ScrollView ScrollToAsync for x, y positions not working

[tekmun]

GitHub2.zip

Steps to Reproduce

1. Run the attached program.
2. Resize app so that the text can be scrolled.
3. Scroll to the bottom and click the button "Click Me!".

Expected Behavior

The scrollview should scroll the text to the top (Position 0, 0)

Actual Behavior

The scrollview scrolls the text to bottom

Environment

=== Visual Studio Community 2019 for Mac ===

Version 8.7.8 (build 4)
Installation UUID: dec104fc-9532-4787-88bd-a5580ee66a6c
	GTK+ 2.24.23 (Raleigh theme)
	Xamarin.Mac 6.18.0.23 (d16-6 / 088c73638)

	Package version: 612000093

=== Mono Framework MDK ===

Runtime:
	Mono 6.12.0.93 (2020-02/620cf538206) (64-bit)
	Package version: 612000093

=== Roslyn (Language Service) ===

3.7.0-6.20427.1+18ede13943b0bfae1b44ef078b2f3923159bcd32

=== NuGet ===

Version: 5.7.0.6702

=== .NET Core SDK ===

SDK: /usr/local/share/dotnet/sdk/3.1.402/Sdks
SDK Versions:
	3.1.402
	3.1.401
	3.1.302
MSBuild SDKs: /Library/Frameworks/Mono.framework/Versions/6.12.0/lib/mono/msbuild/Current/bin/Sdks

=== .NET Core Runtime ===

Runtime: /usr/local/share/dotnet/dotnet
Runtime Versions:
	3.1.8
	3.1.7
	3.1.6
	2.1.22
	2.1.21
	2.1.20

=== Xamarin.Profiler ===

Version: 1.6.15.68
Location: /Applications/Xamarin Profiler.app/Contents/MacOS/Xamarin Profiler

=== Updater ===

Version: 11

=== Apple Developer Tools ===

Xcode 12.0.1 (17220)
Build 12A7300

=== Xamarin.Mac ===

Version: 6.20.2.2 (Visual Studio Community)
Hash: 817b6f72a
Branch: d16-7
Build date: 2020-07-18 18:44:59-0400

=== Xamarin.iOS ===

Version: 14.0.0.0 (Visual Studio Community)
Hash: 7ec3751a1
Branch: xcode12
Build date: 2020-09-16 11:33:15-0400

=== Xamarin Designer ===

Version: 16.7.0.495
Hash: 03d50a221
Branch: remotes/origin/d16-7-vsmac
Build date: 2020-08-28 13:12:52 UTC

=== Xamarin.Android ===

Version: 11.0.2.0 (Visual Studio Community)
Commit: xamarin-android/d16-7/025fde9
Android SDK: /Users/tekmun/Library/Developer/Xamarin/android-sdk-macosx
	Supported Android versions:
		8.0 (API level 26)

SDK Tools Version: 26.1.1
SDK Platform Tools Version: 30.0.4
SDK Build Tools Version: 29.0.2

Build Information: 
Mono: 83105ba
Java.Interop: xamarin/java.interop/d16-7@1f3388a
ProGuard: Guardsquare/proguard/proguard6.2.2@ebe9000
SQLite: xamarin/sqlite/3.32.1@1a3276b
Xamarin.Android Tools: xamarin/xamarin-android-tools/d16-7@017078f

=== Microsoft OpenJDK for Mobile ===

Java SDK: /Users/tekmun/Library/Developer/Xamarin/jdk/microsoft_dist_openjdk_1.8.0.25
1.8.0-25
Android Designer EPL code available here:
https://github.com/xamarin/AndroidDesigner.EPL

=== Android SDK Manager ===

Version: 16.7.0.13
Hash: 8380518
Branch: remotes/origin/d16-7~2
Build date: 2020-09-16 05:12:24 UTC

=== Android Device Manager ===

Version: 16.7.0.24
Hash: bb090a3
Branch: remotes/origin/d16-7
Build date: 2020-09-16 05:12:46 UTC

=== Build Information ===

Release ID: 807080004
Git revision: 9ea7bef96d65cdc3f4288014a799026ccb1993bc
Build date: 2020-09-16 17:22:54-04
Build branch: release-8.7
Xamarin extensions: 9ea7bef96d65cdc3f4288014a799026ccb1993bc

=== Operating System ===

Mac OS X 10.16.0
Darwin 20.1.0 Darwin Kernel Version 20.1.0
    Wed Oct  7 21:17:40 PDT 2020
    root:xnu-7195.40.137.201.1~1/RELEASE_X86_64 x86_64

Build Logs

Example Project (If Possible)

[chamons]

The sample app in question is using ScrollToAsync and the XF ScrollView View.

[tekmun]

Hi,
This is the only outstanding bug in my Xamarin.Forms app ported to MacOS. Is there a timeline when this bug can be resolved? Thanks.

[tekmun]

Hi,
The issue could be related to the Flipped Coordinate System on MacOS. In the sample project, the scrollview is set to scroll to origin (0,0) and it scrolls all the way to the bottom. This is because Cocoa and Core Graphics define the origin differently. One at the top left and the other at the bottom left. Thanks.

[tekmun]

Hi,
I hope that this bug can be resolved in the next major release of Xamarin.Forms 5.0. Is there anything I can help? Or is there a workaround solution that I can implement?

[rmarinho]

@tekmun yeah seems a easy fix. if you want to test the NuGet that is generated on pr #12721

[tekmun]

Thanks for all the speedy hard work.

I presume that I can only test this out in the next X.F. 5.0-pre4 release. Is there a nightly build? If so, how do I download it? Thanks.