot, it creates a lot of noise (and uses CI resources) and risks including bad suggestions that you then have to fix because it didn't understand how we write code and do things in the engine

[akien-mga]

See also #114760.

CC @bruvzg @YeldhamDev

[Clubhouse1661]

Understood, I've disabled the Copilot auto-review feature.

[YeldhamDev]

@akien-mga This PR doesn't affect the bug I fixed, because it doesn't use an OptionButton. 😉

In my PR however, I moved popup->set_shrink_width(false) line to the constructor, as it doesn't make sense to set it every time it pops up. The same could be done here instead.

[Clubhouse1661]

Agreed. Updated to follow @YeldhamDev's suggestion from #114760:

Moved popup->set_shrink_width(false) from show_popup() to the constructor since it's a one-time property

[YeldhamDev]

popup->set_shrink_height(true) should follow suit (unless the fix needs it to be called every popup).

[bruvzg]

popup->set_shrink_height(true)

This is default, so not needed at all.

[Clubhouse1661]

That's right. Removed set_shrink_height(true) as it's the default.
The fix now only adds set_min_size(Size2(0, 0)) in show_popup(), which is a cleaner fix.
Tested with the MRP, and it works correctly.

[scgm0]

I believe the actual fix should be to remove popup->set_shrink_width(false) rather than manually calling popup->set_min_size(Size2(0, 0)). When shrink_width is true, PopupMenu automatically shrinks its width in _pre_popup().
So why was popup->set_shrink_width(false) added in the first place?(#114438)
@bruvzg

[bruvzg]

So why was popup->set_shrink_width(false) added in the first place?

Because, it should not shrink width to anything smaller than the size of the OptionButton only expand.

[bruvzg]

For 4.7 we probably should revert #104399, #112604 and #114438 and fully reconsider how popup auto sizing works.

[scgm0]

For 4.7 we probably should revert #104399, #112604 and #114438 and fully reconsider how popup auto sizing works.

Perhaps we could have _pre_popup() accept the screen_rect from popup(const Rect2i &p_screen_rect), and if screen_rect is valid, use screen_rect.size instead of 0 to adjust the size?

[Clubhouse1661]

Currently it looks like sizing responsibilities are split between Window, PopupMenu, and individual widgets.

If we're considering a full redesign for 4.7, we could introduce a PopupConstraints class which includes all sizing behavior in a single structure, and be called via a new method like popup_with_constraints()

[akien-mga]

Thanks! And congrats for your first merged Godot contribution 🎉