Widget positioning issue when using custom Widget as parent

[John-Glazebrook]

Description: I encountered an issue where child widgets were not being positioned correctly within a custom Widget class. Specifically, when using pos_hint and size_hint on a BoxLayout inside a custom Compass widget (which initially inherited from Widget), the BoxLayout appeared in the bottom-left corner instead of being centered as intended.

The issue was resolved by changing the Compass class to inherit from FloatLayout instead of Widget. This suggests that there might be a bug in how Kivy handles layout properties for child widgets when the parent is a custom Widget class.

Original code (not working as expected): class Compass(Widget): # ... (rest of the class definition)

<Compass>: BoxLayout: size_hint: 0.9, 0.9 pos_hint: {'center_x': 0.5, 'center_y': 0.5} # ... (rest of the BoxLayout definition)

Workaround (working correctly): class Compass(FloatLayout): # ... (rest of the class definition)

<Compass>: BoxLayout: size_hint: 0.9, 0.9 pos_hint: {'center_x': 0.5, 'center_y': 0.5} # ... (rest of the BoxLayout definition)

Environment:

• Kivy version: v2.3.0
• Python version: 3.12.4
• Operating System: Win 11

I would appreciate if the Kivy team could investigate this behavior and clarify if this is a bug or if there's a recommended way to handle custom Widget classes that need to position their children using pos_hint and size_hint.

[ElliotGarbus]

This is not a bug. Layouts are tools (special widgets) for positioning and sizing widgets (their children). I you want to create a Widget where the Widgets children are positioned with sized with hints, use a RelativeLayout or a FloatLayout. These layouts honor the hints.

A horizontal BoxLayout, for example, will not honor 'x' hints. the layout positions the widgets in that dimension. Read the docs about Layouts carefully, this behavior is described. https://kivy.org/doc/stable/api-kivy.uix.boxlayout.html#module-kivy.uix.boxlayout

In the kivy-examples directory, there is an application called kivycalatog. .venv/share/kivy-examples/demo/kivycatalog/main.py It provides an interactive kv authoring tool that lets you explore the layouts interactively. I found this to be very useful when I was getting started.

The github issues section is for reporting bugs. There are forums for support: https://groups.google.com/g/kivy-users https://discord.com/invite/eT3cuQp https://www.reddit.com/r/kivy/

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