Code to parse the font shorthand property

src/tinycss/fonts3.py

@@ -11,7 +11,7 @@ from tinycss.css21 import CSS21Parser, ParseError
 from .tokenizer import tokenize_grouped
 
 
-def parse_font_family(css_string):
+def parse_font_family_tokens(tokens):
     families = []
     current_family = ''
     def commit():
@@ -19,7 +19,7 @@ def parse_font_family(css_string):
         if val:
             families.append(val)
 
-    for token in tokenize_grouped(css_string.strip()):
+    for token in tokens:
         if token.type == 'STRING':
             if current_family:
                 commit()
@@ -35,6 +35,113 @@ def parse_font_family(css_string):
         commit()
     return families
 
+def parse_font_family(css_string):
+    return parse_font_family_tokens(tokenize_grouped(type('')(css_string).strip()))
+
+GLOBAL_IDENTS = frozenset('inherit initial unset normal'.split())
+STYLE_IDENTS = frozenset('italic oblique'.split())
+VARIANT_IDENTS = frozenset(('small-caps',))
+WEIGHT_IDENTS = frozenset('bold bolder lighter'.split())
+STRETCH_IDENTS = frozenset('ultra-condensed extra-condensed condensed semi-condensed semi-expanded expanded extra-expanded ultra-expanded'.split())
+BEFORE_SIZE_IDENTS = STYLE_IDENTS | VARIANT_IDENTS | WEIGHT_IDENTS | STRETCH_IDENTS
+SIZE_IDENTS = frozenset('xx-small x-small small medium large x-large xx-large larger smaller'.split())
+WEIGHT_SIZES = frozenset(map(int, '100 200 300 400 500 600 700 800 900'.split()))
+LEGACY_FONT_SPEC = frozenset('caption icon menu message-box small-caption status-bar'.split())
+
+def parse_font(css_string):
+    # See https://www.w3.org/TR/css-fonts-3/#font-prop
+    style = variant = weight = stretch = size = height = None
+    tokens = list(reversed(tuple(tokenize_grouped(type('')(css_string).strip()))))
+    if tokens and tokens[-1].value in LEGACY_FONT_SPEC:
+        return {'font-family':['sans-serif']}
+    while tokens:
+        tok = tokens.pop()
+        if tok.type == 'STRING':
+            tokens.append(tok)
+            break
+        if tok.type == 'INTEGER':
+            if size is None:
+                if weight is None and tok.value in WEIGHT_SIZES:
+                    weight = tok.as_css()
+                    continue
+                break
+            if height is None:
+                height = tok.as_css()
+                break
+            break
+        if tok.type == 'NUMBER':
+            if size is not None and height is None:
+                height = tok.as_css()
+            break
+        if tok.type == 'DELIM':
+            if tok.value == '/' and size is not None and height is None:
+                continue
+            break
+        if tok.type in ('DIMENSION', 'PERCENTAGE'):
+            if size is None:
+                size = tok.as_css()
+                continue
+            if height is None:
+                height = tok.as_css()
+            break
+        if tok.type == 'IDENT':
+            if tok.value in GLOBAL_IDENTS:
+                if size is not None:
+                    if height is None:
+                        height = tok.value
+                    else:
+                        tokens.append(tok)
+                    break
+                if style is None:
+                    style = tok.value
+                elif variant is None:
+                    variant = tok.value
+                elif weight is None:
+                    weight = tok.value
+                elif stretch is None:
+                    stretch = tok.value
+                elif size is None:
+                    size = tok.value
+                elif height is None:
+                    height = tok.value
+                    break
+                else:
+                    tokens.append(tok)
+                    break
+                continue
+            if tok.value in BEFORE_SIZE_IDENTS:
+                if size is not None:
+                    break
+                if tok.value in STYLE_IDENTS:
+                    style = tok.value
+                elif tok.value in VARIANT_IDENTS:
+                    variant = tok.value
+                elif tok.value in WEIGHT_IDENTS:
+                    weight = tok.value
+                elif tok.value in STRETCH_IDENTS:
+                    stretch = tok.value
+            elif tok.value in SIZE_IDENTS:
+                size = tok.value
+            else:
+                tokens.append(tok)
+                break
+    families = parse_font_family_tokens(reversed(tokens))
+    ans = {}
+    if style is not None:
+        ans['font-style'] = style
+    if variant is not None:
+        ans['font-variant'] = variant
+    if weight is not None:
+        ans['font-weight'] = weight
+    if stretch is not None:
+        ans['font-stretch'] = stretch
+    if size is not None:
+        ans['font-size'] = size
+    if height is not None:
+        ans['line-height'] = height
+    if families:
+        ans['font-family'] = families
+    return ans
 
 class FontFaceRule(object):
 

src/tinycss/tests/fonts3.py

@@ -6,7 +6,7 @@ from __future__ import (unicode_literals, division, absolute_import,
 __license__ = 'GPL v3'
 __copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
 
-from tinycss.fonts3 import CSSFonts3Parser, parse_font_family
+from tinycss.fonts3 import CSSFonts3Parser, parse_font_family, parse_font
 from tinycss.tests import BaseTest
 
 class TestFonts3(BaseTest):
@@ -48,4 +48,16 @@ class TestFonts3(BaseTest):
         for single in ('serif', 'sans-serif', 'A B C'):
             self.ae([single], parse_font_family(single))
 
-
+    def test_parse_font(self):
+        def t(raw, **kw):
+            q = {('line' if k == 'height' else 'font') + '-' + k:v for k, v in kw.iteritems()}
+            self.ae(q, parse_font(raw))
+        t('caption', family=['sans-serif'])
+        t('serif', family=['serif'])
+        t('12pt/14pt sans-serif', size='12pt', height='14pt', family=['sans-serif'])
+        t('80% sans-serif', size='80%', family=['sans-serif'])
+        t('x-large/110% "new century schoolbook", serif', size='x-large', height='110%', family=['new century schoolbook', 'serif'])
+        t('bold italic large Palatino, serif', weight='bold', style='italic', size='large', family=['Palatino', 'serif'])
+        t('normal small-caps 120%/120% fantasy', style='normal', variant='small-caps', size='120%', height='120%', family=['fantasy'])
+        t('condensed oblique 12pt Helvetica Neue, serif', stretch='condensed', style='oblique', size='12pt', family=['Helvetica Neue', 'serif'])
+        t('300 italic 1.3em/1.7em FB Armada, sans-serif', weight='300', style='italic', size='1.3em', height='1.7em', family=['FB Armada', 'sans-serif'])