WPF 변환기 이상한 행동

Question

다음과 같이 내가 그것 Grid를 포함하는의 ActualWidth에 TextBox의 Width 바인딩 오전 :

같이

<TextBlock 
    Grid.Column="0" 
    Text="WorkPortalView UserControl" 
    TextTrimming="CharacterEllipsis" 
    Foreground="White" 
    Margin="5" 
    Width="{Binding ActualWidth, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Grid}}, Converter={StaticResource textWidthConverter}, diag:PresentationTraceSources.TraceLevel=High}" /> 

, 내가 변환기를 사용하고 다음과 같이 :

class TextWidthConverter : IValueConverter 
    { 
     public object Convert(object value, Type targetType, object parameter, CultureInfo culture) 
     { 
      double? d = value as double?; 
      if (d == null) 
       return null; 

      return (d/2); 
     } 

     public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) 
     { 
      throw new NotSupportedException("Cannot convert back"); 
     } 
    } 

이상한 점은 표시된 코드가 제대로 작동한다는 것입니다. 그러나 return (d/2) 문을 return (d - 75D)으로 바꾼다면 속성 변경의 무한 루프가 시작되는 것 같습니다. 무엇에

System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth 
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '429.6' 
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '429.6' 
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '354.6' 
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '354.6' 
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth 
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '441.6' 
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '441.6' 
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '366.6' 
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '366.6' 
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth 
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '453.6' 
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '453.6' 
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '378.6' 
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '378.6' 
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth 
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '465.6' 
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '465.6' 
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '390.6' 
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '390.6' 
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth 
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '477.6' 
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '477.6' 
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '402.6' 
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '402.6' 
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth 
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '489.6' 
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '489.6' 
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '414.6' 
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '414.6' 
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth 
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '501.6' 
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '501.6' 
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '426.6' 
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '426.6' 
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth 
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '513.6' 
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '513.6' 
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '438.6' 
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '438.6' 
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth 
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '525.6' 
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '525.6' 
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '450.6' 
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '450.6' 
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth 
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '537.6' 
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '537.6' 
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '462.6' 
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '462.6' 
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth 
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '549.6' 
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '549.6' 
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '474.6' 
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '474.6' 
System.Windows.Data Warning: 94 : BindingExpression (hash=58235710): Got PropertyChanged event from Grid (hash=43090134) for ActualWidth 
System.Windows.Data Warning: 99 : BindingExpression (hash=58235710): GetValue at level 0 from Grid (hash=43090134) using DependencyProperty(ActualWidth): '561.6' 
System.Windows.Data Warning: 78 : BindingExpression (hash=58235710): TransferValue - got raw value '561.6' 
System.Windows.Data Warning: 80 : BindingExpression (hash=58235710): TransferValue - user's converter produced '486.6' 
System.Windows.Data Warning: 87 : BindingExpression (hash=58235710): TransferValue - using final value '486.6' 

어떤 생각 : - 75D 여기

System.Windows.Data Warning: 71 :  Lookup ancestor of type Grid: queried Grid (hash=19487651) 
System.Windows.Data Warning: 70 : RelativeSource.FindAncestor found Grid (hash=19487651) 
System.Windows.Data Warning: 76 : BindingExpression (hash=35097890): Activate with root item Grid (hash=19487651) 
System.Windows.Data Warning: 106 : BindingExpression (hash=35097890): At level 0 - for Grid.ActualWidth found accessor DependencyProperty(ActualWidth) 
System.Windows.Data Warning: 102 : BindingExpression (hash=35097890): Replace item at level 0 with Grid (hash=19487651), using accessor DependencyProperty(ActualWidth) 
System.Windows.Data Warning: 99 : BindingExpression (hash=35097890): GetValue at level 0 from Grid (hash=19487651) using DependencyProperty(ActualWidth): '417.6' 
System.Windows.Data Warning: 78 : BindingExpression (hash=35097890): TransferValue - got raw value '417.6' 
System.Windows.Data Warning: 80 : BindingExpression (hash=35097890): TransferValue - user's converter produced '208.8' 
System.Windows.Data Warning: 87 : BindingExpression (hash=35097890): TransferValue - using final value '208.8' 

가 D에 대한 진단 추적 태그의 출력입니다 : 여기

/2 D에 대한 진단 추적 태그의 출력입니다 변환기의이 동작을 설명합니까?

Answer 1

분명히 그리드에는 텍스트 블록을위한 공간이 더 필요합니다. 그리드가 각 텍스트 블록 너비 변경시 추가 12 픽셀을 필요로하기 때문에 d-87D에서이 동작의 단점을 찾을 수 있습니다.

그런데 격자 열에 대해 star sizing을 사용하는 것이 좋습니다. 단, 원하는 것은 텍스트 블록에 상대적 크기를 지정하는 것입니다.

Answer 2

이것은 버그 인 것 같습니다. 이 동작은 하나의 "자동 조정"반복에 대해 합리적이지만 무한 루프가 발생해서는 안됩니다. 위의 토론을 참조하십시오.

DockPanel으로 전환하여 원하는 레이아웃을 얻었습니다.