unoplatform/uno

XamlBindingHelper not returning right values

Open

#18,855 opened on Nov 20, 2024

View on GitHub
 (1 comment) (1 reaction) (0 assignees)C# (9,789 stars) (837 forks)batch import
difficulty/starter 🚀good first issuekind/bugproject/core-tools 🛠️

Description

Description

When using XamlBindingHelper.Convert() to test the conversion of specific structures, there are noticeable behavioral differences between Windows (WinUI) and Uno. The expected behavior is that conversion of structures to string using Convert(typeof(string), value) should produce a format similar to .ToString() and should also support reconversion back to the original structure.

Below is a comparison table showing results on each platform and reconversion support for Uno:

Structure Windows Result Uno Result Reconversion Support (Uno)
Matrix(1, 2, 3, 4, 5, 6) 1,2,3,4,5,6 1,2,3,4,5,6 ✅ Yes
Thickness(1, 2, 3, 4) 1,2,3,4 [Thickness: 1-2-3-4] ❌ No
CornerRadius(1,2,3,4) 1,2,3,4 TopLeft: 1, TopRight: 2, BottomRight: 3, BottomLeft: 4 ❌ No
Duration(TimeSpan.FromSeconds(1)) 00:00:01 00:00:01 ✅ Yes
Duration.Automatic Automatic Automatic ✅ Yes
Duration.Forever Forever Forever ✅ Yes
GridLength(1, GridUnitType.Auto) Auto Auto ✅ Yes
GridLength(1, GridUnitType.Star) 1* * ✅ Yes
GridLength(1.5, GridUnitType.Star) 1.5* 1.5* ✅ Yes
GridLength(1, GridUnitType.Pixel) 1 1.0px ✅ Yes BUT WEIRD
GridLength(1.5, GridUnitType.Pixel) 1.5 1.5px ✅ Yes BUT WEIRD
Point(1, 2) 1,2 [1, 2] ❌ No
Rect(1, 2, 3, 4) 1,2,3,4 1,2,3,4 ✅ Yes
Size(1, 2) 1,2 1,2 ❌ No
Color (Colors.Beige) #FFF5F5DC #FFF5F5DC ✅ Yes

Issues to Address

  1. Conversions for Thickness and CornerRadius do not support reconversion to the original structure on Uno.
  2. Conversion of Point results in a different format ([1, 2]) on Uno and does not support reconversion.
  3. Desired format alignment between Uno and Windows for GridLength with pixel unit (1 vs 1.0px).

The goal is for Uno to properly support reconversion to the original structure, and ideally, to align output format with Windows (though this is less critical).

Expected behavior

Uno should be able to convert forward and convert backward to string for those structs. (to and from string).

How to reproduce it (as minimally and precisely as possible)

No response

Workaround

Not using the XamlBindingHelper

Works on UWP/WinUI

Yes

Contributor guide

Tech stack
csharp
Domain
frontend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Understanding of XAML data bindingFamiliarity with Uno Platform type converters
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Investigate the XamlBindingHelper.Convert method in the Uno source code, likely in src/Uno.UI/DataBinding. Compare the conversion logic for Thickness, CornerRadius, Point, and Size structs with the Windows implementation. Focus on the ToString and Parse methods of these structs. Ensure that the output format matches Windows and that reconversion (string to struct) works. Consider adding or fixing IStringProvider implementations for these types.