Extended the Slic3r::GUI::Tab::XXX::_update mechanism to deliver

a set of updated config keys.

lib/Slic3r/GUI/SimpleTab.pm

@@ -70,12 +70,18 @@ sub load_config {
     my $self = shift;
     my ($config) = @_;
     
+    my %keys_modified = ();
     foreach my $opt_key (@{$self->{config}->get_keys}) {
-        next unless $config->has($opt_key);
+        if ($config->has($opt_key)) {
-        $self->{config}->set($opt_key, $config->get($opt_key));
+            if ($self->{config}->serialize($opt_key) ne $config->serialize($opt_key)) {
+                $self->{config}->set($opt_key, $config->get($opt_key));
+                $keys_modified{$opt_key} = 1;
+            }
+        }
     }
+    # Initialize UI components with the config values.
     $_->reload_config for @{$self->{optgroups}};
-    $self->_update;
+    $self->_update(\%keys_modified);
 }
 
 sub load_presets {}
@@ -93,10 +99,9 @@ sub on_presets_changed {}
 
 # propagate event to the parent
 sub _on_value_change {
-    my $self = shift;
+    my ($self, $key, $value) = @_;
-    
+    $self->{on_value_change}->($key, $value) if $self->{on_value_change};
-    $self->{on_value_change}->(@_) if $self->{on_value_change};
+    $self->_update({ $key => 1 });
-    $self->_update;
 }
 
 sub get_field {
@@ -179,7 +184,8 @@ sub build {
 }
 
 sub _update {
-    my ($self) = @_;
+    # $keys_modified is a reference to hash with modified keys set to 1, unmodified keys missing.
+    my ($self, $keys_modified) = @_;
     
     my $config = $self->{config};
     

lib/Slic3r/GUI/Tab.pm

@@ -207,16 +207,17 @@ sub on_presets_changed {
     $self->{on_presets_changed} = $cb;
 }
 
-# This method is supposed to be called whenever new values are loaded
+# This method is called whenever an option field is changed by the user.
-# or changed by user (so also when a preset is loaded).
+# Propagate event to the parent through the 'on_value_changed' callback
-# propagate event to the parent
+# and call _update.
 sub _on_value_change {
-    my $self = shift;
+    my ($self, $key, $value) = @_;
-    
+    $self->{on_value_change}->($key, $value) if $self->{on_value_change};
-    $self->{on_value_change}->(@_) if $self->{on_value_change};
+    $self->_update({ $key => 1 });
-    $self->_update;
 }
 
+# Override this to capture changes of configuration caused either by loading or switching a preset,
+# or by a user changing an option field.
 sub _update {}
 
 sub _on_presets_changed {
@@ -298,15 +299,20 @@ sub on_select_preset {
     my $preset_config = $self->get_preset_config($preset);
     eval {
         local $SIG{__WARN__} = Slic3r::GUI::warning_catcher($self);
+        my %keys_modified = ();
         foreach my $opt_key (@{$self->{config}->get_keys}) {
-            $self->{config}->set($opt_key, $preset_config->get($opt_key))
+            if ($preset_config->has($opt_key)) {
-                if $preset_config->has($opt_key);
+                if ($self->{config}->serialize($opt_key) ne $preset_config->serialize($opt_key)) {
+                    $self->{config}->set($opt_key, $preset_config->get($opt_key));
+                    $keys_modified{$opt_key} = 1;
+                }
+            }
         }
         ($preset->default || $preset->external)
             ? $self->{btn_delete_preset}->Disable
             : $self->{btn_delete_preset}->Enable;
         
-        $self->_update;
+        $self->_update(\%keys_modified);
         $self->on_preset_loaded;
         $self->reload_config;
         $Slic3r::GUI::Settings->{presets}{$self->name} = $preset->file ? basename($preset->file) : '';
@@ -463,12 +469,15 @@ sub load_config {
     my $self = shift;
     my ($config) = @_;
     
+    my %keys_modified = ();
     foreach my $opt_key (@{$self->{config}->diff($config)}) {
         $self->{config}->set($opt_key, $config->get($opt_key));
+        $keys_modified{$opt_key} = 1;
         $self->update_dirty;
     }
+    # Initialize UI components with the config values.
     $self->reload_config;
-    $self->_update;
+    $self->_update(\%keys_modified);
 }
 
 sub get_preset_config {
@@ -797,9 +806,12 @@ sub build {
     }
 }
 
+# Slic3r::GUI::Tab::Print::_update is called after a configuration preset is loaded or switched, or when a single option is modifed by the user.
 sub _update {
-    my ($self) = @_;
+    # $keys_modified is a reference to hash with modified keys set to 1, unmodified keys missing.
-    
+    my ($self, $keys_modified) = @_;
+    $keys_modified //= {};
+
     my $config = $self->{config};
     
     if ($config->spiral_vase && !($config->perimeters == 1 && $config->top_solid_layers == 0 && $config->fill_density == 0)) {
@@ -825,6 +837,10 @@ sub _update {
         }
     }
 
+    if ($keys_modified->{'layer_height'}) {
+        # If the user had set the variable layer height, reset it and let the user know.
+    }
+
     if ($config->support_material) {
         # Ask only once.
         if (! $self->{support_material_overhangs_queried}) {
@@ -1050,8 +1066,10 @@ sub build {
     }
 }
 
+# Slic3r::GUI::Tab::Filament::_update is called after a configuration preset is loaded or switched, or when a single option is modifed by the user.
 sub _update {
-    my ($self) = @_;
+    # $keys_modified is a reference to hash with modified keys set to 1, unmodified keys missing.
+    my ($self, $keys_modified) = @_;
     
     $self->_update_description;
     
@@ -1382,7 +1400,6 @@ sub _extruders_count_changed {
     $self->{extruders_count} = $extruders_count;
     $self->_build_extruder_pages;
     $self->_on_value_change('extruders_count', $extruders_count);
-    $self->_update;
 }
 
 sub _extruder_options { qw(nozzle_diameter extruder_offset retract_length retract_lift retract_lift_above retract_lift_below retract_speed retract_restart_extra retract_before_travel wipe
@@ -1464,8 +1481,10 @@ sub _build_extruder_pages {
     $self->update_tree;
 }
 
+# Slic3r::GUI::Tab::Printer::_update is called after a configuration preset is loaded or switched, or when a single option is modifed by the user.
 sub _update {
-    my ($self) = @_;
+    # $keys_modified is a reference to hash with modified keys set to 1, unmodified keys missing.
+    my ($self, $keys_modified) = @_;
     
     my $config = $self->{config};