Re: [GtkGLExt] Fwd: Re: GtkGlExt & GTK3

[Carlos Pereira <jose carlos pereira ist utl pt>]

Hi Norman,

To bridge GTK and OpenGL we need the following six functions:

1) **gtk_area_query**
a function that asks if OpenGL is available

2) **gtk_gl_area_create**
a function that creates a OpenGL area from a Gtk drawing area.

3) **gtk_area_current**
a function that sets the current OpenGL context

4) **gtk_gl_area_swap**
a function that swaps OpenGL buffers

5) **gtk_gl_area_wait**
a function that flushes previous OpenGL commands

6) **gtk_gl_area_remove**
a function that frees memory and removes a OpenGL area.

With these 6 functions, you can have an unlimited number of simultaneous 
OpenGL graphic areas, sharing pre-compiled lists, with all sorts of 
buffers and lights (exactly as with GtkGLExt).

My own implementation of these 6 functions is here (only for X Window 
system!):
http://www.gamgi.org/gamgi_gtk_area.c
http://www.gamgi.org/gamgi_gtk_area.h

and a diff -r for my package between: 1) using GtkGLExt and 2) using the 
6 functions above is here:
http://www.gamgi.org/diff_gamgi_src_gamgi_exp_src

If you want to compare the actual code just compare these two source 
trees (I can help if someone cares):
http://www.gamgi.org/gamgi-src-0.17-exp.tar.gz (the version with the 6 
functions above)
http://www.gamgi.org/gamgi-src-0.17.tar.gz (the version depending on 
GtkGlExt)

It's true that my own version (154 lines of C code, including comments 
and white lines!) does not support Windows and MAC OS X but is pretty 
clear that the 6 functions above, properly done for all systems around, 
would be just a few hundred lines of code... that's all that is needed 
for GTK to support OpenGL... and after 15 years we are still waiting for 
this...

We really don't need several thousands lines of code as in GtkGLExt 
(although it works just fine for me!), much less higher level toolkits 
such as clutter with new APIs around...

What we need is a single file with these 6 functions inside, written in 
a more professional way, for all systems supported (X11 Wayland Windows 
Mac OS X), and included in the oficial GTK package...

In 2010, I posted working examples to gtk-app-devel-list gnome org, as 
simple as possible, done with GtkGLExt and the 6 functions above, to 
show how simple it was to add OpenGL support to GTK. None replied...

Carlos
> Carlos, I am not an OpenGL expert.  I just wrote my first OpenGL code, 
> based on the SigGraph video "An Introduction to OpenGL Progranmming".  
> It uses a vertex and fragment shader to put put up an orientable cube 
> on the screen.  I ported this to Gtk2GlExtMM, and I don't see how GTK 
> could be offering a better interface.  From what I saw, GTK is 
> offering a fully functional window, allowing for widgets, and an 
> OpenGL region into which to write.  I did not feel encumbered in any 
> way, nor do I think the efficiency of the code was impeded.  But, I 
> have little experience in this field.
>
> How would GTK need to be upgraded to do OpenGL better?  How would it 
> be better?
> -- More efficient at run-time?
> -- More flexibility for the programmer?
> -- Allow a fuller OpenGL functionality?
>
> I am asking out of curiosity, and am not presuming to be arguing 
> against what you have said.
>
> Thank you.
>
>
>
>
>
> On 02/11/2014 12:23 PM, Carlos Pereira wrote:
> > > gtk 3 does support OpenGL. With clutter and cogl you can integrate 
> > > plain
> > > OpenGL into your application. Maybe it's not as smooth as as Qt's 
> > > OpenGl
> > > widget, but it is better to use than this abandoned GtkGlExt.
> > I am sorry this is just not true. As far as I can see Gtk 3 does not 
> > support OpenGL. Like Gtk 2. Like Gtk 1.
> >
> > This is so painfully obvious that it really hurts. Supporting OpenGL 
> > is not to build a new API, a new toolkit, a new software layer 
> > between user code and OpenGL (or even worse, to write a poor 
> > replacement for OpenGL).
> >
> > I have been in the Gtk developers list since 1999, every 5 years we 
> > come again to this issue, to no avail. After almost 15 years watching 
> > Gtk developers telling nonsense about OpenGL, I came to the 
> > conclusion that Gtk developers don't even understand the issue. It is 
> > mildly offensive to ask OpenGL programmers to throw away their 
> > optimized OpenGL code and replace it by some clutter API that 
> > translates to... OpenGL code!
> >
> > There are hundreds of books about OpenGL, please buy one and learn 
> > OpenGL before posting these ridiculous statements.
> >
> > All that is needed to bridge Gtk 2 and OpenGL under X11 are about 250 
> > lines of C code. I know because I distribute two versions of my 
> > package, one uses GtkGLExt, the other uses my own code. If you are 
> > really serious about this, I can point you to these packages and 
> > explain in detail the relevant C code. And I am not even an expert, I 
> > came to this code reading all I could about this...
> >
> > We have been asking for 15 years to include something like these 250 
> > lines of code, that is ALL that is needed to bridge GtK and OpenGL 
> > (some of this code is specific for the X Window System - for Wayland, 
> > Windows and Mac OS X you will need some slightly different code). 
> > Even these 250 lines, many are comments and space lines... This is so 
> > ridiculous...
> >
> > Carlos
>
>
>
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