[gimp] app, libgimp, pdb: improve gimp_vectors_stroke_get_length() docs.

[Jehan <jehanp src gnome org>]

commit fee221167c5cebe85f0ab3803c1428fe292427c4
Author: Jehan <jehan girinstud io>
Date:   Wed Jan 20 20:33:41 2021 +0100

    app, libgimp, pdb: improve gimp_vectors_stroke_get_length() docs.
    
    The `precision` parameter in particular had no min/max, which meant we
    could provide a forbidden parameter (e.g. a negative precision) which
    would cause a core CRITICAL. We must forbid illegal values from PDB side
    (hence outputting a normal plug-in error message, not a core bug).
    
    Also improving a bit the description of this parameter as I was
    wondering what precision was needed exactly to get a stroke length. This
    is the precision for determining whether a portion of the stroke is
    "straight enough" or if we want to break it into smaller pieces until we
    get a straight portion.

 app/pdb/vectors-cmds.c    | 4 ++--
 libgimp/gimpvectors_pdb.c | 2 +-
 pdb/groups/vectors.pdb    | 4 ++--
 3 files changed, 5 insertions(+), 5 deletions(-)
---
diff --git a/app/pdb/vectors-cmds.c b/app/pdb/vectors-cmds.c
index 2b01b78f4d..8d1314c40a 100644
--- a/app/pdb/vectors-cmds.c
+++ b/app/pdb/vectors-cmds.c
@@ -1499,8 +1499,8 @@ register_vectors_procs (GimpPDB *pdb)
   gimp_procedure_add_argument (procedure,
                                g_param_spec_double ("precision",
                                                     "precision",
-                                                    "The precision used for the approximation",
-                                                    -G_MAXDOUBLE, G_MAXDOUBLE, 0,
+                                                    "The precision used for approximating straight portions 
of the stroke",
+                                                    0.0, G_MAXDOUBLE, 0.1,
                                                     GIMP_PARAM_READWRITE));
   gimp_procedure_add_return_value (procedure,
                                    g_param_spec_double ("length",
diff --git a/libgimp/gimpvectors_pdb.c b/libgimp/gimpvectors_pdb.c
index 95b9abc629..51fa5fe3c2 100644
--- a/libgimp/gimpvectors_pdb.c
+++ b/libgimp/gimpvectors_pdb.c
@@ -202,7 +202,7 @@ gimp_vectors_get_strokes (GimpVectors *vectors,
  * gimp_vectors_stroke_get_length:
  * @vectors: The vectors object.
  * @stroke_id: The stroke ID.
- * @precision: The precision used for the approximation.
+ * @precision: The precision used for approximating straight portions of the stroke.
  *
  * Measure the length of the given stroke.
  *
diff --git a/pdb/groups/vectors.pdb b/pdb/groups/vectors.pdb
index 280dd6bfdc..73c394567d 100644
--- a/pdb/groups/vectors.pdb
+++ b/pdb/groups/vectors.pdb
@@ -179,8 +179,8 @@ sub vectors_stroke_get_length {
          desc => 'The vectors object' },
        { name => 'stroke_id', type => 'int32',
          desc => 'The stroke ID' },
-        { name => 'precision', type => 'float',
-          desc => 'The precision used for the approximation' }
+        { name => 'precision', type => '0.0 <= float', default => 0.1,
+          desc => 'The precision used for approximating straight portions of the stroke' }
     );
 
     @outargs = (