/usr/share/psychtoolbox-3/PsychTests/TextInOffscreenWindowTest.m is in psychtoolbox-3-common 3.0.11.20131230.dfsg1-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 | % TextInOffscreenWindowTest
%
% Compare text drawn into an offscreen window to text drawn into an
% onscreen window.
%
% Screen currently fails this test; Screen('DrawText') draws slightly
% differently into onscreen and offscreen windows. Visual examination of
% the difference between onscreen and offscreen text shows that the
% onscreen texts is larger by about two pixels.
%
% Until this is resolved, we recommend not mixing onscreen and offscreen
% text rendering if you require exact matching between text.
%
% We don't yet know why this fails. The problem seems to have to do with
% differences between how textures are rendered into onscreen and offscreen
% windows. That could be either because of a bug in Screen, or because the
% OpenGL software renderer used for offscreen windows rasterizes textures
% slightly differently than the hardware renderer used for onscreen
% windows. We don't yet have a way to compare textures in onscreen and
% offscreen windows indepently of drawing text because 'DrawTexture' still
% uses OpenGL extensions not provided in offscreen contexts.
%
% HISTORY
%
% mm/dd/yy
%
% 3/18/04 awi Wrote it.
s=max(Screen('Screens'));
[w, wRect]=Screen('OpenWindow', s, [], [], 32, 2);
[osw, oswRect]=Screen('OpenOffscreenWindow', w);
Screen('FillRect', osw, 0);
Screen('TextFont',osw, 'Courier');
Screen('TextSize', osw, 50);
Screen('TextStyle', osw, 0);
Screen('DrawText', osw, 'This is text.', 100, 100, [255, 255, 255]);
oswImage=double(Screen('GetImage', osw));
Screen('FillRect', w, 0);
Screen('TextFont',w, 'Courier');
Screen('TextSize', w, 50);
Screen('TextStyle', w, 0);
Screen('DrawText', w, 'This is text.', 100, 100, [255, 255, 255]);
Screen('Flip', w);
wImage=double(Screen('GetImage', w));
Screen('PutImage', w, abs(oswImage - wImage));
%Screen('PutImage', w, oswImage);
Screen('Flip', w);
% % wait for a mouse press
% fprintf('Click the mouse to proceed\n');
% [x,y,buttons] = GetMouse();
% while ~any(buttons)
% [x,y,buttons] = GetMouse();
% end
% fprintf('\n');
Screen('CloseAll');
doesMatch=isempty(find(oswImage ~= wImage));
di=oswImage - wImage;
maxDiff=abs(max(max(max(di))));
if maxDiff ~= 0;
ampFactor=floor(255/maxDiff);
else
ampFactor=1;
end
fprintf('TestTextInOffscreenWindowOSX results:\n\n');
if doesMatch
fprintf(' Passed the test; the contents of onscreen and offscreen windows match\n');
else
fprintf(' Failed the test; the contents of onscreen and offscreen windows do not match.\n');
fprintf(' Displaying the difference between onscreen and offscreen text using MATLAB''s\n');
fprintf(' "IMSHOW" command. To make small errors visible, the difference image has been \n');
fprintf([' multiplied by ' num2str(ampFactor) '.\n']);
fprintf('\n');
fprintf(' For further explanation and advice, see help for "TestTextInOffscreenWindowOSX"\n');
imshow(di* ampFactor);
end
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