AllocScreenBuffer

Get a ScreenBuffer for double-buffering.

Declaration

Source position: intuition.pas line 3933

Arguments

Function result

Pointer to a valid ScreenBuffer structure, or nil if failure. You may render into the resulting BitMap as appropriate. You may use the TScreenBuffer.sb_DBufInfo field to access graphics.library ViewPort-buffering features such as learning when it is safe to reuse the previous BitMap. If not, you risk writing into the on-screen BitMap, which can damage menu or gadget rendering!

Description

Allocates a ScreenBuffer structure and usually a BitMap. This structure can be used for double (or multiple) buffering in Intuition screens. You may use this call to obtain a ScreenBuffer structure for the screen's initial BitMap, or for other BitMaps you intend to swap in.

AllocScreenBuffer() also allocates a graphics.library DBufInfo structure. The ScreenBuffer structure this call returns contains a pointer to that TDBufInfo structure, which is free for your use. See AllocDBufInfo() for full details on using this structure to achieve notification of when it is safe to render into an old buffer and when it is right to switch again.

Flags:

SB_SCREEN_BITMAP

to get a ScreenBuffer referring to the screen's actual BitMap. (For CUSTOMBITMAP screens, just set the BitMap parameter to the BitMap you passed to OpenScreen()).

SB_COPY_BITMAP

If you would like the screen's BitMap copied into this ScreenBuffer's BitMap. This is required to get any menu-bar or gadget imagery into each ScreenBuffer's BitMap. If the screen has no Intuition rendering, you may omit this flag. Also, when allocating a ScreenBuffer for the screen's initial BitMap, this flag should not be set.

See also