 Usage:  ret_event=readevent(which_event{, di, row_num, col_num})   
 
 Input:

  which_event            0 for key; 1 for mouse 
                         
  di                     display 
                         
  row_num                integer 
                         
  col_num                integer 
                         
                         
                         
 Output:

  ret_event              a complex object: 
                         
                         1, if this event happened 
                         
                         0, if this event didn't happen 
                         
                         ret_event can include following elements: 
                         
                         
  ret_event.key          the string of the key if a key has been pressed 
                         
  ret_event.keysym       the integer code of the key if a key has been pressed 
                         (the mapping of keys to integer codes may vary with the operating 
                         system) 
                         
  ret_event.button       one of the integers 1,2,3, returning which mouse button has been pressed 
                         
  ret_event.xy           (only if called with 4 arguments) 
                         
                         a (1x2) vector of integers, returning the window coordinates of 
                         the mouse pointer if a mouse button has been pressed (e.g. 0~0 
                         is the upper left corner of the window) 
                         
  ret_event.xyreal       (only if called with 4 arguments and the plotted data has 2 dimensions) 
                         
                         a (1x2) integer vector returning the real coordinates of the mouse 
                         pointer in the data space. 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
