Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!bloom-beacon!EXPO.LCS.MIT.EDU!kit
From: kit@EXPO.LCS.MIT.EDU (Chris D. Peterson)
Newsgroups: comp.windows.x
Subject: Re: XtNreverseVideo --again--
Message-ID: <8904201507.AA12757@expo.lcs.mit.edu>
Date: 20 Apr 89 15:07:51 GMT
References: <12671@pasteur.Berkeley.EDU>
Sender: daemon@bloom-beacon.MIT.EDU
Organization: The Internet
Lines: 72


> Normally, one would expect the foreground and background colors to be
> reversed.  yet this isn't quite that simple.

Nope, but it is pretty close.  If reverse video is specified by the user
the the values of XtDefaultForground and XtDefaultBackground are swapped.
Thus anything that uses these as their default colores will effectively
have the foreground and background colors swapped.

Without reverse video specified:

XtDefaultForeground = "white"
XtDefaultBackground = "black"

With reverse video specified:

XtDefaultForeground = "black"
XtDefaultBackground = "white"


>     { XtNforeground, XtCForeground, XtRPixel, sizeof(Pixel),
>       XtOffset(widget.foreground), XtRString, XtDefaultForeground},
>     ...
> 
> I have no idea what the foreground color defaults to...

It defaults to "white: when -rv is specified, otherwise to "black".  The use
can override by specifying something like:

test*foreground: blue


>     if (widget.reverseVideo)
> 	widget.foreground = !widget->core.background_pixel;

> This is the only way I'm guaranteed that the two colors will be
> different and that it'll work on both color and monochrome (altho the
> results will probably be incorrect for color servers).

Gaak.  This is really gross.  Don't do this you will get random colors on
a color workstation.


> Now, let's complicate things a little...

> My app-defaults file says:
>
> *foreground: green
> *background: blue

> Yet the user invokes the program with the -rv flag expecting his
> foreground to be blue and background to be green.  What happens now?

you should actually use:

*Foreground: green
*Background: blue

There are programs that set colors that are not named foreground and background
but have class Foreground or Background.  The color of the hands on xclock is a
good example.

Anyway in answer to your initial question.  The user will get the color
green for all resources named foreground and blue for all resources named
background.  This will happen reguardless of whether reverse video is
specified.  The attitude that the toolkit has taken is that reverse video 
is overrided by explict color specifications.  So if you specify colors then
reverse video ceases to have any meaning.


                                                Chris D. Peterson
                                                MIT X Consortium