[sugar] Emulating the laptop display with Xephyr

[Behdad Esfahbod]

On Tue, 2006-08-01 at 15:44 +0200, Manu Cornet wrote:
> Hi all !
> 
> [Reposting from devel at laptop.org, on Marco's request :-) ]
> 
> It seems necessary to emulate the laptop's display and the DCON chip's
> special features (color swizzling, antialiasing) while designing
> Sugar, in order to keep an eye on what things will actually look like,
> and address problems such as small graphic elements (small fonts, thin
> lines).

You should try some filtering (I want to try it out myself but that may
not happen this week or next).  The idea is to use a convolution filter
to distribute the energy among the neighboring pixels that have
different color, such that you don't lose data in the single-channel
pixels.  Try the following for example:

  1 2 3 2 1
  2 4 6 4 2
  3 6 9 6 3     (all divided by 81)
  2 4 6 4 2
  1 2 3 2 1

Check this page out for more details (that's about subpixel text
rendering, but this is quite similar):

  http://www.grc.com/cttech.htm

Note that this technique may be infringing some patents owned by Apple.
Needs further investigation if to be used.


behdad


> Here :
> 
> http://www.manucornet.net/pub/olpc/xephyr_swizzle.diff
> 
> you will find a patch for Xephyr (in particular, the
> hw/kdrive/ephyr/hostx.c file) that emulates the laptop's display, with
> both color swizzling and antialiasing.
> 
> There are a few screenshots on the project's wiki page :
> 
> http://wiki.laptop.org/go/GTK_for_OLPC
> 
> In particular, check out the difference between antialiased and not
> antialiased swizzling :
> 
> http://wiki.laptop.org/go/GTK_for_OLPC#Color_swizzling_and_antialiasing
> 
> If you're designing anything from the Sugar UI, you might want to give
> it a try.
> 
> This display simulation is not actually loyal to the final appearance,
> since the display will have much more luminosity than this (as far as
> I know), but it's already a good preview. Plans are also to make the
> display 16 bit (instead of 24 bit currently) to match the actual
> hardware more closely.
> 
> Of course, feedback is most welcome, especially bug reports and
> screenshots!
> 
> Cheers,
> Manu

-- 
behdad
http://behdad.org/
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