dviread: Skip font map lines with invalid special.

As noted in the pfdtex manual, `SlantFont` and `ExtendFont` are only
allowed for T1 fonts, and within range ±1 and ±2, respectively.

This can be confirmed the same way as the previous commit, by copying
the lines from the `test.map` (though using a _real_ tfmname).

Author: QuLogic

lib/matplotlib/dviread.py

@@ -908,8 +908,6 @@ def _parse_and_cache_line(self, line):
                     basename = unquoted
             elif quoted:
                 special = quoted
-        if basename is None:
-            basename = tfmname
         effects = {}
         if special:
             words = reversed(special.split())
@@ -918,6 +916,24 @@ def _parse_and_cache_line(self, line):
                     effects["slant"] = float(next(words))
                 elif word == b"ExtendFont":
                     effects["extend"] = float(next(words))
+
+        # Verify some properties of the line that would cause it to be ignored
+        # otherwise.
+        is_t1 = False
+        if fontfile is not None:
+            if not fontfile.endswith((b".ttf", b".ttc", b".otf"):
+                is_t1 = True
+        elif basename is not None:
+            is_t1 = True
+        if not is_t1 and ("slant" in effects or "extend" in effects):
+            return
+        if abs(effects.get("slant", 0)) > 1:
+            return
+        if abs(effects.get("extend", 0)) > 2:
+            return
+
+        if basename is None:
+            basename = tfmname
         if encodingfile is not None and not encodingfile.startswith(b"/"):
             encodingfile = find_tex_file(encodingfile)
         if fontfile is not None and not fontfile.startswith(b"/"):

lib/matplotlib/tests/baseline_images/dviread/test.map

@@ -2,7 +2,7 @@
 TeXfont1 PSfont1 <font1.pfb <font1.enc
 TeXfont2 PSfont2 <font2.enc <font2.pfa
 TeXfont3 PSfont3 "1.23 UnknownEffect" <[enc3.foo < font3.pfa
-TeXfont4 PSfont4 "-0.1 SlantFont 2.2 ExtendFont" <font4.enc <font4.pfa
+TeXfont4 PSfont4 "-0.1 SlantFont 1.2 ExtendFont" <font4.enc <font4.pfa
 TeXfont5 PSfont5 <encoding1.enc <encoding2.enc <font5.pfb
 TeXfont6 PSfont6
 TeXfont7 PSfont7 < font7.enc
@@ -11,3 +11,16 @@ TeXfont9 </absolute/font9.pfb
 % Only the first of a duplicate key is used.
 TeXfontA PSfontA1
 TeXfontA PSfontA2
+%
+% Check SlantFont/ExtendFont
+%
+% Options are only allowed on T1 fonts (3 TrueType, 1 bitmap, and 1 T1 below).
+TeXfontB PSfontB1 "-0.1 SlantFont 1.2 ExtendFont" <fontB1.ttf
+TeXfontB PSfontB2 "-0.1 SlantFont" <fontB1.ttc
+TeXfontB PSfontB3 "1.2 ExtendFont" <fontB1.otf
+TeXfontB "0.1 SlantFont 1.2 ExtendFont"
+% Also, only within range ±1 / ±2.
+TeXfontB PSfontB4 "1.1 SlantFont 1.2 ExtendFont"
+TeXfontB PSfontB5 "0.1 SlantFont 2.2 ExtendFont"
+% This is the only one that works:
+TeXfontB PSfontB6

lib/matplotlib/tests/test_dviread.py

@@ -28,7 +28,7 @@ def test_PsfontsMap(monkeypatch):
         else:
             assert entry.filename == b'font%d.pfb' % n
         if n == 4:
-            assert entry.effects == {'slant': -0.1, 'extend': 2.2}
+            assert entry.effects == {'slant': -0.1, 'extend': 1.2}
         else:
             assert entry.effects == {}
     # Some special cases
@@ -47,6 +47,9 @@ def test_PsfontsMap(monkeypatch):
     # First of duplicates only.
     entry = fontmap[b'TeXfontA']
     assert entry.psname == b'PSfontA1'
+    # Slant/Extend only works for T1 fonts.
+    entry = fontmap[b'TeXfontB']
+    assert entry.psname == b'PSfontB6'
     # Missing font
     with pytest.raises(KeyError, match='no-such-font'):
         fontmap[b'no-such-font']