Merge pull request #16476 from anntzer/fix-usetex-baseline

Fix baseline alignment when using usetex.

Conflicts:
	lib/matplotlib/tests/test_usetex.py
          - import np and formatting issues on decorator

Author: QuLogic

lib/matplotlib/backends/backend_ps.py

@@ -543,8 +543,7 @@ def draw_tex(self, gc, x, y, s, prop, angle, ismath='TeX!', mtext=None):
                 r'\psfrag{%s}[Bl][Bl][1][%f]{\fontsize{%f}{%f}%s}' % (
                     thetext, angle, fontsize, fontsize*1.25, tex))
         else:
-            # Stick to the bottom alignment, but this may give incorrect
-            # baseline some times.
+            # Stick to the bottom alignment.
             pos = _nums_to_str(x-corr, y-bl)
             self.psfrag.append(
                 r'\psfrag{%s}[bl][bl][1][%f]{\fontsize{%f}{%f}%s}' % (

lib/matplotlib/dviread.py

@@ -269,6 +269,12 @@ def _output(self):
             maxx = max(maxx, x + w)
             maxy = max(maxy, y + e)
             maxy_pure = max(maxy_pure, y)
+        if self._baseline_v is not None:
+            maxy_pure = self._baseline_v  # This should normally be the case.
+            self._baseline_v = None
+
+        if not self.text and not self.boxes:  # Avoid infs/nans from inf+/-inf.
+            return Page(text=[], boxes=[], width=0, height=0, descent=0)
 
         if self.dpi is None:
             # special case for ease of debugging: output raw dvi coordinates
@@ -296,9 +302,24 @@ def _read(self):
         Read one page from the file. Return True if successful,
         False if there were no more pages.
         """
+        # Pages appear to start with the sequence
+        #   bop (begin of page)
+        #   xxx comment
+        #   down
+        #   push
+        #     down, down
+        #     push
+        #       down (possibly multiple)
+        #       push  <=  here, v is the baseline position.
+        #         etc.
+        # (dviasm is useful to explore this structure.)
+        self._baseline_v = None
         while True:
             byte = self.file.read(1)[0]
             self._dtable[byte](self, byte)
+            if (self._baseline_v is None
+                    and len(getattr(self, "stack", [])) == 3):
+                self._baseline_v = self.v
             if byte == 140:                         # end of page
                 return True
             if self.state is _dvistate.post_post:   # end of file

lib/matplotlib/tests/baseline_images/test_usetex/test_usetex.pdf

@@ -1,3 +1,4 @@
+import numpy as np
 import pytest
 import platform
 
@@ -11,22 +12,38 @@
     pytestmark = pytest.mark.skip('Missing TeX of Ghostscript or dvipng')
 
 
-@image_comparison(baseline_images=['test_usetex'],
-                  extensions=['pdf', 'png'],
-                  tol={'aarch64': 2.868}.get(platform.machine(), 0.3))
+@image_comparison(
+    baseline_images=['test_usetex'],
+    extensions=['pdf', 'png'],
+    style="mpl20")
 def test_usetex():
     mpl.rcParams['text.usetex'] = True
     fig = plt.figure()
     ax = fig.add_subplot(111)
-    ax.text(0.1, 0.2,
+    kwargs = {"verticalalignment": "baseline", "size": 24,
+              "bbox": dict(pad=0, edgecolor="k", facecolor="none")}
+    ax.text(0.2, 0.7,
             # the \LaTeX macro exercises character sizing and placement,
             # \left[ ... \right\} draw some variable-height characters,
             # \sqrt and \frac draw horizontal rules, \mathrm changes the font
             r'\LaTeX\ $\left[\int\limits_e^{2e}'
             r'\sqrt\frac{\log^3 x}{x}\,\mathrm{d}x \right\}$',
-            fontsize=24)
-    ax.set_xticks([])
-    ax.set_yticks([])
+            **kwargs)
+    ax.text(0.2, 0.3, "lg", **kwargs)
+    ax.text(0.4, 0.3, r"$\frac{1}{2}\pi$", **kwargs)
+    ax.text(0.6, 0.3, "$p^{3^A}$", **kwargs)
+    ax.text(0.8, 0.3, "$p_{3_2}$", **kwargs)
+    for x in {t.get_position()[0] for t in ax.texts}:
+        ax.axvline(x)
+    for y in {t.get_position()[1] for t in ax.texts}:
+        ax.axhline(y)
+    ax.set_axis_off()
+
+
+@check_figures_equal()
+def test_empty(fig_test, fig_ref):
+    mpl.rcParams['text.usetex'] = True
+    fig_test.text(.5, .5, "% a comment")
 
 
 @check_figures_equal()

lib/matplotlib/tests/baseline_images/test_usetex/test_usetex.png

@@ -228,7 +228,8 @@ def make_tex(self, tex, fontsize):
 %s
 \pagestyle{empty}
 \begin{document}
-\fontsize{%f}{%f}%s
+%% The empty hbox ensures that a page is printed even for empty inputs.
+\fontsize{%f}{%f}\hbox{}%s
 \end{document}
 """ % (self._get_preamble(), fontsize, fontsize * 1.25, tex)
         with open(texfile, 'wb') as fh:
@@ -388,9 +389,16 @@ def make_png(self, tex, fontsize, dpi):
         # see get_rgba for a discussion of the background
         if not os.path.exists(pngfile):
             dvifile = self.make_dvi(tex, fontsize)
-            self._run_checked_subprocess(
-                ["dvipng", "-bg", "Transparent", "-D", str(dpi),
-                 "-T", "tight", "-o", pngfile, dvifile], tex)
+            cmd = ["dvipng", "-bg", "Transparent", "-D", str(dpi),
+                   "-T", "tight", "-o", pngfile, dvifile]
+            # When testing, disable FreeType rendering for reproducibility; but
+            # dvipng 1.16 has a bug (fixed in f3ff241) that breaks --freetype0
+            # mode, so for it we keep FreeType enabled; the image will be
+            # slightly off.
+            if (getattr(mpl, "_called_from_pytest", False)
+                    and mpl._get_executable_info("dvipng").version != "1.16"):
+                cmd.insert(1, "--freetype0")
+            self._run_checked_subprocess(cmd, tex)
         return pngfile
 
     def get_grey(self, tex, fontsize=None, dpi=None):
@@ -443,7 +451,7 @@ def get_text_width_height_descent(self, tex, fontsize, renderer=None):
             return width, height + depth, depth
 
         else:
-            # use dviread. It sometimes returns a wrong descent.
+            # use dviread.
             dvifile = self.make_dvi(tex, fontsize)
             with dviread.Dvi(dvifile, 72 * dpi_fraction) as dvi:
                 page, = dvi