[Lazarus] TOpenGLControl: multisampling not working (Linux/GLX)

[Mattias Gaertner]

On Tue, 26 Feb 2013 15:51:52 +0100
Reimar Grabowski <reimgrab at web.de> wrote:

> On Tue, 26 Feb 2013 06:17:04 +0100
> Michalis Kamburelis <michalis.kambi at gmail.com> wrote:
> 
> > What is weirder is that I can get multi-sampling on both these systems 
> > (both Radeon and NVidia) with a very similar multi-sampling code inside 
> > my Castle Game Engine TCastleWindow class (that directly uses GTK and 
> > GTKGlExt, without Lazarus TOpenGLControl, to create window with OpenGL 
> > context)
> GTKGLExt may be the thing making it work. 

A quick look at the gtkglext-1.2.0 sources didn't reveal anything
special about multisampling.
The first noticeable thing of gtkglext code is the special color map.


> I don't have enough details but searching around the net showed that
> GTKGLArea does not support multisampling. AFAIR TOpenGLControls code is
> based on this. 

Yes.


> The lazarus forum post I linked to in another mail showed multisampling did work for the OpenGL examples that come with FPC. Multisampling does work with GTKGLExt as your engine shows. So I still think it is a problem with GDK but that is just a gut feeling.

The GLGtkGlxContext only uses the gdk function gdk_colormap_new.
And it let the gtk create the XWindow. It seems gtkglext does not
create the XWindow too.


> Perhaps TOpenGLControl can be rewritten to use GTKGLExt following your code if your license permits it. It's a shame that the GTK guys did not get their act together and don't offer a standard way of context creation like virtually every other widgetset does since years.

Indeed. And the last release of gtkglext is 1.2.0 from 2006.

Mattias