Re: [AD] Missing system vtable entries on OS X

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On 1 Feb 2010, at 5:37 , Elias Pschernig wrote:
> Well, as far as I understand, OpenGL has no concept of a pixel format anyway. If we pass data to OpenGL we use something like glDrawPixels or glTexture2D. In both cases we have to specify the pixel format of the data we pass to it. Same if we read data back with glReadPixels and so on - we always have to tell OpenGL in what format we want it. There is no way to figure out the "native" format from OpenGL itself (as far as I can tell at least).

Ok, good. :)

> So what we do is in X11 we ask GLX. Which has the list of visuals. al_create_display selects one visual and it never can change right now. I don't know if a visual can change during the lifetime of an X11 window... I remember a lot of weird code from A4 dealing with "DirectColor" and "TrueColor" (and some other types of) visuals which might have handled just that...

I always thought that had to do with how you're supposed to treat paletted (8 bit) displays and true colour displays on X11. Of course, the last time I saw an 8 bit X11 display was in 2004, on one of the student SPARC workstations (read: one of the old crappy machines no one in the department wanted to use for anything serious anymore). I'd guess they're extinct by now.

> but I never understood what that was all about. Do you know how you would move an X11 window from one X11 display to another X11 display (say, running on a different VT with different color depth)?

Nope, not a clue. I know that in KDE you can move a window from a context menu, but I think that only lets you move to a different desktop. Never really looked that closely though.
How about having a dual monitor setup, with the desktop split across the two monitors and both of them being driven by a different graphics card? What happens if you drag a window from one monitor to the other?

> I think I actually tried to figure this out with google once but failed... so for now the answer is we don't handle it in X11 since it most likely can't even happen.

Ok. I'm taking that to mean that whatever the OS X port does at the moment is fine. :)
There is one odd thing about the returned display format on OS X: it gets the FLOAT_COLOR flag set. This is weird since the requested mode is certainly not one where the colour components are set with floats (the bit depth is too small for that to begin with). For now, it doesn't actually seem to get in the way so I just left it.

Evert



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