Re: Mouse driver for Ada... how?

[tmoran@bix.com]

> So I had hoped to find some existing code examples.
Here's the spec of a (very old) mouse driver for DOS.  It uses the
INT 33 services.  In Windows you'd use the WM_MOUSEMOVE,
WM_LBUTTONDOWN, etc.  events.  If you don't have an OS service
available, don't have a vendor supplied driver, and are reduced to
handling a serial byte stream yourself, your first need is to find
what bytes your mouse (trackball) sends.  It's probably not too
complex, and thus not too hard to write code to process it.

with system;

package mouse is    -- low level mouse driver interface
                    -- uses int33 functions
                    --   16#00#: reset
                    --   16#0B#: read motion counters
                    --   16#03#: get mouse position and button status
                    --               (ignore logical position from this)
                    -- In 1987 this interface was standard and supported
                    -- by all PC mice.
  type state is
       record
         x,y:integer;
         left_button,middle_button,right_button:boolean;
       end record;
  -- x,y measured in mickeys
  -- button flags are true iff button is currently depressed

  current:state :=
     (x | y => 0,left_button | middle_button | right_button => FALSE);

  driver_missing:exception; -- will be raised at initialization
                            -- iff mouse driver is detected not present
                            -- ie if int33=0 or int33 points to an IRET

  procedure check;  -- updates current (nop if mouse driver is missing)

  -- The public record 'current' is used, rather than having 'out'
  -- parameters to the 'check' routine, for simplicity and efficiency.
  -- There is no way with this interface to have more than one mouse
  -- per OS task, so the generality of out parameters, or a generic
  -- mouse package, would be spurious.

  procedure reset;

  procedure hide_cursor;

  procedure show_cursor;

  procedure horizontal_range(min,max:in natural);

  procedure vertical_range(min,max:in natural);

  type graphic_cursor_bits is array(integer range <>) of system.word;
  subtype normal_graphic_cursor_bits is graphic_cursor_bits(0 .. 15);
  subtype hot_spot_offsets is integer range -16 .. 16;

  procedure set_graphic_cursor_words(screen_mask:in graphic_cursor_bits;
                                     cursor_mask:in graphic_cursor_bits;
                                     x_hot_spot :in hot_spot_offsets;
                                     y_hot_spot :in hot_spot_offsets);

  procedure Set_Cursor_Position(X,Y:in Integer);

end mouse;