Algorithmic Solutions > LEDA > LEDA Guide > Windows and Panels > Buffering


There are situations where it is not desired that drawing operations immediately draw into the drawing area of a window and where it is useful to construct the entire drawing in a memory buffer before copying it (or parts of it) into the drawing area of the window.

On the right there is a screenshot of the example program "Bouncing LEDA".

Picture of Convex Hull

Examples for Buffering


  • Animations where one wants to display a sequence of snapshots of a scene that changes over time
  • Creation of a pixrect copy of a drawing without displaying it


The following operation starts the buffering. All subsequent drawing operations have no effect in the drawing area of the displayed window, but draw into an internal buffer with the same size and coordinates as the drawing area of W.
  void W.start_buffering();
The operations
  void W.flush_buffer();
  void W.flush_buffer(double x0, double y0, double x1, double y1)
copy the contents of the complete internal buffer, respectively the contents of the rectangle (x0,y0,x1,y1) of the buffer, into W. The second variant is much faster if the rectangle is significantly smaller than the drawing area of W. The operation
  void W.stop_buffering(char* & pr);
stops the buffering and converts the internal buffer into pixrect pr.

See also:

Drawing operations

Windows and Panels

Pixrects (Pixmaps)

Manual Pages:

Manual Page Windows

Please send any suggestions, comments or questions to
© Copyright 2001-2003, Algorithmic Solutions Software GmbH