EGL_MESA_screen_surface version 2

[Jon Smirl]

On Fri, 18 Mar 2005 15:54:45 +1100, Benjamin Herrenschmidt
<benh at kernel.crashing.org> wrote:
> On Thu, 2005-03-17 at 23:46 -0500, Jon Smirl wrote:
> > My new opinion on modes is:
> >
> > 1) modes only have two egl attributes, width & height
> 
> That is not new, and I still think you are wrong :) I think frequency is
> important (you seem to be the only one not to think so). I also really
> want more attributes, one important one for example is the LCD pixel
> format (for subpixel rendering) etc... I'll try to come up with a proper
> list asap. I need to read the spec first, this week-end hopefully.

subpixel format is a display attribute, not a mode attribute. I don't
have any problem with more readonly display attributes.

DPI is a problem because the concept doesn't work on projected displays.

> 
> > 2) modes must have name
> 
> Agreed.
> 
> > 3) the internal egl implementation can return multiple modes for each
> > width & height, name is what differentiates them
> 
> You mean the frequency should be just part of the name ? Hrm... maybe. I
> still want more attributes though :) What about things like TV standard,
> etc... putting it all in the name will end up with quite over-long
> names ...

It would all go into the name. But these names don't have to be long
because they would be defined in the lower level system config files.
Why not name them TVOUT, HIREFRESH, LOREFRESH. The only time they
would get long is when the lower layers try to autogenerate them and
the generated name includes all of the low level variables.

> 
> > 4) the multiple mode list is sorted by the internal egl implementation
> > such that most preferable mode comes first and so on.
> 
> So the LCD native mode would just be the first one returned by EGL ?
> Agreed, that makes things simper, no need for a special "native"
> attribute then.

Yes, the low level layers would know about the detailed mode and mode
it to the front of the list.

> 
> > 5) default egl mode choice will be first one in the list at the given
> > resolution.
> >
> > Some observations:
> > 1) Modes are only set on displays. Displays are used by humans. Humans
> > want mode names, not X modelines.
> 
> True, nobody wants actual timings, I think everybody agrees there.
> 
> > 2) Displays are by definition the top most level and have UI's which
> > can present the mode list
> > 3) EGL should not attempt to the order modes even on the refresh rate.
> > The example of LCDs being superior at 60Hz than 72Hz is a good
> > example. Only the lower level systems know how to order the modes. If
> > you want to change the ordering available in EGL you need to adjust
> > things at a lower level.
> > 4) For Ian's case of beat frequency between monitors, the display
> > would start up in 72 and 75Hz. The user would then change one to 72Hz.
> > Or the XGL config could have a mode name in it to override the default
> > setting.
> > 5) It's a requirement to support multiple modes at a given resolution.
> > For example I didn't know that sports and movies recorded for HDTV
> > look better at slightly different frame rates. Only the user knows if
> > they are watching a full screen playback of sports or movies and can
> > set the mode using the human readable names.
> 
> 


-- 
Jon Smirl
jonsmirl at gmail.com