Harmonize wxGraphicsPathData::AddArcToPoint() behaviour across all ports

AddArcToPoint() on macOS port is implemented with native API (CGPathAddArcToPoint) so its behaviour should be considered as a reference for generic implementation used in another ports.

Closes #18086.

interface/wx/graphics.h

@@ -50,9 +50,14 @@ public:
     //@}
 
     /**
-        Appends a an arc to two tangents connecting (current) to (@a x1,@a y1)
+        Adds an arc (of a circle with radius @a r) that is tangent
-        and (@a x1,@a y1) to (@a x2,@a y2), also a straight line from (current)
+        to the line connecting current point and (@a x1, @a y1) and
-        to (@a x1,@a y1).
+        to the line connecting (@a x1, @a y1) and (@a x2, @a y2).
+        If the current point and the starting point of the arc are different,
+        a straight line connecting these points is also appended.
+        After this call the current point will be at the ending point
+        of the arc.
+        @image html drawing-addarctopoint.png
     */
     virtual void AddArcToPoint(wxDouble x1, wxDouble y1, wxDouble x2,
                                wxDouble y2, wxDouble r);

src/common/graphcmn.cpp

@@ -479,7 +479,6 @@ void wxGraphicsPathData::AddArcToPoint( wxDouble x1, wxDouble y1 , wxDouble x2,
          alpha == 0 || alpha == 180 || r == 0 )
     {
         AddLineToPoint(p1.m_x, p1.m_y);
-        AddLineToPoint(p2.m_x, p2.m_y);
         return;
     }
 
@@ -489,8 +488,6 @@ void wxGraphicsPathData::AddArcToPoint( wxDouble x1, wxDouble y1 , wxDouble x2,
     alpha = wxDegToRad(alpha);
     wxDouble distT = r / sin(alpha) * (1.0 + cos(alpha)); // = r / tan(a/2) =  r / sin(a/2) * cos(a/2)
     wxDouble distC = r / sin(alpha / 2.0);
-    wxASSERT_MSG( distT <= v1Length && distT <= v2Length,
-                  wxS("Radius is too big to fit the arc to given points") );
     // Calculate tangential points
     v1.Normalize();
     v2.Normalize();
@@ -513,7 +510,6 @@ void wxGraphicsPathData::AddArcToPoint( wxDouble x1, wxDouble y1 , wxDouble x2,
 
     AddLineToPoint(t1.m_x, t1.m_y);
     AddArc(c.m_x, c.m_y, r, wxDegToRad(a1), wxDegToRad(a2), drawClockwiseArc);
-    AddLineToPoint(p2.m_x, p2.m_y);
 }
 
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