From d3b89857bf4d795b5238f0a1c5a2d68de8eaaf14 Mon Sep 17 00:00:00 2001
From: johanengelen <johanengelen@users.sourceforge.net>
Date: Tue, 7 Apr 2009 22:58:28 +0000
Subject: [PATCH] is_straight_curve now also returns true for straight line
 quadratic and cubic curves. this fixes spiro LPE behavior

---
 src/helper/geom-curves.h | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/helper/geom-curves.h b/src/helper/geom-curves.h
index f3dc364f2..bc5a8213a 100644
--- a/src/helper/geom-curves.h
+++ b/src/helper/geom-curves.h
@@ -7,12 +7,14 @@
  * Author:
  *   Johan Engelen <goejendaagh@zonnet.nl>
  *
- * Copyright (C) 2008 Johan Engelen
+ * Copyright (C) 2008-2009 Johan Engelen
  *
  * Released under GNU GPL
  */
 
 #include <2geom/hvlinesegment.h>
+#include <2geom/line.h>
+#include <2geom/bezier-curve.h>
 
 inline bool is_straight_curve(Geom::Curve const & c) {
     if( dynamic_cast<Geom::LineSegment const*>(&c) ||
@@ -20,9 +22,23 @@ inline bool is_straight_curve(Geom::Curve const & c) {
         dynamic_cast<Geom::VLineSegment const*>(&c) )
     {
         return true;
-    } else {
-        return false;
     }
+    // the curve can be a quad/cubic bezier, but could still be a perfect straight line
+    // if the control points are exactly on the line connecting the initial and final points.
+    else if ( Geom::QuadraticBezier const *quad = dynamic_cast<Geom::QuadraticBezier const*>(&c) ) {
+        Geom::Line line( quad->initialPoint(), quad->finalPoint() );
+        if ( are_near((*quad)[1], line) ) {
+            return true;
+        }
+    }
+    else if ( Geom::CubicBezier const *cubic = dynamic_cast<Geom::CubicBezier const*>(&c) ) {
+        Geom::Line line( cubic->initialPoint(), cubic->finalPoint() );
+        if ( are_near((*cubic)[1], line) && are_near((*cubic)[2], line) ) {
+            return true;
+        }
+    }
+
+    return false;
 }
 
 #endif  // INKSCAPE_HELPER_GEOM_CURVES_H
-- 
2.30.2