some new features

.venv/lib/python3.12/site-packages/matplotlib/tests/test_backend_svg.py

@@ -0,0 +1,707 @@
+import datetime
+from io import BytesIO
+from pathlib import Path
+import xml.etree.ElementTree
+import xml.parsers.expat
+
+import pytest
+
+import numpy as np
+
+import matplotlib as mpl
+from matplotlib.figure import Figure
+from matplotlib.patches import Circle
+from matplotlib.text import Text
+import matplotlib.pyplot as plt
+from matplotlib.testing.decorators import check_figures_equal, image_comparison
+from matplotlib.testing._markers import needs_usetex
+from matplotlib import font_manager as fm
+from matplotlib.offsetbox import (OffsetImage, AnnotationBbox)
+
+
+def test_visibility():
+    fig, ax = plt.subplots()
+
+    x = np.linspace(0, 4 * np.pi, 50)
+    y = np.sin(x)
+    yerr = np.ones_like(y)
+
+    a, b, c = ax.errorbar(x, y, yerr=yerr, fmt='ko')
+    for artist in b:
+        artist.set_visible(False)
+
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg')
+        buf = fd.getvalue()
+
+    parser = xml.parsers.expat.ParserCreate()
+    parser.Parse(buf)  # this will raise ExpatError if the svg is invalid
+
+
+@image_comparison(['fill_black_with_alpha.svg'], remove_text=True)
+def test_fill_black_with_alpha():
+    fig, ax = plt.subplots()
+    ax.scatter(x=[0, 0.1, 1], y=[0, 0, 0], c='k', alpha=0.1, s=10000)
+
+
+@image_comparison(['noscale'], remove_text=True)
+def test_noscale():
+    X, Y = np.meshgrid(np.arange(-5, 5, 1), np.arange(-5, 5, 1))
+    Z = np.sin(Y ** 2)
+
+    fig, ax = plt.subplots()
+    ax.imshow(Z, cmap='gray', interpolation='none')
+
+
+def test_text_urls():
+    fig = plt.figure()
+
+    test_url = "http://test_text_urls.matplotlib.org"
+    fig.suptitle("test_text_urls", url=test_url)
+
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg')
+        buf = fd.getvalue().decode()
+
+    expected = f'<a xlink:href="{test_url}">'
+    assert expected in buf
+
+
+@image_comparison(['bold_font_output.svg'])
+def test_bold_font_output():
+    fig, ax = plt.subplots()
+    ax.plot(np.arange(10), np.arange(10))
+    ax.set_xlabel('nonbold-xlabel')
+    ax.set_ylabel('bold-ylabel', fontweight='bold')
+    ax.set_title('bold-title', fontweight='bold')
+
+
+@image_comparison(['bold_font_output_with_none_fonttype.svg'])
+def test_bold_font_output_with_none_fonttype():
+    plt.rcParams['svg.fonttype'] = 'none'
+    fig, ax = plt.subplots()
+    ax.plot(np.arange(10), np.arange(10))
+    ax.set_xlabel('nonbold-xlabel')
+    ax.set_ylabel('bold-ylabel', fontweight='bold')
+    ax.set_title('bold-title', fontweight='bold')
+
+
+@check_figures_equal(tol=20)
+def test_rasterized(fig_test, fig_ref):
+    t = np.arange(0, 100) * (2.3)
+    x = np.cos(t)
+    y = np.sin(t)
+
+    ax_ref = fig_ref.subplots()
+    ax_ref.plot(x, y, "-", c="r", lw=10)
+    ax_ref.plot(x+1, y, "-", c="b", lw=10)
+
+    ax_test = fig_test.subplots()
+    ax_test.plot(x, y, "-", c="r", lw=10, rasterized=True)
+    ax_test.plot(x+1, y, "-", c="b", lw=10, rasterized=True)
+
+
+@check_figures_equal(extensions=['svg'])
+def test_rasterized_ordering(fig_test, fig_ref):
+    t = np.arange(0, 100) * (2.3)
+    x = np.cos(t)
+    y = np.sin(t)
+
+    ax_ref = fig_ref.subplots()
+    ax_ref.set_xlim(0, 3)
+    ax_ref.set_ylim(-1.1, 1.1)
+    ax_ref.plot(x, y, "-", c="r", lw=10, rasterized=True)
+    ax_ref.plot(x+1, y, "-", c="b", lw=10, rasterized=False)
+    ax_ref.plot(x+2, y, "-", c="g", lw=10, rasterized=True)
+    ax_ref.plot(x+3, y, "-", c="m", lw=10, rasterized=True)
+
+    ax_test = fig_test.subplots()
+    ax_test.set_xlim(0, 3)
+    ax_test.set_ylim(-1.1, 1.1)
+    ax_test.plot(x, y, "-", c="r", lw=10, rasterized=True, zorder=1.1)
+    ax_test.plot(x+2, y, "-", c="g", lw=10, rasterized=True, zorder=1.3)
+    ax_test.plot(x+3, y, "-", c="m", lw=10, rasterized=True, zorder=1.4)
+    ax_test.plot(x+1, y, "-", c="b", lw=10, rasterized=False, zorder=1.2)
+
+
+@check_figures_equal(tol=5, extensions=['svg', 'pdf'])
+def test_prevent_rasterization(fig_test, fig_ref):
+    loc = [0.05, 0.05]
+
+    ax_ref = fig_ref.subplots()
+
+    ax_ref.plot([loc[0]], [loc[1]], marker="x", c="black", zorder=2)
+
+    b = mpl.offsetbox.TextArea("X")
+    abox = mpl.offsetbox.AnnotationBbox(b, loc, zorder=2.1)
+    ax_ref.add_artist(abox)
+
+    ax_test = fig_test.subplots()
+    ax_test.plot([loc[0]], [loc[1]], marker="x", c="black", zorder=2,
+                 rasterized=True)
+
+    b = mpl.offsetbox.TextArea("X")
+    abox = mpl.offsetbox.AnnotationBbox(b, loc, zorder=2.1)
+    ax_test.add_artist(abox)
+
+
+def test_count_bitmaps():
+    def count_tag(fig, tag):
+        with BytesIO() as fd:
+            fig.savefig(fd, format='svg')
+            buf = fd.getvalue().decode()
+        return buf.count(f"<{tag}")
+
+    # No rasterized elements
+    fig1 = plt.figure()
+    ax1 = fig1.add_subplot(1, 1, 1)
+    ax1.set_axis_off()
+    for n in range(5):
+        ax1.plot([0, 20], [0, n], "b-", rasterized=False)
+    assert count_tag(fig1, "image") == 0
+    assert count_tag(fig1, "path") == 6  # axis patch plus lines
+
+    # rasterized can be merged
+    fig2 = plt.figure()
+    ax2 = fig2.add_subplot(1, 1, 1)
+    ax2.set_axis_off()
+    for n in range(5):
+        ax2.plot([0, 20], [0, n], "b-", rasterized=True)
+    assert count_tag(fig2, "image") == 1
+    assert count_tag(fig2, "path") == 1  # axis patch
+
+    # rasterized can't be merged without affecting draw order
+    fig3 = plt.figure()
+    ax3 = fig3.add_subplot(1, 1, 1)
+    ax3.set_axis_off()
+    for n in range(5):
+        ax3.plot([0, 20], [n, 0], "b-", rasterized=False)
+        ax3.plot([0, 20], [0, n], "b-", rasterized=True)
+    assert count_tag(fig3, "image") == 5
+    assert count_tag(fig3, "path") == 6
+
+    # rasterized whole axes
+    fig4 = plt.figure()
+    ax4 = fig4.add_subplot(1, 1, 1)
+    ax4.set_axis_off()
+    ax4.set_rasterized(True)
+    for n in range(5):
+        ax4.plot([0, 20], [n, 0], "b-", rasterized=False)
+        ax4.plot([0, 20], [0, n], "b-", rasterized=True)
+    assert count_tag(fig4, "image") == 1
+    assert count_tag(fig4, "path") == 1
+
+    # rasterized can be merged, but inhibited by suppressComposite
+    fig5 = plt.figure()
+    fig5.suppressComposite = True
+    ax5 = fig5.add_subplot(1, 1, 1)
+    ax5.set_axis_off()
+    for n in range(5):
+        ax5.plot([0, 20], [0, n], "b-", rasterized=True)
+    assert count_tag(fig5, "image") == 5
+    assert count_tag(fig5, "path") == 1  # axis patch
+
+
+# Use Computer Modern Sans Serif, not Helvetica (which has no \textwon).
+@mpl.style.context('default')
+@needs_usetex
+def test_unicode_won():
+    fig = Figure()
+    fig.text(.5, .5, r'\textwon', usetex=True)
+
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg')
+        buf = fd.getvalue()
+
+    tree = xml.etree.ElementTree.fromstring(buf)
+    ns = 'http://www.w3.org/2000/svg'
+    won_id = 'SFSS3583-8e'
+    assert len(tree.findall(f'.//{{{ns}}}path[@d][@id="{won_id}"]')) == 1
+    assert f'#{won_id}' in tree.find(f'.//{{{ns}}}use').attrib.values()
+
+
+def test_svgnone_with_data_coordinates():
+    plt.rcParams.update({'svg.fonttype': 'none', 'font.stretch': 'condensed'})
+    expected = 'Unlikely to appear by chance'
+
+    fig, ax = plt.subplots()
+    ax.text(np.datetime64('2019-06-30'), 1, expected)
+    ax.set_xlim(np.datetime64('2019-01-01'), np.datetime64('2019-12-31'))
+    ax.set_ylim(0, 2)
+
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg')
+        fd.seek(0)
+        buf = fd.read().decode()
+
+    assert expected in buf and "condensed" in buf
+
+
+def test_gid():
+    """Test that object gid appears in output svg."""
+    from matplotlib.offsetbox import OffsetBox
+    from matplotlib.axis import Tick
+
+    fig = plt.figure()
+
+    ax1 = fig.add_subplot(131)
+    ax1.imshow([[1., 2.], [2., 3.]], aspect="auto")
+    ax1.scatter([1, 2, 3], [1, 2, 3], label="myscatter")
+    ax1.plot([2, 3, 1], label="myplot")
+    ax1.legend()
+    ax1a = ax1.twinx()
+    ax1a.bar([1, 2, 3], [1, 2, 3])
+
+    ax2 = fig.add_subplot(132, projection="polar")
+    ax2.plot([0, 1.5, 3], [1, 2, 3])
+
+    ax3 = fig.add_subplot(133, projection="3d")
+    ax3.plot([1, 2], [1, 2], [1, 2])
+
+    fig.canvas.draw()
+
+    gdic = {}
+    for idx, obj in enumerate(fig.findobj(include_self=True)):
+        if obj.get_visible():
+            gid = f"test123{obj.__class__.__name__}_{idx}"
+            gdic[gid] = obj
+            obj.set_gid(gid)
+
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg')
+        buf = fd.getvalue().decode()
+
+    def include(gid, obj):
+        # we need to exclude certain objects which will not appear in the svg
+        if isinstance(obj, OffsetBox):
+            return False
+        if isinstance(obj, Text):
+            if obj.get_text() == "":
+                return False
+            elif obj.axes is None:
+                return False
+        if isinstance(obj, plt.Line2D):
+            xdata, ydata = obj.get_data()
+            if len(xdata) == len(ydata) == 1:
+                return False
+            elif not hasattr(obj, "axes") or obj.axes is None:
+                return False
+        if isinstance(obj, Tick):
+            loc = obj.get_loc()
+            if loc == 0:
+                return False
+            vi = obj.get_view_interval()
+            if loc < min(vi) or loc > max(vi):
+                return False
+        return True
+
+    for gid, obj in gdic.items():
+        if include(gid, obj):
+            assert gid in buf
+
+
+def test_clip_path_ids_reuse():
+    fig, circle = Figure(), Circle((0, 0), radius=10)
+    for i in range(5):
+        ax = fig.add_subplot()
+        aimg = ax.imshow([[i]])
+        aimg.set_clip_path(circle)
+
+    inner_circle = Circle((0, 0), radius=1)
+    ax = fig.add_subplot()
+    aimg = ax.imshow([[0]])
+    aimg.set_clip_path(inner_circle)
+
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg')
+        buf = fd.getvalue()
+
+    tree = xml.etree.ElementTree.fromstring(buf)
+    ns = 'http://www.w3.org/2000/svg'
+
+    clip_path_ids = set()
+    for node in tree.findall(f'.//{{{ns}}}clipPath[@id]'):
+        node_id = node.attrib['id']
+        assert node_id not in clip_path_ids  # assert ID uniqueness
+        clip_path_ids.add(node_id)
+    assert len(clip_path_ids) == 2  # only two clipPaths despite reuse in multiple axes
+
+
+def test_savefig_tight():
+    # Check that the draw-disabled renderer correctly disables open/close_group
+    # as well.
+    plt.savefig(BytesIO(), format="svgz", bbox_inches="tight")
+
+
+def test_url():
+    # Test that object url appears in output svg.
+
+    fig, ax = plt.subplots()
+
+    # collections
+    s = ax.scatter([1, 2, 3], [4, 5, 6])
+    s.set_urls(['https://example.com/foo', 'https://example.com/bar', None])
+
+    # Line2D
+    p, = plt.plot([2, 3, 4], [4, 5, 6])
+    p.set_url('https://example.com/baz')
+
+    # Line2D markers-only
+    p, = plt.plot([3, 4, 5], [4, 5, 6], linestyle='none', marker='x')
+    p.set_url('https://example.com/quux')
+
+    b = BytesIO()
+    fig.savefig(b, format='svg')
+    b = b.getvalue()
+    for v in [b'foo', b'bar', b'baz', b'quux']:
+        assert b'https://example.com/' + v in b
+
+
+def test_url_tick(monkeypatch):
+    monkeypatch.setenv('SOURCE_DATE_EPOCH', '19680801')
+
+    fig1, ax = plt.subplots()
+    ax.scatter([1, 2, 3], [4, 5, 6])
+    for i, tick in enumerate(ax.yaxis.get_major_ticks()):
+        tick.set_url(f'https://example.com/{i}')
+
+    fig2, ax = plt.subplots()
+    ax.scatter([1, 2, 3], [4, 5, 6])
+    for i, tick in enumerate(ax.yaxis.get_major_ticks()):
+        tick.label1.set_url(f'https://example.com/{i}')
+        tick.label2.set_url(f'https://example.com/{i}')
+
+    b1 = BytesIO()
+    fig1.savefig(b1, format='svg')
+    b1 = b1.getvalue()
+
+    b2 = BytesIO()
+    fig2.savefig(b2, format='svg')
+    b2 = b2.getvalue()
+
+    for i in range(len(ax.yaxis.get_major_ticks())):
+        assert f'https://example.com/{i}'.encode('ascii') in b1
+    assert b1 == b2
+
+
+def test_svg_default_metadata(monkeypatch):
+    # Values have been predefined for 'Creator', 'Date', 'Format', and 'Type'.
+    monkeypatch.setenv('SOURCE_DATE_EPOCH', '19680801')
+
+    fig, ax = plt.subplots()
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg')
+        buf = fd.getvalue().decode()
+
+    # Creator
+    assert mpl.__version__ in buf
+    # Date
+    assert '1970-08-16' in buf
+    # Format
+    assert 'image/svg+xml' in buf
+    # Type
+    assert 'StillImage' in buf
+
+    # Now make sure all the default metadata can be cleared.
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg', metadata={'Date': None, 'Creator': None,
+                                                'Format': None, 'Type': None})
+        buf = fd.getvalue().decode()
+
+    # Creator
+    assert mpl.__version__ not in buf
+    # Date
+    assert '1970-08-16' not in buf
+    # Format
+    assert 'image/svg+xml' not in buf
+    # Type
+    assert 'StillImage' not in buf
+
+
+def test_svg_clear_default_metadata(monkeypatch):
+    # Makes sure that setting a default metadata to `None`
+    # removes the corresponding tag from the metadata.
+    monkeypatch.setenv('SOURCE_DATE_EPOCH', '19680801')
+
+    metadata_contains = {'creator': mpl.__version__, 'date': '1970-08-16',
+                         'format': 'image/svg+xml', 'type': 'StillImage'}
+
+    SVGNS = '{http://www.w3.org/2000/svg}'
+    RDFNS = '{http://www.w3.org/1999/02/22-rdf-syntax-ns#}'
+    CCNS = '{http://creativecommons.org/ns#}'
+    DCNS = '{http://purl.org/dc/elements/1.1/}'
+
+    fig, ax = plt.subplots()
+    for name in metadata_contains:
+        with BytesIO() as fd:
+            fig.savefig(fd, format='svg', metadata={name.title(): None})
+            buf = fd.getvalue().decode()
+
+        root = xml.etree.ElementTree.fromstring(buf)
+        work, = root.findall(f'./{SVGNS}metadata/{RDFNS}RDF/{CCNS}Work')
+        for key in metadata_contains:
+            data = work.findall(f'./{DCNS}{key}')
+            if key == name:
+                # The one we cleared is not there
+                assert not data
+                continue
+            # Everything else should be there
+            data, = data
+            xmlstr = xml.etree.ElementTree.tostring(data, encoding="unicode")
+            assert metadata_contains[key] in xmlstr
+
+
+def test_svg_clear_all_metadata():
+    # Makes sure that setting all default metadata to `None`
+    # removes the metadata tag from the output.
+
+    fig, ax = plt.subplots()
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg', metadata={'Date': None, 'Creator': None,
+                                                'Format': None, 'Type': None})
+        buf = fd.getvalue().decode()
+
+    SVGNS = '{http://www.w3.org/2000/svg}'
+
+    root = xml.etree.ElementTree.fromstring(buf)
+    assert not root.findall(f'./{SVGNS}metadata')
+
+
+def test_svg_metadata():
+    single_value = ['Coverage', 'Identifier', 'Language', 'Relation', 'Source',
+                    'Title', 'Type']
+    multi_value = ['Contributor', 'Creator', 'Keywords', 'Publisher', 'Rights']
+    metadata = {
+        'Date': [datetime.date(1968, 8, 1),
+                 datetime.datetime(1968, 8, 2, 1, 2, 3)],
+        'Description': 'description\ntext',
+        **{k: f'{k} foo' for k in single_value},
+        **{k: [f'{k} bar', f'{k} baz'] for k in multi_value},
+    }
+
+    fig = plt.figure()
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg', metadata=metadata)
+        buf = fd.getvalue().decode()
+
+    SVGNS = '{http://www.w3.org/2000/svg}'
+    RDFNS = '{http://www.w3.org/1999/02/22-rdf-syntax-ns#}'
+    CCNS = '{http://creativecommons.org/ns#}'
+    DCNS = '{http://purl.org/dc/elements/1.1/}'
+
+    root = xml.etree.ElementTree.fromstring(buf)
+    rdf, = root.findall(f'./{SVGNS}metadata/{RDFNS}RDF')
+
+    # Check things that are single entries.
+    titles = [node.text for node in root.findall(f'./{SVGNS}title')]
+    assert titles == [metadata['Title']]
+    types = [node.attrib[f'{RDFNS}resource']
+             for node in rdf.findall(f'./{CCNS}Work/{DCNS}type')]
+    assert types == [metadata['Type']]
+    for k in ['Description', *single_value]:
+        if k == 'Type':
+            continue
+        values = [node.text
+                  for node in rdf.findall(f'./{CCNS}Work/{DCNS}{k.lower()}')]
+        assert values == [metadata[k]]
+
+    # Check things that are multi-value entries.
+    for k in multi_value:
+        if k == 'Keywords':
+            continue
+        values = [
+            node.text
+            for node in rdf.findall(
+                f'./{CCNS}Work/{DCNS}{k.lower()}/{CCNS}Agent/{DCNS}title')]
+        assert values == metadata[k]
+
+    # Check special things.
+    dates = [node.text for node in rdf.findall(f'./{CCNS}Work/{DCNS}date')]
+    assert dates == ['1968-08-01/1968-08-02T01:02:03']
+
+    values = [node.text for node in
+              rdf.findall(f'./{CCNS}Work/{DCNS}subject/{RDFNS}Bag/{RDFNS}li')]
+    assert values == metadata['Keywords']
+
+
+@image_comparison(["multi_font_aspath.svg"], tol=1.8)
+def test_multi_font_type3():
+    fp = fm.FontProperties(family=["WenQuanYi Zen Hei"])
+    if Path(fm.findfont(fp)).name != "wqy-zenhei.ttc":
+        pytest.skip("Font may be missing")
+
+    plt.rc('font', family=['DejaVu Sans', 'WenQuanYi Zen Hei'], size=27)
+    plt.rc('svg', fonttype='path')
+
+    fig = plt.figure()
+    fig.text(0.15, 0.475, "There are 几个汉字 in between!")
+
+
+@image_comparison(["multi_font_astext.svg"])
+def test_multi_font_type42():
+    fp = fm.FontProperties(family=["WenQuanYi Zen Hei"])
+    if Path(fm.findfont(fp)).name != "wqy-zenhei.ttc":
+        pytest.skip("Font may be missing")
+
+    fig = plt.figure()
+    plt.rc('svg', fonttype='none')
+
+    plt.rc('font', family=['DejaVu Sans', 'WenQuanYi Zen Hei'], size=27)
+    fig.text(0.15, 0.475, "There are 几个汉字 in between!")
+
+
+@pytest.mark.parametrize('metadata,error,message', [
+    ({'Date': 1}, TypeError, "Invalid type for Date metadata. Expected str"),
+    ({'Date': [1]}, TypeError,
+     "Invalid type for Date metadata. Expected iterable"),
+    ({'Keywords': 1}, TypeError,
+     "Invalid type for Keywords metadata. Expected str"),
+    ({'Keywords': [1]}, TypeError,
+     "Invalid type for Keywords metadata. Expected iterable"),
+    ({'Creator': 1}, TypeError,
+     "Invalid type for Creator metadata. Expected str"),
+    ({'Creator': [1]}, TypeError,
+     "Invalid type for Creator metadata. Expected iterable"),
+    ({'Title': 1}, TypeError,
+     "Invalid type for Title metadata. Expected str"),
+    ({'Format': 1}, TypeError,
+     "Invalid type for Format metadata. Expected str"),
+    ({'Foo': 'Bar'}, ValueError, "Unknown metadata key"),
+    ])
+def test_svg_incorrect_metadata(metadata, error, message):
+    with pytest.raises(error, match=message), BytesIO() as fd:
+        fig = plt.figure()
+        fig.savefig(fd, format='svg', metadata=metadata)
+
+
+def test_svg_escape():
+    fig = plt.figure()
+    fig.text(0.5, 0.5, "<\'\"&>", gid="<\'\"&>")
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg')
+        buf = fd.getvalue().decode()
+        assert '&lt;&apos;&quot;&amp;&gt;"' in buf
+
+
+@pytest.mark.parametrize("font_str", [
+    "'DejaVu Sans', 'WenQuanYi Zen Hei', 'Arial', sans-serif",
+    "'DejaVu Serif', 'WenQuanYi Zen Hei', 'Times New Roman', serif",
+    "'Arial', 'WenQuanYi Zen Hei', cursive",
+    "'Impact', 'WenQuanYi Zen Hei', fantasy",
+    "'DejaVu Sans Mono', 'WenQuanYi Zen Hei', 'Courier New', monospace",
+    # These do not work because the logic to get the font metrics will not find
+    # WenQuanYi as the fallback logic stops with the first fallback font:
+    # "'DejaVu Sans Mono', 'Courier New', 'WenQuanYi Zen Hei', monospace",
+    # "'DejaVu Sans', 'Arial', 'WenQuanYi Zen Hei', sans-serif",
+    # "'DejaVu Serif', 'Times New Roman', 'WenQuanYi Zen Hei',  serif",
+])
+@pytest.mark.parametrize("include_generic", [True, False])
+def test_svg_font_string(font_str, include_generic):
+    fp = fm.FontProperties(family=["WenQuanYi Zen Hei"])
+    if Path(fm.findfont(fp)).name != "wqy-zenhei.ttc":
+        pytest.skip("Font may be missing")
+
+    explicit, *rest, generic = map(
+        lambda x: x.strip("'"), font_str.split(", ")
+    )
+    size = len(generic)
+    if include_generic:
+        rest = rest + [generic]
+    plt.rcParams[f"font.{generic}"] = rest
+    plt.rcParams["font.size"] = size
+    plt.rcParams["svg.fonttype"] = "none"
+
+    fig, ax = plt.subplots()
+    if generic == "sans-serif":
+        generic_options = ["sans", "sans-serif", "sans serif"]
+    else:
+        generic_options = [generic]
+
+    for generic_name in generic_options:
+        # test that fallback works
+        ax.text(0.5, 0.5, "There are 几个汉字 in between!",
+                family=[explicit, generic_name], ha="center")
+        # test deduplication works
+        ax.text(0.5, 0.1, "There are 几个汉字 in between!",
+                family=[explicit, *rest, generic_name], ha="center")
+    ax.axis("off")
+
+    with BytesIO() as fd:
+        fig.savefig(fd, format="svg")
+        buf = fd.getvalue()
+
+    tree = xml.etree.ElementTree.fromstring(buf)
+    ns = "http://www.w3.org/2000/svg"
+    text_count = 0
+    for text_element in tree.findall(f".//{{{ns}}}text"):
+        text_count += 1
+        font_style = dict(
+            map(lambda x: x.strip(), _.strip().split(":"))
+            for _ in dict(text_element.items())["style"].split(";")
+        )
+
+        assert font_style["font-size"] == f"{size}px"
+        assert font_style["font-family"] == font_str
+    assert text_count == len(ax.texts)
+
+
+def test_annotationbbox_gid():
+    # Test that object gid appears in the AnnotationBbox
+    # in output svg.
+    fig = plt.figure()
+    ax = fig.add_subplot()
+    arr_img = np.ones((32, 32))
+    xy = (0.3, 0.55)
+
+    imagebox = OffsetImage(arr_img, zoom=0.1)
+    imagebox.image.axes = ax
+
+    ab = AnnotationBbox(imagebox, xy,
+                        xybox=(120., -80.),
+                        xycoords='data',
+                        boxcoords="offset points",
+                        pad=0.5,
+                        arrowprops=dict(
+                            arrowstyle="->",
+                            connectionstyle="angle,angleA=0,angleB=90,rad=3")
+                        )
+    ab.set_gid("a test for issue 20044")
+    ax.add_artist(ab)
+
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg')
+        buf = fd.getvalue().decode('utf-8')
+
+    expected = '<g id="a test for issue 20044">'
+    assert expected in buf
+
+
+def test_svgid():
+    """Test that `svg.id` rcparam appears in output svg if not None."""
+
+    fig, ax = plt.subplots()
+    ax.plot([1, 2, 3], [3, 2, 1])
+    fig.canvas.draw()
+
+    # Default: svg.id = None
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg')
+        buf = fd.getvalue().decode()
+
+    tree = xml.etree.ElementTree.fromstring(buf)
+
+    assert plt.rcParams['svg.id'] is None
+    assert not tree.findall('.[@id]')
+
+    # String: svg.id = str
+    svg_id = 'a test for issue 28535'
+    plt.rc('svg', id=svg_id)
+
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg')
+        buf = fd.getvalue().decode()
+
+    tree = xml.etree.ElementTree.fromstring(buf)
+
+    assert plt.rcParams['svg.id'] == svg_id
+    assert tree.findall(f'.[@id="{svg_id}"]')