Fix malformed fullscreen attributes on Figure iframe with a height

Figure._repr_html_ has two iframe templates. The one used when height is
None emits the bare boolean attributes

    allowfullscreen webkitallowfullscreen mozallowfullscreen

but the one used when a height is set wrapped each in quotes:

    "allowfullscreen" "webkitallowfullscreen" "mozallowfullscreen"

so the attribute names came out with literal quote characters around
them and browsers ignored all three -- fullscreen did not work whenever
a height was given. The same branch was also missing the space before
the style attribute, giving height="..."style="...".

Emit the attributes the same way as the height-less branch. Output is
now identical to that branch apart from the width/height.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: Htet-Kaung-San

branca/element.py

@@ -425,9 +425,9 @@ def _repr_html_(self, **kwargs) -> str:
             ).format(html=html, width=self.width, ratio=self.ratio)
         else:
             iframe = (
-                '<iframe srcdoc="{html}" width="{width}" height="{height}"'
+                '<iframe srcdoc="{html}" width="{width}" height="{height}" '
                 'style="border:none !important;" '
-                '"allowfullscreen" "webkitallowfullscreen" "mozallowfullscreen">'
+                "allowfullscreen webkitallowfullscreen mozallowfullscreen>"
                 "</iframe>"
             ).format(html=html, width=self.width, height=self.height)
         return iframe

tests/test_element.py

@@ -0,0 +1,44 @@
+"""
+Tests for branca.element
+------------------------
+"""
+
+from html.parser import HTMLParser
+
+import branca.element as elem
+
+
+class _IframeAttrs(HTMLParser):
+    """Collect the attributes of every <iframe> start tag."""
+
+    def __init__(self):
+        super().__init__()
+        self.iframes = []
+
+    def handle_starttag(self, tag, attrs):
+        if tag == "iframe":
+            self.iframes.append(dict(attrs))
+
+
+def _iframe_attrs(html):
+    parser = _IframeAttrs()
+    parser.feed(html)
+    assert len(parser.iframes) == 1
+    return parser.iframes[0]
+
+
+def test_figure_repr_html_fullscreen_attrs_without_height():
+    attrs = _iframe_attrs(elem.Figure()._repr_html_())
+    for name in ("allowfullscreen", "webkitallowfullscreen", "mozallowfullscreen"):
+        assert name in attrs
+
+
+def test_figure_repr_html_fullscreen_attrs_with_height():
+    # The height branch used to quote the boolean attributes, producing
+    # <iframe ... "allowfullscreen" ...>, so the attribute names came out
+    # wrapped in literal quotes and the browser ignored them.
+    attrs = _iframe_attrs(elem.Figure(height="400px")._repr_html_())
+    for name in ("allowfullscreen", "webkitallowfullscreen", "mozallowfullscreen"):
+        assert name in attrs, f"{name!r} missing; got {sorted(attrs)}"
+    assert attrs["height"] == "400px"
+    assert attrs["width"] == "100%"