>Psychtoolbox>PsychGLImageProcessing

rval = kPsychNeedHalfHeightWindow

Return a flag that you can pass to the ‘imagingmode’ parameter of
Screen(‘OpenWindow’) in order to request use of half-height windows. These
onscreen windows are treated by all drawing functions (and geometry query
functions like Screen(‘Rect’, window); or Screen(‘WindowSize’, window);
as if they only have half the height in pixels. This is a trick to handle
line interleaved stereo modes or other special display modes, where useable
vertical drawing area is only half the physical monitor resolution.

Usually user scripts won’t pass this flag, but only special setup routines
that are part of the Psychtoolbox itself.