Hi Olaf:


On Wed, 2006-08-16 at 21:23, Olaf Jan Schmidt wrote:
> [ Bill Haneman ]
> > That strikes me as a surprising statement.  Of course it depends on what
> > you mean by "partially sighted".
> 
> The people I am familiar with for example have light allergy. Large bright 
> areas on the screen hurts their eyes  (e.g. selected text in the GNOME dark 
> background colour scheme).

We designed our 'Inverse' themes with this condition in mind.  We avoid
large bright areas except for the case of 'select all' within a
document.   In actual practice, many users almost never do a "select
all".

> Some additional, intelligent false colour modes would be needed to invert only 
> those parts of the screen with bright colours. But as far as I know, no 
> existing screen magnifier that can this. Hopefully Gunnar will be able to 
> come up with a solution.

This isn't really required - it's easy to modify the colors of an
existing GTK+ theme or create a new one.  We have a "low contrast" theme
for use by folks for whom it's best to have no bright areas at all (this
theme should be used with lowered monitor brightness, in most cases).

But realize that many people with light sensitivity problems like the
one you describe also have reduced visual acuity, and thus need higher
than normal contrast.  It's a trade-off between providing high contrast
and avoiding large bright areas.  In the case of the HighContrastInverse
theme, we manage to avoid bright areas except in the specific case where
a large area is selected.  The "inverting" of selected text is not
built-in to gtk+, but is intentionally part of the HighContrast themes,
in order to provide maximum visibility.  Our own tests and study of
previous research and practice informed this choice.

> > I really wonder where you got this data, it is at odds with the
> > information I have received from domain experts.
> 
> It was one result of our usability test with partially sighted users, but I 
> need to mention that the group was very small.

I have never encountered a complaint about the brightness of the
selected area in the HighContrastInverse theme.  Our sample size was
fairly small too, but we did consult with folks who had experience in
this area.

The fact is that no single theme will be perfect for a large population
of users, as you point out.  I think it might be fairly simple to create
a "light sensitive" theme from the existing HighContrastInverse one, by
making the 'SELECTED' foreground color less bright.

(To do just this, modify the following line in the HighContrastInverse
gtkrc file, under 'style "default"' :
...
-  base[SELECTED]    = "#ffcccc"
+  base[SELECTED]    = "#9988aa"


You could also make this change for multiline-text widgets only, if you
prefer)

> > Doing this requires some sort of re-rendering or overlay feature.  Until
> > the recent introduction of XComposite this sort of thing was technically
> > not very feasible on XWindows.
> 
> Gunnar's magnifier will include something based on XComposite and AT-SPI, and 
> I suggested to make it also useful without the magnification.

"Magnifiers" without magnification are used for similar purposes on
Windows platforms, I believe.  The magnifier itself provides a
convenient way of "re-rendering" anything that's put on screen.

> > Theming is a very important issue and as you no doubt realize, it can be
> > difficult to get applications to comply with themes, it seems that most
> > applications want to define their own color schemes for at least some
> > things.
> 
> We are planning to extend the colour schemes in KDE4 to contain enough colour 
> roles for the applications, and to provide them with suitable functions for 
> gettign additional colours if they really need them. It would be great if we 
> could get a common solution for KDE and GNOME.

I agree.

There has been discussion of moving the theme colors from the current
.gtkrc files into XSettings, which would make it more
toolkit-independent.  I don't know the current status of that work.

> KDE can already apply its colour scheme to Gtk applications, but this is 
> broken, and I have been unable to find a documentation of the Gtk theme 
> settings.
This might help a little:
http://developer.gnome.org/doc/API/2.0/gtk/gtk-Resource-Files.html



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