How to get a character from the keyboard when over the plot window?

Question

I need some input from the keyboard while displaying a plot. With the waitforbuttonpress() function I can detect whether the mouse button or a key on the keyboard has been pressed, but I cannot get the specific key/character selected.

I need a method which works from the plot output window, not from the text console.

This is what I have so far:

clf;
colormap ("default");

filename_orig = "./orig.data"

load("-text", filename_orig, "M")

M

t = 1

h = imagesc (M(:,:,t));

title ("Test data");
xlabel ("x");
ylabel ("y");

# Loop across time
b = 0;
for i = 1:10
  for t = 1:size(M,3)
    title(["Test data; t = ", num2str(t)]);
    set(h, 'cdata', M(:,:,t))   # update latest frame
    pause(0.20)                 # keep >0 to ensure redraw
    b = waitforbuttonpress();
    if(b == 1)
      break;
    endif
  end
  if(b == 1)
    break;
  endif
end

I would like to remove the outer loop, and allow to increment/decrement the t variable according to the user's key presses.

By the way, is it possible to remove that double break to exit from a nested loop?

Ideally, this is what I would like:

# Loop across time
b = 0;
t = 0;
while(1)
  title(["Test data; t = ", num2str(t)]);
  set(h, 'cdata', M(:,:,t))   # update latest frame
  pause(0.20)                 # keep >0 to ensure redraw
  k = readKeyboard();   # pseudo function
  if(k == '+')
    t = t + 1;
  endif
  if(k == '-')
    t = t - 1;
  endif
  if(t < 0)
    t = max;
  endif
  if(t > max)
    t = 0;
  endif
end

Answer 1

You can attach a WindowKeyPressFcn callback function to the figure as:

global t
function my_cbf(object, event)
  k = event.key;
  if(k == '+')
    t = t + 1;
  end
  ...
end

figure_handle = gcf();
set(figure_handle, 'WindowKeyPressFcn', my_cbf)