Re: vc-annotate error, PATCH

[Dan Nicolaescu]

JD Smith <address@hidden> writes:

  > On Tue, 11 Apr 2006 12:57:23 -0400, Richard Stallman wrote:
  > 
  > >     To address this, I created a new colormap with 18 entries which fixes
  > >     saturation at 70%, value at 100%, and rotates from red to blue in
  > >     equal angle ~14 degree increments of hue.  The saturation of 70% keeps
  > >     the text light enough to be readable on the default black background,
  > >     but still usable on a white background.
  > > 
  > > How well does it work on a tty?
  > 
  > I hadn't thought of that, but tried and it does a reasonable job.
  > Less dynamic range in the yellow-green regime, but that is expected
  > given the small number of colors TTY's support. Here is a side by side
  > screen shot comparing the X11 vs. terminal annotations of the same
  > file:
  > 
  >  http://turtle.as.arizona.edu/emacs/annot_color.png
  > 
  > The only drawback is that green doesn't seem to get used much, with
  > yellow showing up instead for many colors.  I believe this is a
  > function of how substitute color are approximated, and the 70%
  > compromise saturation I use (although increasing this doesn't really
  > help that much).
  > 
  > Is there a canonical set of RGB values that terminals typically can
  > display?  Perhaps I could tune the map to spread out among the 5
  > colors more, but at some point you start sacrificing readibility on
  > full color displays, and over-relying on the algorithm for color
  > substitution.  Another option: is it possible or desirable to have a
  > separate color map for TTYs?  I could envision just using all the TTY
  > colors except the background color, in the order they are presented
  > from red to blue (now all but magenta are used).  May be more trouble
  > than it's worth.

If you change anything, please don't change it based on the display
being a TTY, but on the number of colors the TTY supports (see
display-color-cells and the min-color attribute for defface).

Your patch works very well on terminals that support 256 colors.
(Of the terminals in wide use only the Linux console and KDE's konsole
do not support 256 colors. xterm, rxvt, Gnome terminal and putty
support 256 colors.)