Bug#720690: wrong mouse buttons in events

[Mark Weyer <mark@weyer-zuhause.de>]

Package: libsdl-ocaml
Version: 0.9.0-1
Severity: grave

libsdl-ocaml reports left mouse clicks as middle ones, middle mouse clicks as
right ones, and right mouse clicks as mouse-wheel up. This incorrect behaviour
can be verified with the attached program.
Mouse state reporting is not affected.

I believe the origin of the bug to be that the libsdl constants start with
#define SDL_BUTTON_LEFT		1
in SDL_mouse.h (in package libsdl1.2_1.2.15), while the OCaml type
Sdlmouse.button starts with
  | BUTTON_LEFT
at tag value 0.

Thus a fix (until later SDL versions change the constants (again?)) would be
replacing the line
    r = Val_int(b);
in
static value value_of_mouse_button(Uint8 b)
in sdlevent_stub.c by
    r = Val_int(b)-1;

I set the severity to grave, because all reverse-dependencies requiring left
mouse clicks (that should be most, but not all, reverse-dependencies) become
unusable.

Best regards,

  Mark Weyer

open Sdlevent

let string_of_button b =
  let open Sdlmouse in
  match b with
  | BUTTON_LEFT -> "left"
  | BUTTON_MIDDLE -> "middle"
  | BUTTON_RIGHT -> "right"
  | BUTTON_WHEELUP -> "up"
  | BUTTON_WHEELDOWN -> "down"
  | BUTTON_X x -> string_of_int x

;;

Sdl.init [`VIDEO];

let screen = Sdlvideo.set_video_mode ~w:800 ~h:600 ~bpp:32 []  in
Sdlvideo.update_rect screen;

enable_events Sdlevent.mouse_event_mask;

while true do
  let e = wait_event ()  in
  (match e with
  | MOUSEBUTTONDOWN e -> prerr_string ("mousedown "^string_of_button e.mbe_button)
  | MOUSEBUTTONUP e -> prerr_string ("mouseup "^string_of_button e.mbe_button)
  | _ -> prerr_string (string_of_event e));
  let _,_,buttons = Sdlmouse.get_state ()  in
  prerr_string ("("^String.concat "," (List.map string_of_button buttons)^")");
  prerr_string "\n";
  flush stderr;
done;