<h3 dir="auto">Bug report</h3>
<p dir="auto"><strong>Bug summary</strong></p>
<p dir="auto">Setting font as Computer Modern Roman (<code class="notranslate">matplotlib.rcParams.update({'font.family': 'cmr10'})</code>) results in negative signs in ticklabels not rendering. Oddly, negative signs in titles &amp; labels render fine.</p>
<p dir="auto"><strong>Code for reproduction</strong></p>
<div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="import matplotlib
matplotlib.rcParams.update({
    #'mathtext.fontset': 'cm',
    'font.family': 'cmr10'
})
import matplotlib.pyplot as plt

plt.figure()
plt.plot(range(-1, 1), range(-1, 1))
plt.title(r&quot;dash (-) $mathtext:negative (-)\bf{mathtext.bf:negative (-)}$&quot;)
plt.xlabel(r&quot;dash (-) $mathtext:negative (-)\bf{mathtext.bf:negative (-)}$&quot;)"><pre class="notranslate"><span class="pl-k">import</span> <span class="pl-s1">matplotlib</span>
<span class="pl-s1">matplotlib</span>.<span class="pl-s1">rcParams</span>.<span class="pl-en">update</span>({
    <span class="pl-c">#'mathtext.fontset': 'cm',</span>
    <span class="pl-s">'font.family'</span>: <span class="pl-s">'cmr10'</span>
})
<span class="pl-k">import</span> <span class="pl-s1">matplotlib</span>.<span class="pl-s1">pyplot</span> <span class="pl-k">as</span> <span class="pl-s1">plt</span>

<span class="pl-s1">plt</span>.<span class="pl-en">figure</span>()
<span class="pl-s1">plt</span>.<span class="pl-en">plot</span>(<span class="pl-en">range</span>(<span class="pl-c1">-</span><span class="pl-c1">1</span>, <span class="pl-c1">1</span>), <span class="pl-en">range</span>(<span class="pl-c1">-</span><span class="pl-c1">1</span>, <span class="pl-c1">1</span>))
<span class="pl-s1">plt</span>.<span class="pl-en">title</span>(<span class="pl-s">r"dash (-) $mathtext:negative (-)\bf{mathtext.bf:negative (-)}$"</span>)
<span class="pl-s1">plt</span>.<span class="pl-en">xlabel</span>(<span class="pl-s">r"dash (-) $mathtext:negative (-)\bf{mathtext.bf:negative (-)}$"</span>)</pre></div>
<p dir="auto"><strong>Actual outcome</strong></p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="/usr/local/lib/python3.6/dist-packages/matplotlib/backends/backend_agg.py:214: RuntimeWarning: Glyph 8722 missing from current font.
  font.set_text(s, 0.0, flags=flags)
/usr/local/lib/python3.6/dist-packages/matplotlib/backends/backend_agg.py:183: RuntimeWarning: Glyph 8722 missing from current font.
  font.set_text(s, 0, flags=flags)"><pre class="notranslate"><code class="notranslate">/usr/local/lib/python3.6/dist-packages/matplotlib/backends/backend_agg.py:214: RuntimeWarning: Glyph 8722 missing from current font.
  font.set_text(s, 0.0, flags=flags)
/usr/local/lib/python3.6/dist-packages/matplotlib/backends/backend_agg.py:183: RuntimeWarning: Glyph 8722 missing from current font.
  font.set_text(s, 0, flags=flags)
</code></pre></div>
<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/10780059/86539114-19a79e80-bef2-11ea-964a-76f4ef80e04f.png"><img src="https://user-images.githubusercontent.com/10780059/86539114-19a79e80-bef2-11ea-964a-76f4ef80e04f.png" alt="image" style="max-width: 100%;"></a></p>
<p dir="auto"><strong>Matplotlib version</strong></p>

<ul dir="auto">
<li>Operating system: ubuntu</li>
<li>Matplotlib version: 3.2.1</li>
<li>Matplotlib backend (<code class="notranslate">print(matplotlib.get_backend())</code>): module://ipykernel.pylab.backend_inline</li>
<li>Python version: 3.6.9</li>
<li>Jupyter version (if applicable):</li>
</ul>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="jupyter core     : 4.6.3
jupyter-notebook : 6.0.3
qtconsole        : not installed
ipython          : 7.13.0
ipykernel        : 5.2.0
jupyter client   : 6.1.3
jupyter lab      : not installed
nbconvert        : 5.6.1
ipywidgets       : 7.5.1
nbformat         : 5.0.6
traitlets        : 4.3.3"><pre class="notranslate"><code class="notranslate">jupyter core     : 4.6.3
jupyter-notebook : 6.0.3
qtconsole        : not installed
ipython          : 7.13.0
ipykernel        : 5.2.0
jupyter client   : 6.1.3
jupyter lab      : not installed
nbconvert        : 5.6.1
ipywidgets       : 7.5.1
nbformat         : 5.0.6
traitlets        : 4.3.3
</code></pre></div>
<p dir="auto">Installed via <code class="notranslate">conda</code> channel <code class="notranslate">conda-forge</code></p>
<p dir="auto">Hello ,It's very nice to use it ! Someday when I run my code I got a Warning:<br>
RuntimeWarning: Glyph XXX missing from current font.<br>
font.set_text(s, 0.0, flags=flags)<br>
XXX is some numbers, such as 8722 、25329  etc.<br>
Although it doesn't influence the result, I really want to slove this warning. What can I do?<br>
Thanks and best wishes!</p>