SAMPLE: Drawing a Custom Border Around a Control Window

• Microsoft Windows Software Development Kit (SDK) for Windows versions 3.0 and 3.1

SUMMARY

Microsoft Windows is not designed to allow a control to draw its own custom border. If an application subclasses the control and draws a border during the processing of the WM_PAINT message, the control will not be clipped properly because the control does not determine the clipping when it draws outside its client area.

The proper approach is to have the parent of the control draw the border during the processing of a WM_PAINT message. In this case, Windows will perform the appropriate clipping automatically.

There is a sample application in the Microsoft Software Library called DROPSHAD that demonstrates this technique. This program shows how to create an edit control with a "drop shadow." The parent window of the edit control draws the drop shadow on the control's behalf.

Download DROPSHAD.EXE, a self-extracting file, from the Microsoft Software Library (MSL) on the following services:

• Microsoft Download Service (MSDL)

        Dial (206) 936-6735 to connect to MSDL
        Download DROPSHAD.EXE (size: 21448 bytes) 
  

• Internet (anonymous FTP)

        ftp ftp.microsoft.com
        Change to the \SOFTLIB\MSLFILES directory
        Get DROPSHAD.EXE (size: 21448 bytes) 
  

MORE INFORMATION

The following three steps draw the drop shadow:

1. During the processing of the parent window's WM_CREATE message, the parent creates the edit control and sets a static variable to the edit control's HWND (which will be needed to draw the shadow).

2. The parent windows draws the drop shadow during the processing of a WM_PAINT message. The parent window uses GetWindowRect() to determine the rectangle of the edit control in screen coordinates. The ScreenToClient() function converts this data to local coordinates, then OffsetRect() offsets the rectangle to determine the bounds of the shadow. (The code for this step would go very nicely into a DrawShadow() procedure if the application had more than one edit control to shadow.)

3. The parent window calls Rectangle() to draw the two rectangles that create the drop shadow.