Cloning

Graphics and Screen4.0 (8.x)Screen Graphics Subsystem Developer's GuideAPIProgrammingUtilities

Cloning is about duplicating content (e.g., two windows sharing the same content) by sharing buffers.

Cloning can be used to improve performance:

  • The number of updates required can be reduced.

    You can have content shown on multiiple displays, but only have to update one buffer. Video playback is a good example. You can decode once, but playback on multiple displays.

  • The amount of blending in the display can be reduced.

    For example, consider a window that's entirely transparent except for a watermark that needs to be blended in one corner. Blending this entire window is costly and can be avoided altogether by setting the transparency of this window to SCREEN_TRANSPARENCY_DISCARD. However, in order to keep the watermark visible, you can create another window that shares its buffers with the transparent window. This way, the window that's transparent is mostly discarded and only a small area, the size of the watermark, is actually blended.

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