PGF: Clip lines/markers to maximum LaTeX dimensions.

This has been open for many years without any change to LaTeX, so it
seems unlikely they are going to change how their parsing works.

Fixes matplotlib#4482.

Author: QuLogic

lib/matplotlib/backends/backend_pgf.py

@@ -426,8 +426,12 @@ def draw_markers(self, gc, marker_path, marker_trans, path, trans,
                             fill=rgbFace is not None)
         writeln(self.fh, r"}")
 
+        maxcoord = 16383 / 72.27 * self.dpi  # Max dimensions in LaTeX.
+        clip = (-maxcoord, -maxcoord, maxcoord, maxcoord)
+
         # draw marker for each vertex
-        for point, code in path.iter_segments(trans, simplify=False):
+        for point, code in path.iter_segments(trans, simplify=False,
+                                              clip=clip):
             x, y = point[0] * f, point[1] * f
             writeln(self.fh, r"\begin{pgfscope}")
             writeln(self.fh, r"\pgfsys@transformshift{%fin}{%fin}" % (x, y))
@@ -564,11 +568,13 @@ def _print_pgf_path(self, gc, path, transform, rgbFace=None):
         f = 1. / self.dpi
         # check for clip box / ignore clip for filled paths
         bbox = gc.get_clip_rectangle() if gc else None
+        maxcoord = 16383 / 72.27 * self.dpi  # Max dimensions in LaTeX.
         if bbox and (rgbFace is None):
             p1, p2 = bbox.get_points()
-            clip = (p1[0], p1[1], p2[0], p2[1])
+            clip = (max(p1[0], -maxcoord), max(p1[1], -maxcoord),
+                    min(p2[0], maxcoord), min(p2[1], maxcoord))
         else:
-            clip = None
+            clip = (-maxcoord, -maxcoord, maxcoord, maxcoord)
         # build path
         for points, code in path.iter_segments(transform, clip=clip):
             if code == Path.MOVETO:

lib/matplotlib/tests/test_backend_pgf.py

@@ -150,11 +150,19 @@ def test_rcupdate():
 @pytest.mark.style('default')
 @pytest.mark.backend('pgf')
 def test_pathclip():
+    np.random.seed(19680801)
     mpl.rcParams.update({'font.family': 'serif', 'pgf.rcfonts': False})
-    plt.plot([0., 1e100], [0., 1e100])
-    plt.xlim(0, 1)
-    plt.ylim(0, 1)
-    plt.savefig(BytesIO(), format="pdf")  # No image comparison.
+    fig, axs = plt.subplots(1, 2)
+
+    axs[0].plot([0., 1e100], [0., 1e100])
+    axs[0].set_xlim(0, 1)
+    axs[0].set_ylim(0, 1)
+
+    axs[1].scatter([0, 1], [1, 1])
+    axs[1].hist(np.random.normal(size=1000), bins=20, range=[-10, 10])
+    axs[1].set_xscale('log')
+
+    fig.savefig(BytesIO(), format="pdf")  # No image comparison.
 
 
 # test mixed mode rendering