[gimp/gimp-2-8] Bug 684330 - Rectangle tool's "fixed size" option is off-by-one

[Michael Natterer <mitch src gnome org>]

commit 606532f5a8dde1421a0bd948e107004cb839dc07
Author: TÃo Mazars <teo mazars ensimag fr>
Date:   Tue Feb 12 18:36:15 2013 +0100

    Bug 684330 -  Rectangle tool's "fixed size" option is off-by-one
    
    ROUND() is consistent only on positive values, and bad rounding
    creates an offset when negative values are involved. Introduce
    SIGNED_ROUND() and use it in gimprectangletool.c. It should probably
    be used in much more places.
    (cherry picked from commit 4a5a6ef914398ff4d94bc32002d3929e43f63bdf)

 app/tools/gimprectangletool.c |    8 ++++----
 libgimpmath/gimpmath.h        |   10 +++++++++-
 plug-ins/common/curve-bend.c  |    1 -
 3 files changed, 13 insertions(+), 6 deletions(-)
---
diff --git a/app/tools/gimprectangletool.c b/app/tools/gimprectangletool.c
index 666d53a..3d2e942 100644
--- a/app/tools/gimprectangletool.c
+++ b/app/tools/gimprectangletool.c
@@ -4133,13 +4133,13 @@ gimp_rectangle_tool_update_int_rect (GimpRectangleTool *rect_tool)
 {
   GimpRectangleToolPrivate *priv = GIMP_RECTANGLE_TOOL_GET_PRIVATE (rect_tool);
 
-  priv->x1_int = ROUND (priv->x1);
-  priv->y1_int = ROUND (priv->y1);
+  priv->x1_int = SIGNED_ROUND (priv->x1);
+  priv->y1_int = SIGNED_ROUND (priv->y1);
 
   if (gimp_rectangle_tool_rect_rubber_banding_func (rect_tool))
     {
-      priv->width_int  = (gint) ROUND (priv->x2) - priv->x1_int;
-      priv->height_int = (gint) ROUND (priv->y2) - priv->y1_int;
+      priv->width_int  = (gint) SIGNED_ROUND (priv->x2) - priv->x1_int;
+      priv->height_int = (gint) SIGNED_ROUND (priv->y2) - priv->y1_int;
     }
 }
 
diff --git a/libgimpmath/gimpmath.h b/libgimpmath/gimpmath.h
index 843f580..d3abb33 100644
--- a/libgimpmath/gimpmath.h
+++ b/libgimpmath/gimpmath.h
@@ -74,11 +74,19 @@ G_BEGIN_DECLS
  * ROUND:
  * @x: the value to be rounded.
  *
- * This macro rounds its argument @x to the nearest integer.
+ * This macro rounds its positive argument @x to the nearest integer.
  **/
 #define ROUND(x) ((int) ((x) + 0.5))
 
 /**
+ * SIGNED_ROUND:
+ * @x: the value to be rounded.
+ *
+ * This macro rounds its argument @x to the nearest integer.
+ **/
+#define SIGNED_ROUND(x) ((int) ((((x) < 0) ? (x) - 0.5 : (x) + 0.5)))
+
+/**
  * SQR:
  * @x: the value to be squared.
  *
diff --git a/plug-ins/common/curve-bend.c b/plug-ins/common/curve-bend.c
index 340f3bb..65c9fdd 100644
--- a/plug-ins/common/curve-bend.c
+++ b/plug-ins/common/curve-bend.c
@@ -66,7 +66,6 @@
 
 #define MIDDLE 127
 
-#define SIGNED_ROUND(x)  ((int) (((x < 0) ? (x) - 0.5 : (x) + 0.5)  ))
 #define MIX_CHANNEL(a, b, m)  (((a * m) + (b * (255 - m))) / 255)
 
 #define UP_GRAPH              0x1