Fix WASM build of skeleton tool

cgal_skeleton_core/.gitignore

@@ -0,0 +1 @@
+cache

cgal_skeleton_core/Makefile

@@ -0,0 +1,67 @@
+
+CXX ?= clang++
+
+BUILDDIR ?= build
+CACHEDIR ?= cache
+
+CGAL ?= CGAL-6.1
+CGAL_URL ?= https://github.com/CGAL/cgal/releases/download/v6.1/CGAL-6.1-library.tar.xz
+
+BOOST ?= boost_1_90_0
+BOOST_URL ?= https://archives.boost.io/release/1.90.0/source/boost_1_90_0.tar.gz
+
+WASI_SDK_URL ?= https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-29/wasi-sdk-29.0-x86_64-linux.tar.gz
+WASI_SDK ?= $(CACHEDIR)/wasi-sdk-29.0-x86_64-linux
+
+SOURCES := \
+	skeleton_wrapper.cpp
+
+WASI_SOURCES := \
+	$(SOURCES) \
+	exception_stubs.cpp \
+
+INCLUDES := -I$(CACHEDIR)/$(CGAL)/include -I$(CACHEDIR)/$(BOOST)
+CXXFLAGS := -std=c++20 -g -Wall -Wextra -O2 
+WASI_CXXFLAGS := -DCGAL_ALWAYS_ROUND_TO_NEAREST -DCGAL_CORE_USE_BOOST_BACKEND -DCGAL_DISABLE_GMP -DCGAL_USE_BOOST_MP -DFE_UPWARD=FE_TONEAREST -D_WASI_EMULATED_PROCESS_CLOCKS $(CXXFLAGS)
+LDFLAGS :=
+HOST_LDFLAGS := $(LDFLAGS) -lgmp -lmpfr
+WASI_LDFLAGS := $(LDFLAGS) -lwasi-emulated-process-clocks 
+
+WASI_CXX ?= $(WASI_SDK)/bin/clang++
+
+
+BINARY := skeleton
+
+all: $(BUILDDIR)/$(BINARY) wasm
+
+.PHONY: wasm
+wasm: $(BUILDDIR)/$(BINARY).wasm
+
+$(BUILDDIR)/$(BINARY): $(SOURCES)
+	$(CXX) $(CXXFLAGS) $(HOST_LDFLAGS) -o $@ $^
+
+$(WASI_SDK):
+	mkdir -p $(dir $@)
+	cd $(dir $@); curl -L ${WASI_SDK_URL} | tar xzf -
+
+$(CACHEDIR)/$(BOOST):
+	cd $(dir $@); curl -L ${BOOST_URL} | tar xzf -
+
+$(CACHEDIR)/$(CGAL):
+	cd $(dir $@); curl -L ${CGAL_URL} | tar xJf -
+
+$(BUILDDIR)/wasi/%.o: %.cpp $(WASI_SDK) 
+	@mkdir -p $(dir $@) 
+	$(WASI_CXX) -c $(WASI_CXXFLAGS) $(INCLUDES) -o $@ $<
+
+$(BUILDDIR)/$(BINARY).wasm: $(patsubst %.cpp,$(BUILDDIR)/wasi/%.o,$(WASI_SOURCES))
+	@mkdir -p $(dir $@)
+	$(WASI_CXX) $(WASI_LDFLAGS) -o $@ $^
+
+.PHONY: clean
+clean:
+	rm -rf $(BUILDDIR)
+
+.PHONY: mrproper
+mrproper: clean
+	rm -rf $(CACHEDIR)

cgal_skeleton_core/exception_stubs.cpp

@@ -0,0 +1,13 @@
+
+#include <stdlib.h>
+
+extern "C" {
+    void* __cxa_allocate_exception(size_t) {
+        abort();
+    }
+
+    void __cxa_throw(void *, void *, void (*)(void *)) {
+        abort();
+    }
+}
+

cgal_skeleton_core/skeleton_wrapper.cpp

@@ -0,0 +1,90 @@
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+#include <CGAL/Polygon_2.h>
+#include <CGAL/create_straight_skeleton_2.h>
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <memory>
+
+typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
+typedef K::Point_2                   Point;
+typedef CGAL::Polygon_2<K>           Polygon_2;
+typedef CGAL::Straight_skeleton_2<K> Ss;
+typedef std::shared_ptr<Ss>          SsPtr;
+
+int main()
+{
+    // Read polygon from stdin
+    Polygon_2 poly;
+    std::string line;
+
+    while (std::getline(std::cin, line)) {
+        if (line.empty()) {
+            continue;
+        }
+
+        std::istringstream iss(line);
+        double x, y;
+        if (iss >> x >> y) {
+            poly.push_back(Point(x, y));
+        } else {
+            std::cerr << "Error: Invalid input line: " << line << std::endl;
+            return EXIT_FAILURE;
+        }
+    }
+
+    if (poly.size() < 3) {
+        std::cerr << "Error: Polygon must have at least 3 vertices" << std::endl;
+        return EXIT_FAILURE;
+    }
+
+    // Ensure counter-clockwise orientation
+    if (!poly.is_counterclockwise_oriented()) {
+        poly.reverse_orientation();
+    }
+
+    // Create interior straight skeleton
+    SsPtr ss = CGAL::create_interior_straight_skeleton_2(poly.vertices_begin(), poly.vertices_end());
+
+    if (!ss) {
+        std::cerr << "Error: Failed to create straight skeleton" << std::endl;
+        return EXIT_FAILURE;
+    }
+
+    // Output skeleton edges
+    // Iterate through all halfedges in the skeleton
+    for (auto he = ss->halfedges_begin(); he != ss->halfedges_end(); ++he) {
+        // Only output each edge once (skip the opposite halfedge)
+        if (he->id() < he->opposite()->id()) {
+            continue;
+        }
+
+        // Get the vertices at both ends of the halfedge
+        auto v_source = he->vertex();
+        auto v_target = he->opposite()->vertex();
+
+        // Get times (distance from boundary)
+        double t1 = CGAL::to_double(v_source->time());
+        double t2 = CGAL::to_double(v_target->time());
+
+        // Skip contour edges (outline of the input polygon)
+        // Contour edges have both vertices at time 0
+        if (t1 == 0.0 && t2 == 0.0) {
+            continue;
+        }
+
+        // Get coordinates
+        double x1 = CGAL::to_double(v_source->point().x());
+        double y1 = CGAL::to_double(v_source->point().y());
+        double x2 = CGAL::to_double(v_target->point().x());
+        double y2 = CGAL::to_double(v_target->point().y());
+
+        // Output: start_x start_y end_x end_y start_time end_time
+        std::cout << std::setprecision(12) << x1 << " " << y1 << " "
+                  << x2 << " " << y2 << " "
+                  << t1 << " " << t2 << std::endl;
+    }
+
+    return EXIT_SUCCESS;
+}
+