为C＃中的派生标签控件覆盖AutoSize

Question

I am trying to extend the System.Windows.Forms.Label class to support vertically drawn text. I do this by creating a new property called MyLabelOrientation that the user can set to Horizontal or Vertical. When the user changes this setting, the values for width and height are swapped to resize the control to its new orientation. Finally, I override the OnPaint function to draw my Label.

I would like to extend the AutoSize property for this control as well so that my Label will auto-size to the text it contains. For the horizontal orientation, the base functionality implements this for me. For the vertical orientation, I create a Graphics object and set the height of the control to the width of the SizeF object returned from Graphics.MeasureString(Text, Font). You can see an example of the code I'm using below.

using System;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;
using System.ComponentModel.Design;
using System.Windows.Forms.Design;

public class MyLabel : Label
{
    public enum MyLabelOrientation {Horizontal, Vertical};
    protected MyLabelOrientation m_orientation = MyLabelOrientation.Horizontal;

    [Category("Appearance")]
    public virtual MyLabelOrientation Orientation
    {
        get { return m_orientation; }
        set
        {
            m_orientation = value;
            int temp = Height;
            Width = Height;
            Height = temp;
            Refresh();
        }
    }

    private Size ResizeLabel()
    {
        Graphics g = Graphics.FromHwnd(this.Handle);
        SizeF newSize = g.MeasureString(Text, Font);
        if (m_orientation == MyLabelOrientation.Horizontal)
            Width = (int)newSize.Width;
        else
            Height = (int)newSize.Width;
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        Brush textBrush = new SolidBrush(this.ForeColor);

        if (m_orientation == LabelOrientation.Vertical)
        {
            e.Graphics.TranslateTransform(Width, 0);
            e.Graphics.RotateTransform(90);
            e.Graphics.DrawString(Text, Font, textBrush, Padding.Left, Padding.Top);
        }
        else
        {
            base.OnPaint(e);
        }
    }
}

However, setting AutoSize to true seems to prevent and/or override any changes to the size of the control. This means that I can't change the width or height when I want to change the Label's orientation. I'm wondering if this behavior can be overridden, so that I can test whether AutoSize is set, and then adjust the size of the control according to it's orientation.

Answer 1

I have not done this before, I believe you can theoretically override a property declaration (via the new keyword) and check the orientation before proceeding:

override public bool AutoSize
{
   set 
   {
      if( /* orientation is horizontal */ )
      {
          base.AutoSize = value;
      }
      else
      {
          // do what you need to do
      }    
   }    
}

Answer 2

If think a solution is to override OnResize itself :

protected override void OnResize(EventArgs e)
{
    if (AutoSize)
    {
        // Perform your own resizing logic
    }
    else
        OnResize(e);
}

Answer 3

I know this aa pretty old question, but i stumbled across it today and was wondering how to do the same thing.

My solution to the problem was overriding the GetPreferredSize(Size proposedSize) method. I used a button class that houses an arrow in addition to the text which, of course, was not taken into account using the AutoSize property so i added additional space and it works fine for me.

Given the problem of changing orientation or switching width and height, you could completely change the way the preferred size is calculated.

public override Size GetPreferredSize(Size proposedSize)
{
    Size s = base.GetPreferredSize(proposedSize);
    if (AutoSize)
    {
        s.Width += 15;
    }
    return s;
}