New feature: Recommended object thin wall thickness hint.

lib/Slic3r/GUI/Tab.pm

@@ -586,6 +586,15 @@ sub build {
             my $optgroup = $page->new_optgroup('Vertical shells');
             $optgroup->append_single_option_line('perimeters');
             $optgroup->append_single_option_line('spiral_vase');
+            my $line = Slic3r::GUI::OptionsGroup::Line->new(
+                label       => '',
+                full_width  => 1,
+                widget      => sub {
+                    my ($parent) = @_;
+                    return $self->{recommended_thin_wall_thickness_description_line} = Slic3r::GUI::OptionsGroup::StaticText->new($parent);
+                },
+            );
+            $optgroup->append_line($line);
         }
         {
             my $optgroup = $page->new_optgroup('Horizontal shells');
@@ -1055,9 +1064,20 @@ sub _update {
     $self->get_field($_)->toggle($have_wipe_tower)
         for qw(wipe_tower_x wipe_tower_y wipe_tower_width wipe_tower_per_color_wipe);
 
+    $self->{recommended_thin_wall_thickness_description_line}->SetText(
+        Slic3r::GUI::PresetHints::recommended_thin_wall_thickness(wxTheApp->{preset_bundle}));
+
     $self->Thaw;
 }
 
+# Update on activation to recalculate the estimates if the nozzle diameter changed
+# and the extrusion width values were left to zero (automatic, nozzle dependent).
+sub OnActivate {
+    my ($self) = @_;
+    $self->{recommended_thin_wall_thickness_description_line}->SetText(
+        Slic3r::GUI::PresetHints::recommended_thin_wall_thickness(wxTheApp->{preset_bundle}));
+}
+
 package Slic3r::GUI::Tab::Filament;
 use base 'Slic3r::GUI::Tab';
 use Wx qw(wxTheApp);

xs/src/libslic3r/Config.hpp

@@ -1161,6 +1161,8 @@ public:
     const ConfigDef*        def() const override { return nullptr; };
     template<class T> T*    opt(const t_config_option_key &opt_key, bool create = false)
         { return dynamic_cast<T*>(this->option(opt_key, create)); }
+    template<class T> const T* opt(const t_config_option_key &opt_key) const
+        { return dynamic_cast<const T*>(this->option(opt_key)); }
     // Overrides ConfigBase::optptr(). Find ando/or create a ConfigOption instance for a given name.
     ConfigOption*           optptr(const t_config_option_key &opt_key, bool create = false) override;
     // Overrides ConfigBase::keys(). Collect names of all configuration values maintained by this configuration store.

xs/src/slic3r/GUI/PresetHints.cpp

@@ -228,4 +228,42 @@ std::string PresetHints::maximum_volumetric_flow_description(const PresetBundle
  	return out;
 }
 
+std::string PresetHints::recommended_thin_wall_thickness(const PresetBundle &preset_bundle)
+{
+    const DynamicPrintConfig &print_config    = preset_bundle.prints   .get_edited_preset().config;
+    const DynamicPrintConfig &printer_config  = preset_bundle.printers .get_edited_preset().config;
+
+    float   layer_height                        = float(print_config.opt_float("layer_height"));
+    int     num_perimeters                      = print_config.opt_int("perimeters");
+    bool    thin_walls                          = print_config.opt_bool("thin_walls");
+    float   nozzle_diameter                     = float(printer_config.opt_float("nozzle_diameter", 0));
+    
+    Flow    external_perimeter_flow             = Flow::new_from_config_width(
+        frExternalPerimeter, 
+        *print_config.opt<ConfigOptionFloatOrPercent>("external_perimeter_extrusion_width"), 
+        nozzle_diameter, layer_height, false);
+    Flow    perimeter_flow                      = Flow::new_from_config_width(
+        frPerimeter, 
+        *print_config.opt<ConfigOptionFloatOrPercent>("perimeter_extrusion_width"), 
+        nozzle_diameter, layer_height, false);
+
+    std::string out;
+    if (num_perimeters > 0) {
+        int num_lines = std::min(num_perimeters * 2, 10);
+        char buf[256];
+        sprintf(buf, "Recommended object thin wall thickness for layer height %.2f and ", layer_height);
+        out += buf;
+        // Start with the width of two closely spaced 
+        double width = external_perimeter_flow.width + external_perimeter_flow.spacing();
+        for (int i = 2; i <= num_lines; thin_walls ? ++ i : i += 2) {
+            if (i > 2)
+                out += ", ";
+            sprintf(buf, "%d lines: %.2lf mm", i, width);
+            out += buf;
+            width += perimeter_flow.spacing() * (thin_walls ? 1.f : 2.f);
+        }
+    }
+    return out;
+}
+
 }; // namespace Slic3r

xs/src/slic3r/GUI/PresetHints.hpp

@@ -13,11 +13,16 @@ class PresetHints
 public:
     // Produce a textual description of the cooling logic of a currently active filament.
     static std::string cooling_description(const Preset &preset);
+    
     // Produce a textual description of the maximum flow achived for the current configuration
     // (the current printer, filament and print settigns).
     // This description will be useful for getting a gut feeling for the maximum volumetric
     // print speed achievable with the extruder.
     static std::string maximum_volumetric_flow_description(const PresetBundle &preset_bundle);
+
+    // Produce a textual description of a recommended thin wall thickness
+    // from the provided number of perimeters and the external / internal perimeter width.
+    static std::string recommended_thin_wall_thickness(const PresetBundle &preset_bundle);
 };
 
 } // namespace Slic3r

xs/xsp/GUI_Preset.xsp

@@ -184,4 +184,6 @@ PresetCollection::arrayref()
         %code%{ RETVAL = PresetHints::cooling_description(*preset); %};
     static std::string maximum_volumetric_flow_description(PresetBundle *preset) 
         %code%{ RETVAL = PresetHints::maximum_volumetric_flow_description(*preset); %};
+    static std::string recommended_thin_wall_thickness(PresetBundle *preset)
+        %code%{ RETVAL = PresetHints::recommended_thin_wall_thickness(*preset); %};
 };