From 43d9e38325d8190126b5ea5e7268a130dc978798 Mon Sep 17 00:00:00 2001
From: Lukas Matena <lukasmatena@seznam.cz>
Date: Wed, 24 Mar 2021 09:37:39 +0100
Subject: [PATCH] Wipe tower: reorder extruders so first layer starts with
 soluble if possible That way it will not be wiped on first layer

---
 src/libslic3r/GCode/ToolOrdering.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/libslic3r/GCode/ToolOrdering.cpp b/src/libslic3r/GCode/ToolOrdering.cpp
index 8520cf35bd..c45e260158 100644
--- a/src/libslic3r/GCode/ToolOrdering.cpp
+++ b/src/libslic3r/GCode/ToolOrdering.cpp
@@ -329,6 +329,16 @@ void ToolOrdering::reorder_extruders(unsigned int last_extruder_id)
                     lt.extruders.front() = last_extruder_id;
                     break;
                 }
+
+            // On first layer with wipe tower, prefer a soluble extruder
+            // at the beginning, so it is not wiped on the first layer.
+            if (lt == m_layer_tools[0] && m_print_config_ptr && m_print_config_ptr->wipe_tower) {
+                for (size_t i = 0; i<lt.extruders.size(); ++i)
+                    if (m_print_config_ptr->filament_soluble.get_at(lt.extruders[i]-1)) { // 1-based...
+                        std::swap(lt.extruders[i], lt.extruders.front());
+                        break;
+                    }
+            }
         }
         last_extruder_id = lt.extruders.back();
     }