[Caml-list] Problems using graphics

[Caml-list] Problems using graphics

[Sebastien Ailleret]

Hi,

I'm writing a small problem using Graphics and encountered the
following problems :

- Unix.sleep does not work in conjunction with Graphics. I found the
  solution in the archive of the Caml List (
  http://caml.inria.fr/archives/200011/msg00096.html ), but i think
  this point deserves a note in the documentation or in the FAQ.

- The name of a window can be changed only after a window is
  opened. This is a trouble because some window managers use the name
  of the window when it opens to decide its position, type of
  frame... This means it is impossible to differentiate the behavior
  of two different "Caml Graphics" windows.

- "fill_rect x y w h" and "draw_rect x y w h" do not draw the same
  rect. draw_rect is bigger and lower. In my opinion, fill_rect does
  the right thing. In order to see the problem, try :

    set_color black;
    draw_rect 5 5 10 10;
    set_color green;
    fill_rect 5 5 10 10;

  and optionnally :

    set_color red;
    plot 5 5;
    plot 15 15;

Sincerely

Sebastien
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Re: [Caml-list] Problems using graphics

[Xavier Leroy]

Hi Sébastien,

> I'm writing a small problem using Graphics and encountered the
> following problems :
> 
> - Unix.sleep does not work in conjunction with Graphics. I found the
>   solution in the archive of the Caml List (
>   http://caml.inria.fr/archives/200011/msg00096.html ), but i think
>   this point deserves a note in the documentation or in the FAQ.

Fair enough.  Perhaps a function Unix.really_sleep (that ignores
signals) is in order.

> - The name of a window can be changed only after a window is
>   opened. This is a trouble because some window managers use the name
>   of the window when it opens to decide its position, type of
>   frame... This means it is impossible to differentiate the behavior
>   of two different "Caml Graphics" windows.

Good point.  Should be easy to fix.

> - "fill_rect x y w h" and "draw_rect x y w h" do not draw the same
>   rect. draw_rect is bigger and lower. In my opinion, fill_rect does
>   the right thing. In order to see the problem, try :

Well, Caml calls the X Windows drawing primitives XDrawRectangle and
XFillRectangle with exactly the same arguments.  But that seems to run
into an, hmmm, oddity of X Windows, described in colorful language in
the "Unix Haters" handbook:
  http://www.molgen.mpg.de/~wwwutz/Unix_Haters/x-windows.html
Guess we'll have to work around this one.

- Xavier Leroy
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