Re: Event mechanisms for GUI's

["Jeffrey R. Carter" <spam.not.jrcarter@acm.not.spam.org>]

Lucretia wrote:
> 
> The only way I can see of doing this (unless you want to supply some
> code to illustrate) is by providing the listener idiom and separating
> each listener "handler" into a separate interfaces (Ada 2005) and then
> providing a Set_Events_Mask on the component which goes through the bit
> mask and checks if there are interfaces set for the particular events:

That seems overly complicated. Something like

type Window_ID is ...;

type Widget_ID is ...;

type Event_ID is
    (Close, Left_Click, Middle_Click, Right_Click, Double_Click, ...);

type Event_List is array (Positive range <>) of Event_ID;

type Event_Set is private;

function Make (List : Event_List) return Event_Set;

procedure Add (To : in Window_ID; Event : in Event_ID);
procedure Remove (From : in Window_ID; Event : in Event_ID);

procedure Add (To : in Window_ID; Set : in Event_Set);
procedure Remove (From : in Window_ID; Set : in Event_Set);

function Event_Pending (Window : Window_ID) return Boolean;
procedure Get (Event : out Event_ID; Widget : out Widget_ID);

-- 
Jeff Carter
"I fart in your general direction."
Monty Python & the Holy Grail
05