Merge pull request #9498 from jklymak/fixtitle

Move title up if x-axis is on the top of the figure.

Merging as it received 2 approvals, and the small patch that I pushed was also reviewed by @efiring (and actually modified on one of his remarks).

Thanks @jklymak :).

doc/users/next_whats_new/title_will_not_overlap_xaxis.rst

@@ -0,0 +1,15 @@
+Axes title will no longer overlap xaxis
+---------------------------------------
+
+Previously an axes title had to be moved manually if an xaxis overlapped
+(usually when the xaxis was put on the top of the axes).  Now, the title
+will be automatically moved above the xaxis and its decorators (including
+the xlabel) if they are at the top.
+
+If desired, the title can still be placed manually.  There is a slight kludge;
+the algorithm checks if the y-position of the title is 1.0 (the default),
+and moves if it is.  If the user places the title in the default location
+(i.e. ``ax.title.set_position(0.5, 1.0)``), the title will still be moved
+above the xaxis.  If the user wants to avoid this, they can
+specify a number that is close (i.e. ``ax.title.set_position(0.5, 1.01)``)
+and the title will not be moved via this algorithm.

examples/ticks_and_spines/tick_xlabel_top.py

@@ -23,6 +23,6 @@
 fig, ax = plt.subplots()
 
 ax.plot(x)
-ax.set_title('xlabel top', pad=24)  # increase padding to make room for labels
+ax.set_title('xlabel top')  # Note title moves to make room for ticks
 
 plt.show()

lib/matplotlib/axes/_base.py

@@ -1,5 +1,6 @@
 from collections import OrderedDict
 import itertools
+import logging
 import math
 from operator import attrgetter
 import types
@@ -32,6 +33,8 @@
 from matplotlib.rcsetup import cycler
 from matplotlib.rcsetup import validate_axisbelow
 
+_log = logging.getLogger(__name__)
+
 rcParams = matplotlib.rcParams
 
 
@@ -1077,6 +1080,8 @@ def cla(self):
         # refactor this out so it can be called in ax.set_title if
         # pad argument used...
         self._set_title_offset_trans(title_offset_points)
+        # determine if the title position has been set manually:
+        self._autotitlepos = None
 
         for _title in (self.title, self._left_title, self._right_title):
             self._set_artist_props(_title)
@@ -2446,6 +2451,50 @@ def handle_single_axis(scale, autoscaleon, shared_axes, interval,
     def _get_axis_list(self):
         return (self.xaxis, self.yaxis)
 
+    def _update_title_position(self, renderer):
+        """
+        Update the title position based on the bounding box enclosing
+        all the ticklabels and x-axis spine and xlabel...
+        """
+        _log.debug('update_title_pos')
+
+        if self._autotitlepos is not None and not self._autotitlepos:
+            _log.debug('title position was updated manually, not adjusting')
+            return
+
+        titles = (self.title, self._left_title, self._right_title)
+
+        if self._autotitlepos is None:
+            for title in titles:
+                x, y = title.get_position()
+                if not np.isclose(y, 1.0):
+                    self._autotitlepos = False
+                    _log.debug('not adjusting title pos because title was'
+                             ' already placed manually: %f', y)
+                    return
+            self._autotitlepos = True
+
+        for title in titles:
+            x, y0 = title.get_position()
+            y = 1.0
+            # need to check all our twins too...
+            axs = self._twinned_axes.get_siblings(self)
+
+            for ax in axs:
+                try:
+                    if (ax.xaxis.get_label_position() == 'top'
+                            or ax.xaxis.get_ticks_position() == 'top'):
+                        bb = ax.xaxis.get_tightbbox(renderer)
+                        top = bb.ymax
+                        # we don't need to pad because the padding is already
+                        # in __init__: titleOffsetTrans
+                        yn = self.transAxes.inverted().transform((0., top))[1]
+                        y = max(y, yn)
+                except AttributeError:
+                    pass
+
+            title.set_position((x, y))
+
     # Drawing
 
     @allow_rasterization
@@ -2459,6 +2508,7 @@ def draw(self, renderer=None, inframe=False):
         if not self.get_visible():
             return
         renderer.open_group('axes')
+
         # prevent triggering call backs during the draw process
         self._stale = True
         locator = self.get_axes_locator()
@@ -2479,6 +2529,8 @@ def draw(self, renderer=None, inframe=False):
             for spine in self.spines.values():
                 artists.remove(spine)
 
+        self._update_title_position(renderer)
+
         if self.axison and not inframe:
             if self._axisbelow is True:
                 self.xaxis.set_zorder(0.5)
@@ -2507,6 +2559,7 @@ def draw(self, renderer=None, inframe=False):
         # rasterize artists with negative zorder
         # if the minimum zorder is negative, start rasterization
         rasterization_zorder = self._rasterization_zorder
+
         if (rasterization_zorder is not None and
                 artists and artists[0].zorder < rasterization_zorder):
             renderer.start_rasterizing()
@@ -4051,6 +4104,12 @@ def get_tightbbox(self, renderer, call_axes_locator=True):
         else:
             self.apply_aspect()
 
+        bb_xaxis = self.xaxis.get_tightbbox(renderer)
+        if bb_xaxis:
+            bb.append(bb_xaxis)
+
+        self._update_title_position(renderer)
+
         bb.append(self.get_window_extent(renderer))
 
         if self.title.get_visible():
@@ -4060,10 +4119,6 @@ def get_tightbbox(self, renderer, call_axes_locator=True):
         if self._right_title.get_visible():
             bb.append(self._right_title.get_window_extent(renderer))
 
-        bb_xaxis = self.xaxis.get_tightbbox(renderer)
-        if bb_xaxis:
-            bb.append(bb_xaxis)
-
         bb_yaxis = self.yaxis.get_tightbbox(renderer)
         if bb_yaxis:
             bb.append(bb_yaxis)

lib/matplotlib/tests/test_axes.py

@@ -5411,6 +5411,42 @@ def test_axisbelow():
         ax.set_axisbelow(setting)
 
 
+@image_comparison(baseline_images=['titletwiny'], style='mpl20',
+        extensions=['png'])
+def test_titletwiny():
+    # Test that title is put above xlabel if xlabel at top
+    fig, ax = plt.subplots()
+    fig.subplots_adjust(top=0.8)
+    ax2 = ax.twiny()
+    ax.set_xlabel('Xlabel')
+    ax2.set_xlabel('Xlabel2')
+    ax.set_title('Title')
+
+
+def test_titlesetpos():
+    # Test that title stays put if we set it manually
+    fig, ax = plt.subplots()
+    fig.subplots_adjust(top=0.8)
+    ax2 = ax.twiny()
+    ax.set_xlabel('Xlabel')
+    ax2.set_xlabel('Xlabel2')
+    ax.set_title('Title')
+    pos = (0.5, 1.11)
+    ax.title.set_position(pos)
+    renderer = fig.canvas.get_renderer()
+    ax._update_title_position(renderer)
+    assert ax.title.get_position() == pos
+
+
+def test_title_xticks_top():
+    # Test that title moves if xticks on top of axes.
+    fig, ax = plt.subplots()
+    ax.xaxis.set_ticks_position('top')
+    ax.set_title('xlabel top')
+    fig.canvas.draw()
+    assert ax.title.get_position()[1] > 1.04
+
+
 def test_offset_label_color():
     # Tests issue 6440
     fig = plt.figure()