Creating a WYSIWYG font ComboBox using C#

csharp winforms combobox font ownerdraw

This article shows how to use the built in ownerdraw functionality of a standard Windows Forms ComboBox control to display a WYSIWYG font list.

The FontComboBox control in a sample application
The FontComboBox control in a sample application

Setting up the control

To start, we'll create a new class, and inherit this from the ComboBox control.

We are going to use variable ownerdraw for this sample, as it gives us a little more flexibility without having to mess around with the ItemHeight property. We'll add a constructor, and set the ownerdraw mode here. Also, we'll add a new version of the DrawMode property, which we'll both hide and disable the value persistence. We always want the font list to be sorted, so for now we'll do the same with the Sorted property.

csharp
public FontComboBox()
{
  this.DrawMode = DrawMode.OwnerDrawVariable;
  this.Sorted = true;
}

[Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), EditorBrowsable(EditorBrowsableState.Never)]
public new DrawMode DrawMode
{
  get { return base.DrawMode; }
  set { base.DrawMode = value; }
}

[Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), EditorBrowsable(EditorBrowsableState.Never)]
public new bool Sorted
{
  get { return base.Sorted; }
  set { base.Sorted = value; }
}

Caching Font objects

In order to avoid continuously creating and destroying font objects, we'll create a internal cache of fonts. When it's time to draw the control, the cache will be queried - if the requested font exists, it will be returned, otherwise the font will be created and added to the cache. This will be done via the GetFont method below.

csharp
protected virtual Font GetFont(string fontFamilyName)
{
  lock (_fontCache)
  {
    if (!_fontCache.ContainsKey(fontFamilyName))
    {
      Font font;

      font = this.GetFont(fontFamilyName, FontStyle.Regular);
      if (font == null)
        font = this.GetFont(fontFamilyName, FontStyle.Bold);
      if (font == null)
        font = this.GetFont(fontFamilyName, FontStyle.Italic);
      if (font == null)
        font = this.GetFont(fontFamilyName, FontStyle.Bold | FontStyle.Italic);

      _fontCache.Add(fontFamilyName, font);
    }
  }

  return _fontCache[fontFamilyName];
}

protected virtual Font GetFont(string fontFamilyName, FontStyle fontStyle)
{
  Font font;

  try
  {
    font = new Font(fontFamilyName, this.PreviewFontSize, fontStyle);
  }
  catch
  {
    font = null;
  }

  return font;
}

Note: Whilst testing the control, I discovered that some of the fonts installed on the development system only had bold or italic styles. The original version of this method, which always attempts to get the normal style would cause a crash.

Due to this, I changed the method to try and access the normal style, and if that failed, to try the other styles. Perhaps there is a better way of doing this, but I leave that as an exercise for the future.

As we don't want the font size of the dropdown list to necessarily match that of the display/edit portion, we'll add a new property named `PreviewFontSize*.

csharp
public event EventHandler PreviewFontSizeChanged;

[Category("Appearance"), DefaultValue(12)]
public int PreviewFontSize
{
  get { return _previewFontSize; }
  set
  {
    _previewFontSize = value;

    this.OnPreviewFontSizeChanged(EventArgs.Empty);
  }
}

protected virtual void OnPreviewFontSizeChanged(EventArgs e)
{
  if (PreviewFontSizeChanged != null)
    PreviewFontSizeChanged(this, e);

  this.CalculateLayout();
}

When certain actions occur, such as this property changing, we want to calculate the height of items in the dropdown list.

csharp
private void CalculateLayout()
{
  this.ClearFontCache();

  using (Font font = new Font(this.Font.FontFamily, (float)this.PreviewFontSize))
  {
    Size textSize;

    textSize = TextRenderer.MeasureText("yY", font);
    _itemHeight = textSize.Height + 2;
  }
}

Loading the list of font families

In order to avoid slowing the control down without reason, we'll delay loading the list of font families until there is a reason, either when the control's text has changed, or when the control gets focus.

This will be done by creating a LoadFontFamilies method which will be called by overriding OnGotFocus and OnTextChanged.

csharp
public virtual void LoadFontFamilies()
{
  if (this.Items.Count == 0)
  {
    Cursor.Current = Cursors.WaitCursor;

    foreach (FontFamily fontFamily in FontFamily.Families)
      this.Items.Add(fontFamily.Name);

    Cursor.Current = Cursors.Default;
  }
}

protected override void OnGotFocus(EventArgs e)
{
  this.LoadFontFamilies();

  base.OnGotFocus(e);
}

protected override void OnTextChanged(EventArgs e)
{
  base.OnTextChanged(e);

  if (this.Items.Count == 0)
  {
    int selectedIndex;

    this.LoadFontFamilies();

    selectedIndex = this.FindStringExact(this.Text);
    if (selectedIndex != -1)
      this.SelectedIndex = selectedIndex;
  }
}

Drawing the items

Drawing an overdraw ComboBox is done by overriding the OnDrawItem method. However, as we have told the control we are doing variable sized ownerdraw, we also need to override OnMeasureItem. This method allows us to define the size for each item, or in the case of this control to set the height of each item to match the pixel height calculated for the value of the PreviewFontSize property.

csharp
protected override void OnMeasureItem(MeasureItemEventArgs e)
{
  base.OnMeasureItem(e);

  if (e.Index > -1 && e.Index < this.Items.Count)
  {
    e.ItemHeight = _itemHeight;
  }
}

protected override void OnDrawItem(DrawItemEventArgs e)
{
  base.OnDrawItem(e);

  if (e.Index > -1 && e.Index < this.Items.Count)
  {
    e.DrawBackground();

    if ((e.State & DrawItemState.Focus) == DrawItemState.Focus)
      e.DrawFocusRectangle();

    using (SolidBrush textBrush = new SolidBrush(e.ForeColor))
    {
      string fontFamilyName;

      fontFamilyName = this.Items[e.Index].ToString();
      e.Graphics.DrawString(fontFamilyName, this.GetFont(fontFamilyName), textBrush, e.Bounds, _stringFormat);
    }
  }
}

The actual drawing is very simple - we use the built in drawing for the background and focus rectangle, and then use the Graphics object to draw the text using the GetFont method explained above.

You might notice that the above code is referencing a previously defined StringFormat object. This is created using the below method.

csharp
protected virtual void CreateStringFormat()
{
  if (_stringFormat != null)
    _stringFormat.Dispose();

  _stringFormat = new StringFormat(StringFormatFlags.NoWrap);
  _stringFormat.Trimming = StringTrimming.EllipsisCharacter;
  _stringFormat.HotkeyPrefix = HotkeyPrefix.None;
  _stringFormat.Alignment = StringAlignment.Near;
  _stringFormat.LineAlignment = StringAlignment.Center;

  if (this.IsUsingRTL(this))
    _stringFormat.FormatFlags |= StringFormatFlags.DirectionRightToLeft;
}

private bool IsUsingRTL(Control control)
{
  bool result;

  if (control.RightToLeft == RightToLeft.Yes)
    result = true;
  else if (control.RightToLeft == RightToLeft.Inherit && control.Parent != null)
    result = IsUsingRTL(control.Parent);
  else
    result = false;

  return result;
}

Cleaning up

As we are creating a large number of objects, we need to clean these up in the controls Dispose method.

csharp
protected override void Dispose(bool disposing)
{
  this.ClearFontCache();

  if (_stringFormat != null)
    _stringFormat.Dispose();

  base.Dispose(disposing);
}

protected virtual void ClearFontCache()
{
  if (_fontCache != null)
  {
    foreach (string key in _fontCache.Keys)
      _fontCache[key].Dispose();
    _fontCache.Clear();
  }
}

Suggestions for improvement

The control as it stands is a basic example, and depending on your application's needs, it could be further expanded. For example:

  • Currently each instance of the control will use its own font cache. By making the cache and access methods static, a single cache could be used by all instances
  • When you select a font in Word, this is added to a kind of "recently used" list at the top of Word's own font picker. The same sort of functionality could be quite easily added to this control.
  • Currently the font text is displayed on a single line. If the control isn't wide enough, the text is trimmed and therefore it may not be always possible to tell the full name of a font. Either tooltip support or drawing across multiple lines could help with this, or by resizing the dropdown component to be the minimum width required to display all font names without trimming.

Full source

The full source of the class is below.

csharp
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Drawing.Text;
using System.Windows.Forms;

namespace Cyotek.Windows.Forms
{
  public class FontComboBox : ComboBox
  {
  #region  Private Member Declarations  

    private Dictionary<string, Font> _fontCache;
    private int _itemHeight;
    private int _previewFontSize;
    private StringFormat _stringFormat;

    public FontComboBox()
    {
      _fontCache = new Dictionary<string, Font>();

      this.DrawMode = DrawMode.OwnerDrawVariable;
      this.Sorted = true;
      this.PreviewFontSize = 12;

      this.CalculateLayout();
      this.CreateStringFormat();
    }

    public event EventHandler PreviewFontSizeChanged;

    protected override void Dispose(bool disposing)
    {
      this.ClearFontCache();

      if (_stringFormat != null)
        _stringFormat.Dispose();

      base.Dispose(disposing);
    }

    protected override void OnDrawItem(DrawItemEventArgs e)
    {
      base.OnDrawItem(e);

      if (e.Index > -1 && e.Index < this.Items.Count)
      {
        e.DrawBackground();

        if ((e.State & DrawItemState.Focus) == DrawItemState.Focus)
          e.DrawFocusRectangle();

        using (SolidBrush textBrush = new SolidBrush(e.ForeColor))
        {
          string fontFamilyName;

          fontFamilyName = this.Items[e.Index].ToString();
          e.Graphics.DrawString(fontFamilyName, this.GetFont(fontFamilyName), textBrush, e.Bounds, _stringFormat);
        }
      }
    }

    protected override void OnFontChanged(EventArgs e)
    {
      base.OnFontChanged(e);

      this.CalculateLayout();
    }

    protected override void OnGotFocus(EventArgs e)
    {
      this.LoadFontFamilies();

      base.OnGotFocus(e);
    }

    protected override void OnMeasureItem(MeasureItemEventArgs e)
    {
      base.OnMeasureItem(e);

      if (e.Index > -1 && e.Index < this.Items.Count)
      {
        e.ItemHeight = _itemHeight;
      }
    }

    protected override void OnRightToLeftChanged(EventArgs e)
    {
      base.OnRightToLeftChanged(e);

      this.CreateStringFormat();
    }

    protected override void OnTextChanged(EventArgs e)
    {
      base.OnTextChanged(e);

      if (this.Items.Count == 0)
      {
        int selectedIndex;

        this.LoadFontFamilies();

        selectedIndex = this.FindStringExact(this.Text);
        if (selectedIndex != -1)
          this.SelectedIndex = selectedIndex;
      }
    }

    public virtual void LoadFontFamilies()
    {
      if (this.Items.Count == 0)
      {
        Cursor.Current = Cursors.WaitCursor;

        foreach (FontFamily fontFamily in FontFamily.Families)
          this.Items.Add(fontFamily.Name);

        Cursor.Current = Cursors.Default;
      }
    }

    [Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), EditorBrowsable(EditorBrowsableState.Never)]
    public new DrawMode DrawMode
    {
      get { return base.DrawMode; }
      set { base.DrawMode = value; }
    }

    [Category("Appearance"), DefaultValue(12)]
    public int PreviewFontSize
    {
      get { return _previewFontSize; }
      set
      {
        _previewFontSize = value;

        this.OnPreviewFontSizeChanged(EventArgs.Empty);
      }
    }

    [Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden), EditorBrowsable(EditorBrowsableState.Never)]
    public new bool Sorted
    {
      get { return base.Sorted; }
      set { base.Sorted = value; }
    }

    private void CalculateLayout()
    {
      this.ClearFontCache();

      using (Font font = new Font(this.Font.FontFamily, (float)this.PreviewFontSize))
      {
        Size textSize;

        textSize = TextRenderer.MeasureText("yY", font);
        _itemHeight = textSize.Height + 2;
      }
    }

    private bool IsUsingRTL(Control control)
    {
      bool result;

      if (control.RightToLeft == RightToLeft.Yes)
        result = true;
      else if (control.RightToLeft == RightToLeft.Inherit && control.Parent != null)
        result = IsUsingRTL(control.Parent);
      else
        result = false;

      return result;
    }

    protected virtual void ClearFontCache()
    {
      if (_fontCache != null)
      {
        foreach (string key in _fontCache.Keys)
          _fontCache[key].Dispose();
        _fontCache.Clear();
      }
    }

    protected virtual void CreateStringFormat()
    {
      if (_stringFormat != null)
        _stringFormat.Dispose();

      _stringFormat = new StringFormat(StringFormatFlags.NoWrap);
      _stringFormat.Trimming = StringTrimming.EllipsisCharacter;
      _stringFormat.HotkeyPrefix = HotkeyPrefix.None;
      _stringFormat.Alignment = StringAlignment.Near;
      _stringFormat.LineAlignment = StringAlignment.Center;

      if (this.IsUsingRTL(this))
        _stringFormat.FormatFlags |= StringFormatFlags.DirectionRightToLeft;
    }

    protected virtual Font GetFont(string fontFamilyName)
    {
      lock (_fontCache)
      {
        if (!_fontCache.ContainsKey(fontFamilyName))
        {
          Font font;

          font = this.GetFont(fontFamilyName, FontStyle.Regular);
          if (font == null)
            font = this.GetFont(fontFamilyName, FontStyle.Bold);
          if (font == null)
            font = this.GetFont(fontFamilyName, FontStyle.Italic);
          if (font == null)
            font = this.GetFont(fontFamilyName, FontStyle.Bold | FontStyle.Italic);
          if (font == null)
            font = (Font)this.Font.Clone();

          _fontCache.Add(fontFamilyName, font);
        }
      }

      return _fontCache[fontFamilyName];
    }

    protected virtual Font GetFont(string fontFamilyName, FontStyle fontStyle)
    {
      Font font;

      try
      {
        font = new Font(fontFamilyName, this.PreviewFontSize, fontStyle);
      }
      catch
      {
        font = null;
      }

      return font;
    }

    protected virtual void OnPreviewFontSizeChanged(EventArgs e)
    {
      if (PreviewFontSizeChanged != null)
        PreviewFontSizeChanged(this, e);

      this.CalculateLayout();
    }
  }
}

Update History

  • 2011-02-19 - First published
  • 2020-11-21 - Updated formatting

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Comments

# DotNetKicks.com

[b]Creating a WYSIWYG font ComboBox using C#[/b] Creating a WYSIWYG font ComboBox using C# excerpt=You've been kicked (a good thing) - Trackback from DotNetKicks.com

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# DotNetShoutout

[b]Creating a WYSIWYG font ComboBox using C#[/b] Thank you for submitting this cool story - Trackback from DotNetShoutout

Reply

# wmjordan

I noticed that you've used GDI++ to draw the text. It is widely known that GDI++ does not support OpenType fonts or Rastered fonts and consequently those fonts would not show up in the box. Previously I wrote an article about P/Invoking Windows GDI to render those 'unsupported' fonts, in which you may also feel interested. http://www.codeproject.com/Tips/557423/Rendering-Text-with-OpenType-Fonts-Using-GDI

Reply

# Richard Moss

Hello,

Many thanks for the link. I stopped using Graphics.DrawString myself some time ago (either using TextRenderer or using DrawText, DrawTextEx and TextOut directly). I wasn't aware that GDI+ didn't support some fonts properly, I stopped using it because it looks bloody awful and has no consistency with the rest of the OS :)

Regards; Richard Moss

Reply

# Roy

Do you have any example code on how to actually use this combo box in a C# Windows Forms project?

Reply

# Richard Moss

No, I didn't do a sample for this project. Think of it as a list of font names, just drawn prettier. It doesn't handle creation of fonts for you, it's purpose was to allow the selection of a font name in conjunction with other controls for selecting styles, size etc. The Items collection holds all those names, so you can use SelectedItem to return the selected name and so on.

Regards;
Richard Moss

Reply

author
Richard Moss
Founder

The founder of Cyotek, Richard enjoys creating new blog content for the site. Much more though, he likes to develop programs, and can often found writing reams of code. A long term gamer, he has aspirations in one day creating an epic video game - but until that time comes, he is mostly content with adding new bugs to WebCopy and the other Cyotek products.

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