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Use the .NET framework to shorten a path string with an ellipsis

, 8 Apr 2007 CPOL
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Compact a path or any string using built in .NET framework API

Introduction

Remember the Windows API PathCompactPath[Ex] used to take a path and shorten it by inserting an ellipsis in the appropriate place to make it fit a specific pixel width? Ever wonder how to do it native .NET? There's a very simple way to do it with the TextRenderer.MeasureText method but it's relatively undocumented.

Background

If you're familiar with this problem you might already know about using Windows.Forms.TextRenderer.DrawText or Drawing.Graphics.DrawString methods to programmatically draw a shortened string using the framework. But I wanted a way to retrieve a shortened string in memory to later use that string inside an existing control (like a menu item).

Using the Code

Here's a simple function to do the trick, internally I copy the string (to keep it from affecting the source string), call Windows.Forms.TextRenderer.MeasureText with the magic bitwise parameter: TextFormatFlags.ModifyString, and return the string variable that was passed into the function.

Function CompactString(ByVal MyString As String, ByVal Width As Integer,
    ByVal Font As Drawing.Font,
    ByVal FormatFlags As Windows.Forms.TextFormatFlags) As String

Dim Result As String = String.Copy(MyString)

TextRenderer.MeasureText(Result, Font, New Drawing.Size(Width, 0),
    FormatFlags Or TextFormatFlags.ModifyString)

Return Result

End Function

To set a label to a compacted version of the string path you would call:

Label1.Text = CompactString(MyPath, Label1.Width, Label1.Font,
   TextFormatFlags.PathEllipsis)

For example, the string: c:\program files\test app\runme.exe might turn into:

c:\program files\...\runme.exe depending on the font and width.

Check out the Windows.Forms.TextFormatFlags enumerated type for other options on how to compact your string. TextFormatFlags.WordEllipsis for example will insert a "..." at the end of the string instead in between parts of a path.

Points of Interest

You might be thinking, why not just write your own algorithm to break apart a string and insert the ellipsis in a certain spot. And in fact I have seen programmers doing this but I would recommend using the framework to handle this for a couple reasons:

  1. Why reinvent the wheel? Microsoft already did it and it's probably well tested and efficient; do you really have extra time on your hands?
  2. What if the standard for where to put the ellipsis changes? Maybe someday the ellipsis will be commonly inserted just after the drive letter instead of just before the filename. Let MS think about these details and just follow their lead. If MS changes this implementation internally, your app will automatically follow suit.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Tim Greenfield
Software Developer (Senior)
United States United States
I am a software architect and engineer who has been working in the industry since 1994. Although I officially started writing software many years earlier at age 11 by authoring games, graphics demos, or whatever I found interesting. I even landed my first consulting job at age 16 implementing a newly invented mathimatical algorithm for a team of researchers at the local University.
 
I've designed and implemented hundreds if not thousands of applications: client, web, and hybrid of all scales and was a contributing author to the Black Belt programming column of Visual Basic Programmer's Journal.
 
My goals when coding are always to write clean, reusable and optimized code using the latest and technology, tools and techniques.

Comments and Discussions

 
GeneralMy vote of 5 PinmemberJohnPap_CP6-Apr-11 6:52 
QuestionHow about WPF? PinmemberGLLNS18-May-09 9:51 
GeneralMore Information PinmemberAndy Missico26-Feb-09 16:51 
I am providing more information regarding the PathCompactPath function to help programmers avoid its use in .NET Framework version 2.0.
 
http://www.missico.com/personal/support/visual_basic_tips.htm#PathCompactPath[^]
 
''' <summary>
''' Truncates a file path to fit within a given pixel width by replacing path components with ellipses.
''' </summary>
''' <param name="hdc">[in] A handle to the device context used for font metrics.</param>
''' <param name="lpszPath">[in, out] A pointer to a null-terminated string of length MAX_PATH that contains the path to be modified. On return, this buffer will contain the modified string.</param>
''' <param name="dx">[in] The width, in pixels, in which the string must fit.</param>
''' <returns>Returns TRUE if the path was successfully compacted to the specified width. Returns FALSE on failure, or if the base portion of the path would not fit the specified width.</returns>
''' <remarks>
''' <para>This Shell Lightweight Utility function uses the font currently selected in hDC to calculate the width of the text. This function will not compact the path beyond the base file name preceded by ellipses.</para>
''' <para>The .NET Framework version 2.0 contains the TextRenderer.MeasureText method, which can reproduce the functionality of the PathCompactPath function, as shown in the following example.</para>
''' <example>
''' <code>
'''    Public Function CompactPath(ByVal text As String, ByVal control As Control) As String
''' 
'''        'make a copy because the measure text call is instructed to modify string
'''        Dim sResult As String = String.Copy(text)
''' 
'''        TextRenderer.MeasureText(sResult, control.Font, control.ClientSize, TextFormatFlags.PathEllipsis Or TextFormatFlags.ModifyString)
'''  
'''        Return sResult
''' 
'''    End Function
''' </code>
''' </example>
''' </remarks>
<Obsolete("In .NET 2.0, use TextRenderer.MeasureText with TextFormatFlags.PathEllipsis", True)> _
Declare Auto Function PathCompactPath Lib "shlwapi.dll" ( _
    ByVal hdc As IntPtr, _
    ByVal lpszPath As System.Text.StringBuilder, _
    ByVal dx As Int32) As Boolean
 
''' <summary>
''' Truncates a file path to fit within a given pixel width by replacing path components with ellipses.
''' </summary>
''' <returns>Returns the path compacted to the specified width. This function will not compact the path beyond the base file name preceded by ellipses. Therefore, the base portion of the path may not always fit within the specified width.</returns>
''' <remarks>
''' <para>Works well with monospace/fixed-width fonts. Tends to compact text too much when using proportional fonts.</para>
''' </remarks>
Public Function CompactPath(ByVal path As String, ByVal control As Control) As String
    Const MAX_PATH As Integer = 260
 
    Dim oPath As New System.Text.StringBuilder(path, MAX_PATH)
    Dim oGraphics As System.Drawing.Graphics = control.CreateGraphics
 
    Try
 
        If PathCompactPath(oGraphics.GetHdc, oPath, control.ClientSize.Width) Then
            'okay
        Else
            'failure or base name too long for specified width
        End If
 
    Finally
 
        If Not (oGraphics Is Nothing) Then
 
            'if you do not release the device context then you will get
            '   An unhandled exception of type 'System.InvalidOperationException' occurred in system.drawing.dll
            '   The object is currently in use elsewhere.
 
            oGraphics.ReleaseHdc()
            oGraphics.Dispose()
 
        End If
 
    End Try
 
    Return oPath.ToString
End Function

GeneralStrange Behavior Pinmembercjbarth9-Jan-09 11:59 
QuestionHow can we get the modified string? PinmemberWaleed Eissa5-Sep-08 20:10 
GeneralThis code will fail with AccessViolationException PinmemberEugene Sichkar23-Jun-08 14:44 
GeneralTruncate to null PinmemberDon Kackman11-Nov-07 4:03 
Questionshorten path for recent files PinmemberZach198123-Oct-07 2:52 
AnswerRe: shorten path for recent files Pinmemberchr.dev15-Jul-08 3:32 
GeneralRemoved from .NET 3.0 PinmemberRichardCollins224-May-07 23:58 
GeneralRe: Removed from .NET 3.0 PinmemberGreg Osborne8-Jan-09 6:37 
QuestionCopy? PinmemberNchantim10-Apr-07 8:11 
AnswerRe: Copy? PinmemberNchantim10-Apr-07 8:24 
GeneralRe: Copy? PinmemberTim Greenfield12-Apr-07 6:06 
GeneralRe: Copy? PinmemberRichardCollins220-May-07 23:55 
GeneralNice PinmemberPatrick Sears8-Apr-07 15:24 

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