ColumnDefinitions as a StaticResource throws NullReferenceException when assigning to multiple Grids.

[huestack]

Describe the bug

Assigning a ColumnDefinitions resource in two or more Grids throws runtime error.

Exception:

Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.
   at Avalonia.Controls.Grid.ValidateDefinitionsLayout(IReadOnlyList`1 definitions, Boolean treatStarAsAuto)
   at Avalonia.Controls.Grid.MeasureOverride(Size constraint)
   at Avalonia.Layout.Layoutable.MeasureCore(Size availableSize)
   at Avalonia.Layout.Layoutable.Measure(Size availableSize)
   at Avalonia.Controls.StackPanel.MeasureOverride(Size availableSize)
   at Avalonia.Layout.Layoutable.MeasureCore(Size availableSize)
   at Avalonia.Layout.Layoutable.Measure(Size availableSize)
   at Avalonia.Layout.LayoutHelper.MeasureChild(Layoutable control, Size availableSize, Thickness padding, Thickness borderThickness)
   at Avalonia.Controls.Presenters.ContentPresenter.MeasureOverride(Size availableSize)
   at Avalonia.Layout.Layoutable.MeasureCore(Size availableSize)
   at Avalonia.Layout.Layoutable.Measure(Size availableSize)
   at Avalonia.Layout.LayoutHelper.MeasureChild(Layoutable control, Size availableSize, Thickness padding)
   at Avalonia.Controls.Decorator.MeasureOverride(Size availableSize)
   at Avalonia.Controls.Primitives.VisualLayerManager.MeasureOverride(Size availableSize)
   at Avalonia.Layout.Layoutable.MeasureCore(Size availableSize)
   at Avalonia.Layout.Layoutable.Measure(Size availableSize)
   at Avalonia.Layout.Layoutable.MeasureOverride(Size availableSize)
   at Avalonia.Layout.Layoutable.MeasureCore(Size availableSize)
   at Avalonia.Layout.Layoutable.Measure(Size availableSize)
   at Avalonia.Layout.Layoutable.MeasureOverride(Size availableSize)
   at Avalonia.Controls.Window.MeasureOverride(Size availableSize)
   at Avalonia.Controls.WindowBase.MeasureCore(Size availableSize)
   at Avalonia.Layout.Layoutable.Measure(Size availableSize)
   at Avalonia.Layout.LayoutManager.Measure(Layoutable control)
   at Avalonia.Layout.LayoutManager.ExecuteInitialLayoutPass()
   at Avalonia.Controls.Window.ShowCore(Window owner)
   at Avalonia.Controls.Window.Show()
   at Avalonia.Controls.ApplicationLifetimes.ClassicDesktopStyleApplicationLifetime.ShowMainWindow()
   at Avalonia.Controls.ApplicationLifetimes.ClassicDesktopStyleApplicationLifetime.Start(String[] args)
   at Avalonia.ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime(AppBuilder builder, String[] args, Action`1 lifetimeBuilder)
   at AvaloniaListBox.Program.Main(String[] args) in D:\Projects\Git\AvaloniaListBox\Program.cs:line 13

To Reproduce

This works:

<Window.Resources>
    <ColumnDefinitions x:Key="TestDef">
        <ColumnDefinition Width="150" />
        <ColumnDefinition Width="10" />
        <ColumnDefinition Width="Auto" />
    </ColumnDefinitions>
</Window.Resources>

<StackPanel>
    <Grid ColumnDefinitions="{StaticResource TestDef}">
        <TextBlock Grid.Column="0">List</TextBlock>
        <TextBox Grid.Column="2" />
    </Grid>
    <Grid ColumnDefinitions="150, 10, Auto">
        <TextBlock Grid.Column="0">List</TextBlock>
        <TextBox Grid.Column="2" />
    </Grid>
</StackPanel>

This doesn't:

<Window.Resources>
    <ColumnDefinitions x:Key="TestDef">
        <ColumnDefinition Width="150" />
        <ColumnDefinition Width="10" />
        <ColumnDefinition Width="Auto" />
    </ColumnDefinitions>
</Window.Resources>

<StackPanel>
    <Grid ColumnDefinitions="{StaticResource TestDef}">
        <TextBlock Grid.Column="0">List</TextBlock>
        <TextBox Grid.Column="2" />
    </Grid>
    <Grid ColumnDefinitions="{StaticResource TestDef}">
        <TextBlock Grid.Column="0">List</TextBlock>
        <TextBox Grid.Column="2" />
    </Grid>
</StackPanel>

Expected behavior

A resource is expected to be applied to multiple controls.

Avalonia version

11.0.10, 11.1.0-beta-2

OS

Windows

Additional context

No response

[maxkatz6]

Never seen this application of ColumnDefinitions, but looks handy.

[rabbitism]

DefinitionBase holds many calculation and status of groups, especially SharedSizeGroup, i doubt if this is even possible.

[workgroupengineering]

the problem is there

Avalonia/src/Avalonia.Controls/Grid.cs

Lines 177 to 183 in 262c1b0

	set
	{
	if (_extData == null) { _extData = new ExtendedData(); }
	_extData.ColumnDefinitions = value;
	_extData.ColumnDefinitions.Parent = this;
	InvalidateMeasure();
	}

exactly on line 181.

StaticResource return same instance for each grid.

two possible solutions could be:

• Deep cloning like this code:

            set
            {
                if (_extData == null) { _extData = new ExtendedData(); }
                var def = value is null
                    ? new ColumnDefinitions()
                    : new ColumnDefinitions(value.Count);
                if (value is not null)
                {
                    foreach (var item in value)
                    {
                        def.Add(new ColumnDefinition()
                        {
                            MaxWidth = item.MaxWidth,
                            MinWidth = item.MinWidth,
                            SharedSizeGroup = item.SharedSizeGroup,
                            Width = item.Width,
                        });
                    }
                }
                _extData.ColumnDefinitions = def;
                _extData.ColumnDefinitions.Parent = this;
                InvalidateMeasure();
            }

• x:Shared directive like WPF

Personally I prefer x:Shared

[workgroupengineering]

Can i work on x:Shared?

[kekekeks]

Given that we already have support for resource factories for lazy resource loading, x:Shared can be implemented by calling AddNotShared (or smth) instead of AddDeferred.

[timunie]

Can i work on x:Shared?

I talked to the team and we would be happy if you help us to get this implemented.

Nikita [15.05.2024 09:29]
it shouldn't be that hard to implement since we already have resource factories for lazy resource loading

Nikita [15.05.2024 09:30]
so it might be implemented as calling AddShared instead of AddDeferred"