More fixes for Unicode filenames support on Windows and OS X

Build.PL

@@ -22,6 +22,7 @@ my %prereqs = qw(
     IO::Scalar                      0
     threads                         1.96
     Time::HiRes                     0
+    Unicode::Normalize              0
 );
 my %recommends = qw(
     Class::XSAccessor               0

lib/Slic3r.pm

@@ -71,6 +71,7 @@ use Slic3r::Print::SupportMaterial;
 use Slic3r::Surface;
 our $build = eval "use Slic3r::Build; 1";
 use Thread::Semaphore;
+use Unicode::Normalize;
 
 use constant SCALING_FACTOR         => 0.000001;
 use constant RESOLUTION             => 0.0125;
@@ -261,7 +262,13 @@ sub resume_all_threads {
 sub encode_path {
     my ($path) = @_;
 
-    utf8::downgrade($path) if $^O eq 'MSWin32';
+    $path = Unicode::Normalize::NFC($path);
+    if ($^O eq 'MSWin32') {
+        utf8::downgrade($path);
+    } else {
+        utf8::encode($path);
+    }
+
     return $path;
 }
 
@@ -273,6 +280,12 @@ sub decode_path {
     } else {
         utf8::decode($path);
     }
+
+    # The filesystem might force a normalization form (like HFS+ does) so 
+    # if we rely on the filename being comparable after the open() + readdir()
+    # roundtrip (like when creating and then selecting a preset), we need to 
+    # restore our normalization form.
+    $path = Unicode::Normalize::NFC($path);
     return $path;
 }
 

lib/Slic3r/GUI/Tab.pm

@@ -204,6 +204,8 @@ sub select_preset {
 
 sub select_preset_by_name {
     my ($self, $name) = @_;
+
+    $name = Unicode::Normalize::NFC($name);
     $self->select_preset(first { $self->{presets}[$_]->name eq $name } 0 .. $#{$self->{presets}});
 }
 
@@ -1462,7 +1464,7 @@ sub config {
     if ($self->default) {
         return Slic3r::Config->new_from_defaults(@$keys);
     } else {
-        if (!-e $self->file) {
+        if (!-e Slic3r::encode_path($self->file)) {
             Slic3r::GUI::show_error(undef, "The selected preset does not exist anymore (" . $self->file . ").");
             return undef;
         }