font-patcher: Preserve padding around Braille glyphs

[why]
Usually we scale symbols so that they are maximized within one 'cell' of
the font. If we do this for the Braille glyphs the bottom dots from an
upper line will (almost) touch the top dots of the next line. This is
not useful.

[how]
We add padding around the Braille glyphs, to get about the same distance
to the cell borders as the different dots in one glyph have to the
other (~10 %, 5% on each side).

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

font-patcher

@@ -731,6 +731,10 @@ class font_patcher:
             0xf0dd: {'align': 'c', 'valign': '', 'stretch': 'pa', 'params': {}},
             0xf0de: {'align': 'c', 'valign': '', 'stretch': 'pa', 'params': {}}
         }
+        SYM_ATTR_BRAILLE = {
+            # 'pa' == preserve aspect ratio
+            'default': {'align': 'c', 'valign': 'c', 'stretch': 'pa', 'params': {'overlap': -0.05}}
+        }
 
         CUSTOM_ATTR = {
             # 'pa' == preserve aspect ratio
@@ -810,7 +814,7 @@ class font_patcher:
             {'Enabled': self.args.octicons,             'Name': "Octicons",                'Filename': "octicons.ttf",                                   'Exact': True,  'SymStart': 0X26A1, 'SymEnd': 0X26A1, 'SrcStart': None,   'ScaleGlyph': OCTI_SCALE_LIST,  'Attributes': SYM_ATTR_DEFAULT},  # Zap
             {'Enabled': self.args.octicons,             'Name': "Octicons",                'Filename': "octicons.ttf",                                   'Exact': False, 'SymStart': 0xF27C, 'SymEnd': 0xF27C, 'SrcStart': 0xF4A9, 'ScaleGlyph': OCTI_SCALE_LIST,  'Attributes': SYM_ATTR_DEFAULT},  # Desktop
             {'Enabled': self.args.codicons,             'Name': "Codicons",                'Filename': "codicons/codicon.ttf",                           'Exact': True,  'SymStart': 0xEA60, 'SymEnd': 0xEBEB, 'SrcStart': None,   'ScaleGlyph': None,             'Attributes': SYM_ATTR_DEFAULT},
-            {'Enabled': self.args.braille,              'Name': "Braille",                 'Filename': "UBraille.ttf",                                   'Exact': True,  'SymStart': 0x2800, 'SymEnd': 0x28FF, 'SrcStart': None,   'ScaleGlyph': BRAILLE_SCALE_LIST, 'Attributes': SYM_ATTR_DEFAULT},
+            {'Enabled': self.args.braille,              'Name': "Braille",                 'Filename': "UBraille.ttf",                                   'Exact': True,  'SymStart': 0x2800, 'SymEnd': 0x28FF, 'SrcStart': None,   'ScaleGlyph': BRAILLE_SCALE_LIST, 'Attributes': SYM_ATTR_BRAILLE},
             {'Enabled': self.args.custom,               'Name': "Custom",                  'Filename': self.args.custom,                                 'Exact': True,  'SymStart': 0x0000, 'SymEnd': 0x0000, 'SrcStart': None,   'ScaleGlyph': None,             'Attributes': CUSTOM_ATTR}
         ]