Fix deleting mixed filaments from the sidebar

src/libslic3r/Model.cpp

@@ -2669,9 +2669,18 @@ void ModelVolume::update_extruder_count_when_delete_filament(size_t extruder_cou
     // Same stale-assignment cleanup as update_extruder_count, for the filament-delete path.
     // Ported from BambuStudio (STUDIO-15763).
     size_t eid = extruder_id();
-    if (eid > extruder_count) {
+    // Judge out-of-range against the post-remap id, mirroring update_filament_values_for_items_when_delete_filament.
-        // A mixed-color slot is virtual and legitimately sits past the physical filament count,
+    // Using the pre-remap eid would wrongly erase a high extruder that should remap (e.g. 5 -> 4 after
-        // so an assignment to one is not stale and must survive the delete.
+    // deleting filament 1); update_filament_values_for_items_when_delete_filament would then skip it
+    // (!has("extruder")) and the volume would fall back to the object default color.
+    size_t remapped = eid;
+    if (eid == filament_id)
+        remapped = (replace_filament_id > 0) ? (size_t)replace_filament_id : 1;
+    else if (eid > filament_id)
+        remapped = eid - 1;
+    if (remapped > extruder_count) {
+        // filament_is_mixed is the pre-delete snapshot; index it with the ORIGINAL eid (1-based),
+        // not remapped, so we check whether this volume's current slot is a mixed slot.
         bool is_mixed = !filament_is_mixed.empty() && eid >= 1 && (eid - 1) < filament_is_mixed.size() && filament_is_mixed[eid - 1];
         if (!is_mixed)
             this->config.erase("extruder");

src/slic3r/GUI/Plater.cpp

@@ -5294,16 +5294,16 @@ void Sidebar::on_filaments_delete(size_t filament_id)
 {
     auto &choices = combos_filament();
 
-    if (filament_id >= choices.size())
+    // A mixed (virtual) slot has no combo of its own, so there is no combo UI to remove —
-        return;
+    // but the shared refresh below must still run so the mixed filament panel drops its row.
-
+    if (filament_id < choices.size()) {
         if (choices.size() == 1)
             choices[0]->GetDropDown().Invalidate();
 
         wxWindowUpdateLocker noUpdates_scrolled_panel(this);
 
         // delete UI item
-    if (filament_id < p->combos_filament.size()) {
+        {
             const int last            = p->combos_filament.size() - 1;
             auto      sizer_filaments = this->p->sizer_filaments->GetItem(last % 2)->GetSizer();
             sizer_filaments->Remove(last / 2);
@@ -5332,6 +5332,7 @@ void Sidebar::on_filaments_delete(size_t filament_id)
         for (size_t idx = filament_id ; idx < p->combos_filament.size(); ++idx) {
             p->combos_filament[idx]->update();
         }
+    }
 
     update_filaments_area_height(); // ORCA
     recalc_filament_scroll_sizes();
@@ -5368,9 +5369,15 @@ void Sidebar::delete_filament(size_t filament_id, int replace_filament_id) {
         filament_id = filament_count;
     }
 
-    if (filament_id > filament_count)
+    // Mixed (virtual) slots have no combo of their own, so their config index lies past
+    // filament_count; bound explicit ids by the total slot count instead.
+    size_t total_filaments = wxGetApp().preset_bundle->filament_presets.size();
+    if (filament_id > filament_count && filament_id >= total_filaments)
         return;
 
+    bool is_mixed = (filament_id >= p->combos_filament.size());
+
+    if (!is_mixed) {
         if (wxGetApp().preset_bundle->is_the_only_edited_filament(filament_id) || (filament_id == 0)) {
             wxGetApp().get_tab(Preset::TYPE_FILAMENT)->select_preset(wxGetApp().preset_bundle->filament_presets[0], false, "", true);
         }
@@ -5378,6 +5385,7 @@ void Sidebar::delete_filament(size_t filament_id, int replace_filament_id) {
         if (p->editing_filament == filament_id || p->editing_filament >= filament_count) {
             p->editing_filament = -1;
         }
+    }
 
     // update_num_filaments() shrinks filament_is_mixed along with the other per-filament arrays,
     // so snapshot it first — the paint cleanup below needs to know which slots were mixed
@@ -5387,8 +5395,12 @@ void Sidebar::delete_filament(size_t filament_id, int replace_filament_id) {
         is_mixed_snapshot = opt->values;
 
     wxGetApp().preset_bundle->update_num_filaments(filament_id);
-    wxGetApp().plater()->get_partplate_list().on_filament_deleted(filament_count, filament_id);
+
-    wxGetApp().plater()->on_filaments_delete(filament_count, filament_id, replace_filament_id > (int)filament_id ? (replace_filament_id - 1) : replace_filament_id, is_mixed_snapshot);
+    // filament_count only counts physical combos, so with mixed slots present it is not the
+    // new number of slots; recompute from the shrunk preset list for the downstream updates.
+    size_t total_after_delete = wxGetApp().preset_bundle->filament_presets.size();
+    wxGetApp().plater()->get_partplate_list().on_filament_deleted(total_after_delete, filament_id);
+    wxGetApp().plater()->on_filaments_delete(total_after_delete, filament_id, replace_filament_id > (int)filament_id ? (replace_filament_id - 1) : replace_filament_id, is_mixed_snapshot);
     wxGetApp().get_tab(Preset::TYPE_PRINT)->update();
     wxGetApp().preset_bundle->export_selections(*wxGetApp().app_config);
 
@@ -19495,8 +19507,10 @@ void Plater::on_filaments_delete(size_t num_filaments, size_t filament_id, int r
         }
     }
 
-    // update UI
+    // update object/volume/support(object and volume) filament id
-    sidebar().on_filaments_delete(filament_id);
+    // Must run before UI update which triggers update_mixed_filament_list() →
+    // update_objects_list_filament_column() that clips extruders above total count.
+    sidebar().obj_list()->update_objects_list_filament_column_when_delete_filament(filament_id, num_filaments, replace_filament_id);
 
     // update global support filament
     static const char *keys[] = {"support_filament", "support_interface_filament"};
@@ -19510,8 +19524,8 @@ void Plater::on_filaments_delete(size_t num_filaments, size_t filament_id, int r
             }
         }
 
-    // update object/volume/support(object and volume) filament id
+    // update UI — runs after remap so update_mixed_filament_list() won't clip remapped extruder IDs
-    sidebar().obj_list()->update_objects_list_filament_column_when_delete_filament(filament_id, num_filaments, replace_filament_id);
+    sidebar().on_filaments_delete(filament_id);
 
     // update customize gcode
     for (auto item = p->model.plates_custom_gcodes.begin(); item != p->model.plates_custom_gcodes.end(); ++item) {