This MATLAB+Psychtoolbox example script contains naively approach of applying spatial calibration offsets using Psychtoolbox imaging pipeline. It is posted along with support post on the PTB website. Note that this is not production code, it is simply an example to demonstrate a specific concept.

exampleApplyCalOffsets.m

% Demonstrate attempt at applying x, y offsets via PTB processing hooks.
%
% Instructions 
% ------------ 
% After running, press any key to advance offset position. Position will
% not change until key-up event. The script will run indefinitely until the
% escape key is pressed.
%
% Known Issues
% ------------
% 1) If there is not a task for FlipHorizontal in the pipeline, the demo
% fails.
%
% 2) No known way to exclude certain output (e.g. debug bar) from offsets
% being applied. 

%% Setup
clear screen;
ListenChar(2);

Screen('Preference', 'VisualDebugLevel', 3);
Screen('Preference', 'SkipSyncTests', 1); 

featureLevel = 2;
PsychDefaultSetup(featureLevel);
kb_escape = KbName('escape');

PsychImaging('PrepareConfiguration');
PsychImaging('AddTask', 'AllViews', 'FlipHorizontal');

%% Create Window
% What happens to the pipeline if you provide a rect?
winParms = struct( ...
    screenId=1, ...
    color=0.5, ...
    rect=[], ...
    pixelSize=[], ...
    numberOfBuffers=[], ...
    stereoMode=4 ...
);
winParmsCell = struct2cell(winParms);

[winPtr, winRect] = PsychImaging('OpenWindow', winParmsCell{:});

%% Draw dummy stimulus
rectParms = struct( ...
    color=1.0, ...
    rect=CenterRect([0 0 200 200], winRect), ...
    strokeWidthPx=20 ...
);
rectParmsCell = struct2cell(rectParms);

textParms = struct( ...
    text=char("E"), ...
    scaleX='center', ...
    scaleY='center', ...
    color=rectParms.color, ...
    wrapat=[], ...
    flipHorizontal=[], ...
    flipVertical=[], ...
    vSpacing=[], ...
    rightToLeft=[], ...
    winRect=rectParms.rect ...
);
textParmsCell = struct2cell(textParms);

Screen('TextSize', winPtr, RectHeight(rectParms.rect)*.75);

stepSize = 40;
stepDelay = 1/4;
offsets = [0, 1; 1, 0; 0, -1; -1, 0;] .* stepSize;

i = 0;
try
    while true
        for bufferId = [0, 1]
            Screen('SelectStereoDrawBuffer', winPtr, bufferId);
            Screen('FrameRect', winPtr, rectParmsCell{:});
            DrawFormattedText(winPtr, textParmsCell{:});
        end

        Screen('Flip', winPtr);
    
        [~, keyCode, ~] = KbWait([], 2);
        if keyCode(kb_escape)
            break;
        end

        offset = num2cell(offsets(i+1, :));
        fprintf("Applying offset %i, %i\n", offset{:});
        applySpatialOffsets(winPtr, 'StereoLeftCompositingBlit', offset{:});
        i = mod(i + 1, 4);
    end
catch exception
    ListenChar(0);
    rethrow(exception);
end

ListenChar(0);
clear screen;

%% Helper Functions
function applySpatialOffsets(winPtr, hookName, xo, yo)
    [slot, ~, blittercfg, ~, ~, ~, ~] = ...
        Screen('HookFunction', winPtr, 'Query', hookName, 0);

    if slot > -1
        blitterParts = str2double(strsplit(blittercfg, ':'));
        assert(length(blitterParts)==6);
        blitterParams = num2cell(blitterParts(~isnan(blitterParts)));
        [x, y, sx, sy] = blitterParams{:};

        Screen('HookFunction', winPtr, 'Remove', hookName , slot);
    else
        [x, y, sx, sy] = deal(0, 0, 1, 1);
    end

    Screen('HookFunction', winPtr, 'AppendBuiltin', hookName, 'Builtin:IdentityBlit', ...
        sprintf('Offset:%i:%i:Scaling:%f:%f', x+xo, y+yo, sx, sy));

    Screen('HookFunction', winPtr, 'Enable', hookName);
end

See post 4604 on Psychtoolbox forum for additional context.