[gimp] app: fix rotation pivot of GimpCanvasHandle

[N/A <ell src gnome org>]

commit 5cd0ecc9987f0c7e8cdd5bfdefea6d3791e7f27b
Author: Ell <ell_se yahoo com>
Date:   Sat Jan 27 04:16:30 2018 -0500

    app: fix rotation pivot of GimpCanvasHandle
    
    This fixes the erratic 1-pixel movement of transform-grid handles.

 app/display/gimpcanvashandle.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/app/display/gimpcanvashandle.c b/app/display/gimpcanvashandle.c
index 5bd39a9..9543a8d 100644
--- a/app/display/gimpcanvashandle.c
+++ b/app/display/gimpcanvashandle.c
@@ -311,6 +311,9 @@ gimp_canvas_handle_draw (GimpCanvasItem *item,
                                    private->x, private->y,
                                    &tx, &ty);
 
+  tx = floor (tx) + 0.5;
+  ty = floor (ty) + 0.5;
+
   switch (private->type)
     {
     case GIMP_HANDLE_SQUARE: