brent@well.UUCP (Brent Southard) (12/01/88)
Here is an explanation of the CS_SAVEBITS flag, courtesy of Microsoft Technical Support... Question: Page 634 of the "Microsoft Windows Software Development Kit Programmer's Reference" states that there is a "style" type of CS_SAVEBITS defined. If I set this style, does this mean I do not have to maintain my own off-screen bitmap? How do I access the bitmap that is saved? Response: The documentation is slightly misleading as it is currently worded. If the CS_SAVEBITS style is included when registering a POPUP window, a bitmap copy of the screen image that the window will obscure is saved in memory when a window is displayed. The bitmap will be redisplayed at its original location and no WM_PAINT messages will be sent to the obscuring windows if the following is true when the window is removed from the display: 1. The memory used by the saved bitmap has not been discarded. 2. Other screen actions have not invalidated the image that it is storing. As a general rule, you should not set this bit if your 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. ----- I believe the above is probably owned by Microsoft, so be careful what you do with it. :) -- Brent Southard | Everybody's trying to be a friend of mine, Usenet: ...well!brent | Even a dog can shake hands. - W. Zevon CIS: 76657,415 | We fell into love, love's a very deep hole. GEnie: b.southard | - Loudon Wainwright III