text: Fetch line height metrics from the used font itself

We follow the process from [the CSS Inline Layout module](https://www.w3.org/TR/css-inline-3/), specifically: 1. The default ascent and descent come from the `OS/2` font table, or failing that, the `hhea` table, with final fallback to the measurement we used to do. 2. If `linespacing` (cf line height in CSS) is normal, then we do as before and size each line based on the maximum ascent/descent of its contents. Additionally, apply the line gap from the font metrics as half-leading around each line. 3. If `linespacing` is a float, then scale it by font size of the first available font, and keep it fixed for each line. However, if we are drawing a single line, then we do not add the line gap around the line, to keep them a similar height as before.
QuLogic · Mar 20, 2026 · Mar 11, 2026 · Mar 12, 2026 · Mar 12, 2026 · Mar 20, 2026
commit 97f4943cf279c82a4dc64e40ec52dcb1bcd218fe
diff --git a/lib/matplotlib/testing/conftest.py b/lib/matplotlib/testing/conftest.py
@@ -149,6 +149,15 @@ def text_placeholders(monkeypatch):
     """
     from matplotlib.patches import Rectangle
 
+    def patched_get_sfnt_table(font, name):
+        """
+        Replace ``FT2Font.get_sfnt_table`` with empty results.
+
+        This forces ``Text._get_layout`` to fall back to
+        ``get_text_width_height_descent``, which produces results from the patch below.
+        """
+        return None
+
     def patched_get_text_metrics_with_cache(renderer, text, fontprop, ismath, dpi):
         """
         Replace ``_get_text_metrics_with_cache`` with fixed results.
@@ -183,6 +192,8 @@ def patched_text_draw(self, renderer):
                          facecolor=self.get_color(), edgecolor='none')
         rect.draw(renderer)
 
+    monkeypatch.setattr('matplotlib.ft2font.FT2Font.get_sfnt_table',
+                        patched_get_sfnt_table)
     monkeypatch.setattr('matplotlib.text._get_text_metrics_with_cache',
                         patched_get_text_metrics_with_cache)
     monkeypatch.setattr('matplotlib.text.Text.draw', patched_text_draw)
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -7753,7 +7753,7 @@ def test_titletwiny():
     bbox_y0_title = title.get_window_extent(renderer).y0  # bottom of title
     bbox_y1_xlabel2 = xlabel2.get_window_extent(renderer).y1  # top of xlabel2
     y_diff = bbox_y0_title - bbox_y1_xlabel2
-    assert np.isclose(y_diff, 3)
+    assert y_diff >= 3
 
 
 def test_titlesetpos():
@@ -8525,8 +8525,8 @@ def test_normal_axes():
 
     # test the axis bboxes
 >
-        [124.0, 76.89, 982.0, 32.0],
-        [86.89, 100.5, 52.0, 992.0],
+        [124.0, 75.56, 982.0, 33.33],
+        [86.89, 99.33, 52.0, 993.33],
     ]
     for nn, b in enumerate(bbaxis):
         targetbb = mtransforms.Bbox.from_bounds(*target[nn])
@@ -8546,7 +8546,7 @@ def test_normal_axes():
     targetbb = mtransforms.Bbox.from_bounds(*target)
     assert_array_almost_equal(bbax.bounds, targetbb.bounds, decimal=2)
 
- 76.89, 1019.11, 1015.61]
+ 75.56, 1019.11, 1017.11]
     targetbb = mtransforms.Bbox.from_bounds(*target)
     assert_array_almost_equal(bbtb.bounds, targetbb.bounds, decimal=2)
 

diff --git a/lib/matplotlib/tests/test_legend.py b/lib/matplotlib/tests/test_legend.py
@@ -481,27 +481,27 @@ def test_figure_legend_outside():
     todos += ['left ' + pos for pos in ['lower', 'center', 'upper']]
     todos += ['right ' + pos for pos in ['lower', 'center', 'upper']]
 
-    upperext = [20.722556, 26.722556, 790.333, 545.999]
-    lowerext = [20.722556, 70.056556, 790.333, 589.333]
-    leftext = [152.056556, 26.722556, 790.333, 589.333]
-    rightext = [20.722556, 26.722556, 658.999, 589.333]
+    upperext = [20.722556, 26.389222, 790.333, 545.16762]
+    lowerext = [20.722556, 70.723222, 790.333, 589.50162]
+    leftext = [152.056556, 26.389222, 790.333, 589.50162]
+    rightext = [20.722556, 26.389222, 658.999, 589.50162]
     axbb = [upperext, upperext, upperext,
             lowerext, lowerext, lowerext,
             leftext, leftext, leftext,
             rightext, rightext, rightext]
 
-    legbb = [[10., 555., 133., 590.],     # upper left
-             [338.5, 555., 461.5, 590.],  # upper center
-             [667, 555., 790.,  590.],    # upper right
-             [10., 10., 133.,  45.],      # lower left
-             [338.5, 10., 461.5,  45.],   # lower center
-             [667., 10., 790.,  45.],     # lower right
-             [10., 10., 133., 45.],       # left lower
-             [10., 282.5, 133., 317.5],   # left center
-             [10., 555., 133., 590.],     # left upper
-             [667, 10., 790., 45.],       # right lower
-             [667., 282.5, 790., 317.5],  # right center
-             [667., 555., 790., 590.]]    # right upper
+    legbb = [[10., 554., 133., 590.],     # upper left
+             [338.5, 554., 461.5, 590.],  # upper center
+             [667, 554., 790.,  590.],    # upper right
+             [10., 10., 133.,  46.],      # lower left
+             [338.5, 10., 461.5,  46.],   # lower center
+             [667., 10., 790.,  46.],     # lower right
+             [10., 10., 133., 46.],       # left lower
+             [10., 282., 133., 318.],     # left center
+             [10., 554., 133., 590.],     # left upper
+             [667, 10., 790., 46.],       # right lower
+             [667., 282., 790., 318.],    # right center
+             [667., 554., 790., 590.]]    # right upper
 
     for nn, todo in enumerate(todos):
         print(todo)

diff --git a/lib/matplotlib/tests/test_polar.py b/lib/matplotlib/tests/test_polar.py
@@ -332,7 +332,7 @@ def test_get_tightbbox_polar():
     fig.canvas.draw()
     bb = ax.get_tightbbox(fig.canvas.get_renderer())
     assert_allclose(
-        bb.extents, [108.27778, 28.7778, 539.7222, 451.2222], rtol=1e-03)
+        bb.extents, [108.27778, 29.1111, 539.7222, 450.8889], rtol=1e-03)
 
 
 @check_figures_equal()

diff --git a/lib/matplotlib/tests/test_text.py b/lib/matplotlib/tests/test_text.py
@@ -14,7 +14,7 @@
 from matplotlib.backend_bases import MouseEvent
 from matplotlib.backends.backend_agg import RendererAgg
 from matplotlib.figure import Figure
-from matplotlib.font_manager import FontProperties
+from matplotlib.font_manager import FontProperties, fontManager, get_font
 import matplotlib.patches as mpatches
 import matplotlib.pyplot as plt
 from matplotlib.gridspec import GridSpec
@@ -1061,8 +1061,16 @@ def test_text_annotation_get_window_extent():
 
     _, _, d = renderer.get_text_width_height_descent(
         'text', annotation._fontproperties, ismath=False)
-    _, _, lp_d = renderer.get_text_width_height_descent(
-        'lp', annotation._fontproperties, ismath=False)
+    font = get_font(fontManager._find_fonts_by_props(annotation._fontproperties))
+    for name, key in [('OS/2', 'sTypoDescender'), ('hhea', 'descent')]:
+        if (table := font.get_sfnt_table(name)) is not None:
+            units_per_em = font.get_sfnt_table('head')['unitsPerEm']
+            fontsize = annotation._fontproperties.get_size_in_points()
+            lp_d = -table[key] / units_per_em * fontsize * figure.dpi / 72
+            break
+    else:
+        _, _, lp_d = renderer.get_text_width_height_descent(
+            'lp', annotation._fontproperties, ismath=False)
     below_line = max(d, lp_d)
 
     # These numbers are specific to the current implementation of Text
@@ -1101,7 +1109,7 @@ def test_text_with_arrow_annotation_get_window_extent():
     assert bbox.width == text_bbox.width + 50.0
     # make sure the annotation text bounding box is same size
     # as the bounding box of the same string as a Text object
-    assert ann_txt_bbox.height == text_bbox.height
+    assert_almost_equal(ann_txt_bbox.height, text_bbox.height)
     assert ann_txt_bbox.width == text_bbox.width
     # compute the expected bounding box of arrow + text
     expected_bbox = mtransforms.Bbox.union([ann_txt_bbox, arrow_bbox])

diff --git a/lib/matplotlib/text.py b/lib/matplotlib/text.py
@@ -15,7 +15,7 @@
 import matplotlib as mpl
 from . import _api, artist, cbook, _docstring, colors as mcolors
 from .artist import Artist
-from .font_manager import FontProperties
+from .font_manager import FontProperties, fontManager, get_font
 from .patches import FancyArrowPatch, FancyBboxPatch, Rectangle
 from .textpath import TextPath, TextToPath  # noqa # Logically located here
 from .transforms import (
@@ -433,16 +433,40 @@ def _get_layout(self, renderer):
         xs = []
         ys = []
 
-        # Full vertical extent of font, including ascenders and descenders:
-        _, lp_h, lp_d = _get_text_metrics_with_cache(
-            renderer, "lp", self._fontproperties,
-            ismath="TeX" if self.get_usetex() else False,
-            dpi=self.get_figure(root=True).dpi)
-        lp_a = lp_h - lp_d
-        linespacing = 1.2 if self._linespacing == 'normal' else self._linespacing
-        min_dy = lp_a * linespacing
-
-        for i, line in enumerate(lines):
+        min_ascent = min_descent = line_gap = None
+        dpi = self.get_figure(root=True).dpi
+        # Determine full vertical extent of font, including ascenders and descenders:
+        if not self.get_usetex():
+            font = get_font(fontManager._find_fonts_by_props(self._fontproperties))
+            possible_metrics = [
+                ('OS/2', 'sTypoLineGap', 'sTypoAscender', 'sTypoDescender'),
+                ('hhea', 'lineGap', 'ascent', 'descent')
+            ]
+            for table_name, linegap_key, ascent_key, descent_key in possible_metrics:
+                table = font.get_sfnt_table(table_name)
+                if table is None:
+                    continue
+                # Rescale to font size/DPI if the metrics were available.
+                fontsize = self._fontproperties.get_size_in_points()
+                units_per_em = font.get_sfnt_table('head')['unitsPerEm']
+                line_gap = table[linegap_key] / units_per_em * fontsize * dpi / 72
+                min_ascent = table[ascent_key] / units_per_em * fontsize * dpi / 72
+                min_descent = -table[descent_key] / units_per_em * fontsize * dpi / 72
+                break
+        if None in (min_ascent, min_descent):
+            # Fallback to font measurement.
+            _, h, min_descent = _get_text_metrics_with_cache(
+                renderer, "lp", self._fontproperties,
+                ismath="TeX" if self.get_usetex() else False,
+                dpi=dpi)
+            min_ascent = h - min_descent
+            line_gap = 0
+
+        # Don't increase text height too much if it's not multiple lines.
+        if len(lines) == 1:
+            line_gap = 0
+
+        for line in lines:
             clean_line, ismath = self._preprocess_math(line)
             if clean_line:
                 w, h, d = _get_text_metrics_with_cache(
@@ -452,18 +476,24 @@ def _get_layout(self, renderer):
                 w = h = d = 0
 
             a = h - d
-            # To ensure good linespacing, pretend that the ascent (resp.
-            # descent) of all lines is at least as large as "l" (resp. "p").
-            a = max(a, lp_a)
-            d = max(d, lp_d)
+
+            if self.get_usetex() or self._linespacing == 'normal':
+                # To ensure good linespacing, pretend that the ascent / descent of all
+                # lines is at least as large as the measured sizes.
+                a = max(a, min_ascent) + line_gap / 2
+                d = max(d, min_descent) + line_gap / 2
+            else:
+                # If using a fixed line spacing, then every line's spacing will be
+                # determined by the font metrics of the first available font.
+                line_height = self._linespacing * (min_ascent + min_descent)
+                leading = line_height - (a + d)
+                a += leading / 2
+                d += leading / 2
 
             # Metrics of the last line that are needed later:
             baseline = a - thisy
 
-            if i == 0:  # position at baseline
-                thisy = -a
-            else:  # put baseline a good distance from bottom of previous line
-                thisy -= max(min_dy, a * linespacing)
+            thisy -= a
 
             wads.append((w, a, d))
             xs.append(thisx)  # == 0.