Matlab has button click callbacks for graphical types. There's always multiple ways to approach a problem, but this is the route I'd take:
function testPiano
% Create a figure and axis
fh = figure;
ax = axes;
% Make a button click response for the axis
ax.ButtonDownFcn = @(src, event) mouseClickCallback(src, event);
ax.Color = [0.8 0.8 0.8]; % Make the axis light grey
% Make two rectangular keys out of patches
% Using the "UserData" property to store what key it is here. You could
% also pass extra arguments throught the callback (e.g., a third input)
whiteKey = patch([0 0.5 0.5 0 0], [0 0 1 1 0], [1 1 1], 'EdgeColor', [0 0 0], 'UserData', 'C1');
blackKey = patch([0.25 0.75 0.75 0.25 0.25], [0.35 0.35 1 1 0.35], [0.1 0.1 0.1], 'EdgeColor', [0 0 0], 'UserData', 'C#1');
% Make the keys respond to mouse click
whiteKey.ButtonDownFcn = @(src, event) mouseClickCallback(src, event);
blackKey.ButtonDownFcn = @(src, event) mouseClickCallback(src, event);
% Probably want this to make sure the X and Y axis have the same step size
ax.DataAspectRatio = [1 1 1];
function mouseClickCallback(src, event)
% Single callback function, but switching behavior based on the
% source of the callback
switch class(src)
case {'matlab.graphics.primitive.Patch'}
% Patch clicked, so let's respond with the key value we
% stored
fprintf('Clicked key %s\n', src.UserData);
case {'matlab.graphics.axis.Axes'}
% Axis clicked, so let's respond with the (X, Y) position
% that was clicked
fprintf('Clicked axis at point %0.3f, %0.3f\n', src.CurrentPoint(1, 1), src.CurrentPoint(1, 2));
otherwise
fprintf('Unknown object of type ''%s'' clicked\n', class(src));
end
end
end
This demo code uses callbacks from patches and axes to make some kind of unique response. If you're going the "grid" route, you'll have to supply your own logic for detecting which key you're actually over using the mouse position data. As a side note, if you don't want something to intercept mouse click events (like text labels), just turn the "HitTest" property of the object to "off".
