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#define INCL_WINMESSAGEMGR
 
WM_CALCVALIDRECTS
parclWindow = (PRECTL) PVOIDFROMMP(mp1);   /* source rectangle   */
pswpDest = (PSWP) PVOIDFROMMP(mp2);        /* destination window */
 
The WM_CALCVALIDRECTS message is sent when a window is about to be resized.
This allows the application to specify the coordinates of a rectangle that
will be preserved and to designate where this rectangle will be moved in the
resized window. Areas outside this rectangle will be redrawn.
 
Parameter    Description
────────────────────────────────────────────────────────────────────────────
 
parclWindow  Low and high word of mp1. Points to an array of two RECTL
             structures that contain the dimensions of the window before and
             after resizing. The first RECTL structure contains the source
             rectangle; the second RECTL structure contains the destination
             rectangle. The coordinates of the rectangles are relative to
             the parent window of the window.
 
pswpDest     Low and high word of mp2. Points to the SWP structure that
             contains information about the window after it is resized.
 
Return Value
 
If an application processes this message, it can return zero to indicate it
has changed the rectangle itself, CVR_REDRAW if the entire window is to be
redrawn, or a combination of the following values:
 
Value            Meaning
────────────────────────────────────────────────────────────────────────────
CVR_ALIGNBOTTOM  Align with the bottom edge of the window.
 
CVR_ALIGNLEFT    Align with the left edge of the window.
 
CVR_ALIGNRIGHT   Align with the right edge of the window.
 
CVR_ALIGNTOP     Align with the top edge of the window.
 
Comments
 
The WM_CALCVALIDRECTS message is not sent if a window has the CS_SIZEREDRAW
style because such windows are always completely redrawn when resized.
 
See Also
 
WM_ADJUSTWINDOWPOS, RECTL, SWP
 
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