Scale to Fit Print Volume: centre on the active plate

The command centred the selection on the bed at the origin, so scaling a model
that sat on plate 2 moved it back onto plate 1. Every plate shares the bed size,
so only the centre differs: pass the active plate's centre and, for a circular
bed, shift the print circle by it.

src/slic3r/GUI/Plater.cpp

@@ -11034,7 +11034,13 @@ void Plater::priv::split_volume()
 void Plater::priv::scale_selection_to_fit_print_volume()
 {
 #if ENABLE_ENHANCED_PRINT_VOLUME_FIT
-    this->view3D->get_canvas3d()->get_selection().scale_to_fit_print_volume(this->bed.build_volume());
+    const BuildVolume volume = this->bed.build_volume();
+    // Every plate shares the bed size, but each sits at its own origin: fit onto the
+    // plate the selection is on instead of always onto the first one.
+    PartPlate*    plate      = this->partplate_list.get_curr_plate();
+    const Vec3d   bed_center = plate != nullptr ? plate->get_center_origin() :
+                                                  Vec3d(volume.bed_center().x(), volume.bed_center().y(), 0.);
+    this->view3D->get_canvas3d()->get_selection().scale_to_fit_print_volume(volume, Vec2d(bed_center.x(), bed_center.y()));
 #else
     this->view3D->get_canvas3d()->get_selection().scale_to_fit_print_volume(*config);
 #endif // ENABLE_ENHANCED_PRINT_VOLUME_FIT

src/slic3r/GUI/Selection.cpp

@@ -1496,7 +1496,7 @@ void Selection::scale(const Vec3d& scale, TransformationType transformation_type
 }
 
 #if ENABLE_ENHANCED_PRINT_VOLUME_FIT
-void Selection::scale_to_fit_print_volume(const BuildVolume& volume)
+void Selection::scale_to_fit_print_volume(const BuildVolume& volume, const Vec2d& bed_center)
 {
     auto fit = [this](double s, Vec3d offset) {
         if (s <= 0.0 || s == 1.0)
@@ -1526,7 +1526,7 @@ void Selection::scale_to_fit_print_volume(const BuildVolume& volume)
         //wxGetApp().obj_manipul()->set_dirty();
     };
 
-    auto fit_rectangle = [this, fit](const BuildVolume& volume) {
+    auto fit_rectangle = [this, fit, &bed_center](const BuildVolume& volume) {
         const BoundingBoxf3 print_volume = volume.bounding_volume();
         const Vec3d print_volume_size = print_volume.size();
 
@@ -1538,10 +1538,10 @@ void Selection::scale_to_fit_print_volume(const BuildVolume& volume)
         const double sz = (box_size.z() != 0.0) ? print_volume_size.z() / box_size.z() : 0.0;
 
         if (sx != 0.0 && sy != 0.0 && sz != 0.0)
-            fit(std::min(sx, std::min(sy, sz)), print_volume.center() - get_bounding_box().center());
+            fit(std::min(sx, std::min(sy, sz)), Vec3d(bed_center.x(), bed_center.y(), print_volume.center().z()) - get_bounding_box().center());
     };
 
-    auto fit_circle = [this, fit](const BuildVolume& volume) {
+    auto fit_circle = [this, fit, &bed_center](const BuildVolume& volume) {
         const Geometry::Circled& print_circle = volume.circle();
         double print_circle_radius = unscale<double>(print_circle.radius);
 
@@ -1572,7 +1572,9 @@ void Selection::scale_to_fit_print_volume(const BuildVolume& volume)
         const double s = std::min(print_circle_radius / circle_radius, volume.printable_height() / max_z);
         const Vec3d sel_center = get_bounding_box().center();
         const Vec3d offset = s * (Vec3d(unscale<double>(circle.center.x()), unscale<double>(circle.center.y()), 0.5 * max_z) - sel_center);
-        const Vec3d print_center = { unscale<double>(print_circle.center.x()), unscale<double>(print_circle.center.y()), 0.5 * volume.printable_height() };
+        // The active plate's bed is the same circle, moved by its centre.
+        const Vec3d plate_shift = Vec3d(bed_center.x() - volume.bed_center().x(), bed_center.y() - volume.bed_center().y(), 0.);
+        const Vec3d print_center = Vec3d(unscale<double>(print_circle.center.x()), unscale<double>(print_circle.center.y()), 0.5 * volume.printable_height()) + plate_shift;
         fit(s, print_center - (sel_center + offset));
     };
 

src/slic3r/GUI/Selection.hpp

@@ -354,7 +354,9 @@ public:
     void flattening_rotate(const Vec3d& normal);
     void scale(const Vec3d& scale, TransformationType transformation_type);
 #if ENABLE_ENHANCED_PRINT_VOLUME_FIT
-    void scale_to_fit_print_volume(const BuildVolume& volume);
+    // bed_center is the centre of the plate the selection is on: every plate shares the
+    // bed size, but each sits at its own origin.
+    void scale_to_fit_print_volume(const BuildVolume& volume, const Vec2d& bed_center);
 #else
     void scale_to_fit_print_volume(const DynamicPrintConfig& config);
 #endif // ENABLE_ENHANCED_PRINT_VOLUME_FIT