Auto Size a Combo Box's Drop Down Width

Category:

Forms and Controls

Type:

Snippets

Difficulty:

Intermediate

Author:

Intelligent Solutions Inc.

Version Compatibility:

More information:

This code automatically sizes the drop-down width of a combo box based on the width of the longest item in the combo box. Refer to the comments within the code for example and usage considerations.

Instructions: Copy the declarations and code below and paste directly into your VB project.

Declarations:
Option Explicit Private Const CB_SETDROPPEDWIDTH = &H160 Private Const CB_GETDROPPEDWIDTH = &H15F Private Const DT_CALCRECT = &H400 Private Type RECT Left As Long Top As Long Right As Long Bottom As Long End Type Private Declare Function SendMessageLong Lib "user32" Alias _ "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, _ ByVal wParam As Long, ByVal lParam As Long) As Long Private Declare Function DrawText Lib "user32" Alias _ "DrawTextA" (ByVal hdc As Long, ByVal lpStr As String, _ ByVal nCount As Long, lpRect As RECT, ByVal wFormat _ As Long) As Long

Code:

Public Function AutoSizeDropDownWidth(Combo As Object) As Boolean
'**************************************************************
'PURPOSE: Automatically size the combo box drop down width 
'         based on the width of the longest item in the combo box

'PARAMETERS: Combo - ComboBox to size

'RETURNS: True if successful, false otherwise

'ASSUMPTIONS: 1. Form's Scale Mode is vbTwips, which is why
'                conversion from twips to pixels are made.  
'                API functions require units in pixels
'
'             2. Combo Box's parent is a form or other 
'                container that support the hDC property

'EXAMPLE: AutoSizeDropDownWidth Combo1
'****************************************************************
Dim lRet As Long
Dim bAns As Boolean
Dim lCurrentWidth As Single
Dim rectCboText As RECT
Dim lParentHDC As Long
Dim lListCount As Long
Dim lCtr As Long
Dim lTempWidth As Long
Dim lWidth As Long
Dim sSavedFont As String
Dim sngSavedSize As Single
Dim bSavedBold As Boolean
Dim bSavedItalic As Boolean
Dim bSavedUnderline As Boolean
Dim bFontSaved As Boolean

On Error GoTo ErrorHandler

If Not TypeOf Combo Is ComboBox Then Exit Function
lParentHDC = Combo.Parent.hdc
If lParentHDC = 0 Then Exit Function
lListCount = Combo.ListCount
If lListCount = 0 Then Exit Function

'Change font of parent to combo box's font
'Save first so it can be reverted when finished
'this is necessary for drawtext API Function
'which is used to determine longest string in combo box
With Combo.Parent

sSavedFont = .FontName
    sngSavedSize = .FontSize
    bSavedBold = .FontBold
    bSavedItalic = .FontItalic
    bSavedUnderline = .FontUnderline
    
    .FontName = Combo.FontName
    .FontSize = Combo.FontSize
    .FontBold = Combo.FontBold
    .FontItalic = Combo.FontItalic
    .FontUnderline = Combo.FontItalic

End With

bFontSaved = True

'Get the width of the largest item
For lCtr = 0 To lListCount
   DrawText lParentHDC, Combo.List(lCtr), -1, rectCboText, _
        DT_CALCRECT
   'adjust the number added (20 in this case to
   'achieve desired right margin
   lTempWidth = rectCboText.Right - rectCboText.Left + 20

If (lTempWidth > lWidth) Then
      lWidth = lTempWidth
   End If
Next
 
lCurrentWidth = SendMessageLong(Combo.hwnd, CB_GETDROPPEDWIDTH, _
    0, 0)

If lCurrentWidth > lWidth Then 'current drop-down width is 
'                               sufficient

AutoSizeDropDownWidth = True
    GoTo ErrorHandler
    Exit Function
End If
 
'don't allow drop-down width to
'exceed screen.width
 
   If lWidth > Screen.Width \ Screen.TwipsPerPixelX - 20 Then _
    lWidth = Screen.Width \ Screen.TwipsPerPixelX - 20

lRet = SendMessageLong(Combo.hwnd, CB_SETDROPPEDWIDTH, lWidth, 0)

AutoSizeDropDownWidth = lRet > 0
ErrorHandler:
On Error Resume Next
If bFontSaved Then
'restore parent's font settings
  With Combo.Parent
    .FontName = sSavedFont
    .FontSize = sngSavedSize
    .FontUnderline = bSavedUnderline
    .FontBold = bSavedBold
    .FontItalic = bSavedItalic
 End With
End If
End Function