Re: About OpenGL and NSView

[Xavier Glattard]

Fred Kiefer a écrit :
> Xavier Glattard wrote:
> > I would like to post some changes about OpenGL support.
> > (in gui and x11-back, soon in win32-back)
>
> Great.
>
> > I need to add a flag in NSView (in the _rFlags bit field). I think it
> > would not break anything but i may miss something.
> >
> > Any advice ? Thanks!
>
> There is plenty of space in that field left. Soem time ago I wanted to
> move all the other boolean flags of NSView into that field too, but
> didn't dare to do this as it might break subclasses. But a new entry
> wont cause trouble.
>
> What will that new bit be used for?

I found out that the backing store of the OpenGLView is marked as dirty 
then flushed after each drawing loop. This is useless because openGL 
does not draw anything on the backing store. So I created a 
'ignore_backing' flag that says the NSView does not need to trigger a 
flush. This flag is set by GLContext when it is attached to a view.
I get a 30% speed improvement! (same speed than non retained backing store)
Moreover i think this change will fix the bug I submitted some days ago 
about flickering win32 opengl window. I'm about to check this.

> > Fred: I've just updated my tree with your last changes some days ago.
> > Revision 27944 seems to break NSOpenGLView position: the view is moves
> > left and up -ward.
> > IMHO settting the background color (Rev 27945) is useless because the GL
> > context MUST clear the background (on my system).
>
> I only set the background colour to avoid random patterns being
> displayed before the OpenGL rendering starts. It made a difference for me.

I understand. I suppose my computer is too fast... (???)

> As for the change 27944, most likely the removal of that strange
> coordinate conversion makes the difference for you. With the current
> code things look correct for me with and without GNUstep drawing the
> windows decoration. (This being on Linux, not Windows) I have attached
> two screen shots of Gears to show the result.
>
> If things look different for you, we need to find out what may cause the
> difference. Are you using any GNUstep additions or themes?

If you look carefully your screenshots you can see that the GL view is 
shifted upward and to the right. It looks slightly different on my 
system because I use WMaker. I think the shift comes from the width of 
the window decorations : bottom and left borders. These are small on 
your system. The bottom border width is larger with WMaker.

I dont understand where these come from. It looks like the window 
decorations widths are always used to convert coordinates, even if the 
backend does not handle them. There is no problem with NSViews because 
they are relative to the contentView. But the OpenGL subwindow is 
relative to the XWindow!

If you draw the background of the GL view (with NSRectFill) you can see 
that only the sub-window is shifted, not the NSView.