From 01613d1977c232c156da0925e48fc15b21ba2c1c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mario=20H=C3=BCttel?= <mario.huettel@gmx.net>
Date: Tue, 19 Apr 2022 22:14:52 +0200
Subject: [PATCH] Implement simple hole stencil to resolve holes in GDS
 polygons.

---
 .../poly2tri-wrapper/src/poly2tri-wrapper.cpp | 74 +++++++++++++++++++
 preview-rendering/src/preview-rendering-gui.c | 41 ++++++++--
 2 files changed, 108 insertions(+), 7 deletions(-)

diff --git a/preview-rendering/poly2tri-wrapper/src/poly2tri-wrapper.cpp b/preview-rendering/poly2tri-wrapper/src/poly2tri-wrapper.cpp
index 506d284..1344fce 100644
--- a/preview-rendering/poly2tri-wrapper/src/poly2tri-wrapper.cpp
+++ b/preview-rendering/poly2tri-wrapper/src/poly2tri-wrapper.cpp
@@ -4,6 +4,74 @@
 //#include <gds-render/gds-utils/gds-types.h>
 #include <vector>
 
+class Hole {
+private:
+	std::vector <p2t::Point *> hole_vertices;
+public:
+	const std::vector <p2t::Point *> &get_vertices()
+	{
+		return hole_vertices;
+	}
+
+	void add_vertex(const p2t::Point &point)
+	{
+		auto pt = new p2t::Point(point);
+		hole_vertices.push_back(pt);
+	}
+
+	Hole(std::vector<p2t::Point *>::iterator start, std::vector<p2t::Point *>::iterator end)
+	{
+		hole_vertices = std::vector<p2t::Point *>(start, end);
+	}
+
+};
+
+
+static std::vector<Hole> resolve_holes_in_polyline(std::vector<p2t::Point *> &polyline)
+{
+	bool found = false;
+	std::vector<Hole> holes;
+	std::vector<std::pair<
+			std::vector<p2t::Point *>::iterator,
+			std::vector<p2t::Point *>::iterator>
+			> points_to_remove;
+
+	for (auto start_it = polyline.begin(); start_it != polyline.end(); start_it++) {
+		for (auto check_it = std::next(start_it); check_it != polyline.end(); check_it++) {
+			/* Check if points are equal */
+			if (**start_it == **check_it) {
+				if (**std::prev(check_it) == **std::next(start_it)) {
+					/* Found a hole. Everything between start_it and check_it can be removed */
+					auto hole = Hole(std::next(start_it)+1, check_it);
+					holes.push_back(hole);
+					auto tbd = std::make_pair(start_it, check_it);
+					points_to_remove.push_back(tbd);
+					found = true;
+					break;
+				}
+			}
+		}
+		if (found)
+			break;
+	}
+
+	/* Remove form polyline */
+	for (auto it_pair_it = points_to_remove.begin(); it_pair_it != points_to_remove.end(); it_pair_it++) {
+		auto it_pair = *it_pair_it;
+		delete *it_pair.first;
+		delete *std::next(it_pair.first);
+		polyline.erase(it_pair.first, it_pair.second);
+	}
+
+	if (found) {
+		auto new_holes = resolve_holes_in_polyline(polyline);
+		holes.insert(holes.end(), new_holes.begin(), new_holes.end());
+	}
+
+
+	return holes;
+}
+
 int tesselator_triangulate_polygon(const struct gds_graphics *gfx, double scale, float** output_vertices, size_t *vertex_count)
 {
 	GList *vertex_iter;
@@ -18,8 +86,14 @@ int tesselator_triangulate_polygon(const struct gds_graphics *gfx, double scale,
 		polyline.push_back(pt);
 	}
 
+	auto holes = resolve_holes_in_polyline(polyline);
+
 	auto my_cdt = p2t::CDT(polyline);
 
+	for (auto hole_it = holes.begin(); hole_it != holes.end(); hole_it++) {
+		my_cdt.AddHole((*hole_it).get_vertices());
+	}
+
 	my_cdt.Triangulate();
 
 	auto triangles = my_cdt.GetTriangles();
diff --git a/preview-rendering/src/preview-rendering-gui.c b/preview-rendering/src/preview-rendering-gui.c
index 489bf59..c602fa2 100644
--- a/preview-rendering/src/preview-rendering-gui.c
+++ b/preview-rendering/src/preview-rendering-gui.c
@@ -8,6 +8,7 @@ struct _OpenGlPreviewGui {
 	GtkGLArea *gl_area;
 	unsigned int polygon_shader_prog;
 	unsigned int vao;
+	unsigned int vao_vertex_count;
 	unsigned int vbo;
 	float color[4];
 	gboolean line;
@@ -54,7 +55,7 @@ static gboolean gl_area_render(GtkGLArea *area, GdkGLContext *context, gpointer
 	glBindVertexArray(gui->vao);
 	loc = glGetUniformLocation(gui->polygon_shader_prog, "const_color");
 	glUniform4fv(loc, 1, gui->color);
-	glDrawArrays(GL_TRIANGLES, 0, 10*3);
+	glDrawArrays(GL_TRIANGLES, 0, gui->vao_vertex_count);
 
 	glFlush();
 
@@ -94,7 +95,7 @@ static gboolean gl_area_realize(GtkGLArea *area, gpointer user)
 	OpenGlPreviewGui *gui;
 	int success;
 	struct gds_graphics gfx;
-	struct gds_point points[12];
+	struct gds_point points[20];
 	size_t vertex_count;
 
 	gui = GDS_RENDER_OPENGL_PREVIEW_GUI(user);
@@ -158,28 +159,54 @@ static gboolean gl_area_realize(GtkGLArea *area, gpointer user)
 	points[7].x = 20;
 	points[7].y = 20;
 
-	points[8].x = 1;
+	points[8].x = 0;
 	points[8].y = 20;
 
-	points[9].x = 1;
+	points[9].x = 0;
 	points[9].y = 100;
 
 	points[10].x = 100;
 	points[10].y = 100;
 
+
 	points[11].x = 100;
-	points[11].y = -100;
+	points[11].y = 5;
+
+	points[12].x = 60;
+	points[12].y = 5;
+
+	points[13].x = 60;
+	points[13].y = 20;
+
+	points[14].x = 50;
+	points[14].y = 20;
+
+	points[15].x = 50;
+	points[15].y = 0;
+
+	points[16].x = 60;
+	points[16].y = 0;
+
+	points[17].x = 60;
+	points[17].y = 5;
+
+	points[18].x = 100;
+	points[18].y = 5;
+
+
+	points[19].x = 100;
+	points[19].y = -100;
 
 	gfx.gfx_type = GRAPHIC_POLYGON;
 
-	for (int i = 0; i < 12; i++) {
+	for (int i = 0; i < 20; i++) {
 		gfx.vertices = g_list_append(gfx.vertices, &points[i]);
 	}
 
 	float *vertices = NULL;
 
 	tesselator_triangulate_polygon(&gfx, 180.0, &vertices, &vertex_count);
-
+	gui->vao_vertex_count = vertex_count;
 
 	glGenVertexArrays(1, &vao);
 	glBindVertexArray(vao);