Defer Plugin Dock Panes Until the Plater Is Shown

A plugin enabled at startup loads before the main frame exists, so a
dock panel it opens from on_load was dropped by the one-shot CallAfter
that found no plater. Opened a moment later, before the frame was laid
out, the pane was sized against the unsized frame and track_docked_size
kept that width. Poll until the plater is shown on screen, then build
the pane; release the reserved id instead when the app is closing.

.claude/skills/orca-profiles/references/extruder-variants.md

@@ -105,11 +105,12 @@ Rules:
    `single_extruder_multi_material` off, and in the app when the printer tab loads a printer with a
    different number of extruders, the pair is rebuilt from `extruder_variant_list` (one
    `Direct Drive Standard` per extruder when the list is absent) and the variant arrays are resized to
-   the rebuilt pair, padded with their first value or cut. The resize skips the `machine_max_*` limits
+   the rebuilt pair, padded with their first value or cut. The `machine_max_*` limits are padded the
-   and `hotend_heating_rate` / `hotend_cooling_rate`: they keep their width, and an extruder beyond it
+   same way, so extruder 2 and up of a list-less printer take extruder 1's normal limit as their
-   reads their first value, so extruder 2 and up of a list-less printer take extruder 1's normal limit
+   silent one too. The resize skips `hotend_heating_rate` / `hotend_cooling_rate`: they keep their
-   as their silent one too. With the three in agreement that changes nothing; a pair written without
+   width, and an extruder beyond it reads their first value. With the three in agreement that changes
-   the list is replaced. A listed variant the pair lacks is a menu choice that reads variant index 0.
+   nothing; a pair written without the list is replaced. A listed variant the pair lacks is a menu
+   choice that reads variant index 0.
    - The pair without `extruder_variant_list` slices, but the sidebar offers no variant switch and
      the app cannot add variants to a list-less process: nothing is lost while every extruder
      has exactly one variant, and every further variant is unreachable.

scripts/appimage_lib_policy.sh

@@ -23,7 +23,13 @@ appimage_is_host_library() {
 }
 
 appimage_is_elf_file() {
-    file -b "$1" 2>/dev/null | grep -q '^ELF '
+    # Read the four-byte ELF magic rather than asking file(1): this runs once per candidate, and an
+    # AppDir holds thousands of them (the bundled Python runtime alone is ~5k files, none of them
+    # ELF). Two processes per call made this ~14 s of a ~95 s image build on its own.
+    local magic
+    [[ -f "$1" && -r "$1" ]] || return 1
+    IFS= read -r -n 4 -d '' magic < "$1" 2>/dev/null
+    [[ $magic == $'\177ELF' ]]
 }
 
 appimage_list_direct_dependencies() {

src/dev-utils/platform/unix/build_linux_image.sh.in

@@ -118,9 +118,13 @@ bundle_dependency_closure() {
     # (scripts/check_appimage_libs.sh).
     local -a search_dirs=("$dst_dir")
 
-    while [ ${#queue[@]} -gt 0 ]; do
+    # Walked with a read index rather than by reslicing the array: "${queue[@]:1}" rebuilds the whole
-        target="${queue[0]}"
+    # queue on every pop, so draining it costs O(n^2). At the ~5k entries this bundle reaches that was
-        queue=("${queue[@]:1}")
+    # ~22 s of the image build spent copying an array around.
+    local head=0
+    while [ "$head" -lt ${#queue[@]} ]; do
+        target="${queue[$head]}"
+        head=$((head + 1))
 
         if [ ! -e "$target" ] || ! appimage_is_elf_file "$target"; then
             continue

src/libslic3r/PrintConfig.cpp

@@ -10030,6 +10030,13 @@ static void extend_extruder_variant(DynamicPrintConfig& config, const unsigned i
             printer_extruder_variant_opt->values.insert(printer_extruder_variant_opt->values.end(), variants_list.begin(), variants_list.end());
         }
     }
+
+    // 3. Size the machine limits to the rebuilt variants, padded with their first value like the other variant keys.
+    // They are not extruder option keys, so the resize loop in set_num_extruders skips them.
+    const auto &defaults = FullPrintConfig::defaults();
+    for (const std::string &key : printer_options_with_variant_2)
+        if (auto *opt = config.option<ConfigOptionFloats>(key))
+            opt->resize(config.get_parameter_size(key, num_extruders), defaults.option(key));
 }
 
 void DynamicPrintConfig::set_num_extruders(unsigned int num_extruders)

src/slic3r/GUI/PublishSettingsDialog.cpp

@@ -14,6 +14,7 @@
 #include "Widgets/DialogButtons.hpp"
 #include "Widgets/StaticLine.hpp"
 #include "Widgets/StateColor.hpp"
+#include "Widgets/SwitchButton.hpp"
 
 #include "libslic3r/PrintConfig.hpp"
 #include "libslic3r/Preset.hpp"
@@ -864,34 +865,25 @@ void PublishSettingsDialog::build_option_model()
     };
 
     // --- Phase 1: printer per-extruder retraction settings (first, mirroring the sidebar's
-    // Printer group), from the printer tab's "Extruder"/"Extruder N" pages. One inner tab per
+    // Printer group), from the printer tab's "Extruder" page. One inner tab per extruder (named
-    // extruder (e.g. "Left Extruder"/"Right Extruder" via Tab::translate_category), each holding
+    // as on the printer tab's switch, e.g. "Left Extruder"/"Right Extruder" via
-    // that extruder's Retraction and Z-Hop rows with per-extruder "#N" values.
+    // Tab::translate_category), each holding that extruder's Retraction and Z-Hop rows with
+    // per-extruder "#N" values.
     {
         size_t g = section_group_for(Section::Printer);
         std::set<std::string> printer_added;
         for (Tab* tab : wxGetApp().tabs_list) {
-            if (tab->m_type != Preset::TYPE_PRINTER)
+            // The page's controls edit the extruder chosen on the printer tab's switch, so its
+            // option list is read once per extruder.
+            auto*       printer_tab = dynamic_cast<TabPrinter*>(tab);
+            const Page* page        = printer_tab ? printer_tab->extruder_page() : nullptr;
+            if (page == nullptr)
                 continue;
-            for (const PageShp& page : tab->m_pages) {
+            const size_t extruders_count = printer_tab->m_extruders_count;
-                if (!page->title().StartsWith("Extruder"))
+            for (size_t extruder_idx = 0; extruder_idx < extruders_count; ++extruder_idx) {
-                    continue;
+                const wxString page_title = Tab::translate_category(extruders_count > 1 ? wxString::Format("Extruder %d", int(extruder_idx + 1)) : wxString("Extruder"), tab->m_type);
-                // The extruder index of this page: its options are appended with the same
+                // Retraction and Z-Hop values are stored per variant column, not per extruder.
-                // "#N" opt_index (opt.second.second), so derive the tab's index from the first
+                const int variant_index = printer_tab->extruder_variant_index(int(extruder_idx));
-                // allowlisted option; skip the page when none is found (defensive).
-                int extruder_idx = -1;
-                for (const ConfigOptionsGroupShp& optgroup : page->m_optgroups) {
-                    if (optgroup->title != "Retraction" && optgroup->title != "Z-Hop")
-                        continue;
-                    for (const auto& opt : optgroup->opt_map())
-                        if (extruder_idx < 0)
-                            extruder_idx = opt.second.second;
-                    if (extruder_idx >= 0)
-                        break;
-                }
-                if (extruder_idx < 0)
-                    continue;
-                const wxString page_title = Tab::translate_category(page->title(), tab->m_type);
                 for (const ConfigOptionsGroupShp& optgroup : page->m_optgroups) {
                     // Allowlist on the untranslated optgroup title; the "Retraction when
                     // switching material" group is intentionally skipped.
@@ -899,17 +891,17 @@ void PublishSettingsDialog::build_option_model()
                         continue;
                     const wxString subcategory = _(optgroup->title);
                     for (const auto& opt : optgroup->opt_map()) {
-                        const std::string& opt_id   = opt.first;
                         const std::string& pure_key = opt.second.first;
                         // Rows are keyed by the full per-extruder "#N" opt_id so each extruder
                         // tab publishes its own value; GetPublishedKeys() emits the checked rows
                         // as-is.
+                        const std::string opt_id = pure_key + "#" + std::to_string(variant_index);
                         if (!printer_added.insert(opt_id).second)
                             continue;
                         wxString label, value, unit;
                         if (!option_text(opt_id, pure_key, label, value, unit))
                             continue;
-                        size_t cat_index = category_index_for(page_title, Section::Printer, g, size_t(extruder_idx));
+                        size_t cat_index = category_index_for(page_title, Section::Printer, g, extruder_idx);
                         size_t sub_index = subcategory_index_for(cat_index, subcategory, optgroup->icon);
                         add_row_ui(opt_id, label, value, unit, cat_index, sub_index);
                     }
@@ -1098,6 +1090,10 @@ void PublishSettingsDialog::build_option_model()
     for (SectionGroup& section : m_sections)
         if (!section.categories.empty())
             section.tabs->SelectItem(0);
+    // Orca: the Printer section shows its extruders on the same switch as the printer tab's Extruder page.
+    for (size_t s = 0; s < m_sections.size(); ++s)
+        if (m_sections[s].kind == Section::Printer && m_sections[s].categories.size() > 1)
+            setup_variant_switch(s);
     if (!m_sections.empty()) {
         m_outer_tabs->SelectItem(0);
         show_outer_page(0);
@@ -1630,6 +1626,8 @@ void PublishSettingsDialog::show_inner_page(size_t section_index, int inner_inde
         section.selected_mixed = -1;
     }
     section.selected_inner = inner_index;
+    if (section.variant_switch != nullptr)
+        section.variant_switch->SetSelection(inner_index); // fires its event, which ignores the shown page
     Category& category     = m_categories[section.categories[inner_index]];
     category.page->Show();
     category.scroll->FitInside();
@@ -1639,6 +1637,32 @@ void PublishSettingsDialog::show_inner_page(size_t section_index, int inner_inde
     section.page_host_sizer->Layout();
 }
 
+void PublishSettingsDialog::setup_variant_switch(size_t section_index)
+{
+    SectionGroup& section = m_sections[section_index];
+    std::vector<wxString> titles;
+    for (size_t category : section.categories)
+        titles.push_back(m_categories[category].title);
+
+    section.variant_switch = new MultiSwitchButton(section.page);
+    section.variant_switch->SetFitToOptions();
+    section.variant_switch->SetOptions(titles);
+    section.variant_switch->SetSelection(section.selected_inner);
+    section.variant_switch->Bind(wxCUSTOMEVT_MULTISWITCH_SELECTION, [this, section_index](wxCommandEvent& evt) {
+        evt.Skip();
+        // The hidden tab strip stays the selection model; its event shows the page.
+        SectionGroup& sec = m_sections[section_index];
+        if (evt.GetInt() != sec.selected_inner)
+            sec.tabs->SelectItem(evt.GetInt());
+    });
+
+    // The switch takes the place of the tab strip, centered like on the printer tab.
+    wxSizer* page_sizer = section.page->GetSizer();
+    page_sizer->Insert(1, section.variant_switch, 0, wxALIGN_CENTER_HORIZONTAL | wxTOP, FromDIP(4));
+    section.tabs->Hide();
+    section.page->Layout();
+}
+
 void PublishSettingsDialog::show_mixed_page(size_t section_index, int mixed_index)
 {
     if (section_index >= m_sections.size())
@@ -2184,6 +2208,13 @@ void PublishSettingsDialog::refresh_tab_indicators()
         for (size_t i = 0; i < section.categories.size(); ++i) {
             const bool on = category_has_selection(m_categories[section.categories[i]]);
             section.tabs->SetItemIndicator(static_cast<unsigned int>(i), on);
+            // The switch has no indicator dot; mark its option text instead.
+            if (section.variant_switch != nullptr) {
+                const wxString& title = m_categories[section.categories[i]].title;
+                const wxString  text  = on ? title + wxString(" ") + wxString(wxUniChar(0x2022)) : title;
+                if (section.variant_switch->GetOptionText(static_cast<unsigned int>(i)) != text)
+                    section.variant_switch->SetOptionText(static_cast<unsigned int>(i), text);
+            }
             any = any || on;
         }
         if (section.mixed_tabs != nullptr)
@@ -2248,6 +2279,8 @@ void PublishSettingsDialog::on_dpi_changed(const wxRect& suggested_rect)
         section.tabs->Rescale();
         if (section.mixed_tabs != nullptr)
             section.mixed_tabs->Rescale();
+        if (section.variant_switch != nullptr)
+            section.variant_switch->Rescale();
     }
 
     // Refresh the per-row Color chips at the new DPI (they carry the slot number too).

src/slic3r/GUI/PublishSettingsDialog.hpp

@@ -37,6 +37,7 @@ namespace Slic3r { class DynamicPrintConfig; }
 class TextInput;
 class StaticLine;
 class CheckBox;
+class MultiSwitchButton;
 
 namespace Slic3r { namespace GUI {
 
@@ -195,6 +196,10 @@ private:
         ScalableBitmap icon_bmp;      // tab icon next to the title; rescaled on DPI change
         wxPanel* page{nullptr};
         TabCtrl* tabs{nullptr};
+        // Printer section with several extruders: the extruder switch shown instead of `tabs`, the
+        // same MultiSwitchButton (and option names) as the printer tab's Extruder page. One option
+        // per entry of `categories`, named by its title; `tabs` stays as the hidden selection model.
+        MultiSwitchButton* variant_switch{nullptr};
         // Second tab strip, below the main one, listing only the mixed-color filament slots.
         // Present on the Material section only (null elsewhere).
         TabCtrl* mixed_tabs{nullptr};
@@ -277,6 +282,8 @@ private:
     bool row_is_visible(const Row& row) const;
     void apply_visibility();
     void bind_tab_events();
+    // Replaces a section's inner tab strip with a variant switch (see SectionGroup::variant_switch).
+    void setup_variant_switch(size_t section_index);
 
     TabCtrl* m_outer_tabs{nullptr};
     wxPanel* m_outer_host{nullptr};

src/slic3r/GUI/Tab.cpp

@@ -811,6 +811,12 @@ wxString Tab::translate_category(const wxString& title, Preset::Type preset_type
         }
         return _("Extruder") + title.SubString(8, title.Last());
     }
+    // Orca: one "Extruder" page serves all extruders; name it "Extruders" when there are several.
+    if (preset_type == Preset::TYPE_PRINTER && title == "Extruder") {
+        auto preset = wxGetApp().preset_bundle;
+        if (preset && preset->get_printer_extruder_count() > 1)
+            return _("Extruders");
+    }
     return _(title);
 }
 
@@ -1153,6 +1159,38 @@ std::string Tab::options_list_storage_key(const std::string& opt_key) const
     return (serialized || is_plugin_field) ? opt_key : opt_key + "#0";
 }
 
+// Orca: deep_diff() flags every vector entry at or past the reference vector's length as changed,
+// whatever its value (e.g. the values of an extruder added by raising the extruder count). A vector
+// grows by copying its first entry (ConfigOptionVector::resize), so such an entry only counts as
+// changed when it differs from the reference's first entry, as before Orca's deep_diff() change.
+// The change of the count itself shows on "extruders_count".
+static void drop_unchanged_added_entries(std::vector<std::string> &options, const DynamicPrintConfig &current, const Preset *reference)
+{
+    if (reference == nullptr)
+        return;
+    // deep_diff() lists a key's entries one after another, so serialize each key's vectors once.
+    std::string              serialized_key;
+    std::vector<std::string> cur_values;
+    std::string              ref_first;
+    options.erase(std::remove_if(options.begin(), options.end(), [&](const std::string &opt) {
+        const auto pos = opt.find('#');
+        if (pos == std::string::npos)
+            return false;
+        const std::string key = opt.substr(0, pos);
+        const size_t      idx = size_t(std::atoi(opt.c_str() + pos + 1));
+        auto ref = dynamic_cast<const ConfigOptionVectorBase *>(reference->config.option(key));
+        auto cur = dynamic_cast<const ConfigOptionVectorBase *>(current.option(key));
+        if (ref == nullptr || cur == nullptr || idx < ref->size() || ref->size() == 0 || idx >= cur->size())
+            return false;
+        if (key != serialized_key) {
+            serialized_key = key;
+            cur_values     = cur->vserialize();
+            ref_first      = ref->vserialize().front();
+        }
+        return cur_values[idx] == ref_first;
+    }), options.end());
+}
+
 void Tab::update_all_extruder_options_status()
 {
     if (!m_extruder_switch && !m_variant_combo) {
@@ -1183,6 +1221,8 @@ void Tab::update_all_extruder_options_status()
 
     auto dirty_options = m_presets->current_dirty_options(true);
     auto nonsys_options = m_presets->current_different_from_parent_options(true);
+    if (m_type == Preset::TYPE_PRINTER)
+        update_custom_dirty(dirty_options, nonsys_options);
     auto filter_extruder_options = [](const std::vector<std::string>& options) {
         std::vector<std::string> filtered_options;
         for (const auto& opt : options) {
@@ -1231,7 +1271,7 @@ void Tab::update_extruder_switch_colors()
 
         if (m_active_page) {
             if (m_active_page->title() == "Speed" || m_active_page->title() == "Motion ability" || m_active_page->title() == "Filament" ||
-                m_active_page->title() == "Setting Overrides" || m_active_page->title() == "Multimaterial") {
+                m_active_page->title() == "Setting Overrides" || m_active_page->title() == "Multimaterial" || is_printer_extruder_page(m_active_page)) {
                 for (auto page_ptr : m_pages) {
                     if (page_ptr.get() == m_active_page) {
                         pages_to_check.push_back(page_ptr);
@@ -1262,8 +1302,8 @@ void Tab::update_extruder_switch_colors()
 void Tab::check_extruder_options_status(int index, bool &sys_extruder, bool &modified_extruder, const std::vector<PageShp>& pages_to_check)
 {
     int config_index = index;
+    int extruder_id  = index;
     if (m_type == Preset::TYPE_PRINT || m_type == Preset::TYPE_PRINTER || m_type == Preset::TYPE_MODEL) {
-        int extruder_id;
         NozzleVolumeType nozzle_type;
         parse_extruder_selection(index, extruder_id, nozzle_type);
 
@@ -1296,6 +1336,10 @@ void Tab::check_extruder_options_status(int index, bool &sys_extruder, bool &mod
                 }
 
                 std::string target_opt_key = base_opt_key + "#" + std::to_string(config_index * stride);
+                // Orca: on the printer's Extruder page only per-variant options use the variant column,
+                // the others (nozzle_diameter, extruder_offset, ...) are indexed by the extruder.
+                if (is_printer_extruder_page(page.get()) && printer_options_with_variant_1.count(base_opt_key) == 0)
+                    target_opt_key = base_opt_key + "#" + std::to_string(extruder_id);
 
                 auto status_iter = m_all_extruder_options_status.find(target_opt_key);
                 if (status_iter != m_all_extruder_options_status.end()) {
@@ -1336,18 +1380,6 @@ void TabPrinter::init_options_list()
     Tab::init_options_list();
     if (m_printer_technology == ptFFF)
         m_options_list.emplace("extruders_count", m_opt_status_value);
-    for (size_t i = 1; i < m_extruders_count; ++i) {
-        wxString target_title = wxString::Format("Extruder %d", int(i + 1));
-        for (auto &page : m_pages) {
-            if (page->title() == target_title) {
-                for (auto group : page->m_optgroups) {
-                    for (auto &opt : group->opt_map())
-                        m_options_list.emplace(opt.first, m_opt_status_value);
-                }
-                break;
-            }
-        }
-    }
 }
 
 void TabPrinter::msw_rescale()
@@ -1437,7 +1469,7 @@ void Tab::update_changed_tree_ui()
                     get_sys_and_mod_flags("compatible_printers", sys_page, modified_page);
                 }
             }
-            if (page->title() == "Speed" || page->title() == "Motion ability" || page->title() == "Filament" || page->title() == "Setting Overrides" || page->title() == "Multimaterial") {
+            if (page->title() == "Speed" || page->title() == "Motion ability" || page->title() == "Filament" || page->title() == "Setting Overrides" || page->title() == "Multimaterial" || is_printer_extruder_page(page.get())) {
                 auto options = generate_extruder_options();
                 for (size_t switch_index = 0; switch_index < options.size(); ++switch_index) {
                     std::vector<PageShp> pages_to_check = { page };
@@ -1540,6 +1572,10 @@ void Tab::on_roll_back_value(const bool to_sys /*= true*/)
 
     m_postpone_update_ui = false;
 
+    // Orca: the restored config may have another extruder count than the tab shows.
+    if (auto printer_tab = dynamic_cast<TabPrinter *>(this))
+        printer_tab->sync_extruders_count();
+
     // When all values are rolled, then we have to update whole tab in respect to the reverted values
     update();
     if (m_active_page)
@@ -1877,6 +1913,17 @@ static wxString pad_combo_value_for_config(const DynamicPrintConfig &config)
     return config.opt_bool("pad_enable") ? (config.opt_bool("pad_around_object") ? _("Around object") : _("Below object")) : _("None");
 }
 
+// Rebuilds the variant switch of every tab that has one, e.g. after the extruder count or a nozzle volume type changed.
+static void update_all_extruder_variants(int extruder_idx = -1)
+{
+    for (auto tab : wxGetApp().tabs_list)
+        tab->update_extruder_variants(extruder_idx);
+    if (auto tab = wxGetApp().plate_tab)
+        tab->update_extruder_variants(extruder_idx);
+    for (auto tab : wxGetApp().model_tabs_list)
+        tab->update_extruder_variants(extruder_idx);
+}
+
 void Tab::on_value_change(const std::string& opt_key, const boost::any& value)
 {
     // Orca:
@@ -2319,15 +2366,7 @@ void Tab::on_value_change(const std::string& opt_key, const boost::any& value)
 
     if (opt_key.find("nozzle_volume_type") != std::string::npos) {
         int extruder_idx = std::atoi(opt_key.substr(opt_key.find_last_of('#') + 1).c_str());
-        for (auto tab : wxGetApp().tabs_list) {
+        update_all_extruder_variants(extruder_idx);
-            tab->update_extruder_variants(extruder_idx);
-        }
-        if (auto tab = wxGetApp().plate_tab) {
-            tab->update_extruder_variants(extruder_idx);
-        }
-        for (auto tab : wxGetApp().model_tabs_list) {
-            tab->update_extruder_variants(extruder_idx);
-        }
         if (wxGetApp().app_config->get("auto_calculate_flush") == "all") {
             wxGetApp().plater()->sidebar().auto_calc_flushing_volumes(-1,extruder_idx);
         }
@@ -5685,9 +5724,13 @@ if (is_marlin_flavor)
             size_t extruders_count = size_t(boost::any_cast<int>(v));
             wxTheApp->CallAfter([this, opt_key, value, extruders_count]() {
                 if (opt_key == "extruders_count" || opt_key == "single_extruder_multi_material") {
+                    const size_t old_extruders_count = m_extruders_count;
                     extruders_count_changed(extruders_count);
                     init_options_list(); // m_options_list should be updated before UI updating
                     update_dirty();
+                    // Orca: the variant switches (here, Process in the sidebar, ...) list one option per extruder.
+                    if (m_extruders_count != old_extruders_count)
+                        update_all_extruder_variants();
                     if (opt_key == "single_extruder_multi_material") { // the single_extruder_multimaterial was added to force pages
                         on_value_change(opt_key, value);                      // rebuild - let's make sure the on_value_change is not skipped
 
@@ -5697,6 +5740,7 @@ if (is_marlin_flavor)
 // Orca: we use a different logic here. If SEMM is enabled, we set extruder count to 1.
 #if 1
                             extruders_count_changed(1);
+                            update_all_extruder_variants();
 #else
 
                             std::vector<double> nozzle_diameters =
@@ -5768,14 +5812,13 @@ if (is_marlin_flavor)
         m_pages.insert(m_pages.end() - n_after_single_extruder_MM, page);
     }
 
-    // Orca: build missed extruder pages
+    // Orca: a single "Extruder" page serves all extruders. Its controls are created once for extruder 0;
-    for (auto extruder_idx = m_extruders_count_old; extruder_idx < m_extruders_count; ++extruder_idx) {
+    // switch_excluder() re-targets them to the extruder selected on the variant switch (m_extruder_switch),
-        const wxString& page_name = (m_extruders_count > 1) ? wxString::Format("Extruder %d", int(extruder_idx + 1)) : wxString::Format("Extruder");
+    // which the printer tab shows on this page too.
-
+    if (extruder_page() == nullptr && m_extruders_count > 0) {
-        //# build page
+        const size_t extruder_idx = 0;
-        //const wxString& page_name = wxString::Format("Extruder %d", int(extruder_idx + 1));
+        auto page = add_options_page(L("Extruder"), "custom-gcode_extruder", true); // ORCA: icon only visible on placeholders
-        auto page = add_options_page(page_name, "custom-gcode_extruder", true); // ORCA: icon only visible on placeholders
+        m_pages.insert(m_pages.begin() + n_before_extruders, page);
-        m_pages.insert(m_pages.begin() + n_before_extruders + extruder_idx, page);
 
         auto optgroup = page->new_optgroup(L("Basic information"), L"param_information", -1, true);
             optgroup->append_single_option_line("nozzle_diameter", "printer_extruder_basic_information#nozzle-diameter", extruder_idx);
@@ -5788,8 +5831,10 @@ if (is_marlin_flavor)
             option.opt.full_width = true;
             optgroup->append_single_option_line(option, "printer_extruder_basic_information#extruder-offset-position");
 
-            optgroup->m_on_change = [this, extruder_idx](const t_config_option_key& opt_key, boost::any value)
+            optgroup->m_on_change = [this](const t_config_option_key& opt_key, boost::any value)
             {
+                // The page edits the extruder selected on the variant switch.
+                const size_t extruder_idx = size_t(get_current_active_extruder());
                 bool is_SEMM = m_config->opt_bool("single_extruder_multi_material");
                 if (is_SEMM && m_extruders_count > 1 && boost::starts_with(opt_key, "nozzle_diameter"))
                 {
@@ -5884,22 +5929,22 @@ if (is_marlin_flavor)
             //optgroup->append_line(line);
 #endif
     }
-    // BBS. No extra extruder page for single physical extruder machine
+
-    // # remove extra pages
+    // The page holds only the "#0" controls, so register every extruder's options with the search
-    auto &first_extruder_title = const_cast<wxString &>(m_pages[n_before_extruders]->title());
+    // index under "Extruder N"; a search hit selects that extruder (TabPrinter::activate_option()).
-    if (m_extruders_count < m_extruders_count_old) {
+    if (Page *page = extruder_page()) {
-        m_pages.erase(	m_pages.begin() + n_before_extruders + m_extruders_count,
+        auto &index = wxGetApp().sidebar().settings_index();
-                        m_pages.begin() + n_before_extruders + m_extruders_count_old);
+        for (auto &group : page->m_optgroups) {
-        if (m_extruders_count == 1)
+            group->set_config_category_and_type(page->title(), m_type);
-            first_extruder_title = wxString::Format("Extruder");
+            for (auto &opt : group->opt_map()) {
-    } else if (m_extruders_count_old == 1) {
+                if (opt.second.second < 0)
-        first_extruder_title = wxString::Format("Extruder %d", 1);
+                    continue;
-    }
+                for (size_t i = 0; i < m_extruders_count; ++i) {
-    auto & index = wxGetApp().sidebar().settings_index();
+                    const wxString category = m_extruders_count > 1 ? wxString::Format("Extruder %d", int(i + 1)) : wxString("Extruder");
-    for (auto &group : m_pages[n_before_extruders]->m_optgroups) {
+                    index.add_key(opt.second.first + "#" + std::to_string(i), m_type, group->title, category, group->icon);
-        group->set_config_category_and_type(first_extruder_title, m_type);
+                }
-        for (auto &opt : group->opt_map())
+            }
-            index.add_key(opt.first + "#0", m_type, group->title, first_extruder_title, group->icon);
+        }
     }
 
     Thaw();
@@ -6180,12 +6225,6 @@ void TabPrinter::toggle_options()
         return;
 
     auto nozzle_volumes = m_preset_bundle->project_config.option<ConfigOptionEnumsGeneric>("nozzle_volume_type");
-    auto extruders      = m_config->option<ConfigOptionEnumsGeneric>("extruder_type");
-        auto get_index_for_extruder =
-            [this, &extruders](int extruder_id, int stride = 1) {
-        return m_config->get_index_for_extruder(extruder_id + 1, "printer_extruder_id",
-            ExtruderType(extruders->values[extruder_id]), get_actual_nozzle_volume_type(extruder_id), "printer_extruder_variant", stride);
-    };
 
     //BBS: whether the preset is Bambu Lab printer
     bool is_BBL_printer = false;
@@ -6260,14 +6299,13 @@ void TabPrinter::toggle_options()
         toggle_option("tool_change_on_wipe_tower", !bSEMM && supports_wipe_tower_2 && extruders_count > 1);
         toggle_option("wait_for_temp_on_wipe_tower", !bSEMM && supports_wipe_tower_2 && extruders_count > 1);
     }
-    wxString extruder_number;
+    if (m_active_page->title() == L("Extruder") && m_extruders_count > 0)
-    long val = 1;
-    if ( m_active_page->title().IsSameAs(L("Extruder")) ||
-        (m_active_page->title().StartsWith("Extruder ", &extruder_number) && extruder_number.ToLong(&val) &&
-        val > 0 && (size_t)val <= m_extruders_count))
     {
-        size_t i = size_t(val - 1);
+        // Orca: the single Extruder page edits the extruder selected on the variant switch; its
-        int variant_index = get_index_for_extruder(i);
+        // controls carry field index 0 (i), the values are read for `extruder`.
+        const size_t i        = 0;
+        const size_t extruder = std::min<size_t>(size_t(get_current_active_extruder()), m_extruders_count - 1);
+        const int    variant_index = extruder_variant_index(int(extruder));
         bool have_retract_length = m_config->opt_float("retraction_length", variant_index) > 0;
 
         toggle_option("extruder_printable_area", false, i);          // disable
@@ -6294,7 +6332,7 @@ void TabPrinter::toggle_options()
         vec.resize(0);
         vec = {"retract_lift_above", "retract_lift_below", "retract_lift_enforce"};
         for (auto el : vec)
-          toggle_option(el, retraction && (m_config->opt_float("z_hop", i) > 0), i);
+          toggle_option(el, retraction && (m_config->opt_float("z_hop", variant_index) > 0), i);
 
         // some options only apply when not using firmware retraction
         vec.resize(0);
@@ -6347,7 +6385,7 @@ void TabPrinter::toggle_options()
         toggle_option("long_retractions_when_cut", !use_firmware_retraction && m_config->opt_int("enable_long_retraction_when_cut"), i);
         toggle_line("retraction_distances_when_cut", m_config->opt_bool("long_retractions_when_cut", variant_index), i);
 
-        toggle_option("travel_slope", m_config->opt_enum("z_hop_types", i) != ZHopType::zhtNormal, i);
+        toggle_option("travel_slope", m_config->opt_enum("z_hop_types", variant_index) != ZHopType::zhtNormal, i);
     }
 
     if (m_active_page->title() == L("Motion ability")) {
@@ -6421,12 +6459,16 @@ void TabPrinter::on_value_change(const std::string& opt_key, const boost::any& v
         return;
 
     const int pos = opt_key.find("#");
+    // Orca: fields of the single Extruder page keep index 0 but edit the selected extruder.
+    const int data_idx = pos > 0 ? extruder_page_data_index(opt_key) : -1;
 
     if (pos > 0) {
         std::string temp_str = opt_key;
         boost::erase_head(temp_str, pos + 1);
         int orig_opt_idx = static_cast<size_t>(atoi(temp_str.c_str()));
         int opt_idx = orig_opt_idx >= 0 ? orig_opt_idx : 0;
+        if (data_idx >= 0)
+            opt_idx = data_idx;
 
         std::string opt_key_pure = opt_key;
         boost::erase_tail(opt_key_pure, opt_key_pure.size() - pos);
@@ -6461,7 +6503,12 @@ void TabPrinter::on_value_change(const std::string& opt_key, const boost::any& v
         }
     }
 
-    Tab::on_value_change(opt_key, value);
+    // Orca: report Extruder page changes as "key#<extruder>", as the former "Extruder N" pages did,
+    // so per-extruder handling in Tab::on_value_change() sees the extruder that was edited.
+    if (data_idx >= 0)
+        Tab::on_value_change(opt_key.substr(0, pos) + "#" + std::to_string(get_current_active_extruder()), value);
+    else
+        Tab::on_value_change(opt_key, value);
 }
 
 void TabPrinter::update()
@@ -7393,12 +7440,7 @@ bool Tab::tree_sel_change_delayed(wxCommandEvent& event)
         // update_undo_buttons();
         this->OnActivate();
         m_parent->set_active_tab(this);
-        if (m_variant_sizer) {
+        update_variant_sizer_visibility();
-            wxWindow *variant_ctrl = m_extruder_switch ? (wxWindow *) m_extruder_switch : m_variant_combo;
-            m_main_sizer->Show(m_variant_sizer, variant_ctrl->IsThisEnabled() && !m_active_page->m_opt_id_map.empty() && !m_active_page->title().StartsWith("Extruder "));
-            if (m_extruder_sync) m_extruder_sync->Show(variant_ctrl->IsShown());
-            GetParent()->Layout();
-        }
 
         m_page_view->Thaw();
         return false;
@@ -7409,12 +7451,7 @@ bool Tab::tree_sel_change_delayed(wxCommandEvent& event)
         return false;
 
     m_active_page = page;
-    if (m_variant_sizer) {
+    update_variant_sizer_visibility();
-        wxWindow *variant_ctrl = m_extruder_switch ? (wxWindow *) m_extruder_switch : m_variant_combo;
-        m_main_sizer->Show(m_variant_sizer, variant_ctrl->IsThisEnabled() && !m_active_page->m_opt_id_map.empty() && !m_active_page->title().StartsWith("Extruder"));
-        if (m_extruder_sync) m_extruder_sync->Show(variant_ctrl->IsShown());
-        GetParent()->Layout();
-    }
 
     auto throw_if_canceled = std::function<void()>([this](){
 #ifdef WIN32
@@ -8240,9 +8277,11 @@ void Tab::update_extruder_variants(int extruder_id, bool reload)
         m_actual_nozzle_volumes.resize(extruder_nums, NozzleVolumeType::nvtStandard);
         for (int i = 0; i < extruder_nums; i++) m_actual_nozzle_volumes[i] = (NozzleVolumeType)nozzle_volumes->values[i];
 
-        // Orca: a non-Bambu dual-nozzle printer has two extruders but a single variant column, so
+        // Orca: when every extruder uses the same variant (e.g. a non-Bambu dual-nozzle printer), the
-        // the nozzle switch and sync button have nothing to act on. Only enable with real variants.
+        // switch has no nozzle variants to select and nothing to sync. The printer tab still enables it
-        if (extruder_nums >= 2 && m_preset_bundle->support_different_extruders()) {
+        // to choose the extruder its Extruder and Motion ability pages edit.
+        m_extruder_switch_variants = extruder_nums >= 2 && m_preset_bundle->support_different_extruders();
+        if (m_extruder_switch_variants || (m_type == Preset::TYPE_PRINTER && extruder_nums >= 2)) {
             auto options = generate_extruder_options();
             m_extruder_switch->SetOptions(options);
 
@@ -8281,12 +8320,8 @@ void Tab::update_extruder_variants(int extruder_id, bool reload)
     if (m_type == Preset::TYPE_PRINT) {
         update_pages_with_multi_variant();
     }
-    if (m_variant_sizer) {
+    update_extruder_switch_colors();
-        wxWindow *variant_ctrl = m_extruder_switch ? (wxWindow *) m_extruder_switch : m_variant_combo;
+    update_variant_sizer_visibility();
-        m_main_sizer->Show(m_variant_sizer, variant_ctrl->IsThisEnabled() && m_active_page && !m_active_page->m_opt_id_map.empty() && !m_active_page->title().StartsWith("Extruder "));
-        if (m_extruder_sync) m_extruder_sync->Show(variant_ctrl->IsShown());
-        GetParent()->Layout();
-    }
 }
 
 // The variant switch tags are the narrowest place a volume type is named, so they abbreviate it;
@@ -8361,12 +8396,21 @@ std::vector<wxString> Tab::generate_extruder_options()
         return options;
     }
 
+    // Orca: the printer tab has one tag per extruder, named as its former "Extruder N" pages were.
+    // parse_extruder_selection() counts a hybrid extruder as two tags; that still lines up because
+    // only the last extruder can be hybrid.
+    if (m_type == Preset::TYPE_PRINTER) {
+        for (int i = 0; i < extruder_nums; ++i)
+            options.push_back(translate_category(wxString::Format("Extruder %d", i + 1), m_type));
+        return options;
+    }
+
     std::string pt = m_preset_bundle->printers.get_edited_preset().get_printer_type(m_preset_bundle);
-    // Orca: the main/deputy toolhead names describe a dual-nozzle printer, where extruder 0 is the
+    // Orca: the main/deputy toolhead names describe a Bambu dual-nozzle printer, where extruder 0 is
-    // left (deputy) and extruder 1 the right (main) nozzle. From three extruders on the tools are
+    // the left (deputy) and extruder 1 the right (main) nozzle. Other printers number their tools.
-    // interchangeable, so name them by index instead of repeating one side.
+    const bool toolhead_names = extruder_nums == 2 && m_preset_bundle->is_bbl_vendor();
     for (int i = 0; i < extruder_nums; ++i) {
-        wxString extruder_name = extruder_nums > 2 ? wxString::Format("T%d", i + 1) :
+        wxString extruder_name = !toolhead_names ? wxString::Format("T%d", i + 1) :
                                                      _L(DevPrinterConfigUtil::get_toolhead_display_name(
                                                          pt, (i == 0) ? DEPUTY_EXTRUDER_ID : MAIN_EXTRUDER_ID,
                                                          ToolHeadComponent::Nozzle, ToolHeadNameCase::TitleCase, true));
@@ -8383,6 +8427,71 @@ std::vector<wxString> Tab::generate_extruder_options()
     return options;
 }
 
+Page *TabPrinter::extruder_page() const
+{
+    for (const PageShp &page : m_pages)
+        if (page->title() == "Extruder")
+            return page.get();
+    return nullptr;
+}
+
+int TabPrinter::extruder_page_data_index(const std::string &field_id) const
+{
+    if (Page *page = extruder_page())
+        for (const auto &group : page->m_optgroups)
+            if (auto it = group->opt_map().find(field_id); it != group->opt_map().end())
+                return it->second.second;
+    return -1;
+}
+
+int TabPrinter::extruder_variant_index(int extruder)
+{
+    const auto *extruders = m_config->option<ConfigOptionEnumsGeneric>("extruder_type");
+    const int   index     = extruder < int(extruders->size()) ?
+                                m_config->get_index_for_extruder(extruder + 1, "printer_extruder_id", ExtruderType(extruders->values[extruder]),
+                                                                 get_actual_nozzle_volume_type(extruder), "printer_extruder_variant") :
+                                -1;
+    return index < 0 ? extruder : index;
+}
+
+void TabPrinter::update_custom_dirty(std::vector<std::string> &dirty_options, std::vector<std::string> &nonsys_options)
+{
+    drop_unchanged_added_entries(dirty_options, *m_config, &m_presets->get_selected_preset());
+    drop_unchanged_added_entries(nonsys_options, *m_config, m_presets->get_selected_preset_parent());
+}
+
+void TabPrinter::sync_extruders_count()
+{
+    if (m_printer_technology != ptFFF)
+        return;
+    const auto *nozzle_diameter = m_config->option<ConfigOptionFloats>("nozzle_diameter");
+    if (nozzle_diameter == nullptr || nozzle_diameter->size() == m_extruders_count)
+        return;
+    extruders_count_changed(nozzle_diameter->size());
+    init_options_list();
+    update_all_extruder_variants();
+}
+
+void TabPrinter::activate_option(const std::string &opt_key, const wxString &category)
+{
+    wxString number;
+    long     n = 0;
+    const bool numbered = category.StartsWith("Extruder ", &number) && number.ToLong(&n);
+    if (extruder_page() == nullptr || (!numbered && category != "Extruder")) {
+        Tab::activate_option(opt_key, category);
+        return;
+    }
+
+    // Selecting fires the switch's event, which re-targets the page (switch_excluder()).
+    const int extruder_idx = (n >= 1 && n <= long(m_extruders_count)) ? int(n - 1) : 0;
+    if (m_extruder_switch && m_extruder_switch->IsThisEnabled() && extruder_idx != get_current_active_extruder())
+        m_extruder_switch->SetSelection(calculate_selection_index_for_extruder(extruder_idx, get_actual_nozzle_volume_type(extruder_idx)));
+
+    // The page's controls are created for index 0.
+    const auto pos = opt_key.find('#');
+    Tab::activate_option(pos == std::string::npos ? opt_key : opt_key.substr(0, pos) + "#0", "Extruder");
+}
+
 NozzleVolumeType Tab::get_actual_nozzle_volume_type(int extruder_id)
 {
     int extruder_count = m_preset_bundle->get_printer_extruder_count();
@@ -8459,18 +8568,44 @@ bool Tab::get_extruder_sync_enable_state(int extruder_id)
     return false;
 }
 
+bool Tab::variant_switch_active() const
+{
+    if (m_extruder_switch)
+        return m_extruder_switch->IsThisEnabled();
+    return m_variant_combo && m_variant_combo->IsThisEnabled();
+}
+
+void Tab::update_variant_sizer_visibility()
+{
+    if (!m_variant_sizer)
+        return;
+    const bool show = variant_switch_active() && m_active_page && !m_active_page->m_opt_id_map.empty();
+    m_main_sizer->Show(m_variant_sizer, show);
+    if (m_extruder_sync) {
+        m_extruder_sync->Show(show);
+        // Orca: copying between extruders is offered only between nozzle variants, and not on the Extruder page.
+        m_extruder_sync->Enable(m_extruder_switch_variants && !is_printer_extruder_page(m_active_page) &&
+                                get_extruder_sync_enable_state(get_current_active_extruder()));
+    }
+    GetParent()->Layout();
+}
+
 void Tab::switch_excluder(int extruder_id, bool reload)
 {
     Preset & printer_preset = m_preset_bundle->printers.get_edited_preset();
     auto nozzle_volumes = m_preset_bundle->project_config.option<ConfigOptionEnumsGeneric>("nozzle_volume_type");
     auto extruders      = printer_preset.config.option<ConfigOptionEnumsGeneric>("extruder_type");
 
+    // Orca: the printer tab re-targets its pages to the extruder selected on the switch. Resolved before
+    // the range check below, which keeps the extruder_type read in get_index_for_extruder in range.
+    if (m_type == Preset::TYPE_PRINTER && extruder_id == -1)
+        extruder_id = get_current_active_extruder();
     if (!m_variant_combo && (extruder_id >= (int)nozzle_volumes->size() || extruder_id >= (int)extruders->size()))
         extruder_id = 0;
     if (m_extruder_switch) {
         int current_extruder = get_current_active_extruder();
         bool sync_enable = get_extruder_sync_enable_state(current_extruder);
-        m_extruder_sync->Enable(m_extruder_switch->IsThisEnabled() && sync_enable);
+        m_extruder_sync->Enable(m_extruder_switch_variants && sync_enable && !is_printer_extruder_page(m_active_page));
         m_extruder_sync->Show();
         if (m_type != Preset::TYPE_PRINTER) {
             if (extruder_id == -1)
@@ -8497,24 +8632,26 @@ void Tab::switch_excluder(int extruder_id, bool reload)
         return;
     if (m_extruder_switch) m_extruder_switch->SetClientData(reinterpret_cast<void*>(static_cast<std::uintptr_t>(index)));
     if (m_variant_combo) m_variant_combo->SetClientData(reinterpret_cast<void *>(static_cast<std::uintptr_t>(index)));
-    wxWindow *variant_ctrl = m_extruder_switch ? (wxWindow *) m_extruder_switch : m_variant_combo;
     for (auto page : m_pages) {
         bool is_extruder = false;
+        int  page_index  = index;
         if (m_type == Preset::TYPE_PRINTER) {
-            if (page->title().StartsWith("Extruder")) {
+            if (page->title() == "Extruder")
-                int extruder_id2 = std::atoi(page->title().Mid(9).ToUTF8()) - 1;
-                if (extruder_id >= 0 && extruder_id2 != extruder_id)
-                    continue;
-                if (extruder_id2 > 0)
-                    index = get_index_for_extruder(extruder_id2);
                 is_extruder = true;
-            } else if (page->title().StartsWith("Motion ability")) {
+            else if (page->title().StartsWith("Motion ability"))
-                index = get_index_for_extruder(extruder_id == -1 ? 0 : extruder_id, 2);
+                page_index = get_index_for_extruder(extruder_id == -1 ? 0 : extruder_id, 2);
-            }
         }
         page->m_opt_id_map.clear();
         for (auto group : page->m_optgroups) {
             for (auto &opt : group->opt_map()) {
+                if (is_extruder && opt.second.second >= 0) {
+                    // Per-variant options use the variant column, the others (nozzle_diameter,
+                    // extruder_offset, ...) are sized by the extruder count and use the extruder.
+                    const int idx = printer_options_with_variant_1.count(opt.second.first) > 0 ? page_index : extruder_id;
+                    const_cast<int &>(opt.second.second) = idx;
+                    page->m_opt_id_map.insert({opt.second.first + "#" + std::to_string(idx), opt.first});
+                    continue;
+                }
                 auto iter = std::find(printer_extruder_options.begin(), printer_extruder_options.end(), opt.second.first);
                 if (iter != printer_extruder_options.end()) {
                     page->m_opt_id_map.insert({opt.first, opt.first});
@@ -8522,9 +8659,9 @@ void Tab::switch_excluder(int extruder_id, bool reload)
                 }
 
                 if (opt.second.second >= 0) {
-                    const_cast<int &>(opt.second.second) = index;
+                    const_cast<int &>(opt.second.second) = page_index;
-                    page->m_opt_id_map.insert({opt.second.first + "#" + std::to_string(index), opt.first});
+                    page->m_opt_id_map.insert({opt.second.first + "#" + std::to_string(page_index), opt.first});
-                    group->draw_multi_extruder = !is_extruder && variant_ctrl->IsThisEnabled();
+                    group->draw_multi_extruder = variant_switch_active();
                 }
             }
         }

src/slic3r/GUI/Tab.hpp

@@ -331,6 +331,10 @@ public:
     MultiSwitchButton *  m_variant_combo   = nullptr;
     ScalableButton *m_extruder_sync   = nullptr;
 	wxPanel *       m_extruder_sync_box  = nullptr;
+    // Orca: whether m_extruder_switch switches nozzle variants (it then offers sync between them).
+    // The printer tab also enables the switch for printers without variants, to choose the extruder
+    // its Extruder and Motion ability pages edit.
+    bool            m_extruder_switch_variants = false;
     std::vector<NozzleVolumeType> m_actual_nozzle_volumes;
 
 public:
@@ -387,6 +391,13 @@ public:
     void        update_changed_tree_ui();
 	void		update_undo_buttons();
     void        update_extruder_switch_colors();
+    // Whether the variant switch (m_extruder_switch / m_variant_combo) is enabled: on the printer tab for
+    // any multi-extruder printer, on the other tabs when it switches nozzle variants.
+    bool        variant_switch_active() const;
+    // Orca: whether `page` is the printer tab's single "Extruder" page, which edits the extruder selected on the switch.
+    bool        is_printer_extruder_page(const Page* page) const { return m_type == Preset::TYPE_PRINTER && page && page->title() == "Extruder"; }
+    // Shows the variant switch row on pages with options that follow it.
+    void        update_variant_sizer_visibility();
     void        update_all_extruder_options_status();
     void        check_extruder_options_status(int index, bool &sys_extruder, bool &modified_extruder, const std::vector<PageShp>& pages_to_check);
 
@@ -444,7 +455,7 @@ public:
 	virtual void    on_value_change(const std::string& opt_key, const boost::any& value);
 
     void            update_wiping_button_visibility();
-	void			activate_option(const std::string& opt_key, const wxString& category);
+	virtual void	activate_option(const std::string& opt_key, const wxString& category);
     void			apply_searcher();
 	void			cache_config_diff(const std::vector<std::string>& selected_options, const DynamicPrintConfig* config = nullptr);
 	void			apply_config_from_cache();
@@ -710,6 +721,25 @@ public:
 	void		cache_extruder_cnt(const DynamicPrintConfig* config = nullptr);
 	bool		apply_extruder_cnt_from_cache();
 	void		refresh_printer_agent_dropdown() const;
+
+	// Orca: a single "Extruder" page for all extruders. Its controls are created once (index 0) and
+	// switch_excluder() re-targets them to the extruder selected on m_extruder_switch.
+	Page*		extruder_page() const;
+	// Config index an "Extruder" page field (e.g. "retraction_length#0") currently edits, -1 if not on that page.
+	int			extruder_page_data_index(const std::string& field_id) const;
+	// Config index of an extruder's per-variant options (Retraction, Z-Hop, ...): its variant column
+	// for the nozzle selected on the switch, or the extruder index on a printer without variants.
+	int			extruder_variant_index(int extruder);
+	// After the config was restored (roll back): follow its extruder count, if it differs.
+	void		sync_extruders_count();
+	// Search jump to "Extruder N" / "key#N": selects extruder N on the switch, then activates the
+	// page's own field on the "Extruder" page.
+	void		activate_option(const std::string& opt_key, const wxString& category) override;
+
+protected:
+	// Orca: values of extruders added by raising the extruder count have no saved / system value to
+	// revert to; the change is shown on "extruders_count", not on each of their parameters.
+	void		update_custom_dirty(std::vector<std::string> &dirty_options, std::vector<std::string> &nonsys_options) override;
 };
 
 class TabSLAMaterial : public Tab

src/slic3r/plugin/host/PluginHostUi.cpp

@@ -28,6 +28,7 @@
 #include <wx/app.h>
 #include <wx/defs.h>
 #include <wx/thread.h>
+#include <wx/timer.h>
 #include <wx/toplevel.h>
 #include <wx/event.h>
 #include <wx/progdlg.h>
@@ -415,6 +416,44 @@ struct UiDockPanelHandle
     int id{0};
 };
 
+// Polls until the plater is shown on screen, then runs the callback with it (null when the app
+// is closing instead) and deletes itself. A plugin loaded at startup opens its panes from
+// on_load, before the main window exists, and a pane added before that window is laid out is
+// sized against the unsized frame and keeps that width (AuiMgr::track_docked_size).
+class PlaterShownWaiter : public wxTimer
+{
+public:
+    explicit PlaterShownWaiter(std::function<void(GUI::Plater*)> fn) : m_fn(std::move(fn)) {}
+
+    // True once the callback ran.
+    bool try_run()
+    {
+        const bool   closing = GUI::wxGetApp().is_closing();
+        GUI::Plater* plater  = closing ? nullptr : GUI::wxGetApp().plater();
+        if (!closing && (plater == nullptr || !plater->IsShownOnScreen()))
+            return false;
+        Stop();
+        m_fn(plater);
+        // Off the timer callback's stack: wxGTK's timeout callback still reads the timer after Notify().
+        GUI::wxGetApp().CallAfter([this]() { delete this; });
+        return true;
+    }
+
+    void Notify() override { try_run(); }
+
+private:
+    std::function<void(GUI::Plater*)> m_fn;
+};
+
+void run_when_plater_shown(std::function<void(GUI::Plater*)> fn)
+{
+    GUI::wxGetApp().CallAfter([fn = std::move(fn)]() mutable {
+        auto* waiter = new PlaterShownWaiter(std::move(fn));
+        if (!waiter->try_run())
+            waiter->Start(100);
+    });
+}
+
 py::object ui_create_dock_panel(const std::string& html, const std::string& title, int width, int height,
                                 py::object on_message, py::object on_close, const std::string& dock)
 {
@@ -434,14 +473,13 @@ py::object ui_create_dock_panel(const std::string& html, const std::string& titl
     const int new_id = UiRegistry::instance().reserve_id();
     UiRegistry::instance().bind(new_id, nullptr, plugin_key);
 
-    GUI::wxGetApp().CallAfter([new_id, plugin_key, html, title, dock, w, h,
+    run_when_plater_shown([new_id, plugin_key, html, title, dock, w, h,
-                               msg_adapter = std::move(msg_adapter),
+                           msg_adapter = std::move(msg_adapter),
-                               close_holder = std::move(close_holder)]() mutable {
+                           close_holder = std::move(close_holder)](GUI::Plater* plater) mutable {
         if (!UiRegistry::instance().is_open(new_id))
             return;
 
-        GUI::Plater* plater = GUI::wxGetApp().plater();
+        if (plater == nullptr) {
-        if (plater == nullptr || GUI::wxGetApp().is_closing()) {
             UiRegistry::instance().remove(new_id);
             return;
         }

tests/libslic3r/test_config_variant_expansion.cpp

@@ -800,6 +800,43 @@ TEST_CASE("A per-variant filament option read with a single value gives it to ev
     REQUIRE(config.option<ConfigOptionFloats>("pressure_advance")->values == std::vector<double>({0.021, 0.021, 0.021}));
 }
 
+// Machine limits (printer_options_with_variant_2) hold a (normal, silent) pair per printer variant, so the
+// printer Tab's Motion ability page can edit each extruder's own limits.
+TEST_CASE("set_num_extruders gives every printer variant its own pair of machine limits", "[Config]")
+{
+    DynamicPrintConfig config = DynamicPrintConfig::full_print_config();
+    auto speed_x = [&config]() { return config.option<ConfigOptionFloats>("machine_max_speed_x")->values; };
+
+    SECTION("a new extruder's pair is padded with the first value, like the other variant keys") {
+        config.option<ConfigOptionFloats>("machine_max_speed_x")->values = {500., 200.};
+        config.set_num_extruders(3);
+        REQUIRE(config.option<ConfigOptionStrings>("printer_extruder_variant")->size() == 3);
+        REQUIRE(speed_x() == std::vector<double>({500., 200., 500., 500., 500., 500.}));
+    }
+
+    SECTION("per-extruder pairs are kept, and removing an extruder removes its pair") {
+        config.option<ConfigOptionFloats>("machine_max_speed_x")->values = {500., 200., 400., 150., 300., 100.};
+        config.set_num_extruders(3);
+        REQUIRE(speed_x() == std::vector<double>({500., 200., 400., 150., 300., 100.}));
+        config.set_num_extruders(2);
+        REQUIRE(speed_x() == std::vector<double>({500., 200., 400., 150.}));
+    }
+
+    SECTION("a printer with nozzle variants gets a pair per variant") {
+        // 2 extruders x 2 variants each = 4 variants
+        config.option<ConfigOptionStrings>("extruder_variant_list", true)->values = {"Direct Drive Standard,Direct Drive High Flow",
+                                                                                     "Direct Drive Standard,Direct Drive High Flow"};
+        const std::vector<double> per_variant = {500., 200., 510., 210., 520., 220., 530., 230.};
+        config.option<ConfigOptionFloats>("machine_max_speed_x")->values = per_variant;
+        config.set_num_extruders(2);
+        REQUIRE(speed_x() == per_variant);
+
+        config.option<ConfigOptionFloats>("machine_max_speed_x")->values = {500., 200.};
+        config.set_num_extruders(2);
+        REQUIRE(speed_x() == std::vector<double>({500., 200., 500., 500., 500., 500., 500., 500.}));
+    }
+}
+
 // The device drying options hold several values per filament, as many as each filament preset gives.
 TEST_CASE("The device drying options are rebuilt as each filament's values in slot order", "[Config]")
 {