>Psychtoolbox>PsychTests

TextBug
Demonstrates an off-by-one bug in Screen(‘Drawtext’). The rendered text
is drawn +1 pixel to the right of where it should be. This leaves the
leftmost pixel unused, and clips off the rightmost pixel of the string.
The bug is demonstrated here by drawing a letter twice, first in green as
part of a string that has a space added (so no clipping occurs) and is
then overwritten in black, without the added space. A green right edge is
apparent in many rendered characters, at least in the Sloan font whose
characters have no built-in spacing. The program also finds the bounding
box of each character. For Sloan, the top bound is always zero, which is
correct, but the left bound is always 1, which should also be zero.

Denis Pelli March 21, 2007
denis.pelli@…
The Sloan font may be downloaded from here:
http://psych.nyu.edu/pelli/software.html