From 35fb1ca821a29ff72d8c9ced7794b39809b93b6a Mon Sep 17 00:00:00 2001
From: Vasilis Liaskovitis <vliaskov@gmail.com>
Date: Tue, 3 Dec 2013 01:14:17 +0200
Subject: [PATCH] Implement shape drag-and-drop

A user may find it useful in some cases to drag and drop a whole shape, instead
of moving each vertex separately. This patch implements shape drag-and-drop by
pressing and holding the right mouse button. Point inclusion algorithm should
work for non-convex and convex polygons, as suggested in
http://www.cs.tufts.edu/comp/163/notes05/point_inclusion_handout.pdf
---
 MapperGLCanvas.cpp | 30 ++++++++++++++++++++++++++
 MapperGLCanvas.h   |  2 ++
 Shape.h            | 52 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 84 insertions(+)

diff --git a/MapperGLCanvas.cpp b/MapperGLCanvas.cpp
index 1261b25..275ee44 100644
--- a/MapperGLCanvas.cpp
+++ b/MapperGLCanvas.cpp
@@ -119,12 +119,22 @@ void MapperGLCanvas::mousePressEvent(QMouseEvent* event)
       _mousepressed = true;
     }
   }
+  if (event->buttons() & Qt::RightButton)
+  {
+    Shape* shape = getCurrentShape();
+    if (shape->includesPoint(xmouse, ymouse))
+    {
+      _shapegrabbed = true;
+      _shapefirstgrab = true;
+    }
+  }
 }
 
 void MapperGLCanvas::mouseReleaseEvent(QMouseEvent* event)
 {
   // std::cout << "Mouse Release event " << std::endl;
   _mousepressed = false;
+  _shapegrabbed = false;
 }
 
 void MapperGLCanvas::mouseMoveEvent(QMouseEvent* event)
@@ -145,6 +155,26 @@ void MapperGLCanvas::mouseMoveEvent(QMouseEvent* event)
       emit quadChanged();
     }
   }
+  else if (_shapegrabbed)
+  {
+    // std::cout << "Move event " << std::endl;
+    Shape* shape = getCurrentShape();
+    static Point p(0,0);
+    if (shape)
+    {
+      if (_shapefirstgrab == false)
+      {    
+        shape->translate(event->x() - p.x, event->y() - p.y);  
+        update();
+        emit quadChanged();
+      }  
+      else
+        _shapefirstgrab = false;
+    }
+    p.x = event->x();
+    p.y = event->y();
+
+  }
 }
 
 void MapperGLCanvas::keyPressEvent(QKeyEvent* event)
diff --git a/MapperGLCanvas.h b/MapperGLCanvas.h
index 4870aa8..010c97d 100644
--- a/MapperGLCanvas.h
+++ b/MapperGLCanvas.h
@@ -65,6 +65,8 @@ private:
   virtual void doDraw() = 0;
   void exitDraw();
   bool _mousepressed;
+  bool _shapegrabbed;
+  bool _shapefirstgrab;
 
 signals:
   void quadChanged();
diff --git a/Shape.h b/Shape.h
index 54ef9a3..03177db 100644
--- a/Shape.h
+++ b/Shape.h
@@ -22,6 +22,7 @@
 
 #include <vector>
 #include <tr1/memory>
+#include <iostream>
 
 /**
  * Point (or vertex) on the 2-D canvas.
@@ -68,6 +69,57 @@ public:
   }
   void setActiveVertex(int x) {active_vertex = x;}
   int getActiveVertex() {return active_vertex;}
+  /** Return true if Shape includes point (x,y), false otherwise
+   *  Algorithm should work for all polygons, including non-convex
+   *  Found at http://www.cs.tufts.edu/comp/163/notes05/point_inclusion_handout.pdf
+   */
+  bool includesPoint(int x, int y)
+  {
+    Point *prev = NULL, *cur;
+    int left = 0, right = 0, maxy, miny;
+    for (std::vector<Point>::iterator it = vertices.begin() ; it !=
+            vertices.end(); it++)
+    {
+      if (!prev) {
+          prev = &vertices.back();
+      }
+      cur = &(*it);
+      miny = std::min(cur->y, prev->y);
+      maxy = std::max(cur->y, prev->y);
+
+      if (y > miny && y < maxy) {
+        if (prev->x == cur->x) 
+        {
+          if (x < cur->x)
+            right++;
+          else left++;
+        }
+        else
+        {
+          double slope = (cur->y - prev->y) / (cur->x - prev->x);
+          double offset = cur->y - slope * cur->x;
+          int xintersect = int((y - offset ) / slope);
+          if (x < xintersect)
+            right++;
+          else left++;
+        }
+      }
+      prev = &(*it);
+    }
+    if (right % 2 && left % 2)
+        return true;
+    return false;
+  }
+  /* Translate all vertices of shape by the vector (x,y) */
+  void translate(int x, int y)
+  {
+    for (std::vector<Point>::iterator it = vertices.begin() ; it !=
+            vertices.end(); ++it) 
+    {
+      it->x += x;
+      it->y += y;
+    }
+  }  
 };
 
 /**