Avalonia: Add support for Auto for Width and Height properties

[wieslawsoltes]

Repro:

<DockPanel LastChildFill="True" Background="Pink">
    <DockPanel LastChildFill="True" Width="180" DockPanel.Dock="Left">
        <Border Background="Red" Width="180" Height="250" DockPanel.Dock="Top"/>
        <Border Background="Blue" Width="180" Height="Auto" DockPanel.Dock="Bottom"/>
    </DockPanel>
    <DockPanel LastChildFill="True" Width="240" DockPanel.Dock="Right">
        <Border Background="Green" Width="240" Height="250" DockPanel.Dock="Top"/>
        <Border Background="Orange" Width="240" Height="Auto" DockPanel.Dock="Bottom"/>
    </DockPanel>
    <Grid>
        <Border Background="Gray" Width="300" Height="300"/>
    </Grid>
</DockPanel>

Exception:

Portable.Xaml.XamlObjectWriterException
  HResult=0x80131500
  Message=Could not convert object 'Auto' (of type System.String) to {http://schemas.microsoft.com/winfx/2006/xaml}Double: Auto is not a valid value for Double.
  Source=Avalonia.Markup.Xaml
  StackTrace:
   at Portable.Xaml.XamlObjectWriterInternal.GetCorrectlyTypedValue(XamlMember xm, XamlType xt, Object value)
   at Portable.Xaml.XamlObjectWriterInternal.StoreAppropriatelyTypedValue(ObjectState state, MemberAndValue ms, Object obj, Object keyObj)
   at Portable.Xaml.XamlObjectWriterInternal.OnWriteValue(Object value)
   at Portable.Xaml.XamlServices.Transform(XamlReader xamlReader, XamlWriter xamlWriter, Boolean closeWriter)
   at Avalonia.Markup.Xaml.AvaloniaXamlLoader.LoadFromReader(XamlReader reader, AvaloniaXamlContext context, IAmbientProvider parentAmbientProvider)
   at Avalonia.Markup.Xaml.AvaloniaXamlLoader.Load(Stream stream, Assembly localAssembly, Object rootInstance, Uri uri)
   at Avalonia.Markup.Xaml.AvaloniaXamlLoader.Load(Type type, Object rootInstance)
   at Avalonia.Markup.Xaml.AvaloniaXamlLoader.Load(Object obj)
   at Core2D.Avalonia.Views.MainControl.InitializeComponent() in D:\DOWNLOADS\GitHub-Avalonia\Core2D\src\Core2D.Avalonia\Views\MainControl.xaml.cs:line 26
   at Core2D.Avalonia.Views.MainControl..ctor() in D:\DOWNLOADS\GitHub-Avalonia\Core2D\src\Core2D.Avalonia\Views\MainControl.xaml.cs:line 18

Inner Exception 1:
Exception: Auto is not a valid value for Double.

Inner Exception 2:
FormatException: Input string was not in a correct format.

[wieslawsoltes]

In WPF:

In addition to acceptable Double values, this property can also be Double.NaN. This is how you specify auto sizing behavior in code. In XAML you set the value to the string "Auto" (case insensitive) to enable the auto sizing behavior. Auto sizing behavior implies that the element will fill the height available to it. Note however that specific controls frequently supply default values through their default theme styles that will disable the auto sizing behavior unless it is specifically re-enabled.

https://msdn.microsoft.com/en-us/library/system.windows.frameworkelement.height%28v=vs.110%29.aspx?f=255&MSPPError=-2147217396

[grokys]

Wow, I didn't even know this was supported in WPF. Yes we should do this too.

[wieslawsoltes]

That would be great, I came across this when doing docking control, without Auto (from code you have to set double.NaN) its impossible to position correctly the controls automatically using DockPanel for my docking control.

[wieslawsoltes]

@grokys Not sure how currently double.NaN is handled for Width and Height in Avalonia across different layouts. The double.NaN seems to be default value: https://github.com/AvaloniaUI/Avalonia/blob/44da9df5d490b4a203740c4c8e906ad03fb2698a/src/Avalonia.Layout/Layoutable.cs#L75-L85

Source: WPF 4.5 Unleashed

So actually Auto is just synonym got NaN when used in Xaml.

[wieslawsoltes]

@grokys Looks like I don't need Auto to get functionality as this works fine (using NaN instead of Auto):

<DockPanel LastChildFill="True" Background="Pink">
    <DockPanel LastChildFill="True" Width="180" DockPanel.Dock="Left">
        <Border Background="Red" Width="180" Height="250" DockPanel.Dock="Top"/>
        <Border Background="Blue" Width="180" Height="NaN" DockPanel.Dock="Bottom"/>
    </DockPanel>
    <DockPanel LastChildFill="True" Width="240" DockPanel.Dock="Right">
        <Border Background="Green" Width="240" Height="250" DockPanel.Dock="Top"/>
        <Border Background="Orange" Width="240" Height="NaN" DockPanel.Dock="Bottom"/>
    </DockPanel>
    <Grid>
        <Border Background="Gray" Width="300" Height="300"/>
    </Grid>
</DockPanel>

Anyway in the feature implementing support for Auto would be nice.

[Gillibald]

This would involve adding a DoubleConverter the rest is just straight forward.

[Banyc]

And also something like Width="*"

[derekantrican]

Is there a workaround for this that already exists?

[maxkatz6]

@derekantrican

Is there a workaround for this that already exists?

Width="NaN"

[derekantrican]

That doesn't seem to work (maybe I'm doing something wrong). I would imagine that my ComboBox should fill the remaining space of the column here, right?

XAML:

  <Grid>
    <Grid.RowDefinitions>
      <RowDefinition Height="Auto"/>
      <RowDefinition Height="*"/>
      <RowDefinition Height="Auto"/>
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
      <ColumnDefinition Width="Auto"/>
      <ColumnDefinition Width="Auto"/>
      <ColumnDefinition Width="*"/>
      <ColumnDefinition Width="Auto"/>
    </Grid.ColumnDefinitions>
    <StackPanel Orientation="Horizontal">
      <TextBlock Text="Calendar:" VerticalAlignment="Center" Margin="5"/>
      <ComboBox Height="25" Width="NaN" VerticalAlignment="Center" Margin="5"/>
    </StackPanel>
    ...
</Grid>

Screenshot:

[maxkatz6]

Do you need HorizontalAlignment set to Stretch?

[derekantrican]

I don't think that was required in the WPF world, but even so - setting HorizontalAlignment="Stretch" doesn't produce any different results for my situation here