ex11, plotting and Cairo ...

Joe Armstrong (AL/EAB) <>
Wed Jul 20 13:47:45 CEST 2005


Vlad Dumitrescu wrote

 
> From: "Joe Armstrong (AL/EAB)" <>
> > I see things the problem is more one of "programming 
> models" than making
> > an Erlang interface to X (replace X by your favourite package).
> 
> Hi,
> 
> As I've also been struggling with this, I'd like to throw in 
> my two cents.
> 
> About programming models: One important feature of an Ernalg graphics 
> package would be (for me) that it is "erlangish", and doesn't 
> force me to 
> use C-like code. A good example of what I mean is ex11, but 
> one reason why 
> it works so easily is that X itself works just like we want 
> it to. Making a 
> regular graphics package work like that is much harder.
> 
> > One thing I did find was that the only model I like is 
> based on a canvas
> > widget. To create buttons (and controls in general) I just 
> draw rectangles 
> > and lines
> > onto a canvas widget and animate them on mouse clicks.
> 
> That's what all toolkits do :-) If an "erlang programming 
> model" is to be 
> enforced, then this is probably the only way, to use external 
> code for the 
> low-level drawing.
> 
> > << aside - why can't we just define a low-level API and then layer 
> > graphics
> > on top of this. The low level could be implemented using 
> your favorite 
> > package.
> >
> >      The following API would suffice
> >
> > mkWin(X, Y, Width, Ht) => Win
> > draw(Win, rectangle, X, Y, Width, Ht, Color) => Tag
> > draw(Win, line, X1, Y1, X2, Y2, Width, Color) => Tag
> > draw(Win, text, X, Y, Font, Size, Text) => Tag
> > draw(Win, image, X, Y, ImageFile) => Tag
> > ...
> > add_event_handler(Win, X, Y, Width, Ht, mouse_click, Fun) => Tag
> > delete(Win, Tag) => true
> >
> > So you can create a window (mkWin) - draw things (draw) - add event 
> > handlers
> > and deleted tagged things.
> >
> > Given this (or something like this) then pretty fancy 
> applications can be 
> > layered on
> > top of this.
> > >>
> 
> First of all, agreeing on an API isn't easy at all! ;-)

Why not? - given the above I can program a wide range of apps.
Much better to have a stable well defined low-level than nothing.

Actually to make a "drop-dead-beautiful" interface all I need is 
anti-aliased fonts and alpha-blending of all display objects.

If we could agree on a set of stable cross-platform low-level primitives
then life would be much easier. 

 
> That said, I think the problem is that once the basic 
> functionality is in 
> place, one will want to add more features. In this day and 
> age, nobody will 
> want to use a GUI that looks like Windows 1.0... So the API 
> should be able 
> to take in new functionality without breaking. A suggestion 
> for such an API 
> is the PS/PDF model.
> 

YES * 10000 - Then I could take my erlguten code and put it into the GUIs
proper kerning and ligatures in the text in the menus!!!

> One backend that is reasonably stable, reasonably portable 
> and lends itself 
> to advanced graphics use is OpenGL. Esdl is a good start, 
> just look at 
> Wings. The only drawback is that SDL only supports one 
> top-level window, but 
> I know that Dan and the esdl team are working on something.

Go Dan, go ...

/Joe


> 
> best regards,
> Vlad
> 
> 



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