Getting Font Kerning Values

Hi,

I am trying to manually adjust character spacing between letters when drawing text with GDI. I am doing this by drawing each letter at a time. The problem is that you lose all the font kerning when you do this.

Does anyone know how to get kerning data for fonts? Presumably you would send it the letter pair you want to get the offset for. Then when I draw each letter at a time I can subtract the offset for each letter pair.

many thanks
Paul

While I am unsure about actually getting the Font kerning from a particular type face, my KerningFont class will draw a Font with a custom kerning value:

vb.net Code:

Public Class Form1
 
    Private Sub Form1_Paint(ByVal sender As Object, _
                            ByVal e As System.Windows.Forms.PaintEventArgs) _
                            Handles Me.Paint
 
        Using kerningFont = New KerningFont(New Font("Calibri", 10.0F), 2)
 
            '//draw your kerning font
            kerningFont.DrawString(Me, "This is a test string demonstrating kerning!", _
                             10, 10)
            '//change kerning
            kerningFont.Kerning = 6
 
            '//draw another kerning font
            kerningFont.DrawString(Me, "This is a test string demonstrating kerning!", _
                                   10, 30)
 
        End Using
 
    End Sub
 
End Class

vb.net Code:

Public Class KerningFont
    Implements IDisposable
 
    '//APIs
    <System.Runtime.InteropServices.DllImport("gdi32")> _
    Protected Shared Function SelectObject(ByVal handle As IntPtr, _
                                           ByVal hgdiobj As IntPtr) As IntPtr
    End Function
 
    <System.Runtime.InteropServices.DllImport("gdi32")> _
    Protected Shared Function SetTextCharacterExtra(ByVal handle As IntPtr, _
                                                    ByVal nCharExtra As Integer) _
                                                    As Integer
    End Function
 
    <System.Runtime.InteropServices.DllImport("gdi32")> _
    Protected Shared Function TextOut(ByVal handle As IntPtr, ByVal x As Integer, _
                                      ByVal y As Integer, ByVal text As String, _
                                      ByVal charCount As Integer) As Boolean
    End Function
 
    <System.Runtime.InteropServices.DllImport("gdi32", EntryPoint:="SetBkColor")> _
    Protected Shared Function SetBackColor(ByVal handle As IntPtr, _
                                           ByVal color As Integer) As UInt32
    End Function
 
    <System.Runtime.InteropServices.DllImport("gdi32")> _
    Protected Shared Function DeleteObject(ByVal handle As IntPtr) As Boolean
    End Function
 
    <System.Runtime.InteropServices.DllImport("gdi32")> _
    Protected Shared Function SetTextColor(ByVal handle As IntPtr, _
                                           ByVal color As Integer) As UInt32
    End Function
 
    '//fields
    Private disposedValue As Boolean = False
 
    '//properties
    Private _font As Font = Nothing
    Public ReadOnly Property Font() As Font
        Get
            Return Me._font
        End Get
    End Property
 
    Private _kerning As Integer = 0
    Public Property Kerning() As Integer
        Get
            Return Me._kerning
        End Get
        Set(ByVal value As Integer)
            Me._kerning = value
        End Set
    End Property
 
    '//constructors
    Public Sub New(ByVal f As Font, _
                   ByVal kerning As Integer)
        Me._kerning = kerning
        Me._font = f
    End Sub
 
    '//methods
    Public Sub DrawString(ByVal c As Control, ByVal text As String, _
                          ByVal x As Integer, ByVal y As Integer)
        Me.DrawString(c, text, New Point(x, y))
    End Sub
 
    Public Sub DrawString(ByVal c As Control, ByVal text As String, _
                          ByVal pt As Point)
        Me.DrawString(c, text, pt, c.ForeColor)
    End Sub
 
    Public Sub DrawString(ByVal c As Control, ByVal text As String, _
                          ByVal x As Integer, ByVal y As Integer, _
                          ByVal foreColor As Color)
        Me.DrawString(c, text, New Point(x, y), foreColor)
    End Sub
 
    Public Sub DrawString(ByVal c As Control, ByVal text As String, _
                          ByVal pt As Point, ByVal foreColor As Color)
        If c.IsHandleCreated Then
            Using g = Graphics.FromHwnd(c.Handle)
                Using f = New Font(Me._font, Me._font.Style)
                    Dim graphicsHandle As IntPtr = IntPtr.Zero
                    Dim fontHandle As IntPtr = IntPtr.Zero
                    Try
                        graphicsHandle = g.GetHdc()
                        fontHandle = KerningFont.SelectObject(graphicsHandle, _
                                                              f.ToHfont())
                        KerningFont.SetBackColor(graphicsHandle, _
                                                 ColorTranslator.ToWin32(c.BackColor))
                        KerningFont.SetTextColor(graphicsHandle, _
                                                 ColorTranslator.ToWin32(foreColor))
                        KerningFont.SetTextCharacterExtra(graphicsHandle, _
                                                          Me._kerning)
                        KerningFont.TextOut(graphicsHandle, pt.X + Me._kerning, _
                                            pt.Y, text, text.Length)
                    Catch ex As Exception
                        '//suppress
                    Finally
                        KerningFont.DeleteObject(fontHandle)
                        g.ReleaseHdc()
                    End Try
                End Using
            End Using
        End If
    End Sub
 
    Public Sub Dispose() Implements IDisposable.Dispose
        Try
            Me.Dispose(True)
        Finally
            GC.SuppressFinalize(Me)
        End Try
    End Sub
 
    Protected Overridable Sub Dispose(ByVal disposing As Boolean)
        If Not Me.disposedValue Then
            If disposing Then
                If Me._font IsNot Nothing Then
                    Me._font.Dispose()
                    Me._font = Nothing
                End If
            End If
        End If
        Me.disposedValue = True
    End Sub
 
End Class