WIP: Moved sources int src/, separated most of the source code from Perl.

The XS was left only for the unit / integration tests, and it links
libslic3r only. No wxWidgets are allowed to be used from Perl starting
from now.

src/libslic3r/Fill/FillRectilinear.cpp

@@ -0,0 +1,130 @@
+#include "../ClipperUtils.hpp"
+#include "../ExPolygon.hpp"
+#include "../PolylineCollection.hpp"
+#include "../Surface.hpp"
+
+#include "FillRectilinear.hpp"
+
+namespace Slic3r {
+
+void FillRectilinear::_fill_surface_single(
+    const FillParams                &params,
+    unsigned int                     thickness_layers,
+    const std::pair<float, Point>   &direction,
+    ExPolygon                       &expolygon,
+    Polylines                       &polylines_out)
+{
+    // rotate polygons so that we can work with vertical lines here
+    expolygon.rotate(- direction.first);
+
+    this->_min_spacing = scale_(this->spacing);
+    assert(params.density > 0.0001f && params.density <= 1.f);
+    this->_line_spacing = coord_t(coordf_t(this->_min_spacing) / params.density);
+    this->_diagonal_distance = this->_line_spacing * 2;
+    this->_line_oscillation = this->_line_spacing - this->_min_spacing; // only for Line infill
+    BoundingBox bounding_box = expolygon.contour.bounding_box();
+    
+    // define flow spacing according to requested density
+    if (params.density > 0.9999f && !params.dont_adjust) {
+        this->_line_spacing = this->_adjust_solid_spacing(bounding_box.size()(0), this->_line_spacing);
+        this->spacing = unscale<double>(this->_line_spacing);
+    } else {
+        // extend bounding box so that our pattern will be aligned with other layers
+        // Transform the reference point to the rotated coordinate system.
+        bounding_box.merge(_align_to_grid(
+            bounding_box.min, 
+            Point(this->_line_spacing, this->_line_spacing), 
+            direction.second.rotated(- direction.first)));
+    }
+
+    // generate the basic pattern
+    coord_t x_max = bounding_box.max(0) + SCALED_EPSILON;
+    Lines lines;
+    for (coord_t x = bounding_box.min(0); x <= x_max; x += this->_line_spacing)
+        lines.push_back(this->_line(lines.size(), x, bounding_box.min(1), bounding_box.max(1)));
+    if (this->_horizontal_lines()) {
+        coord_t y_max = bounding_box.max(1) + SCALED_EPSILON;
+        for (coord_t y = bounding_box.min(1); y <= y_max; y += this->_line_spacing)
+            lines.push_back(Line(Point(bounding_box.min(0), y), Point(bounding_box.max(0), y)));
+    }
+
+    // clip paths against a slightly larger expolygon, so that the first and last paths
+    // are kept even if the expolygon has vertical sides
+    // the minimum offset for preventing edge lines from being clipped is SCALED_EPSILON;
+    // however we use a larger offset to support expolygons with slightly skewed sides and 
+    // not perfectly straight
+    //FIXME Vojtech: Update the intersecton function to work directly with lines.
+    Polylines polylines_src;
+    polylines_src.reserve(lines.size());
+    for (Lines::const_iterator it = lines.begin(); it != lines.end(); ++ it) {
+        polylines_src.push_back(Polyline());
+        Points &pts = polylines_src.back().points;
+        pts.reserve(2);
+        pts.push_back(it->a);
+        pts.push_back(it->b);
+    }
+    Polylines polylines = intersection_pl(polylines_src, offset(to_polygons(expolygon), scale_(0.02)), false);
+
+    // FIXME Vojtech: This is only performed for horizontal lines, not for the vertical lines!
+    const float INFILL_OVERLAP_OVER_SPACING = 0.3f;
+    // How much to extend an infill path from expolygon outside?
+    coord_t extra = coord_t(floor(this->_min_spacing * INFILL_OVERLAP_OVER_SPACING + 0.5f));
+    for (Polylines::iterator it_polyline = polylines.begin(); it_polyline != polylines.end(); ++ it_polyline) {
+        Point *first_point = &it_polyline->points.front();
+        Point *last_point  = &it_polyline->points.back();
+        if (first_point->y() > last_point->y())
+            std::swap(first_point, last_point);
+        first_point->y() -= extra;
+        last_point->y() += extra;
+    }
+
+    size_t n_polylines_out_old = polylines_out.size();
+
+    // connect lines
+    if (! params.dont_connect && ! polylines.empty()) { // prevent calling leftmost_point() on empty collections
+        // offset the expolygon by max(min_spacing/2, extra)
+        ExPolygon expolygon_off;
+        {
+            ExPolygons expolygons_off = offset_ex(expolygon, this->_min_spacing/2);
+            if (! expolygons_off.empty()) {
+                // When expanding a polygon, the number of islands could only shrink. Therefore the offset_ex shall generate exactly one expanded island for one input island.
+                assert(expolygons_off.size() == 1);
+                std::swap(expolygon_off, expolygons_off.front());
+            }
+        }
+        Polylines chained = PolylineCollection::chained_path_from(
+            std::move(polylines), 
+            PolylineCollection::leftmost_point(polylines), false); // reverse allowed
+        bool first = true;
+        for (Polylines::iterator it_polyline = chained.begin(); it_polyline != chained.end(); ++ it_polyline) {
+            if (! first) {
+                // Try to connect the lines.
+                Points &pts_end = polylines_out.back().points;
+                const Point &first_point = it_polyline->points.front();
+                const Point &last_point = pts_end.back();
+                // Distance in X, Y.
+                const Vector distance = last_point - first_point;
+                // TODO: we should also check that both points are on a fill_boundary to avoid 
+                // connecting paths on the boundaries of internal regions
+                if (this->_can_connect(std::abs(distance(0)), std::abs(distance(1))) && 
+                    expolygon_off.contains(Line(last_point, first_point))) {
+                    // Append the polyline.
+                    pts_end.insert(pts_end.end(), it_polyline->points.begin(), it_polyline->points.end());
+                    continue;
+                }
+            }
+            // The lines cannot be connected.
+            polylines_out.emplace_back(std::move(*it_polyline));
+            first = false;
+        }
+    }
+
+    // paths must be rotated back
+    for (Polylines::iterator it = polylines_out.begin() + n_polylines_out_old; it != polylines_out.end(); ++ it) {
+        // No need to translate, the absolute position is irrelevant.
+        // it->translate(- direction.second(0), - direction.second(1));
+        it->rotate(direction.first);
+    }
+}
+
+} // namespace Slic3r