failFlag=
AlphaBlendSettingTest([screenNumber])
Test that
Screen('
BlendFunction') recalls the same alpha blending values
as previoulsy set.
If no return argument is provided, then
TestAlphaBlendSetting issues an error
when a test fails. If a return argument is supplied then it signals a
failed test only by returning true, without issuing an error.
See also:
AlphaBlendingTest,
PsychAlphaBlending
Psychtoolbox/PsychTests/AlphaBlendSettingTest.m