Declares
We’re going to make a function which, when given a file name, will find the default icon for it’s type (by its extension) and then draw it onto an object. It needs two inputs, the file name and the “hDC” of the object that it is going to draw onto.
My advice to you would be to make this in a module and refer back to the subroutine we are about to write (GetDefaultIcon). You will also need (for testing purposes at least) a form containing
- A picture box (With AutoRedraw = true). You could draw onto most things but they must have a device context (hDC value at runtime).
- A text box (or some way of entering a file name)
- A command button (or something to generate an event)
So lets start by declaring every thing:
'For looking at registry keys
'To: Open key ready to look at
Private Declare Function RegOpenKey
Lib "advapi32.dll" Alias
"RegOpenKeyA" (ByVal hKey As
Long, ByVal lpSubKey As
String, phkResult As Long) As
Long
'To: Look at key
Private Declare Function
RegQueryValueEx Lib "advapi32.dll" Alias "RegQueryValueExA" (ByVal hKey
As Long, ByVal lpValueName As String, ByVal lpReserved As Long, lpType As Long, ByVal lpData As Any, lpcbData As Long) As Long
'To: Close the key when it's finished
with
Private Declare
Function RegCloseKey Lib "advapi32.dll" (ByVal hKey As Long) As Long
Private Const HKEY_CLASSES_ROOT = &H80000000
Private Const
KEY_READ = &H20019 'To allow us to READ the registery
keys
'For Drawing the icon
'To:
Retrieve the icon from the .EXE, .DLL or .ICO
Private Declare Function
ExtractIcon Lib "shell32.dll" Alias "ExtractIconA" (ByVal hInst
As Long, ByVal lpszExeFileName
As String, ByVal nIconIndex
As Long) As Long
'To: Draw the icon into our picture box
Private
Declare Function DrawIcon Lib "user32.dll" (ByVal hDC As Long, ByVal X As Long, ByVal Y As Long, ByVal hIcon As Long) As Long
'To: Clean
up after our selves (destroy the icon that "ExtractIcon" created)
Private Declare Function
DestroyIcon Lib "user32.dll" (ByVal hIcon As Long) As Long
'For Finding the System folder
Private Declare
Function GetSystemDirectory Lib "kernel32.dll"
Alias "GetSystemDirectoryA" (ByVal lpBuffer As String, ByVal nSize As Long) As Long
If none of this code means anything to you then don’t worry too much, just accept that what it is doing is adding seven extra functions to this program that aren’t normally in VB. If you are interested then there is an article written by James Crowley on the subject (Windows APIs) available here.
Now we need to declare the function and all its private/temporary
variables:
Private Sub GetDefaultIcon(FileName As
String, Picture_hDC As Long )
Dim TempFileName
As String 'Never manipulate an input unless it doubles as an
output
Dim lngError As Long'For receiving error numbers
Dim
lngRegKeyHandle As Long'Stores the
"handle" of the registry key that is currently open
Dim
strProgramName As String'Stores the
contents of the first registry key
Dim
strDefaultIcon As String'Stores the
contents of the second registry key
Dim
lngStringLength As Long'Sets /
Returns the length of the output string
Dim
lngIconNumber As Long'Stores the icon
number within a file
Dim lngIcon As Long'Stores the "Icon Handle" for the default icon
Dim intN As
Integer 'For any temporary numbers