New way to find point intersection of an arc with a segment.

--HG--
branch : develop

src/app/tools/drawTools/vtoolpointofcontact.cpp

@@ -95,27 +95,31 @@ void VToolPointOfContact::setDialog()
 QPointF VToolPointOfContact::FindPoint(const qreal &radius, const QPointF &center, const QPointF &firstPoint,
                                        const QPointF &secondPoint)
 {
-    QPointF pArc;
+    QPointF p1, p2;
-    qreal s = 0.0, s_x, s_y, step = 0.01, distans;
+    qint32 res = LineIntersectCircle(center, radius, QLineF(firstPoint, secondPoint), p1, p2);
-    while ( s < 1)
+    switch (res)
     {
-        s_x = secondPoint.x()-(qAbs(secondPoint.x()-firstPoint.x()))*s;
+        case 0:
-        s_y = secondPoint.y()-(qAbs(secondPoint.y()-firstPoint.y()))*s;
+            return QPointF();
-        distans = QLineF(center.x(), center.y(), s_x, s_y).length();
+            break;
-        if (fabs(distans*10 - radius*10) < 0.1)
+        case 1:
+            return p1;
+            break;
+        case 2:
+            if (QLineF(firstPoint, p1).length() <= QLineF(firstPoint, p2).length())
             {
-            pArc.rx() = s_x;
+                return p1;
-            pArc.ry() = s_y;
+            }
+            else
+            {
+                return p2;
+            }
+            break;
+        default:
+            qDebug() << "Unxpected value" << res;
+            return QPointF();
             break;
     }
-        if (distans<radius)
-        {
-            pArc.rx() = s_x;
-            pArc.ry() = s_y;
-        }
-        s = s + step;
-    }
-    return pArc;
 }
 
 //---------------------------------------------------------------------------------------------------------------------

src/app/tools/vabstracttool.cpp

@@ -206,7 +206,7 @@ qint32 VAbstractTool::LineIntersectCircle(const QPointF &center, qreal radius, c
         }
     }
     // find distance from projection to points of intersection
-    qreal k = qSqrt (radius * radius - d * d);
+    qreal k = qSqrt (qAbs(radius * radius - d * d));
     qreal t = QLineF (QPointF (0, 0), QPointF (b, - a)).length();
     // add to projection a vectors aimed to points of intersection
     p1 = addVector (p, QPointF (0, 0), QPointF (- b, a), k / t);