GetEdgeEndpoint
(
VertexDrawingHistory otherVertexDrawingHistory,
out Point edgeEndpoint
)
{
AssertValid();
Point oVertexLocation = this.VertexLocation;
// A diamond is just a rotated square, so the
// VertexDrawingHistory.GetEdgePointOnRectangle() can be used if the
// diamond and the other vertex location are first rotated 45 degrees
// about the diamond's center.
Double dHalfSquareWidth = m_dHalfWidth / Math.Sqrt(2.0);
Rect oRotatedDiamond = new Rect(
oVertexLocation.X - dHalfSquareWidth,
oVertexLocation.Y - dHalfSquareWidth,
2.0 * dHalfSquareWidth,
2.0 * dHalfSquareWidth
);
Matrix oMatrix = WpfGraphicsUtil.GetRotatedMatrix(oVertexLocation, 45);
Point oRotatedOtherVertexLocation =
oMatrix.Transform(otherVertexDrawingHistory.VertexLocation);
Point oRotatedEdgeEndpoint;
GetEdgeEndpointOnRectangle(oVertexLocation, oRotatedDiamond,
oRotatedOtherVertexLocation, out oRotatedEdgeEndpoint);
// Now rotate the computed edge endpoint in the other direction.
oMatrix = WpfGraphicsUtil.GetRotatedMatrix(oVertexLocation, -45);
edgeEndpoint = oMatrix.Transform(oRotatedEdgeEndpoint);
}
GetEdgeEndpoint
(
Point otherEndpoint,
out Point edgeEndpoint
)
{
AssertValid();
Point oVertexLocation = this.VertexLocation;
// Instead of doing geometry calculations similar to what is done in
// VertexDrawingHistory.GetEdgePointOnRectangle(), make use of that
// method by making the triangle look like a rectangle. First, figure
// out how to rotate the triangle about the vertex location so that the
// side containing the endpoint is vertical and to the right of the
// vertex location.
Double dEdgeAngle = WpfGraphicsUtil.GetAngleBetweenPointsRadians(
oVertexLocation, otherEndpoint);
Double dEdgeAngleDegrees = MathUtil.RadiansToDegrees(dEdgeAngle);
Double dAngleToRotateDegrees;
if (dEdgeAngleDegrees >= -30.0 && dEdgeAngleDegrees < 90.0)
{
dAngleToRotateDegrees = 30.0;
}
else if (dEdgeAngleDegrees >= -150.0 && dEdgeAngleDegrees < -30.0)
{
dAngleToRotateDegrees = 270.0;
}
else
{
dAngleToRotateDegrees = 150.0;
}
// Now create a rotated rectangle that is centered on the vertex
// location and that has the vertical, endpoint-containing triangle
// side as the rectangle's right edge.
Double dWidth = 2.0 * m_dHalfWidth;
Rect oRotatedRectangle = new Rect(
oVertexLocation.X,
oVertexLocation.Y - m_dHalfWidth,
dWidth * WpfGraphicsUtil.Tangent30Degrees,
dWidth
);
Matrix oMatrix = WpfGraphicsUtil.GetRotatedMatrix(oVertexLocation,
dAngleToRotateDegrees);
// Rotate the other vertex location.
Point oRotatedOtherVertexLocation = oMatrix.Transform(otherEndpoint);
// GetEdgeEndpointOnRectangle will compute an endpoint on the
// rectangle's right edge.
Point oRotatedEdgeEndpoint;
GetEdgeEndpointOnRectangle(oVertexLocation, oRotatedRectangle,
oRotatedOtherVertexLocation, out oRotatedEdgeEndpoint);
// Now rotate the edge endpoint in the other direction.
oMatrix = WpfGraphicsUtil.GetRotatedMatrix(oVertexLocation,
-dAngleToRotateDegrees);
edgeEndpoint = oMatrix.Transform(oRotatedEdgeEndpoint);
}
DrawArrow
(
DrawingContext oDrawingContext,
Point oArrowTipLocation,
Double dArrowAngle,
Color oColor,
Double dEdgeWidth
)
{
Debug.Assert(oDrawingContext != null);
Debug.Assert(dEdgeWidth > 0);
AssertValid();
// Compute the arrow's dimensions. The width factor is arbitrary and
// was determined experimentally.
const Double WidthFactor = 1.5;
Double dArrowTipX = oArrowTipLocation.X;
Double dArrowTipY = oArrowTipLocation.Y;
Double dArrowWidth = WidthFactor * dEdgeWidth * m_dRelativeArrowSize;
Double dArrowHalfHeight = dArrowWidth / 2.0;
Double dX = dArrowTipX - dArrowWidth;
// Compute the arrow's three points as if the arrow were at an angle of
// zero degrees, then use a rotated transform to adjust for the actual
// specified angle.
Point [] aoPoints = new Point [] {
// Index 0: Arrow tip.
oArrowTipLocation,
// Index 1: Arrow bottom.
new Point(dX, dArrowTipY - dArrowHalfHeight),
// Index 2: Arrow top.
new Point(dX, dArrowTipY + dArrowHalfHeight),
// Index 3: Center of the flat end of the arrow.
//
// Note: The 0.2 is to avoid a gap between the edge endcap and the
// flat end of the arrow, but it sometimes causes the two to
// overlap slightly, and that can show if the edge isn't opaque.
// What is the correct way to get the endcap to merge invisibly
// with the arrow?
new Point(dX + 0.2, dArrowTipY)
};
Matrix oMatrix = WpfGraphicsUtil.GetRotatedMatrix(oArrowTipLocation,
-MathUtil.RadiansToDegrees(dArrowAngle));
oMatrix.Transform(aoPoints);
PathGeometry oArrow = WpfGraphicsUtil.PathGeometryFromPoints(
aoPoints[0], aoPoints[1], aoPoints[2]);
oDrawingContext.DrawGeometry(GetBrush(oColor), null, oArrow);
return(aoPoints[3]);
}
