自定义 Winforms 控件中的基线对齐线

Question

我有一个带有文本框的自定义用户控件，我想在自定义控件之外公开（文本框中文本的）对齐线的基线。 我知道您创建一个设计器（继承自 ControlDesigner）并重写 SnapLines 以访问对齐线，但我想知道如何获取我通过自定义用户控件公开的控件的文本基线。

Answer 1

VB.Net版本：
注意：您必须将 txtDescription 更改为文本框或您使用的其他内部控件名称。 和 ctlUserControl 到您的 usercontrol 名称

<Designer(GetType(ctlUserControl.MyCustomDesigner))> _
Partial Public Class ctlUserControl
   '... 
   'Your Usercontrol class specific code
   '... 
    Class MyCustomDesigner
        Inherits ControlDesigner
        Public Overloads Overrides ReadOnly Property SnapLines() As IList
            Get
                ' Code from above 

                Dim lines As IList = MyBase.SnapLines

                ' *** This will need to be modified to match your user control
                Dim control__1 As ctlUserControl = TryCast(Me.Control, ctlUserControl)
                If control__1 Is Nothing Then Return lines

                ' *** This will need to be modified to match the item in your user control
                ' This is the control in your UC that you want SnapLines for the entire UC
                Dim designer As IDesigner = TypeDescriptor.CreateDesigner(control__1.txtDescription, GetType(IDesigner))
                If designer Is Nothing Then
                    Return lines
                End If

                ' *** This will need to be modified to match the item in your user control
                designer.Initialize(control__1.txtDescription)

                Using designer
                    Dim boxDesigner As ControlDesigner = TryCast(designer, ControlDesigner)
                    If boxDesigner Is Nothing Then
                        Return lines
                    End If

                    For Each line As SnapLine In boxDesigner.SnapLines
                        If line.SnapLineType = SnapLineType.Baseline Then
                            ' *** This will need to be modified to match the item in your user control
                            lines.Add(New SnapLine(SnapLineType.Baseline, line.Offset + control__1.txtDescription.Top, line.Filter, line.Priority))
                            Exit For
                        End If
                    Next
                End Using

                Return lines
            End Get
        End Property
    End Class

End Class

Answer 2

你走在正确的轨道上。 您需要在设计器中覆盖 SnapLines 属性并执行如下操作：

Public Overrides ReadOnly Property SnapLines() As System.Collections.IList
    Get
        Dim snapLinesList As ArrayList = TryCast(MyBase.SnapLines, ArrayList)

        Dim offset As Integer
        Dim ctrl As MyControl = TryCast(Me.Control, MyControl)
        If ctrl IsNot Nothing AndAlso ctrl.TextBox1 IsNot Nothing Then
            offset = ctrl.TextBox1.Bottom - 5
        End If

        snapLinesList.Add(New SnapLine(SnapLineType.Baseline, offset, SnapLinePriority.Medium))

        Return snapLinesList

    End Get
End Property

在本示例中，用户控件包含一个文本框。 该代码添加了一条新的对齐线，表示文本框的基线。 重要的是正确计算偏移量。

Answer 3

感谢所有人的帮助。 这是一件难以下咽的事。 在每个 UserControl 中都有一个私有子类的想法不太令人愉快。

我想出了这个基类来帮助您。

[Designer(typeof(UserControlSnapLineDesigner))]
public class UserControlBase : UserControl
{
    protected virtual Control SnapLineControl { get { return null; } }

    private class UserControlSnapLineDesigner : ControlDesigner
    {
        public override IList SnapLines
        {
            get
            {
                IList snapLines = base.SnapLines;

                Control targetControl = (this.Control as UserControlBase).SnapLineControl;

                if (targetControl == null)
                    return snapLines;

                using (ControlDesigner controlDesigner = TypeDescriptor.CreateDesigner(targetControl,
                    typeof(IDesigner)) as ControlDesigner)
                {
                    if (controlDesigner == null)
                        return snapLines;

                    controlDesigner.Initialize(targetControl);

                    foreach (SnapLine line in controlDesigner.SnapLines)
                    {
                        if (line.SnapLineType == SnapLineType.Baseline)
                        {
                            snapLines.Add(new SnapLine(SnapLineType.Baseline, line.Offset + targetControl.Top,
                                line.Filter, line.Priority));
                            break;
                        }
                    }
                }
                return snapLines;
            }
        }
    }
}

接下来，从这个基类派生您的 UserControl：

public partial class MyControl : UserControlBase
{
    protected override Control SnapLineControl
    {
        get
        {
            return txtTextBox;
        }
    }

    ...

}

再次感谢您发布此内容。

Answer 4

我只是有类似的需求，我是这样解决的：

 public override IList SnapLines
{
    get
    {
        IList snapLines = base.SnapLines;

        MyControl control = Control as MyControl;
        if (control == null) { return snapLines; }

        IDesigner designer = TypeDescriptor.CreateDesigner(
            control.textBoxValue, typeof(IDesigner));
        if (designer == null) { return snapLines; }
        designer.Initialize(control.textBoxValue);

        using (designer)
        {
            ControlDesigner boxDesigner = designer as ControlDesigner;
            if (boxDesigner == null) { return snapLines; }

            foreach (SnapLine line in boxDesigner.SnapLines)
            {
                if (line.SnapLineType == SnapLineType.Baseline)
                {
                    snapLines.Add(new SnapLine(SnapLineType.Baseline,
                        line.Offset + control.textBoxValue.Top,
                        line.Filter, line.Priority));
                    break;
                }
            }
        }

        return snapLines;
    }
}

这样它实际上是为子控件创建一个临时子设计器，以便找出“真正的”基线对齐线在哪里。

这在测试中似乎表现相当不错，但如果性能成为一个问题（并且如果内部文本框不移动），那么大部分代码可以提取到 Initialize 方法。

这还假设文本框是 UserControl 的直接子级。 如果还有其他影响布局的控件，那么偏移计算会变得更加复杂。

Answer 5

作为 Miral 答案的更新.. 对于正在寻找如何做到这一点的新人来说，这里有一些“缺失的步骤”。 :) 上面的 C# 代码几乎已经“直接”准备就绪，除了更改一些值以引用将要修改的 UserControl 之外。

可能需要的参考资料：
System.Design (@robyaw)

所需的使用：

using System.Windows.Forms.Design;
using System.Windows.Forms.Design.Behavior;
using System.ComponentModel;
using System.ComponentModel.Design;
using System.Collections;

在您的 UserControl 上，您需要以下属性：

[Designer(typeof(MyCustomDesigner))]

然后您需要一个具有 SnapLines 覆盖的“设计器”类：

private class MyCustomerDesigner : ControlDesigner {
  public override IList SnapLines {
    get {
     /* Code from above */
    IList snapLines = base.SnapLines;

    // *** This will need to be modified to match your user control
    MyControl control = Control as MyControl;
    if (control == null) { return snapLines; }

    // *** This will need to be modified to match the item in your user control
    // This is the control in your UC that you want SnapLines for the entire UC
    IDesigner designer = TypeDescriptor.CreateDesigner(
        control.textBoxValue, typeof(IDesigner));
    if (designer == null) { return snapLines; }

    // *** This will need to be modified to match the item in your user control
    designer.Initialize(control.textBoxValue);

    using (designer)
    {
        ControlDesigner boxDesigner = designer as ControlDesigner;
        if (boxDesigner == null) { return snapLines; }

        foreach (SnapLine line in boxDesigner.SnapLines)
        {
            if (line.SnapLineType == SnapLineType.Baseline)
            {
                // *** This will need to be modified to match the item in your user control
                snapLines.Add(new SnapLine(SnapLineType.Baseline,
                    line.Offset + control.textBoxValue.Top,
                    line.Filter, line.Priority));
                break;
            }
        }
    }

    return snapLines;
}

    }
  }
}