[dia] [path] tweaking of rotate via handle

[Hans Breuer <hans src gnome org>]

commit cc832ef9b9cb980e719ac0c18a94f7236fd56181
Author: Hans Breuer <hans breuer org>
Date:   Thu Dec 19 21:51:31 2013 +0100

    [path] tweaking of rotate via handle
    
    This is still not completely working as expected, e.g. no proper undo.
    Maybe rotation should not be done via handle but via context menu or
    properties instead?

 lib/standard-path.c |   18 ++++++++++--------
 1 files changed, 10 insertions(+), 8 deletions(-)
---
diff --git a/lib/standard-path.c b/lib/standard-path.c
index 18610f6..1aa1b6f 100644
--- a/lib/standard-path.c
+++ b/lib/standard-path.c
@@ -678,16 +678,18 @@ stdpath_move_handle (StdPath *stdpath,
     } while (revert);
   } else if (handle->id == _HANDLE_ROTATE) {
     Point p1 = stdpath->handles[1].pos;
-    real dy = to->y - p1.y;
-    real dx = p1.x - p0.x;
+    Point pr = stdpath->handles[3].pos;
+    Point pc = {stdpath->handles[1].pos.x, stdpath->handles[3].pos.y };
+    real dx = to->x - p1.x;
+    real dy = pr.y - p1.y;
     DiaMatrix m;
     int i;
 
     g_assert(stdpath->handles[1].id == handle->id);
 
-    if (fabs(dy) < 0.001)
+    if (fabs(dx) < 0.001)
       return NULL;
-    dia_matrix_set_angle_and_scales (&m, asin (dy/dx), 1.0, 1.0);
+    dia_matrix_set_angle_and_scales (&m, -atan2 (dy, dx), 1.0, 1.0);
 
     for (i = 0; i < stdpath->num_points; ++i) {
       BezPoint *bp = &stdpath->points[i];
@@ -697,11 +699,11 @@ stdpath_move_handle (StdPath *stdpath,
        Point *p = j == 0 ? &bp->p1 : (j == 1 ? &bp->p2 : &bp->p3);
         real w, h;
 
-       w = p->x - p0.x;
-       h = p->y - p0.y;
+       w = p->x - pc.x;
+       h = p->y - pc.y;
 
-       p->x = p0.x + w * m.xx + h * m.xy;
-       p->y = p1.y + w * m.yx + h * m.yy;
+       p->x = pc.x + w * m.xx + h * m.xy;
+       p->y = pc.y + w * m.yx + h * m.yy;
       }
     }