Update AbsoluteLayout Flags Extensions

[brminnick]

Description of Change

This Proposal adds two new APIs to AbsoluteLayoutExtensions and updates the functionality of the existing .LayoutFlags() API to add existing AbsoluteLayoutFlags instead of overwriting existing AbsoluteLayoutFlags.

1. New APIs

public static TBindable ClearLayoutFlags<TBindable>(this TBindable bindable) where TBindable : BindableObject;

public static TBindable LayoutFlags<TBindable>(this TBindable bindable, params AbsoluteLayoutFlags[] flags) where TBindable : BindableObject;

2. Updating LayoutFlags Functionality

Current Functionality

The current functionality of LayoutFlags overwrites any existing AbsoluteLayoutFlags that are already defined by the BindableObject.

For example, the resulting AbosluteLayoutFlag property of the Label in the following sample will be only AbsoluteLayoutFlags.PositionProportional, because the current functionality overwrites any existing AbsoluteLayoutFlag.

new Label() // The label's final `AbsoluteLayoutFlags` value is `AbsoluteLayoutFlags.PositionProportional`
  .LayoutFlags(AbsoluteLayoutFlags.SizeProportional)
  .LayoutFlags(AbsoluteLayoutFlags.PositionProportional)  // Overwrites existing `AbsoluteLayoutFlags`

Updated Functionality

The updated functionality of LayoutFlags will append the incoming AbsoluteLayoutFlags to every existing AbsoluteLayoutFlags.

For example, the resulting AbosluteLayoutFlag property of the Label in the following sample will be AbsoluteLayoutFlags.PositionProportional | AbsoluteLayoutFlags.PositionProportional, because the incoming value combined with any existing AbsoluteLayoutFlag values using a bitwise OR operator.

new Label() // The label's final `AbsoluteLayoutFlags` value is `AbsoluteLayoutFlags.PositionProportional | AbsoluteLayoutFlags.SizeProportional `
  .LayoutFlags(AbsoluteLayoutFlags.SizeProportional)
  .LayoutFlags(AbsoluteLayoutFlags.PositionProportional)  // Combined with existing `AbsoluteLayoutFlags`

Linked Issues

• Fixes [Proposal] Add AbsoluteLayout Flags Extension Methods #215

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Documentation created or updated: https://github.com/MicrosoftDocs/CommunityToolkit/pulls/XYZ
  

[bijington]

Looks good!