Minor tweaks of UI texts,

optimization of the wipe tower invalidation,
show collisions of the wipe tower with known dimensions.

xs/src/libslic3r/GCode.cpp

@@ -524,13 +524,21 @@ void GCode::_do_export(Print &print, FILE *file, GCodePreviewData *preview_data)
             m_silent_time_estimator.set_axis_max_jerk(GCodeTimeEstimator::Y, print.config.machine_max_jerk_y.values[1]);
             m_silent_time_estimator.set_axis_max_jerk(GCodeTimeEstimator::Z, print.config.machine_max_jerk_z.values[1]);
             m_silent_time_estimator.set_axis_max_jerk(GCodeTimeEstimator::E, print.config.machine_max_jerk_e.values[1]);
+            if (print.config.single_extruder_multi_material) {
+                // As of now the fields are shown at the UI dialog in the same combo box as the ramming values, so they
+                // are considered to be active for the single extruder multi-material printers only.
                 m_silent_time_estimator.set_filament_load_times(print.config.filament_load_time.values);
                 m_silent_time_estimator.set_filament_unload_times(print.config.filament_unload_time.values);
             }
         }
+    }
     // Filament load / unload times are not specific to a firmware flavor. Let anybody use it if they find it useful.
+    if (print.config.single_extruder_multi_material) {
+        // As of now the fields are shown at the UI dialog in the same combo box as the ramming values, so they
+        // are considered to be active for the single extruder multi-material printers only.
         m_normal_time_estimator.set_filament_load_times(print.config.filament_load_time.values);
         m_normal_time_estimator.set_filament_unload_times(print.config.filament_unload_time.values);
+    }
 
     // resets analyzer
     m_analyzer.reset();

xs/src/libslic3r/Print.cpp

@@ -128,7 +128,6 @@ bool Print::invalidate_state_by_config_options(const std::vector<t_config_option
         "gcode_comments",
         "gcode_flavor",
         "infill_acceleration",
-        "infill_first",
         "layer_gcode",
         "min_fan_speed",
         "max_fan_speed",
@@ -177,15 +176,6 @@ bool Print::invalidate_state_by_config_options(const std::vector<t_config_option
     std::vector<PrintObjectStep> osteps;
     bool invalidated = false;
 
-    // Always invalidate the wipe tower. This is probably necessary because of the wipe_into_infill / wipe_into_objects
-    // features - nearly anything can influence what should (and could) be wiped into.
-    // Only these three parameters don't invalidate the wipe tower (they only affect the gcode export):
-    for (const t_config_option_key &opt_key : opt_keys)
-        if (opt_key != "wipe_tower_x" && opt_key != "wipe_tower_y" && opt_key != "wipe_tower_rotation_angle") {
-            steps.emplace_back(psWipeTower);
-            break;
-        }
-
     for (const t_config_option_key &opt_key : opt_keys) {
         if (steps_ignore.find(opt_key) != steps_ignore.end()) {
             // These options only affect G-code export or they are just notes without influence on the generated G-code,
@@ -218,6 +208,7 @@ bool Print::invalidate_state_by_config_options(const std::vector<t_config_option
             || opt_key == "filament_cooling_final_speed"
             || opt_key == "filament_ramming_parameters"
             || opt_key == "gcode_flavor"
+            || opt_key == "infill_first"
             || opt_key == "single_extruder_multi_material"
             || opt_key == "spiral_vase"
             || opt_key == "temperature"

xs/src/libslic3r/PrintConfig.cpp

@@ -511,11 +511,10 @@ PrintConfigDef::PrintConfigDef()
 
     def = this->add("filament_minimal_purge_on_wipe_tower", coFloats);
     def->label = L("Minimal purge on wipe tower");
-    def->tooltip = L("After a toolchange, certain amount of filament is used for purging. This "
+    def->tooltip = L("After a tool change, the exact position of the newly loaded filament inside "
-                     "can end up on the wipe tower, infill or sacrificial object. If there was "
+                     "the nozzle may not be known, and the filament pressure is likely not yet stable. "
-                     "enough infill etc. available, this could result in bad quality at the beginning "
+                     "Before purging the print head into an infill or a sacrificial object, Slic3r will always prime "
-                     "of purging. This is a minimum that must be wiped on the wipe tower before "
+                     "this amount of material into the wipe tower to produce successive infill or sacrificial object extrusions reliably.");
-                     "Slic3r considers moving elsewhere. ");
     def->cli = "filament-minimal-purge-on-wipe-tower=f@";
     def->sidetext = L("mm³");
     def->min = 0;

xs/src/slic3r/GUI/3DScene.cpp

@@ -715,6 +715,7 @@ int GLVolumeCollection::load_wipe_tower_preview(
     v.select_group_id = obj_idx * 1000000;
     v.drag_group_id = obj_idx * 1000;
     v.is_wipe_tower = true;
+    v.shader_outside_printer_detection_enabled = ! size_unknown;
     return int(this->volumes.size() - 1);
 }
 

xs/src/slic3r/GUI/Field.cpp

@@ -98,7 +98,7 @@ namespace Slic3r { namespace GUI {
             tooltip_text = tooltip + "\n" + _(L("default value")) + "\t: " +
             (boost::iends_with(m_opt_id, "_gcode") ? "\n" : "") + default_string +
             (boost::iends_with(m_opt_id, "_gcode") ? "" : "\n") + 
-            _(L("variable name")) + "\t: " + m_opt_id;
+            _(L("parameter name")) + "\t: " + m_opt_id;
 
 		return tooltip_text;
 	}