No DropShadowPanel alternative when targeting latest LTSC (17763).

[pfresnay]

Describe the bug

AttachedDropShadow and AttachedCardShadow use CompositionVisualSurface that is only available starting with Build 18362. DropShadowPanel is marked as deprecated and there isn't any alternative when targeting 17763 witch is the latest LTSC windows 10 edition.

Steps to Reproduce

1. Create a new UWP app that use DropShadowPanel
2. Build
3. See warning CS0618 is compiler logs

Steps to reproduce the behavior:

Expected behavior

1. Make sure that DropShadowPanel will not be removed while there isn't any real alternative on latest LTSC (17763)
2. A DropShadowPanel alternative on 17763 :-)

Environment

Package Version(s): 7.1

Windows 10 Build Number:

• [ ] Fall Creators Update (16299)
• [ ] April 2018 Update (17134)
• [] October 2018 Update (17763)
• [X] May 2019 Update (18362)
• [ ] May 2020 Update (19041)
• [ ] Insider Build ({build_number})

App min and target version:

• [ ] Fall Creators Update (16299)
• [ ] April 2018 Update (17134)
• [X] October 2018 Update (17763)
• [ ] May 2019 Update (18362)
• [ ] May 2020 Update (19041)
• [ ] Insider Build ({build_number})

Device form factor:

• [X] Desktop
• [ ] Xbox
• [X] Surface Hub
• [ ] IoT

Visual Studio version:

• [ ] 2017 (15.{minor_version})
• [X] 2019 (16.{minor_version})
• [X] 2022 (17.{minor_version})

Additional context

[ghost]

Hello pfresnay, thank you for opening an issue with us!

I have automatically added a "needs triage" label to help get things started. Our team will analyze and investigate the issue, and escalate it to the relevant team if possible. Other community members may also look into the issue and provide feedback 🙌

[michael-hawker]

@pfresnay as long as you don't try and round the corners of the shadow on 17763, it should work just the same as DropShadowPanel does:

https://github.com/CommunityToolkit/WindowsCommunityToolkit/blob/72ab567a06b986e615b67289cc303fcad64f4d71/Microsoft.Toolkit.Uwp.UI/Shadows/AttachedDropShadow.cs#L279

It just uses CompositionVisualSurface for better performance to make a rounded rectangle shadow when not masking (which isn't the default behavior).

[pfresnay]

@michael-hawker thanks for feedback! Great news if AttachedDropShadow can work on 17763. Maybe compiler can only warn when using CornerRadius?