Font size for labels made by legend.jnl are inconsistent

[ACManke]

This thread discusses this issue
https://www.pmel.noaa.gov/maillists/tmap/ferret_users/fu_2019/msg01171.html @ryofurue

The legend.jnl script uses ppl commands to draw colored lines labeled with user-generated labels, in one corner of a plot being drawn. It uses "ppl labs" to define pplus moveable labels, which are enumerated labels at a particular location on the plot page, relative to the plot origin in either /USER units (world coordinate units) or /NOUSER units (plot "inches" relative to the plot origin).

The size of moveable labels should be controllable using the PPL labset command, but as summarized by Ryo here,

1. The PLOT command sets up automatic labels (logo, dataset name, regions, etc.).
2. The "legend" script overwrites some of those labels (using PPL's label command, which is PPL LABS).
3. But the labels retain their sizes set at step (1).

So, there is a bug in the moveable-labels code somewhere, but in the meantime, we can add a little logic to the legend.jnl script: Add an optional argument so the user can specify the label size to be used for the legend labels, with a default sizez of 0.12 plot inches. Then issue the PPL HLABS command to set the label size for each label created.

[ACManke]

Proposed updated version of legend.jnl

\cancel mode verify

! Contributed by Hein Zelle, 11-December-2003
! Run test_legend.jnl for an example which calls this script.

! script to add a legend line to a plot
! use this between plot/set_up and ppl plot.
! it may also work before a plot/overlay, but I'm not sure.
! if it doesn't, change it to use immediate mode: remove the "on"
! argument to ppl aline. For skipping lines we'll need to write a more
! advanced script that keeps track of how many times we've been called
! so far.
!
! go legend line# title [location] [size]
! 
! where location is one of ul, ur, ll or lr
! default location is ul
! Size for legend text is in plot inches, default 0.12

query/ignore $1%<usage: go legend line# title [location: ul* ur ll lr] [label_size]%
query/ignore $2%<usage: go legend line# title [location: ul* ur ll lr] [label_size]%
query/ignore $3%1|ul>1|ur>2|ll>3|lr>4|<location must be ul, ur, ll or lr%

let legend_labsize = $4%0.12%
IF `legend_labsize le 0` then 
  say **ERROR legend.jnl Argument 4 size must be positive `legend_labsize,p=4`
  exit/prompt
endif
ppl hlabs,$1,`legend_labsize`

if `$3%1|ul>1|ur>2|ll>3|lr>4|% eq 1` then     ! left top

  ppl aline/nouser $1,0.1,`($PPL$YLEN)-0.2*$1`,0.5,`($PPL$YLEN)-0.2*$1`,on
  ppl labs/nouser $1,0.6,`($PPL$YLEN)-0.05-0.2*$1`,-1,"$2"

elif `$3%1|ul>1|ur>2|ll>3|lr>4|% eq 2` then   ! right top

  ppl aline/nouser $1,`($PPL$XLEN)-0.1`,`($PPL$YLEN)-0.2*$1`,`($PPL$XLEN)-0.5`,`($PPL$YLEN)-0.2*$1`,on
  ppl labs/nouser $1,`($PPL$XLEN)-0.6`,`($PPL$YLEN)-0.05-0.2*$1`,1,"$2"

elif `$3%1|ul>1|ur>2|ll>3|lr>4|% eq 3` then   ! left bottom

  ppl aline/nouser $1,0.1,`0.2*$1`,0.5,`0.2*$1`,on
  ppl labs/nouser $1,0.6,`-0.05+0.2*$1`,-1,"$2"

else                                          ! right bottom

  ppl aline/nouser $1,`($PPL$XLEN)-0.1`,`0.2*$1`,`($PPL$XLEN)-0.5`,`0.2*$1`,on
  ppl labs/nouser $1,`($PPL$XLEN)-0.6`,`-0.05+0.2*$1`,1,"$2"

endif

say label `$1`: "$2"
cancdel variable legend_labsize

set mode /last verify