The new 24-bit Z-buffer device is nice for generating graphics on a
device without a display, as is common with servers, for example. It is
easier to configure and use than Xvfb, for example.
Unfortunately, some of the default device settings are different between
the Z-buffer device and the X-Windows device. (I haven't checked the
WIN device because I don't have a Windows machine).
IDL> window, xsize=1024, ysize=768
IDL> help, !d, /str
** Structure !DEVICE, 17 tags, length=84, data length=84:
NAME STRING 'X'
X_CH_SIZE LONG 6
Y_CH_SIZE LONG 10
IDL> set_plot, 'z'
IDL> device, set_resolution = [1024, 768], set_pixel_depth = 24
IDL> help, !d, /str
** Structure !DEVICE, 17 tags, length=84, data length=84:
NAME STRING 'Z'
X_CH_SIZE LONG 8
Y_CH_SIZE LONG 12
Because IDL scales margins and plot sizes based on the character size,
switching devices means that the resulting graphs are not identical,
despite identical window/device sizes.
This can be rectified by setting the character size of the Z-buffer
device with
DEVICE, SET_CHARACTER_SIZE = [6, 10]
or doing the reverse for the X-Windows device, but this seems to me to
be a pointless and unnecessary device dependence.
I am annoyed enough to post about this because I just spend longer than
I should have figuring out why the graphics output from the two devices
was not identical.
Ken Bowman
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