# Objective
* There is no way to read the fields of `GridPlacement` once set.
* Values of `0` for `GridPlacement`'s fields are invalid but can be set.
* A non-zero representation would be half the size.
fixes#9474
## Solution
* Add `get_start`, `get_end` and `get_span` accessor methods.
* Change`GridPlacement`'s constructor functions to panic on arguments of
zero.
* Use non-zero types instead of primitives for `GridPlacement`'s fields.
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## Changelog
`bevy_ui::ui_node::GridPlacement`:
* Field types have been changed to `Option<NonZeroI16>` and
`Option<NonZeroU16>`. This is because zero values are not valid for
`GridPlacement`. Previously, Taffy interpreted these as auto variants.
* Constructor functions for `GridPlacement` panic on arguments of `0`.
* Added accessor functions: `get_start`, `get_end`, and `get_span`.
These return the inner primitive value (if present) of the respective
fields.
## Migration Guide
`GridPlacement`'s constructor functions no longer accept values of `0`.
Given any argument of `0` they will panic with a `GridPlacementError`.
a2bd93aedc