INFO: CS_SAVEBITS Class Style Bit

ID: Q31073

The information in this article applies to:

Microsoft Windows Software Development Kit (SDK)
Microsoft Win32 Software Development Kit (SDK)

SUMMARY

If the CS_SAVEBITS style is included when registering a pop-up window, a bitmap copy of the screen image that the window will obscure is saved in memory when the window is displayed.

The bitmap is redisplayed at its original location and no WM_PAINT messages are sent to the obscured windows if the following is true when the window is removed from the display:

The memory used by the saved bitmap has not been discarded.

Other screen actions have not invalidated the image that has been stored.

As a general rule, this bit should not be set if the window will cover more than half the screen; a lot of memory is required to store color bitmaps.

The window will take longer to be displayed because memory needs to be allocated. The bitmap also needs to be copied over each time the window is shown.

Use should be restricted to small windows that come up and are then removed before much other screen activity takes place. Any memory calls that will discard all discardable memory, and any actions that take place "under" the window, will invalidate the bitmap.


Keywords          : kbNTOS kbGrpUser kbWinOS kbWndw kbWndwClass kbWndwProp 
Version           : 
Platform          : 
Issue type        : kbinfo

Last Reviewed: March 5, 1999