# Objective
fixes#8516
* Give `CalculatedSize` a more specific and intuitive name.
* `MeasureFunc`s should only be updated when their `CalculatedSize` is
modified by the systems managing their content.
For example, suppose that you have a UI displaying an image using an
`ImageNode`. When the window is resized, the node's `MeasureFunc` will
be updated even though the dimensions of the texture contained by the
node are unchanged.
* Fix the `CalculatedSize` API so that it no longer requires the extra
boxing and the `dyn_clone` method.
## Solution
* Rename `CalculatedSize` to `ContentSize`
* Only update `MeasureFunc`s on `CalculatedSize` changes.
* Remove the `dyn_clone` method from `Measure` and move the `Measure`
from the `ContentSize` component rather than cloning it.
* Change the measure_func field of `ContentSize` to type
`Option<taffy::node::MeasureFunc>`. Add a `set` method that wraps the
given measure appropriately.
---
## Changelog
* Renamed `CalculatedSize` to `ContentSize`.
* Replaced `upsert_leaf` with a function `update_measure` that only
updates the node's `MeasureFunc`.
* `MeasureFunc`s are only updated when the `ContentSize` changes and not
when the layout changes.
* Scale factor is no longer applied to the size values passed to the
`MeasureFunc`.
* Remove the `ContentSize` scaling in `text_system`.
* The `dyn_clone` method has been removed from the `Measure` trait.
* `Measure`s are moved from the `ContentSize` component instead of
cloning them.
* Added `set` method to `ContentSize` that replaces the `new` function.
## Migration Guide
* `CalculatedSize` has been renamed to `ContentSize`.
* The `upsert_leaf` function has been removed from `UiSurface` and
replaced with `update_measure` which updates the `MeasureFunc` without
node insertion.
* The `dyn_clone` method has been removed from the `Measure` trait.
* The new function of `CalculatedSize` has been replaced with the method
`set`.
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