January 17, 2021
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Quickstart Guide to Screensavers

  • By Karl Moore
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Previewing your screensaver means recreating a smaller version of it in the 'Preview' panel in the Display applet. This is not as difficult as it sounds and simply requires you to copy-and-paste a chunk of code.

Previewing your Screensaver

  • Add the following code to a module in your screensaver application:
Private Type RECT   Left As Long   Top As Long   Right As Long   Bottom As LongEnd TypePrivate Const WS_CHILD = &H40000000Private Const GWL_STYLE = (-16)Private Const GWL_HWNDPARENT = (-8)Private Const HWND_TOP = 0&Private Const SWP_NOZORDER = &H4Private Const SWP_NOACTIVATE = &H10Private Const SWP_SHOWWINDOW = &H40Declare Function GetClientRect Lib "user32" _    (ByVal hwnd As Long, lpRect As RECT) As LongDeclare Function GetWindowLong Lib "user32" _    Alias "GetWindowLongA" (ByVal hwnd As Long, _    ByVal nIndex As Long) As LongDeclare Sub SetWindowPos Lib "user32" (ByVal _    hwnd As Long, ByVal hWndInsertAfter As Long, _    ByVal X As Long, ByVal Y As Long, ByVal _    cx As Long, ByVal cy As Long, ByVal wFlags As Long)Declare Function SetWindowLong Lib "user32" _    Alias "SetWindowLongA" (ByVal hwnd As Long, _    ByVal nIndex As Long, ByVal dwNewLong As Long) As LongDeclare Function SetParent Lib "user32" _    (ByVal hWndChild As Long, _    ByVal hWndNewParent As Long) As LongPublic Sub DoPreviewMode(PreviewForm As Form)        Dim lngStyle As Long, dispHWND As Long, DispRec As RECT        dispHWND = CLng(Right(Command, Len(Command) - 3))        Load PreviewForm    GetClientRect dispHWND, DispRec    lngStyle = GetWindowLong(PreviewForm.hwnd, GWL_STYLE)    lngStyle = lngStyle Or WS_CHILD ' Append "WS_CHILD"    SetWindowLong PreviewForm.hwnd, GWL_STYLE, lngStyle    SetParent PreviewForm.hwnd, dispHWND    SetWindowLong PreviewForm.hwnd, GWL_HWNDPARENT, dispHWND    SetWindowPos PreviewForm.hwnd, HWND_TOP, 0&, 0&, _        DispRec.Right, DispRec.Bottom, _        SWP_NOZORDER Or SWP_NOACTIVATE Or SWP_SHOWWINDOW        End Sub
  • When a preview is requested (see Determining the Mode), run the DoPreviewMode method, passing it your form to preview as an argument

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This article was originally published on November 20, 2002

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