Self intersection in dashed plotter

[AdyanOchirov]

const std = @import("std");
const z2d = @import("z2d");

const Point = struct { x: f64, y: f64 };

pub fn main(init: std.process.Init) !void {
    const points: []const Point = &.{
        .{ .x = 50 + 0, .y = 150 + 0 },
        .{ .x = 50 + 100, .y = 150 + 100 },
        .{ .x = 50 + 200, .y = 150 + -100 },
        .{ .x = 50 + 1, .y = 150 + -50 },
    };
    var surface: z2d.Surface = try .init(.image_surface_rgba, init.gpa, 300, 300);
    defer surface.deinit(init.gpa);
    surface.paintPixel(.{ .rgba = .{ .r = 0, .g = 0, .b = 0, .a = 255 } });
    var context: z2d.Context = .init(init.io, init.gpa, &surface);
    defer context.deinit();

    try context.moveTo(points[0].x, points[0].y);
    for (1..points.len) |i| {
        try context.lineTo(points[i].x, points[i].y);
    }
    try context.closePath();

    var transform = z2d.Transformation.identity;
    transform = transform.scale(3.0, 3.0);
    context.setTransformation(transform);

    context.setDashes(&.{ 10, 20, 30 });
    context.setSourceToPixel(.{ .rgba = .{ .r = 255, .g = 255, .b = 255, .a = 255 } });
    try context.stroke();

    try z2d.png_exporter.writeToPNGFile(init.io, surface, "test.png", .{});
}

Produces the following on 47fc1030c1636dcfb75ea1cc238f706dd1feb379

Here is geometry of broken dash

[vancluever]

@AdyanOchirov fixed in #187!