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## bitmap-stream

A class of object similar to windows in that you can draw onto it but it is never visible on the screen. Its contents, however, can be copied onto a visible window using copy-stream-area. A `bitmap-window` (or `bitmap-pane`) has the functionality of a bitmap-stream hardwired into it, implementing the backing-store for automatically refreshing and redisplaying the window. Bitmap-stream is provided in case you want to manage the drawings stored in memory independently. For an example using bitmap-streams, choose the Help menu | CG Examples and look for Bitmap-streams: custom backing store.

One creates a bitmap-stream by calling open-stream, passing the desired size as the value of page-width and page-height keyword arguments. Below is an example expression that creates a bitmap-stream; the two `nil` arguments are required due to the two deprecated optional parameters of open-stream.

    (open-stream 'bitmap-stream nil nil
      :page-width 600 :page-height 400
      :background-color yellow)

A diagram of window and widget classes is shown in Widget and window classes in cgide.htm.

Copyright (c) 1998-2019, Franz Inc. Oakland, CA., USA. All rights reserved.
This page was not revised from the 8.2 page.
Created 2012.5.30.

|  | ToC | DocOverview | CGDoc | RelNotes | FAQ | Index | PermutedIndex
| Allegro CL version 9.0 Unrevised from 8.2 to 9.0. 8.2 version