[gimp] libgimpbase: improve gimp_unit_is_metric()

[Michael Natterer <mitch src gnome org>]

commit 9ffa9ac6e36ee0b3854a0eb2dc895d536e8e16fd
Author: Michael Natterer <mitch gimp org>
Date:   Sun Nov 17 21:03:37 2013 +0100

    libgimpbase: improve gimp_unit_is_metric()
    
    Don't directly compare doubles, use "ABS (foo - bar) < epsilon".

 libgimpbase/gimpunit.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)
---
diff --git a/libgimpbase/gimpunit.c b/libgimpbase/gimpunit.c
index a941c7d..1898fa6 100644
--- a/libgimpbase/gimpunit.c
+++ b/libgimpbase/gimpunit.c
@@ -715,8 +715,8 @@ gimp_unit_is_metric (GimpUnit unit)
   if (factor == 0.0)
     return FALSE;
 
-  return (factor == 25.4  ||
-          factor == 2.54  ||
-          factor == 0.254 ||
-          factor == 0.0254);
+  return ((ABS (factor -  0.0254) < 1e-7) || /* m  */
+          (ABS (factor -  0.254)  < 1e-6) || /* dm */
+          (ABS (factor -  2.54)   < 1e-5) || /* cm */
+          (ABS (factor - 25.4)    < 1e-4));  /* mm */
 }