[Proposal] ScrollView inside a VerticalStackLayout

[kubaflo]

Description of Change

ScrollView inside a VerticalStackLayout will not scroll unless its height is explicitly set because it defaults to having an infinite height. This behavior often confuses developers and results in a poor experience when working with .NET MAUI. For example

• ScrollView Does Not Work When Inside A VerticalStackLayout #8990

• https://stackoverflow.com/questions/75465567/workaround-for-scrollview-not-scrolling-inside-a-stacklayout-in-maui
  To improve this, the height of a ScrollView inside a VerticalStackLayout can automatically adjust to occupy the remaining available space in the layout, rather than defaulting to infinity. This would allow the ScrollView to either:

• Adjust to the minimum size required to fit its content, or

• Expand to fill the available space, enabling scrolling when the content exceeds the allocated area.

If developers explicitly set a height for the ScrollView, that value would keep on taking precedence over the calculated height.

Issues Fixed

Fixes https://stackoverflow.com/questions/75465567/workaround-for-scrollview-not-scrolling-inside-a-stacklayout-in-maui

Workarounds

For developers who happen to encounter this PR and are looking for a workaround:

• Instead of VerticalStackLayout use StackLayout and add FillAndExpand to VerticalOptions of your scroll view
• Use grid and * as row definition
• Explicitly calculate the height of your ScrollView and assign it to its HeightRequest

[dotnet-policy-service]

Hey there @kubaflo! Thank you so much for your PR! Someone from the team will get assigned to your PR shortly and we'll get it reviewed.

[PureWeen]

What if you have multiple scroll views?

If the scroll view is off the screen because of the content above it how do we define "available space"

The operating behavior of a vsl is that it's infinite so any constraints you try to assume start to rabbit hole a bit.

Current behaviour is consistent with wpf/winui

I do think this is a problem that would be nice to have a wider out of success though.

Like maybe a way to use a grid measurement system against the stack layout.

[kubaflo]

@PureWeen yea you're right. I'm closing this PR for now then. At least, now, some developers will know why sv might not work as expected in the stack layout