Re: [AD] keyboard buffer (proposal)

[Thomas Fjellstrom <tfjellstrom@xxxxxxxxxx>]

On December 20, 2008, Peter Wang wrote:
> On 2008-12-20, Matthew Leverton <meffer@xxxxxxxxxx> wrote:
> > On Sat, Dec 20, 2008 at 3:06 PM, Elias Pschernig
> >
> > <elias.pschernig@xxxxxxxxxx> wrote:
> > > My vote is to completely remove ALLEGRO_KEYBOARD_STATE and al_key_down.
> > >
> > > It's not easier to use than events, and means you randomly lose key
> > > presses whenever the user starts typing/playing fast. So basically as
> > > soon as you use them, your game is broken. There's simply no reason at
> > > all to ever use them.
> >
> > I disagree. And plus, as SiegeLord pointed out, using events could
> > break your game too.
>
> It shouldn't.  At least for the mouse, if you hold down a mouse button
> in one window then release it outside that window, the original window
> should get the release event, not whatever window the mouse cursor is
> on top of now.

That only works if the window explicitly grabs mouse input. Its something we 
should think about doing on all platforms.

> > However, I wouldn't mind removing ALLEGRO_KEYBOARD_STATE from the
> > programmer's view. How would people use it, other than:
> >
> > al_poll_keyboard();
> > if (al_key_down(ALLEGRO_KEY_LEFT)) p.x--;
> >
> > i.e., is that sufficient, or is there a good reason to expose
> > ALLEGRO_KEYBOARD_STATE?
>
> Yes, due to multiple threads.  One thread could be updating the keyboard
> state with al_poll_keyboard() while another is calling al_key_down().
> Practically speaking, I *think* we can get away with only locking in
> al_poll_keyboard() and just letting al_key_down() read from the internal
> buffer without any synchronisation, but I'd rather not introduce a known
> design defect.
>
> I don't see that your example all that different from:
>
>     ALLEGRO_KEYBOARD_STATE kst;	/* global */
>     ...
>     al_get_keyboard_state(&kst);
>     if (al_key_down(&kst, ALLEGRO_KEY_LEFT)) p.x--;
>
> Peter
>
>
> ---------------------------------------------------------------------------
>---


-- 
Thomas Fjellstrom
tfjellstrom@xxxxxxxxxx