Scilab 5.X is doing an advanced use of JOGL (the Java Binding for the OpenGL). For performance reasons, we are using the Java2D OpenGL Pipeline. From a more technical aspect, it is using the internal buffer of the graphic cards called pbuffer.

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Workaround
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From Scilab, execute the function:

  system_setproperty("jogl.gljpanel.nohw","");

Or launch Scilab wih hardware acceleration deactivated:

  LIBGL_ALWAYS_SOFTWARE=1 bin/scilab-adv-cli