Fix PopupMenu doesn't respect its ScrollContainer's margins

[WhalesState]

Fixes #87461

Removed the MarginContainer and applied the PopupMenu panel style to the ScrollContainer.

This results in the same old behavior, instead of applying the panel's content margins to the margin container and drawing the panel style manually.

Removing the include of the margin container header file has resulted in errors in 8 other files which was depending on it, so I have included the header in each one of them.

[YuriSizov]

Why take the stylebox specifically into account, and not just the minimum size of the node itself, which should already include the stylebox?

[WhalesState]

Why take the stylebox specifically into account, and not just the minimum size of the node itself, which should already include the stylebox?

I didn't expect this question! but the answer is in the underlying line, why it's taking in mind the VScrollBar width ? because it's already calculated in the ScrollContainer minsize when it appears!
I don't know the answer! but yes it seems that it ignores the ScrollContainer's child minsize. but maybe because the ScrollContainer doesn't calculate minsize properly until we disable both vertical and horizontal scrolling.

I don't know what's the best way to fix this issue, but my project needs some margins by default for the ScrollContainer and I'm using a theme, so it do override the PopupMenu's ScrollContainer margins too and all the popups appears with the VerticalSlider visible, this was the only issue since everything else is fine.

[KoBeWi]

I think the reason is that PopupMenu already has its own panel style and it's not expected that ScrollContainer will have another one.
Either the minimum size should be max of internal panel size and ScrollContainer minimum size or (better), the internal ScrollContainer should have an override for its panel style to force-disable it, because it's redundant.

[WhalesState]

or (better), the internal ScrollContainer should have an override for its panel style to force-disable it, because it's redundant

I'm trying to do this without creating a new StyleBoxEmpty in every instance. but I don't know how. all I need is just one static empty style box. if creating a new one in every instance is fine just tell me.

The best fix is to override the ScrollContainer's panel style box with the PopupMenu panel instead of drawing it manually. also this may result in removing the MarginContainer from the node since it can be replaced with the panel content margins.

[KoBeWi]

Left some comments, otherwise looks fine.

[WhalesState]

while testing i have found some bugs related to items and size and it took me a long time to make sure that the popup menu will work fine when changing the item's v_separation and the panel_style's content margins.

I have noticed that the ScrollContainer is no longer drawing the scroll over it's children, and it adds the margins automatically for the Scroll Bar, so I have removed the extra space used for the Vertical Scroll Bar since it will be added automatically when it's visible.

After applying the stylebox directly to the ScrollContainer and testing with large v_separation value to force the scroll to appear, i have noticed some issues and i have changed the calculactions to take into account the new items size with v_separation and the correct mouse hover while taking into account the panel's top margin.

[KoBeWi]

Thanks for reminding, I actually forgot to test the scrollbar 🤦‍♂️
And it made me find 2 regressions:

• the ScrollBar can't be clicked. Clicking it will activate an item under it (can be tested with language list in editor settings)
• when opening menu at the edge of the screen, the scrollbar goes outside the screen (can be tested with resource list in the inspector)

suddenly regressions

[WhalesState]

I have found that this issue presents in all github windows builds, but it doesn't exist when building locally without d3d12=yes so it may be an issue related to d3d 12.

Edit: my branch wasn't rebased and the issue appeared after rebasing.

• the ScrollBar can't be clicked. Clicking it will activate an item under it (can be tested with language list in editor settings)

Fixed:

• when opening menu at the edge of the screen, the scrollbar goes outside the screen (can be tested with resource list in the inspector)

Fixed another two issues:

• when dragging the menu slider and releasing the mouse over an item, the item gets selected and the menu hides. on the next menu popup the slider dragging continues after popup when the mouse enters the slider's area because it didn't recieve the mouse release event.

• when dragging the scroll bar's slider and hovering over a submenu item, the submenu appears and the scroll bar continues scrolling when mouse enters after the submenu hides.

[WhalesState]

Please have a look on this #88392 (comment)

[KoBeWi]

Needs rebase after #86952 was reverted.

[akien-mga]

Thanks!