WM_SETREDRAW
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4/8/2010
This message is sent by an application to a window to enable changes in that window to be redrawn or to prevent changes in that window from being redrawn.
Syntax
WM_SETREDRAW wParam = (WPARAM) fRedraw;
lParam = 0;
Parameters
fRedraw
Specifies the state of the redraw flag.If set to TRUE, the redraw flag is set.
If set to FALSE, the flag is cleared.
- lParam
Unused.
Return Value
An application should return zero if it processes this message.
Remarks
The window manager provides no default processing for this message. However, certain controls do support this message, list box, tree view, and combo box.
This message sets or clears the redraw flag. However, if the redraw flag is cleared, the content of the given window is not updated after each change, and the window is not repainted until the redraw flag is set. For example, an application that must add several items to a list box can clear the redraw flag, add the items, and then set the redraw flag.
Use the RedrawWindow function rather than the InvalidateRect function to repaint the list box. Some controls can have a non-client area on their own and some controls may be based on window styles (WS_THICKFFRAME/WS_BORDER/WS_EX_CLIENTEDGE and other like styles) that cause them to be given a non-client area. Therefore, call the RedrawWindow function using the parameters RDW_INVALIDATE|RDW_ERASE|RDW_FRAME|RDW_ALLCHILDREN. If the control does not have a non-client area, the RedrawWindow function with the specified flags will do only as much invalidation as InvalidateRect would.
Requirements
| Header | winuser.h |
| Windows Embedded CE | Windows CE 1.0 and later |
| Windows Mobile | Windows Mobile Version 5.0 and later |