/// <summary>
/// Dynamically compute the desired angle of an element along a segment of the route.
/// </summary>
/// <param name="elt">the <c>UIElement</c> being rotated</param>
/// <param name="orient">the <see cref="LabelOrientation"/> declared for the element</param>
/// <param name="angle">the angle of the segment of the route where the element is attached</param>
/// <returns>the intended angle for the element</returns>
/// <remarks>
/// This method is not called unless the <see cref="GetOrientation"/> attached property value is
/// not <see cref="LabelOrientation.None"/>.
/// </remarks>
protected virtual double ComputeAngle(UIElement elt, LabelOrientation orient, double angle)
{
double a;
switch (orient)
{
default:
case LabelOrientation.None: a = 0; break;
case LabelOrientation.Along: a = angle; break;
case LabelOrientation.Plus90: a = angle + 90; break;
case LabelOrientation.Minus90: a = angle - 90; break;
case LabelOrientation.Opposite: a = angle + 180; break;
case LabelOrientation.Upright: // like Along
a = Geo.NormalizeAngle(angle);
if (a > 90 && a < 270)
{
a -= 180; // make sure never upside-down
}
break;
case LabelOrientation.Plus90Upright: // like Plus90
a = Geo.NormalizeAngle(angle + 90);
if (a > 90 && a < 270)
{
a -= 180; // make sure never upside-down
}
break;
case LabelOrientation.Minus90Upright: // like Minus90
a = Geo.NormalizeAngle(angle - 90);
if (a > 90 && a < 270)
{
a -= 180; // make sure never upside-down
}
break;
case LabelOrientation.Upright45: // like Along
a = Geo.NormalizeAngle(angle);
if (a > 45 && a < 135)
{
return(0); // make sure never angled too much
}
if (a > 225 && a < 315)
{
return(0);
}
if (a > 90 && a < 270)
{
a -= 180; // make sure never upside-down
}
break;
}
return(Geo.NormalizeAngle(a));
}