Problem with cbrange default for color-by-z-value in 2D plots

Hi,

Many thanks for implementing color-by-z-value in 2D plots, which is a
feature that I have been wanting for a long time. However, by default
the color box does not seem to adjust to the data as it does with 3D
plots.

Minimal example:
With the latest CVS version (downloaded today). I created "temp.dat"
with the contents
0.5 0.5 0.5
1. 1. 1.
1.5 1.5 0.5

and tried
plot "temp.dat" pal

and

plot "temp.dat" u 1:2:3 pal z

(Checked in x11 and wxt terminals.)

All the points look like the same color. The color box runs from -10
to 10.

After

set cbrange [0.5:1.5]

the colors are indeed visible.
The latter is the default cbrange in the 3D version:

set view map
splot "temp.dat" u 1:2:(0):3 pal z

Could the default cbrange be fitted to the data?  Or am I doing
something wrong?

Thanks and best wishes,
David.

Output of show version long:

        Version 4.3 patchlevel 0
        last modified September 2008
        System: Linux 2.6.24-16-generic

Compile options:
-READLINE  +LIBREADLINE  +HISTORY  -BACKWARDS_COMPATIBILITY
+BINARY_DATA
+GD_PNG  +GD_JPEG  +GD_TTF  +GD_GIF  +ANIMATION
-NOCWDRC  +X11  +X11_POLYGON  +MULTIBYTE  +X11_EXTERNAL +USE_MOUSE
+HIDDEN3D_QUADTREE
+DATASTRINGS  +HISTOGRAMS  +OBJECTS  +STRINGVARS  +MACROS  +IMAGE