[goffice] Rotation selector: avoid rounding errors.

[Morten Welinder <mortenw src gnome org>]

commit af365f3c9322ab4bc52f828785b5254c47cca39a
Author: Morten Welinder <terra gnome org>
Date:   Sat Jan 17 21:24:27 2015 -0500

    Rotation selector: avoid rounding errors.

 ChangeLog                     |    5 +++++
 goffice/gtk/go-rotation-sel.c |   13 +++++++------
 2 files changed, 12 insertions(+), 6 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 8cf62af..f70539b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2015-01-17  Morten Welinder  <terra gnome org>
+
+       * goffice/gtk/go-rotation-sel.c (cb_rotate_changed): Avoid
+       rounding errors by using go_cospi and go_sinpi.
+
 2015-01-16  Jean Brefort  <jean brefort normalesup org>
 
        * plugins/plot_distrib/gog-histogram.c
diff --git a/goffice/gtk/go-rotation-sel.c b/goffice/gtk/go-rotation-sel.c
index 4cc7024..5ff0202 100644
--- a/goffice/gtk/go-rotation-sel.c
+++ b/goffice/gtk/go-rotation-sel.c
@@ -75,12 +75,13 @@ cb_rotate_changed (GORotationSel *grs)
                }
 
        if (grs->line != NULL) {
-               double rad = grs->angle * M_PI / 180.;
+               double c = go_cospi (grs->angle / 180.);
+               double s = go_sinpi (grs->angle / 180.);
                goc_item_set (grs->line,
-                             "x0", x0 + cos (rad) * grs->rot_width,
-                             "y0", 100 - sin (rad) * grs->rot_width,
-                             "x1", x0 + cos (rad) * 72.,
-                             "y1", 100 - sin (rad) * 72.,
+                             "x0",  x0 + c * grs->rot_width,
+                             "y0", 100 - s * grs->rot_width,
+                             "x1",  x0 + c * 72.,
+                             "y1", 100 - s * 72.,
                              NULL);
        }
 
@@ -161,7 +162,7 @@ set_rot_from_point (GORotationSel *grs, double x, double y)
        x -= grs->full? 100.: 15.;      if (!grs->full && x < 0.) x = 0.;
        y -= 100.;
 
-       degrees = atan2 (-y, x) * 180 / M_PI;
+       degrees = go_atan2pi (-y, x) * 180;
 
        gtk_spin_button_set_value (GTK_SPIN_BUTTON (grs->rotate_spinner),
                go_fake_round (degrees));