added font-face style attribute to load custom fonts from local path

Author: ambi7

lib/matplotlib/font_manager.py

@@ -380,6 +380,25 @@ def findSystemFonts(fontpaths=None, fontext='ttf'):
     return [fname for fname in fontfiles if os.path.exists(fname)]
 
 
+def fontentry_helper_repr_html_(fontent):
+    html = (f"<span style='font-family:{fontent.name}'>"
+            f'{fontent.name}'
+            '</span>')
+
+    if fontent.fname == '':
+        return html
+    else:
+        return ('<span>'
+                '<style>'
+                '@font-face { '
+                f'font-family: {fontent.name}; '
+                f'src: url({fontent.fname}); '
+                '} '
+                '</style>'
+                f'{html}'
+                '</span>')
+
+
 FontEntry = dataclasses.make_dataclass(
     'FontEntry', [
         ('fname', str, dataclasses.field(default='')),
@@ -396,7 +415,7 @@ def findSystemFonts(fontpaths=None, fontext='ttf'):
 
     It is used when populating the font lookup dictionary.
     """,
-        '_repr_html_': lambda self: f"<span style='font-family:{self.name}'>{self.name}</span>",  # noqa: E501
+        '_repr_html_': lambda self: fontentry_helper_repr_html_(self),
     }
 )
 

lib/matplotlib/tests/test_font_manager.py

@@ -270,10 +270,12 @@ def test_fontcache_thread_safe():
 
 
 def test_fontentry_dataclass():
-    entry = FontEntry(name="font-name")
+    fontent1 = FontEntry(name='font-name')
+    fontent2 = FontEntry(fname='/random', name='font-name')
 
-    assert type(entry.__doc__) == str
-    assert entry._repr_html_() == "<span style='font-family:font-name'>font-name</span>"  # noqa: E501
+    assert type(fontent1.__doc__) == str
+    assert '@font-face' not in fontent1._repr_html_()
+    assert '@font-face' in fontent2._repr_html_()
 
 
 @pytest.mark.skipif(sys.platform == 'win32', reason='Linux or OS only')