Add alignment option to arrange settings dialog

Also make it work

src/libslic3r/Arrange.cpp

@@ -85,7 +85,13 @@ template<class PConf>
 void fill_config(PConf& pcfg, const ArrangeParams &params) {
 
     // Align the arranged pile into the center of the bin
-    pcfg.alignment = PConf::Alignment::CENTER;
+    switch (params.alignment) {
+    case Pivots::Center: pcfg.alignment = PConf::Alignment::CENTER; break;
+    case Pivots::BottomLeft: pcfg.alignment = PConf::Alignment::BOTTOM_LEFT; break;
+    case Pivots::BottomRight: pcfg.alignment = PConf::Alignment::BOTTOM_RIGHT; break;
+    case Pivots::TopLeft: pcfg.alignment = PConf::Alignment::TOP_LEFT; break;
+    case Pivots::TopRight: pcfg.alignment = PConf::Alignment::TOP_RIGHT; break;
+    }
 
     // Start placing the items from the center of the print bed
     pcfg.starting_point = PConf::Alignment::CENTER;

src/libslic3r/Arrange.hpp

@@ -75,6 +75,10 @@ struct ArrangePolygon {
 
 using ArrangePolygons = std::vector<ArrangePolygon>;
 
+enum class Pivots {
+    Center, TopLeft, BottomLeft, BottomRight, TopRight
+};
+
 struct ArrangeParams {
 
     /// The minimum distance which is allowed for any 
@@ -93,6 +97,12 @@ struct ArrangeParams {
 
     bool allow_rotations = false;
 
+    /// Final alignment of the merged pile after arrangement
+    Pivots alignment = Pivots::Center;
+
+    /// Starting position hint for the arrangement
+    Pivots starting_point = Pivots::Center;
+
     /// Progress indicator callback called when an object gets packed. 
     /// The unsigned argument is the number of items remaining to pack.
     std::function<void(unsigned)> progressind;

src/slic3r/GUI/GLCanvas3D.cpp

@@ -4145,6 +4145,7 @@ bool GLCanvas3D::_render_arrange_menu(float pos_x)
     std::string dist_key = "min_object_distance";
     std::string dist_bed_key = "min_bed_distance";
     std::string rot_key = "enable_rotation";
+    std::string align_key = "alignment";
     std::string postfix;
 
     if (ptech == ptSLA) {
@@ -4163,6 +4164,7 @@ bool GLCanvas3D::_render_arrange_menu(float pos_x)
     dist_key += postfix;
     dist_bed_key += postfix;
     rot_key += postfix;
+    align_key += postfix;
 
     imgui->text(GUI::format_wxstr(_L("Press %1%left mouse button to enter the exact value"), shortkey_ctrl_prefix()));
 
@@ -4186,6 +4188,12 @@ bool GLCanvas3D::_render_arrange_menu(float pos_x)
         settings_changed = true;
     }
 
+    if (imgui->combo(_("Alignment"), {"Center", "Top left", "Bottom left", "Bottom right", "Top right", "Random"}, settings.alignment)) {
+        settings_out.alignment = settings.alignment;
+        appcfg->set("arrange", align_key.c_str(), std::to_string(settings_out.alignment));
+        settings_changed = true;
+    }
+
     ImGui::Separator();
 
     if (imgui->button(_L("Reset"))) {

src/slic3r/GUI/GLCanvas3D.hpp

@@ -463,6 +463,7 @@ public:
 //        float distance_sla       = 6.;
         float accuracy           = 0.65f; // Unused currently
         bool  enable_rotation    = false;
+        int   alignment          = 0;
     };
 
 private:

src/slic3r/GUI/Jobs/ArrangeJob.cpp

@@ -298,6 +298,21 @@ arrangement::ArrangeParams get_arrange_params(Plater *p)
     params.min_obj_distance = scaled(settings.distance);
     params.min_bed_distance = scaled(settings.distance_from_bed);
 
+    arrangement::Pivots pivot = arrangement::Pivots::Center;
+
+    int pivot_max = static_cast<int>(arrangement::Pivots::TopRight);
+    if (settings.alignment > pivot_max) {
+        // means it should be random
+        std::random_device rd{};
+        std::mt19937 rng(rd());
+        std::uniform_int_distribution<std::mt19937::result_type> dist(0, pivot_max);
+        pivot = static_cast<arrangement::Pivots>(dist(rng));
+    } else {
+        pivot = static_cast<arrangement::Pivots>(settings.alignment);
+    }
+
+    params.alignment = pivot;
+
     return params;
 }