Drawing Polylines

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Go Up to Drawing Lines and Polylines

In addition to individual lines, the canvas can also draw polylines, which are groups of any number of connected line segments.

To draw a polyline on a canvas, call the Polyline method of the canvas.

The parameter passed to the Polyline method is an array of points. You can think of a polyline as performing a MoveTo on the first point and LineTo on each successive point. For drawing multiple lines, Polyline is faster than using the MoveTo method and the LineTo method because it eliminates a lot of call overhead.

The following method, for example, draws a rhombus in a form:

void __fastcall TForm1::FormPaint(TObject *Sender) {
    TPoint vertices[5];
    vertices[0] = Point(0, 0);
    vertices[1] = Point(50, 0);
    vertices[2] = Point(75, 50);
    vertices[3] = Point(25, 50);
    vertices[4] = Point(0, 0);
    Canvas->Polyline(vertices, 4);

Note that the last parameter to Polyline is the index of the last point, not the number of points.

See Also