Make line-overlap detection more conservative.

(Tried a lot of other things as well, which makes it less predictable.) Clean up experiments, bring it back to basics, be quite conservative as this is only a patch and solving the whole 'scan-segments can be too close to the connector paths' probably requires properly rewriting the zig-zag algorithm -- which is way more like a feature.

part of CURA-11597

include/infill/ZigzagConnectorProcessor.h

@@ -175,6 +175,8 @@ class ZigzagConnectorProcessor
      */
     void addZagConnector(std::vector<Point2LL>& points, bool is_endpiece);
 
+    bool handleConnectorToCloseToSegment(const coord_t scanline_x, const coord_t min_distance_to_scanline);
+
 protected:
     const PointMatrix& rotation_matrix_; //!< The rotation matrix used to enforce the infill angle
     Polygons& result_; //!< The result of the computation

src/infill.cpp

@@ -751,7 +751,7 @@ void Infill::generateLinearBasedInfill(
                 assert(scanline_idx - scanline_min_idx >= 0 && scanline_idx - scanline_min_idx < int(cut_list.size()) && "reading infill cutlist index out of bounds!");
                 cut_list[scanline_idx - scanline_min_idx].push_back(y);
                 Point2LL scanline_linesegment_intersection(x, y);
-                zigzag_connector_processor.registerScanlineSegmentIntersection(scanline_linesegment_intersection, scanline_idx, line_distance / 2);
+                zigzag_connector_processor.registerScanlineSegmentIntersection(scanline_linesegment_intersection, scanline_idx, line_distance / 4);
                 crossings_per_scanline[scanline_idx - min_scanline_index].emplace_back(scanline_linesegment_intersection, poly_idx, point_idx);
             }
             zigzag_connector_processor.registerVertex(p1);

src/infill/ZigzagConnectorProcessor.cpp

@@ -83,6 +83,15 @@ bool ZigzagConnectorProcessor::shouldAddCurrentConnector(int start_scanline_idx,
     return should_add;
 }
 
+bool ZigzagConnectorProcessor::handleConnectorToCloseToSegment(const coord_t scanline_x, const coord_t min_distance_to_scanline)
+{
+    bool all_within_min_dist = ! current_connector_.empty();
+    for (const auto& point : current_connector_)
+    {
+        all_within_min_dist &= std::abs(point.X - scanline_x) < min_distance_to_scanline;
+    }
+    return all_within_min_dist;
+}
 
 void ZigzagConnectorProcessor::registerScanlineSegmentIntersection(const Point2LL& intersection, int scanline_index, coord_t min_distance_to_scanline)
 {
@@ -97,20 +106,11 @@ void ZigzagConnectorProcessor::registerScanlineSegmentIntersection(const Point2L
     else
     {
         // add the current connector if needed
-        if (shouldAddCurrentConnector(last_connector_index_, scanline_index))
+        if (shouldAddCurrentConnector(last_connector_index_, scanline_index) && ! handleConnectorToCloseToSegment(intersection.X, min_distance_to_scanline))
         {
             const bool is_this_endpiece = scanline_index == last_connector_index_;
-            bool close_to_line_except_intersect = true;
-            const coord_t min_dist2 = min_distance_to_scanline * min_distance_to_scanline;
-            for (const auto& point : current_connector_)
-            {
-                close_to_line_except_intersect &= std::abs(point.X - intersection.X) < min_distance_to_scanline;
-            }
-            if (current_connector_.empty() || ! close_to_line_except_intersect)
-            {
-                current_connector_.push_back(intersection);
-                addZagConnector(current_connector_, is_this_endpiece);
-            }
+            current_connector_.push_back(intersection);
+            addZagConnector(current_connector_, is_this_endpiece);
         }
     }