Shrlalgo.RvKits/WPFluent/Controls/GridView/GridViewColumn.cs




using System.Reflection;

namespace WPFluent.Controls;

/// <summary>
/// Extends <see cref="System.Windows.Controls.GridViewColumn"/> with MinWidth and MaxWidth properties. It can be used
/// with <see cref="ListView"/> when in GridView mode.
/// </summary>
/// <example>
/// <code lang="xml"> /// &lt;ui:ListView&gt; ///     &lt;ui:ListView.View&gt; ///         &lt;ui:GridView&gt; ///      
///       &lt;ui:GridViewColumn ///                 MinWidth="100" ///                 MaxWidth="200" ///               
///  DisplayMemberBinding="{Binding FirstName}" ///                 Header="First Name" /&gt; ///        
/// &lt;/ui:GridView&gt; ///     &lt;/ui:ListView.View&gt; /// &lt;/ui:ListView&gt; ///</code>
/// </example>
public class GridViewColumn : System.Windows.Controls.GridViewColumn
{
    // use reflection to get the `_desiredWidth` private field.
    private static readonly Lazy<FieldInfo> _desiredWidthField = new(
        () => typeof(System.Windows.Controls.GridViewColumn).GetField(
                "_desiredWidth",
                BindingFlags.NonPublic | BindingFlags.Instance) ??
            throw new InvalidOperationException("The `_desiredWidth` field was not found."));

    // use reflection to get the `UpdateActualWidth` private method.
    private static readonly Lazy<MethodInfo> _updateActualWidthMethod = new(
        () =>
        {
            MethodInfo methodInfo =
            typeof(System.Windows.Controls.GridViewColumn).GetMethod(
                        "UpdateActualWidth",
                        BindingFlags.NonPublic | BindingFlags.Instance) ??
                throw new InvalidOperationException("The `UpdateActualWidth` method was not found.");
            return methodInfo;
        });

    /// <summary>
    /// Identifies the <see cref="MaxWidth"/> dependency property.
    /// </summary>
    public static readonly DependencyProperty MaxWidthProperty = DependencyProperty.Register(
        nameof(MaxWidth),
        typeof(double),
        typeof(GridViewColumn),
        new FrameworkPropertyMetadata(double.PositiveInfinity, OnMaxWidthChanged));

    /// <summary>
    /// Identifies the <see cref="MinWidth"/> dependency property.
    /// </summary>
    public static readonly DependencyProperty MinWidthProperty = DependencyProperty.Register(
        nameof(MinWidth),
        typeof(double),
        typeof(GridViewColumn),
        new FrameworkPropertyMetadata(0.0, OnMinWidthChanged));

    private static void OnMaxWidthChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if(d is not GridViewColumn self)
        {
            return;
        }

        self.OnMaxWidthChanged(e);
    }

    private static void OnMinWidthChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if(d is not GridViewColumn self)
        {
            return;
        }

        self.OnMinWidthChanged(e);
    }

    private static FieldInfo DesiredWidthField => _desiredWidthField.Value;

    private static MethodInfo UpdateActualWidthMethod => _updateActualWidthMethod.Value;

    protected virtual void OnMaxWidthChanged(DependencyPropertyChangedEventArgs e)
    {
        // Hook for derived classes to react to MaxWidth property changes
    }

    protected virtual void OnMinWidthChanged(DependencyPropertyChangedEventArgs e)
    {
        // Hook for derived classes to react to MinWidth property changes
    }

    /// <summary>
    /// Updates the desired width of the column to be clamped between MinWidth and MaxWidth).
    /// </summary>
    /// <remarks>
    /// Uses reflection to directly set the private `_desiredWidth` field on the
    /// `System.Windows.Controls.GridViewColumn`.
    /// </remarks>
    /// <exception cref="InvalidOperationException">
    /// Thrown if reflection fails to access the `_desiredWidth` field
    /// </exception>
    internal void UpdateDesiredWidth()
    {
        double currentWidth = (double)(DesiredWidthField.GetValue(this) ??
            throw new InvalidOperationException("Failed to get the current `_desiredWidth`."));
        double clampedWidth = Math.Max(MinWidth, Math.Min(currentWidth, MaxWidth));
        DesiredWidthField.SetValue(this, clampedWidth);
        UpdateActualWidthMethod.Invoke(this, null);
    }

    /// <summary>
    /// gets or sets the maximum width of the column.
    /// </summary>
    public double MaxWidth { get => (double)GetValue(MaxWidthProperty); set => SetValue(MaxWidthProperty, value); }

    /// <summary>
    /// Gets or sets the minimum width of the column.
    /// </summary>
    public double MinWidth { get => (double)GetValue(MinWidthProperty); set => SetValue(MinWidthProperty, value); }
}