font-patcher: Use standard filenames

[why]
The filenames of the patched fonts are rather ... unique:
- they contain blanks to separate name parts
- they do not separate name and style/weight

This is in part due to history reasons, because the names were not
parsed at all and just some suffix added.

Example (contrived):
  Victor Mono Nerd Font Propo Bold.ttf

Normally font file names would be:
  VictorMonoNerdFontPropo-Bold.ttf

We ourselves relied in part on that naming scheme, but do not follow it.
There are a lot powerline fonts out there that all add blanks to the
filename.

Some filename recommendation can be found in [1].

[how]
The filename is now always constructed directly from name ID 16
and name ID 17. If one of them is empty ID 1 and ID 2 are used as
fallback, as customary.
ID 16 (ID 1) and ID 17 (ID 2) are separated by a hyphen.

The result is that in can differ from the fontname (ID 6) and uses
always the longest most readable name parts.

[1] https://forum.fontlab.com/fontlab-studio-tips-and-tricks/font-family-naming-in-fontlab-studio-5/

Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>

font-patcher

@@ -300,6 +300,17 @@ def get_old_average_x_width(font):
         s += font[g].width * weights[g]
     return int(s / 1000)
 
+def create_filename(fonts):
+    """ Determine filename from font object(s) """
+    sfnt = { k: v for l, k, v in fonts[0].sfnt_names }
+    sfnt_pfam = sfnt.get('Preferred Family', sfnt['Family'])
+    sfnt_psubfam = sfnt.get('Preferred Styles', sfnt['SubFamily'])
+    if len(fonts) > 1:
+        return sfnt_pfam
+    if len(sfnt_psubfam) > 0:
+        sfnt_psubfam = '-' + sfnt_psubfam
+    return (sfnt_pfam + sfnt_psubfam).replace(' ', '')
+
 
 class font_patcher:
     def __init__(self, args):
@@ -403,11 +414,11 @@ class font_patcher:
                     break
             outfile = os.path.normpath(os.path.join(
                 sanitize_filename(self.args.outputdir, True),
-                sanitize_filename(sourceFont.familyname) + ".ttc"))
+                sanitize_filename(create_filename(sourceFonts)) + ".ttc"))
             sourceFonts[0].generateTtc(outfile, sourceFonts[1:], flags=gen_flags, layer=layer)
             message = "   Generated {} fonts\n   \===> '{}'".format(len(sourceFonts), outfile)
         else:
-            fontname = sourceFont.fullname
+            fontname = create_filename(sourceFonts)
             if not fontname:
                 fontname = sourceFont.cidfontname
             outfile = os.path.normpath(os.path.join(