simplify the hatch-fill algorithm (0ee6ce9f) · Commits · github_fork / Clip

core/graphics/shape_hatch.cc

+45 −16

Original line number	Diff line number	Diff line
		@@ -18,14 +18,10 @@ namespace fviz {

		Path shape_hatch(
		const Rectangle& clip,
		vec2 origin,
		double angle_deg,
		double offset,
		double stride,
		double width) {
		auto direction = vec2_from_deg(angle_deg);
		auto ortho = vec2_from_deg(angle_deg + 90);

		Polygon2 clip_poly;
		clip_poly.vertices = {
		{clip.x, clip.y + clip.h},
		@@ -34,29 +30,62 @@ Path shape_hatch(
		{clip.x, clip.y},
		};

		auto origin = vec2_mean(clip_poly.vertices.data(), clip_poly.vertices.size());
		auto direction = vec2_from_deg(angle_deg);
		auto ortho = vec2_from_deg(angle_deg + 90);

		Path p;
		for (size_t i = 0; i < 100; ++i) {
		for (size_t i = 0; ; ++i) {
		bool edge_reached = true;

		// symmetry around the origin
		for (double s = (i == 0 ? 0 : -1); s <= 1; s += 2) {
		std::vector<Point> vertices;

		// offset lines perpendicularly
		auto o = vec2_add(origin, vec2_mul(ortho, i * s * stride + offset));

		// find the intersections with the four borders of the clipping rectangle
		std::vector<Point> intersections;
		// find the intersections of two lines with the clipping rectangle
		// - a "top" line that is offset by half the width in one direction
		// - a "bottom" line that is offset by half the width in the other direction
		intersect_poly_line(
		clip_poly,
		vec2_add(origin, vec2_mul(ortho, i * s * stride + offset + width * 0.5)),
		direction,
		&vertices);

		intersect_poly_line(
		clip_poly,
		o,
		vec2_add(origin, vec2_mul(ortho, i * s * stride + offset + width * -0.5)),
		direction,
		&intersections);
		&vertices);

		// TODO: find all vertices of the bounding polygon the lie between the
		// two lines and add them to the vertex list

		if (vertices.size() >= 3) {
		// we still had something to draw, so we're not ready yet
		edge_reached = false;
		} else {
		// if we end up with less than three vertices we are outside of the
		// clipping polygon
		continue;
		}

		// build a simple polygon from the resulting points by connecting them
		// in clockwise order
		vec2_sort_cw(vertices.data(), vertices.size());

		// stroke line between edge points
		if (intersections.size() >= 2) {
		p.moveTo(intersections[0].x, clip.h - intersections[0].y);
		p.lineTo(intersections[1].x, clip.h - intersections[1].y);
		for (size_t i = 0; i < vertices.size(); ++i) {
		if (i == 0) {
		p.moveTo(vertices[i].x, vertices[i].y);
		} else {
		p.lineTo(vertices[i].x, vertices[i].y);
		}
		}

		}

		if (edge_reached) {
		break;
		}
		}

		return p;

core/graphics/shape_hatch.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -30,7 +30,6 @@ namespace fviz {
		*/
		Path shape_hatch(
		const Rectangle& clip,
		vec2 origin,
		double angle_deg,
		double offset,
		double stride,

tests/unit/test_graphics_pattern_hatch.cc

+5 −7

Original line number	Diff line number	Diff line
		@@ -36,16 +36,14 @@ int main(int argc, char** argv) {
		&layer);

		auto p = shape_hatch(
		Rectangle(0, 0, 1200, 800),
		vec2(600, 400),
		Rectangle(100, 100, 1000, 600),
		45,
		0,
		150,
		70);
		40,
		20);

		StrokeStyle ss;
		ss.line_width = from_unit(70);
		strokePath(layer.get(), p, ss);
		FillStyle fs;
		fillPath(layer.get(), p, fs);

		layer_submit(layer.get());
		}

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