RandR version 1.2 revisited, subpixels, point-spread function
ajax at nwnk.net
Wed Sep 13 15:38:29 PDT 2006
On Wednesday 13 September 2006 11:27, Keith Packard wrote:
> On Wed, 2006-09-13 at 10:10 +0100, Markus Kuhn wrote:
> > Keith Packard wrote on 2006-09-13 06:56 UTC:
> > > 2. How to describe the sub-pixel geometry per-monitor, and what to
> > > do with that information when we have it.
> > The most generic and flexible solution is to provide a raster image of
> > the point-spread function of a single pixel. Imagine a single white
> > pixel on a black background, and now take a microscopic photograph of
> > that pixel and send it as a PNG file or the like to the application,
> > such that it gets an accurate picture of what the display will do to its
> > idealized pixels.
> Hmm. With all of the informative data about outputs that people want,
> how about I just add the ability to set properties on the output. Then
> we can build conventions about what that data looks like as we need it,
> without needing to rev the protocol, server or client libraries.
Of course, one obvious choice of property would simply be the complete EDID
block. Right now we post a root window property whenever someone calls
xf86SetDDCproperties, which means the last monitor touched wins. This also
has the pleasant property of detaching monitors from root windows.
On the topic of subpixels, the DI-EXT extension to EDID has three full bytes
for describing subpixel layout, configuration, and shape. The raster idea is
flexible but I can imagine it becoming a parsing nightmare - how do you
represent diagonal subpixels? Except in very limited situations the driver
is unlikely to be able to tell you any more about subpixel geometry than it
gets from EDID anyway.
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