New Layout Option to Expand Visual Elements

[janne-hmp]

Description

I'd like to have an additional horizontal layout option that makes the control try to use as much space as possible, subject to MaximumWidthRequest, like Fill, but honoring Start / Center / End HorizontalOptions. Fill seems to be always Center aligned, if it hits MaximumWidthRequest. This could be a boolean option named HorizontalExpansion, which defaults to False.

And the same vertically.

This is a bit like what *AndExpand layout options are doing in StackLayout. Currently, it is impossible to make a resizing End-aligned button that is, say, 200 wide, but does not expand beyond container boundaries, which is a basic case in Xamarin with WidthRequest="200" HorizontalOptions="End".

An alternative would be to make *AndExpand to work for other controls in addition to StackLayout. This might result in layout changes from Xamarin, but could be more intuitive. I like the new MaximumWidthRequest, but it really needs to be paired with an option to force expansion / fill while preserving Start / Center / End layout option (so changing that to Fill won't do).

Public API Changes

var button = new Button();
button.HorizontalOptions = LayoutOptions.End;
button.MaximumWidthRequest=200;
button.HorizontalExpansion=true;

Intended Use-Case

I like to make a basic button that is End-aligned, is 200 wide, and honors container boundaries, like what I got with Xamarin when I had WidthRequest="200" and HorizontalOptions="End". This would help with migrating from Xamarin to .NET MAUI.

[janne-hmp]

There is a related bug (see #21917) that would be good to be fixed: WidthRequest does not contain margins, but MaximumWidthRequest does, so WidthRequest="150" Margin="50,0,50,0" gives a button of 150 wide while MaximumWidthRequest="150" Margin="50,0,50,0" HorizontalOptions="Fill" gives a button with 50 width.