/// <summary>
/// Draws the specified <see cref="PolygonGrid"/> to the specified <see
/// cref="StreamGeometry"/>, with optimization to remove duplicate lines.</summary>
/// <param name="grid">
/// The <see cref="PolygonGrid"/> to draw.</param>
/// <param name="context">
/// The <see cref="StreamGeometryContext"/> that receives <paramref name="grid"/>.</param>
/// <param name="offset">
/// The offset by which to shift <paramref name="grid"/>.</param>
/// <exception cref="ArgumentNullException">
/// <paramref name="grid"/> or <paramref name="context"/> is a null reference.</exception>
/// <remarks><para>
/// <b>DrawOptimized</b> shifts the <see cref="RegularPolygon.Vertices"/> of each <see
/// cref="PolygonGrid.Element"/> in the specified <paramref name="grid"/> by the
/// corresponding <see cref="PolygonGrid.GridToDisplay"/> result plus the specified
/// <paramref name="offset"/>.
/// </para><para>
/// <b>DrawOptimized</b> skips any <see cref="RegularPolygon"/> edges that coincide with an
/// edge drawn for a previous <see cref="PolygonGrid.Element"/>. This optimization results
/// in a total number of lines drawn to the specified <paramref name="context"/> that is
/// about half that of the unoptimized <see cref="Draw"/> method.
/// </para><para>
/// There are two disadvantages. First, <b>DrawOptimized</b> requires more time and memory
/// than <see cref="Draw"/> due to the additional vertex comparisons. Second, most polygons
/// are not represented by closed figures within the specified <paramref name="context"/>,
/// and so the area covered by the specified <paramref name="grid"/> is never considered
/// filled for hit-testing, rendering, and clipping.</para></remarks>
public static void DrawOptimized(this PolygonGrid grid,
StreamGeometryContext context, PointD offset)
{
HashSet <LineI> lines = new HashSet <LineI>();
double epsilon = grid.Element.Length / 4.0;
PointD[] vertices = grid.Element.Vertices;
int width = grid.Size.Width, height = grid.Size.Height;
for (int x = 0; x < width; x++)
{
for (int y = 0; y < height; y++)
{
PointD element = grid.GridToDisplay(x, y) + offset;
// get & remember first element vertex
PointD start = vertices[0] + element;
PointD elementStart = start;
bool lineSkipped = true;
for (int i = 1; i <= vertices.Length; i++)
{
// close figure by returning to first vertex
PointD next = (i == vertices.Length ? elementStart : vertices[i] + element);
// reduce line to unique hash coordinates
LineI line = new LineI(
(int)(start.X / epsilon), (int)(start.Y / epsilon),
(int)(next.X / epsilon), (int)(next.Y / epsilon));
// skip lines that were drawn (in either direction)
if (lines.Contains(line) ||
lines.Contains(new LineI(line.End, line.Start)))
{
lineSkipped = true;
}
else
{
// restart figure after skipping lines
if (lineSkipped)
{
context.BeginFigure(start.ToWpfPoint(), false, false);
lineSkipped = false;
}
// draw & remember current line
context.LineTo(next.ToWpfPoint(), true, true);
lines.Add(line);
}
// prepare for next vertex
start = next;
}
}
}
}
/// <overloads>
/// Draws the specified <see cref="RegularPolygon"/> or <see cref="PolygonGrid"/> to the
/// specified <see cref="StreamGeometry"/>.</overloads>
/// <summary>
/// Draws the specified <see cref="RegularPolygon"/> to the specified <see
/// cref="StreamGeometry"/>.</summary>
/// <param name="polygon">
/// The <see cref="RegularPolygon"/> to draw.</param>
/// <param name="context">
/// The <see cref="StreamGeometryContext"/> that receives <paramref name="polygon"/>.
/// </param>
/// <param name="offset">
/// The offset by which to shift <paramref name="polygon"/>.</param>
/// <param name="isFilled">
/// <c>true</c> to use the area covered by <paramref name="polygon"/> for hit-testing,
/// rendering, and clipping; otherwise, <c>false</c>.</param>
/// <exception cref="ArgumentNullException">
/// <paramref name="polygon"/> or <paramref name="context"/> is a null reference.
/// </exception>
/// <remarks>
/// <b>Draw</b> issues one <see cref="StreamGeometryContext.BeginFigure"/> call with the
/// specified <paramref name="isFilled"/> parameter for the first <see
/// cref="RegularPolygon.Vertices"/> element of the specified <paramref name="polygon"/>,
/// and then one <see cref="StreamGeometryContext.LineTo"/> call for each remaining element.
/// All coordinates are shifted by the specified <paramref name="offset"/>.</remarks>
public static void Draw(this RegularPolygon polygon,
StreamGeometryContext context, PointD offset, bool isFilled)
{
PointD[] vertices = polygon.Vertices;
PointD start = vertices[0] + offset;
context.BeginFigure(start.ToWpfPoint(), isFilled, true);
for (int i = 1; i < vertices.Length; i++)
{
PointD next = vertices[i] + offset;
context.LineTo(next.ToWpfPoint(), true, true);
}
}
/// <summary>
/// Converts the specified <see cref="RegularPolygon"/> to a closed <see
/// cref="PathFigure"/>, shifted by a specified offset.</summary>
/// <param name="polygon">
/// The <see cref="RegularPolygon"/> to convert.</param>
/// <param name="offset">
/// The offset by which to shift the <see cref="PathFigure"/>.</param>
/// <returns>
/// A closed and frozen <see cref="PathFigure"/> containing all <see
/// cref="RegularPolygon.Vertices"/> of the specified <paramref name="polygon"/>, shifted by
/// the specified <paramref name="offset"/>.</returns>
/// <exception cref="ArgumentNullException">
/// <paramref name="polygon"/> is a null reference.</exception>
public static PathFigure ToFigure(this RegularPolygon polygon, PointD offset)
{
PointD[] vertices = polygon.Vertices;
PathFigure figure = new PathFigure();
figure.StartPoint = (vertices[0] + offset).ToWpfPoint();
for (int i = 1; i < vertices.Length; i++)
{
PointD next = vertices[i] + offset;
figure.Segments.Add(new LineSegment(next.ToWpfPoint(), true));
}
figure.IsClosed = true;
figure.Freeze();
return(figure);
}
