Tip 192: Selecting a New Desktop Wallpaper

December 5, 1995

Abstract
This article explains how to select desktop wallpaper from a Microsoft?
Visual Basic? application when using the Microsoft Windows? 95 operating
system.

Using the SystemParametersInfo Function
Using the Microsoft? Windows? 95 operating system, you can change the
Control Panel settings to display any wallpaper image you want. From the
Start menu, click Settings and click Control Panel. Next, double-click
Desktop Themes. You can then choose a new wallpaper from the Themes
drop-down list box.

In a Microsoft Visual Basic? application, however, you can use the Windows
application programming interface (API) SystemParametersInfo function to
select a new wallpaper. This function can be used to retrieve or set many
different Control Panel settings. The following code is the Declare
statement for this function:

Private Declare Function SystemParametersInfo Lib "user32" Alias
   "SystemParametersInfoA" (ByVal uAction As Long, ByVal uParam
   As Long, ByVal lpvParam As String, ByVal fuWinIni As Long) As Long

Note that the SystemParametersInfo function requires four arguments. The
first argument, uAction, is the setting that you want to retrieve or set.
In this case, you want to change the desktop wallpaper, so you use the
SPI_SETDESKWALLPAPER constant The second argument, uParam, is set to zero,
because the wallpaper setting does not use this argument. For the third
argument, lpvParam, you must tell the SystemParametersInfo function the
filename for the wallpaper you want to use. You must be sure to specify
the file's full path in this argument. The fourth argument, fuWinIni, can
be one of two values that tells Windows 95 how to preserve the new
settings.

If the SPIF_UPDATEINIFILE constant is specified for the fuWinIni argument,
Windows 95 saves the new settings to its user profile. If the constant
SPIF_SENDWININICHANGE is specified, however, the change is broadcast to
Windows 95 after the user profile is updated.

In the example program below, you can change the wallpaper setting to None
or to the PINSTRIPE bitmap image. When you change the current wallpaper
setting to None, the desktop is presented as a black background. In all
other cases, the desktop wallpaper displays the image stored in the
specified bitmap file.

Example Program
This program below shows how to change the wallpaper in Windows 95.

 1. Create a new project in Visual Basic. Form1 is created by default.
 2. Add the following code to the General Declarations section of Form1
    (note that the Declare statement must be typed as a single line of
    code):

Private Declare Function SystemParametersInfo Lib "user32" Alias
   "SystemParametersInfoA" (ByVal uAction As Long, ByVal uParam
   As Long, ByVal lpvParam As String, ByVal fuWinIni As Long) As Long
Const SPIF_UPDATEINIFILE = &H1
Const SPI_SETDESKWALLPAPER = 20
Const SPIF_SENDWININICHANGE = &H2

 3. Add a Command Button control to Form1. Command1 is created by default.
    Set its Caption property to "Remove Wallpaper".
 4. Add the following code to the Click event for Command1:

Private Sub Command1_Click()
    Dim X As Long
    X = SystemParametersInfo(SPI_SETDESKWALLPAPER, 0&, "(None)", SPIF_UPDATEINIFILE Or
    SPIF_SENDWININICHANGE) MsgBox "Wallpaper was removed"
End Sub

 5. Add a second Command Button control to Form1. Command2 is created by
    default. Set its Caption property to "Change Wallpaper".
 6. Add the following code to the Click event for Command2:

Private Sub Command2_Click()
    Dim FileName As String
    Dim X As Long
    FileName = "c:\windows\pinstripe.bmp"
    X = SystemParametersInfo(SPI_SETDESKWALLPAPER, 0&, FileName, SPIF_UPDATEINIFILE Or
    SPIF_SENDWININICHANGE) MsgBox "Wallpaper was changed"
End Sub

Run the example program by pressing F5. Click the Remove Wallpaper command
button. The wallpaper is removedWindows 95 displays a black background
with no graphics. Click the Change Wallpaper command button. The wallpaper
is changed to the PINSTRIPE bitmap image.