PanelContainer hint does not show if it has a MarginContainer child

[ntsik]

Godot version: 3.2.stable.official

Issue description: Controls have a hint_tooltip field which displays a hint when hovered. For a PanelContainer with a MarginContainer child, this hint does not display when hovered (by default).

By default, MarginContainer's mouse_filter is set to MOUSE_FILTER_STOP. If it's changed to MOUSE_FILTER_IGNORE, then the parent PanelContainer's hint tooltip will work again.

Steps to reproduce:

1. Create a PanelContainer
2. Add a hint_tooltip to the PanelContainer
3. Add a MarginContainer child to the PanelContainer (by default using MOUSE_FILTER_STOP)
4. Observe the hint tooltip does not appear upon hovering

Minimal reproduction project:
panel_container_hint_bug.zip

[akien-mga]

This is not a bug per se, it's as you described it: if a Control has MOUSE_FILTER_STOP, it will prevent its parent container's tooltip from being shown. You should change to MOUSE_FILTER_PASS if you want to forward the event to the parent.

The default mouse filter has been changed for containers in #35068, which incidentally solves this. It's a compat breaking change so it will not be backported to 3.2.