Re: [boost] RE: Re: GUI library - another one

From: Peter Dimov (pdimov_at_[hidden])
Date: 2004-03-04 08:39:15

Vladimir Prus wrote:
>
> So, if I want to create a widget for drawing graph, I'll have to
> write:
>
>    void draw_the_graph(window w, ....)
>    {
>           .....
>    }
>
>    void handle_click(window w, ....)
>    {
>         // Add new vertex
>    }
>
>    void handle_right_click(window w, ...)
>    {
>         // show vertex properties, if mouse points
>         // to a vertex
>    }
>
>    window make_graph_widget()
>    {
>          windows w;
>          w.on_draw = &draw_the_graph;
>          w.on_mouse_click = &handle_click;
>          w.on_mouse_right_click = &handle_right_click;
>          return w;
>    }
>
> ? What are the chances that handle_right_click can be reused anywhere
> else,

Slim, but possible.

> is it really independent from GUI,

No, but irrelevant.

> and isn't this too complex a solution?

No. The alternative solution is comparable in complexity, and as soon as you
add another graph widget that has different left or right click behaviors,
or make w change its appearance dynamically on response to a combo box cb
(by just assigning different drawing functions to w.on_draw in
cb.on_change), you'll see why the event-based model is superior. It's not a
new invention, just look at Delphi.