Fix plugin configuration not taking effect, and improve the plugin config UI (#14944)

# Description

Changing a slicing plugin's configuration had no effect on the sliced
result until you forced a re-slice some other way; it now applies
immediately. Print, printer and filament presets also keep their plugin
configuration separately, so configuring a plugin on one no longer wipes
out what you set on another.

A plugin's custom configuration page gets the same round of improvements
in both the Plugins dialog and the per-preset dialog: it follows the
app's light/dark theme, keeps its state while you edit instead of
resetting under the cursor, and can tell whether it is being edited
globally or for a preset, so "Restore defaults" can be labeled for what
it will actually do. The two bundled examples show this off — Twistify
now ships a custom configuration UI, and Inspector is themed, groups

# Screenshots/Recordings/Graphs



https://github.com/user-attachments/assets/02ca062a-5143-49a3-abe0-a2a040b3a928



## Tests

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src/libslic3r/Preset.cpp

@@ -1203,7 +1203,7 @@ static std::vector<std::string> s_Preset_print_options{
     "post_process",
     "slicing_pipeline_plugin",
     "plugins",
-    "plugin_config_overrides",
+    "print_plugin_config_overrides",
     "process_change_extrusion_role_gcode",
     "min_length_factor",
     "wall_maximum_resolution",
@@ -1378,7 +1378,7 @@ static std::vector<std::string> s_Preset_filament_options {/*"filament_colour",
     "filament_preheat_temperature_delta", "filament_retract_length_nc",
     "filament_change_length_nc", "filament_prime_volume", "filament_prime_volume_nc",
     "long_retractions_when_ec", "retraction_distances_when_ec",
-    "plugin_config_overrides",
+    "filament_plugin_config_overrides",
     //ams chamber
     "filament_dev_ams_drying_ams_limitations", "filament_dev_ams_drying_temperature", "filament_dev_ams_drying_time", "filament_dev_ams_drying_heat_distortion_temperature",
     "filament_dev_chamber_drying_bed_temperature", "filament_dev_chamber_drying_time",
@@ -1430,7 +1430,7 @@ static std::vector<std::string> s_Preset_printer_options {
     // Fast-purge printer flag + device/firmware-facing per-variant extruder-change
     // deretraction speed (unconsumed by the slicer; carried by H2D/A2L/X2D/P2S machine profiles).
     "support_fast_purge_mode", "deretract_speed_extruder_change",
-    "plugin_config_overrides"
+    "printer_plugin_config_overrides"
     };
 
 static std::vector<std::string> s_Preset_sla_print_options {
@@ -1542,6 +1542,15 @@ const std::vector<std::string>& Preset::printer_options()
     return s_opts;
 }
 
+const char* Preset::plugin_overrides_key(Type type)
+{
+    switch (type) {
+    case TYPE_PRINTER:  return "printer_plugin_config_overrides";
+    case TYPE_FILAMENT: return "filament_plugin_config_overrides";
+    default:            return "print_plugin_config_overrides";
+    }
+}
+
 PresetCollection::PresetCollection(Preset::Type type, const std::vector<std::string> &keys, const Slic3r::StaticPrintConfig &defaults, const std::string &default_name) :
     m_type(type),
     m_edited_preset(type, "", false),

src/libslic3r/Preset.hpp

@@ -407,6 +407,11 @@ public:
     // Printer machine limits, those are contained in printer_options().
     static const std::vector<std::string>&  machine_limits_options();
 
+    // Option key holding this preset type's plugin capability overrides. Each type has its own key so
+    // the values survive the merge into a single full config; print is the fallback for the types with
+    // no plugin-backed options.
+    static const char*                      plugin_overrides_key(Type type);
+
     static const std::vector<std::string>&  sla_printer_options();
     static const std::vector<std::string>&  sla_material_options();
     static const std::vector<std::string>&  sla_print_options();

src/libslic3r/Print.cpp

@@ -285,6 +285,7 @@ bool Print::invalidate_state_by_config_options(const ConfigOptionResolver & /* n
             steps.emplace_back(psSkirtBrim);
         } else if (
                opt_key == "slicing_pipeline_plugin"
+            || opt_key == "print_plugin_config_overrides"
             || opt_key == "initial_layer_print_height"
             || opt_key == "nozzle_diameter"
             || opt_key == "filament_shrink"

src/libslic3r/PrintConfig.cpp

@@ -1081,16 +1081,21 @@ void PrintConfigDef::init_common_params()
         def->set_default_value(new ConfigOptionString());
     }
 
-    def = this->add("plugin_config_overrides", coString);
-    def->label = L("Capabilities");
-    def->tooltip = L("Configuration for the plugin capabilities this preset uses, overriding the global "
-                     "Capabilities configuration. Stored as a raw JSON array and edited through the dialog "
-                     "behind the button, never typed in directly.");
-    // Never shown as a text field: GUIType::plugin_config renders a button that opens PluginsConfigDialog.
-    def->gui_type = ConfigOptionDef::GUIType::plugin_config;
-    def->mode = comAdvanced;
-    def->cli = ConfigOptionDef::nocli;
-    def->set_default_value(new ConfigOptionString(""));
+    // One key per preset type (Preset::plugin_overrides_key), so the print, printer and filament
+    // overrides don't clobber each other when the presets merge into one full config. No handle_legacy
+    // migration from the shared "plugin_config_overrides" they replace: it only ever shipped in
+    // nightlies. Never a text field — GUIType::plugin_config renders a button opening PluginsConfigDialog.
+    for (const char* key : {"print_plugin_config_overrides", "printer_plugin_config_overrides", "filament_plugin_config_overrides"}) {
+        def = this->add(key, coString);
+        def->label = L("Capabilities");
+        def->tooltip = L("Configuration for the plugin capabilities this preset uses, overriding the global "
+                         "Capabilities configuration. Stored as a raw JSON array and edited through the dialog "
+                         "behind the button, never typed in directly.");
+        def->gui_type = ConfigOptionDef::GUIType::plugin_config;
+        def->mode = comAdvanced;
+        def->cli = ConfigOptionDef::nocli;
+        def->set_default_value(new ConfigOptionString(""));
+    }
 }
 
 void PrintConfigDef::init_fff_params()

src/libslic3r/PrintConfig.hpp

@@ -1780,6 +1780,7 @@ PRINT_CONFIG_CLASS_DERIVED_DEFINE(
     ((ConfigOptionString,             filename_format))
     ((ConfigOptionStrings,            post_process))
     ((ConfigOptionStrings,            slicing_pipeline_plugin))
+    ((ConfigOptionString,             print_plugin_config_overrides))
     ((ConfigOptionString,             printer_model))
     ((ConfigOptionFloat,              resolution))
     ((ConfigOptionFloats,             retraction_minimum_travel))