FIJISettingsViewer: improve LFSR polynomial usability

 - show maximum polynomial for current LFSR width in tooltip
 - set maximum polynomial when changing LFSR width

bin/Tk/FIJISettingsViewer.pm

@@ -529,7 +529,7 @@ sub _populate_widget {
         # let entries eat up all the remaining space
         $config_frame->gridColumnconfigure(2, -weight => 1);
 
-        # add tooltip the config frame
+        # add tooltip to the config frame
         if (defined DISPLAYGROUPS->{$displaygroup}->{'description'}) {
             $balloon->attach(
                 $config_frame,
@@ -541,6 +541,8 @@ sub _populate_widget {
         # add matching widgets for all values in this displaygroup
         foreach my $k (sort { DESIGNMAP->{$a}->{'order'} <=> DESIGNMAP->{$b}->{'order'} } @keys) {
 
+            my $tooltip;
+
             # label
             my $label = $config_frame->Label(
                 '-text'    => DESIGNMAP->{$k}->{'description'},
@@ -655,6 +657,12 @@ sub _populate_widget {
                     -column   => 2,
                     '-sticky' => 'ew'
                 );
+                my $lfsr_width = $self->{'settings'}->{'design'}->{'LFSR_WIDTH'};
+                my $lpc = LFSR_POLY_CHOICES;
+                my $c   = $lpc->{$lfsr_width};
+                my $tmp =  FIUMAP->{'FIU_LFSR_MASK'}->{'help'} . " [" . FIUMAP->{'FIU_LFSR_MASK'}->{'ini_name'} . "]\nPossible maximum polynomials for a LFSR with a width of ".$lfsr_width.": " . join(",", @{$c});
+                $tooltip = \$tmp;
+                $entry->{'LFSR_tooltip'} = \$tmp;
             } elsif (defined($type) && $type eq 'boolean') {
 
                 # checkbutton for values which can only be "enabled" or "disabled"
@@ -743,7 +751,7 @@ sub _populate_widget {
 
             # add tooltip for widget
             if (defined DESIGNMAP->{$k}->{'help'}) {
-                my $tooltip = DESIGNMAP->{$k}->{'help'} . " [" . DESIGNMAP->{$k}->{'ini_name'} . "]";
+                $tooltip = DESIGNMAP->{$k}->{'help'} . " [" . DESIGNMAP->{$k}->{'ini_name'} . "]" if (!defined($tooltip));
                 $balloon->attach(
                     $entry,
                     -balloonposition => 'mouse',
@@ -1700,17 +1708,25 @@ sub _validate_entry {
         $$old_ref = $$new_ref;
     }
 
-    # if we are validating the LFSR WIDTH widget, update the list of
-    # suggested polynomials
+    # if we are validating the LFSR WIDTH widget, set the polynomial to the first known maximum,
+    # update the list of suggestions and add them to the respective tooltip
     if ($name eq 'LFSR_WIDTH') {
-        for my $depending_widget (grep { ref($_) eq "Tk::CompleteEntry" } @{$self->{'depends'}->{$name}}) {
+        # Fetch and change only the LFSR_POLY widget
+        for my $lfsr_poly_widget (grep { $_->{'key'} eq "LFSR_POLY" } @{$self->{'depends'}->{$name}}) {
             my $lpc = LFSR_POLY_CHOICES;
             my $c   = $lpc->{$$new_ref};
             if (defined $c) {
-                $depending_widget->configure(-choices => $c);
+                $lfsr_poly_widget->configure(-choices => $c);
+                ${$lfsr_poly_widget->cget('-textvariable')} = @{$c}[0];
+
+                # Replace the previous tooltip pointed to by the reference stored in LFSR_tooltip with two regexes.
+                my $replacement_width = "width of ".$$new_ref;
+                ${$lfsr_poly_widget->{'LFSR_tooltip'}} =~ s/width of [0-9]+/$replacement_width/;
+                my $replacement_poly = ": ".join(",", @{$c});
+                ${$lfsr_poly_widget->{'LFSR_tooltip'}} =~ s/:.*/$replacement_poly/;
             } else {
-                $logger->debug("No LFSR_POLY suggestion for LFSR_LENGTH $$new_ref");
-                $depending_widget->configure(-choices => []);
+                $logger->debug("No LFSR_POLY suggestion for LFSR_WIDTH $$new_ref");
+                $lfsr_poly_widget->configure(-choices => []);
             }
         }
     }