Re: Best way to put an array-based pixmap on a screen?

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2017-03-26 03:01, LaeMing Ai wrote:
> I am hoping to learn some Ada with an explicit interest in simple
> software 3D rendering (ie: writing the render code in Ada, NOT calling
> external libraries such as OpenGL).

Usually there is no access to the display around the OS. You will have 
to use some external library this or that way.

> I particularly don't want event loops, or anything else dragged in
> from outside the Ada environment if at all possible - the point of
> using Ada is to learn to do all that /in/ Ada!

You cannot draw into the RAMDAC, for obvious reasons. You do into a 
window controlled by the window manager. The window can get exposed, 
obscured, minimized etc. That brings a lot of stuff with it, events 
included.

> I have played around with some AdaGTK examples but keep getting bogged down :-( .

That is because you looked at the wrong place. Rendering under Gtk is 
done through Cairo (or far less frequently through OpenGL). Earlier 
versions of Gtk (<3.0) used other, very limited compared to Cairo, 
means. This is the stuff you probably found. Forget it, it is no longer 
supported.

Cairo rendering is more or less simple:

    https://www.cairographics.org/tutorial

 From the Gtk side you need a widget to draw into. The best candidate is 
Gtk_Drawing_Area for which you have to provide a handler of "draw" 
event. In the handler you receive a Cairo context, where all your 
drawing goes.

As an example you can take the Gtk_Layered widget. It consists of layers 
drawn upon each other:

    http://www.dmitry-kazakov.de/ada/aicwl.htm#2

You also can derive your own layer from the Abstract_Layer and let 
Gtk_Layered draw it.

If drawing pixmaps is the only thing you need, that is even simpler:

    http://www.dmitry-kazakov.de/ada/gtkada_contributions.htm#3

You can compile an XPM image into Ada code and use that to either to 
draw into a Cairo context (see above) or as a stand-alone image widget 
Gtk_Image.

P.S. An alternative to Gtk/Cairo is Qt. There are Ada Qt bindings as 
well. People here will surely help you with that too.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de