FIX: Handle height units in broken_barh() (matplotlib#31685)

* FIX: Handle height units in brohen_barh()

* Apply suggestions from code review

Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

---------

Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>

Author: timhoffm

galleries/examples/lines_bars_and_markers/broken_barh.py

@@ -19,16 +19,14 @@
 
 fig, ax = plt.subplots()
 # broken_barh(xranges, (ypos, height))
-ax.broken_barh(cpu_1, (0, 0.4), align="center")
-ax.broken_barh(cpu_2, (1, 0.4), align="center")
-ax.broken_barh(cpu_3, (2, 0.4), align="center")
-ax.broken_barh(cpu_4, (3, 0.4), align="center")
-ax.broken_barh(disk, (4, 0.4), align="center", color="tab:orange")
-ax.broken_barh(network, (5, 0.4), align="center", color="tab:green")
+ax.broken_barh(cpu_1, ("CPU 1", 0.4), align="center")
+ax.broken_barh(cpu_2, ("CPU 2", 0.4), align="center")
+ax.broken_barh(cpu_3, ("CPU 3", 0.4), align="center")
+ax.broken_barh(cpu_4, ("CPU 4", 0.4), align="center")
+ax.broken_barh(disk, ("disk", 0.4), align="center", color="tab:orange")
+ax.broken_barh(network, ("network", 0.4), align="center", color="tab:green")
 ax.set_xlim(0, 10)
-ax.set_yticks(range(6),
-              labels=["CPU 1", "CPU 2", "CPU 3", "CPU 4", "disk", "network"])
-ax.invert_yaxis()
+ax.invert_yaxis()  # order the bars from top to bottom
 ax.set_title("Resource usage")
 
 plt.show()

lib/matplotlib/axes/_axes.py

@@ -2243,13 +2243,10 @@ def _convert_dx(dx, x0, xconv, convert):
             except (TypeError, IndexError, KeyError):
                 x = xconv
 
-            delist = False
-            if not np.iterable(dx):
-                dx = [dx]
-                delist = True
-            dx = [convert(x0 + ddx) - x for ddx in dx]
-            if delist:
-                dx = dx[0]
+            if np.iterable(dx):
+                dx = [convert(x0 + ddx) - x for ddx in dx]
+            else:
+                dx = convert(x0 + dx) - x
         except (ValueError, TypeError, AttributeError):
             # if the above fails (for any reason) just fallback to what
             # we do by default and convert dx by itself.
@@ -3037,15 +3034,20 @@ def broken_barh(self, xranges, yrange, align="bottom", **kwargs):
             [("x", xdata), ("y", ydata)], kwargs, convert=False)
 
         vertices = []
-        y0, dy = yrange
+        ypos, height = yrange
+
+        # Unit conversion: handling of the difference quantity height is done through
+        # _convert_dx() in the same way as width handling in bar().
+        y0 = self.convert_yunits(ypos)
+        dy = self._convert_dx(height, ypos, np.array(y0), self.convert_yunits)
 
         _api.check_in_list(['bottom', 'center', 'top'], align=align)
         if align == "bottom":
-            y0, y1 = self.convert_yunits((y0, y0 + dy))
+            y1 = y0 + dy
         elif align == "center":
-            y0, y1 = self.convert_yunits((y0 - dy/2, y0 + dy/2))
+            y0, y1 = y0 - dy / 2, y0 + dy / 2
         else:
-            y0, y1 = self.convert_yunits((y0 - dy, y0))
+            y0, y1 = y0 - dy, y0
 
         for xr in xranges:  # convert the absolute values, not the x and dx
             try:

lib/matplotlib/tests/test_axes.py

@@ -7747,6 +7747,18 @@ def test_broken_barh_align():
         assert_array_equal(path.get_extents().intervaly, [18, 20])
 
 
+def test_broken_barh_categorical():
+    fig, ax = plt.subplots()
+    pc = ax.broken_barh([(0, 10)], ('a', 0.8))
+    assert tuple(pc.get_datalim(ax.transData).intervaly) == (0, 0.8)
+
+    pc = ax.broken_barh([(0, 10)], ('a', 0.8), align="center")
+    assert tuple(pc.get_datalim(ax.transData).intervaly) == (-0.4, 0.4)
+
+    pc = ax.broken_barh([(0, 10)], ('a', 0.8), align="top")
+    assert tuple(pc.get_datalim(ax.transData).intervaly) == (-0.8, 0)
+
+
 def test_pandas_pcolormesh(pd):
     time = pd.date_range('2000-01-01', periods=10)
     depth = np.arange(20)