drop use of bounding box to determine whether an item covers a point; add Item::covers(Duple const&)

Default implementation for Item still uses bounding box, but specializations for Arc (Circle), Polygon, Line and PolyLine have been added

1 files changed, 78 insertions, 0 deletions

diff --git a/libs/canvas/polygon.cc b/libs/canvas/polygon.cc
index 1103cedbee..37046f4d4a 100644
--- a/libs/canvas/polygon.cc
+++ b/libs/canvas/polygon.cc
@@ -25,10 +25,19 @@ Polygon::Polygon (Group* parent)
 	: Item (parent)
 	, PolyItem (parent)
 	, Fill (parent)
+	, multiple (0)
+	, constant (0)
+	, cached_size (0)
 {
 
 }
 
+Polygon::~Polygon ()
+{
+	delete [] multiple;
+	delete [] constant;
+}
+
 void
 Polygon::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const
 {
@@ -51,3 +60,72 @@ Polygon::render (Rect const & area, Cairo::RefPtr<Cairo::Context> context) const
 	}
 }
 
+void 
+Polygon::cache_shape_computation () const
+{
+	Points::size_type npoints = _points.size();
+
+	if (npoints == 0) {
+		return;
+	}
+
+	Points::size_type i;
+	Points::size_type j = npoints -1;
+
+	if (cached_size < npoints) {
+		cached_size = npoints;
+		delete [] multiple;
+		multiple = new float[cached_size];
+		delete [] constant;
+		constant = new float[cached_size];
+	}
+
+	for (i = 0; i < npoints; i++) {
+		if (_points[j].y == _points[i].y) {
+			constant[i] = _points[i].x;
+			multiple[i] = 0; 
+		} else {
+			constant[i] = _points[i].x-(_points[i].y*_points[j].x)/(_points[j].y-_points[i].y)+(_points[i].y*_points[i].x)/(_points[j].y-_points[i].y);
+			multiple[i] = (_points[j].x-_points[i].x)/(_points[j].y-_points[i].y); 
+		}
+
+		j = i; 
+	}
+}
+
+bool 
+Polygon::covers (Duple const & point) const
+{
+	Duple p = canvas_to_item (point);
+
+	Points::size_type npoints = _points.size();
+
+	if (npoints == 0) {
+		return false;
+	}
+
+	Points::size_type i;
+	Points::size_type j = npoints -1;
+	bool oddNodes = false;
+	
+	if (_bounding_box_dirty) {
+		compute_bounding_box ();
+	}
+	
+	for (i = 0; i < npoints; i++) {
+		if (((_points[i].y < p.y && _points[j].y >= p.y) || (_points[j].y < p.y && _points[i].y >= p.y))) {
+			oddNodes ^= (p.y * multiple[i] + constant[i] < p.x); 
+		}
+		j = i; 
+	}
+	
+	return oddNodes; 
+} 
+
+void
+Polygon::compute_bounding_box () const
+{
+	PolyItem::compute_bounding_box ();
+	cache_shape_computation ();
+}
+