A problem that often causes the loss of part (or all) of the
last frame of a graphics session occurs because many of the
do not automatically advance to a new picture when they
are called. This is to allow you to write multiple graphics on a
single picture and include graphics from multiple utilities. The
user may forget to advance to a new picture at the end of an
application as well. At the end of a job you must remember to
issue a call to flush the
(CALL SFLUSH), or a call to advance to the next
picture (CALL FRAME) which will call SFLUSH.
For details on SFLUSH or FRAME, consult the man pages.
For reasons of efficiency,
SPPS maintains an
internal buffer which
accumulates polyline coordinates. This buffer is automatically flushed
when it is full, or when FRAME is called, or it can be flushed by the
user with a call to SFLUSH. If polyline attributes are changed between
SPPS calls that produce lines, then failure to flush the polyline
buffer in SPPS between the line-producing calls can cause
For example, if you set line color to pink,
then call LINE to draw a line, then set line color to blue and call
LINE to draw another line, and then call FRAME, you will get two blue
lines unless you flush the polyline buffer after drawing the first line.
This is because the order in which things are done is: put line color pink
to the output stream; put out coordinates for the first line call in the SPPS
buffer; put line color blue to the output stream; put coordinates for the
second line in the SPPS buffer; put polyline elements to the output stream
when the call to FRAME is encountered. If you are using direct GKS
calls (such as
GPL), then the buffer flush
is not necessary because
the buffer is a feature of SPPS and not a feature of GKS.
All of the Hershey fonts available through
GSTXFP are available via the
documentation for Plotchar is available.
Plotchar also supports a number of filled, scalable,
fonts. If you are using a
PostScript output workstation,
the PostScript interpreter used to draw the plots will be used.
The GKS standard requires that marker type 1
always be displayed
as the smallest possible dot. For this reason, the dot polymarker will
not be affected by the marker size scale factor as set by
get filled dots of any size and color use the
If you use NGSETI (or
escape function -1391) to set a value
for 'ME' to provide a metafile name
within your code, this name will be superceded by the name supplied
as the setting of the environment variable NCARG_GKS_OUTPUT. Make
sure that NCARG_GKS_OUTPUT is not set when specifying a metafile name
in your code.
See the man pages for NGSETI, NGSETR, NGSETC, and ngmisc_params for
setting values for NCAR GKS escape functions, such as a metafile name.
See ncargex to run example
pgkex26 showing how to name metafiles within your code.
When positioning characters it can often be convenient to use normalized
device coordinates in the range of 0. to 1. in both dimensions, as
opposed to an arbitrary set of units as defined by the user coordinate
system. You should generate the desired text output, then return to
the original set of user coordinates. The four steps involved are:
- Call GQCNTN
(ERRIND, TRNUM) to get TRNUM, the current
normalization transformation number.
- If TRNUM is not 0, invoke normalization transformation 0
with a call to
- Write your text using Plotchar, or
- Return to the original normalization transformation, TRNUM,
with a call to