/// <summary>
/// Returns the type of manipulation that will happen when interacting with the element at the specified point.
/// </summary>
/// <param name="point">The point to start manipulating.</param>
/// <param name="altDown">Whether any alt key is pressed.</param>
/// <param name="preview">whether to set the preview manipulation, or the real one.</param>
/// <param name="translateOnly">Whether to ignore any special manipulations and only use translate.</param>
/// <returns>The manipulation type for the specified point. <c>null</c> if no manipulation would happen
/// at this point.</returns>
/// <remarks>Manipulation preview is used to show what would be modified on a selected element. We cannot
/// keep updating the element manipulation as the mouse moves, but do want to provide a visual indicator.</remarks>
public override bool StartManipulating(Point point, bool altDown, bool preview = false, bool translateOnly = false)
{
SizeF d = point - this.Location;
if (d.Length() > this.Radius + 2)
{
this.PreviewManipulation = null;
return(false);
}
// Scale if mouse over the outter edge.
if (Math.Sqrt(Math.Abs(Math.Pow(d.Width, 2) + Math.Pow(d.Height, 2) - Math.Pow(this.Radius, 2))) < 16 && !translateOnly)
{
this.SetManipulation(
new ElementManipulation
{
Type = ElementManipulationType.Scale,
Index = 0,
Direction = d.GetUnitVector()
},
preview);
return(true);
}
this.SetManipulation(
new ElementManipulation
{
Type = ElementManipulationType.Translate,
Index = 0
},
preview);
return(true);
}
/// <summary>
/// Projects <paramref name="toProject"/> onto <paramref name="projectOn"/>.
/// </summary>
/// <param name="toProject">The speed to project.</param>
/// <param name="projectOn">The speed to project on.</param>
/// <returns>The projected speed.</returns>
public static SizeF ProjectOn(this SizeF toProject, SizeF projectOn)
{
/* Projecting is easiest on a unit matrix. Therefore we call u the unit matrix of projectOn.
* The projection matrix is then:
*
| ux^2 ux * uy |
| ux * uy uy^2 |
*/
var unitVector = projectOn.GetUnitVector();
var projectionMatrix = new Matrix(
unitVector.Width * unitVector.Width, unitVector.Width * unitVector.Height,
unitVector.Width * unitVector.Height, unitVector.Height * unitVector.Height,
0, 0);
var inputList = new[] { new PointF(toProject.Width, toProject.Height) };
projectionMatrix.TransformVectors(inputList);
return(new SizeF(inputList[0].X, inputList[0].Y));
}
