[gimp] libgimpbase: add gimp_unit_is_metric()

[Michael Natterer <mitch src gnome org>]

commit f473653889a3ad193de8aad1adc7b4ec7a3fd9d5
Author: Michael Natterer <mitch gimp org>
Date:   Sat Oct 12 18:54:34 2013 +0200

    libgimpbase: add gimp_unit_is_metric()
    
    which currently returns TRUE if the unit has a factor that matches mm,
    cm, dm or m. Incomplete, but at least now extendable in one place,
    just need to use the new function everywhere.

 libgimpbase/gimpbase.def |    1 +
 libgimpbase/gimpunit.c   |   33 +++++++++++++++++++++++++++++++++
 libgimpbase/gimpunit.h   |    2 ++
 3 files changed, 36 insertions(+), 0 deletions(-)
---
diff --git a/libgimpbase/gimpbase.def b/libgimpbase/gimpbase.def
index 9eeb82b..a6330e0 100644
--- a/libgimpbase/gimpbase.def
+++ b/libgimpbase/gimpbase.def
@@ -120,6 +120,7 @@ EXPORTS
        gimp_unit_get_singular
        gimp_unit_get_symbol
        gimp_unit_get_type
+       gimp_unit_is_metric
        gimp_unit_new
        gimp_unit_set_deletion_flag
        gimp_units_to_pixels
diff --git a/libgimpbase/gimpunit.c b/libgimpbase/gimpunit.c
index 1f46209..a941c7d 100644
--- a/libgimpbase/gimpunit.c
+++ b/libgimpbase/gimpunit.c
@@ -687,3 +687,36 @@ gimp_units_to_points (gdouble  value,
   return (value *
           gimp_unit_get_factor (GIMP_UNIT_POINT) / gimp_unit_get_factor (unit));
 }
+
+/**
+ * gimp_unit_is_metric:
+ * @unit: The unit
+ *
+ * Checks if the given @unit is metric. A simplistic test is used
+ * that looks at the unit's factor and checks if it is 2.54 multiplied
+ * by some common powers of 10. Currently it checks for mm, cm, dm, m.
+ *
+ * See also: gimp_unit_get_factor()
+ *
+ * Returns: %TRUE if the @unit is metric.
+ *
+ * Since: GIMP 2.10
+ **/
+gboolean
+gimp_unit_is_metric (GimpUnit unit)
+{
+  gdouble factor;
+
+  if (unit == GIMP_UNIT_MM)
+    return TRUE;
+
+  factor = gimp_unit_get_factor (unit);
+
+  if (factor == 0.0)
+    return FALSE;
+
+  return (factor == 25.4  ||
+          factor == 2.54  ||
+          factor == 0.254 ||
+          factor == 0.0254);
+}
diff --git a/libgimpbase/gimpunit.h b/libgimpbase/gimpunit.h
index 2d1860e..2311a54 100644
--- a/libgimpbase/gimpunit.h
+++ b/libgimpbase/gimpunit.h
@@ -100,6 +100,8 @@ gdouble       gimp_units_to_points          (gdouble      value,
                                              GimpUnit     unit,
                                              gdouble      resolution);
 
+gboolean      gimp_unit_is_metric           (GimpUnit     unit);
+
 
 G_END_DECLS