Suppress repeated logwarns in postscript output.

anntzer · anntzer · commit 4e7a5bc4b508 · 2021-06-16T11:47:26.000+02:00
For a given call to savefig(), we only need to warn once about alpha or
usetex support.  (RendererPS is generated afresh for each savefig()
call, so it's fine to do the caching on it.)
diff --git a/lib/matplotlib/backends/backend_ps.py b/lib/matplotlib/backends/backend_ps.py
@@ -5,6 +5,7 @@
 import codecs
 import datetime
 from enum import Enum
+import functools
 import glob
 from io import StringIO
 import logging
@@ -251,6 +252,21 @@ def __init__(self, width, height, pswriter, imagedpi=72):
         self._path_collection_id = 0
 
         self._character_tracker = _backend_pdf_ps.CharacterTracker()
+        self._logwarn_once = functools.lru_cache(None)(_log.warning)
+
+    def _is_transparent(self, rgb_or_rgba):
+        if rgb_or_rgba is None:
+            return True  # Consistent with rgbFace semantics.
+        elif len(rgb_or_rgba) == 4:
+            if rgb_or_rgba[3] == 0:
+                return True
+            if rgb_or_rgba[3] != 1:
+                self._logwarn_once(
+                    "The PostScript backend does not support transparency; "
+                    "partially transparent artists will be rendered opaque.")
+            return False
+        else:  # len() == 3.
+            return False
 
     def set_color(self, r, g, b, store=True):
         if (r, g, b) != self.color:
@@ -447,7 +463,7 @@ def draw_markers(
 
         ps_color = (
             None
-            if _is_transparent(rgbFace)
+            if self._is_transparent(rgbFace)
             else '%1.3f setgray' % rgbFace[0]
             if rgbFace[0] == rgbFace[1] == rgbFace[2]
             else '%1.3f %1.3f %1.3f setrgbcolor' % rgbFace[:3])
@@ -540,7 +556,7 @@ def draw_path_collection(self, gc, master_transform, paths, all_transforms,
     def draw_tex(self, gc, x, y, s, prop, angle, *, mtext=None):
         # docstring inherited
         if not hasattr(self, "psfrag"):
-            _log.warning(
+            self._logwarn_once(
                 "The PS backend determines usetex status solely based on "
                 "rcParams['text.usetex'] and does not support having "
                 "usetex=True only for some elements; this element will thus "
@@ -579,7 +595,7 @@ def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None):
         if debugPS:
             self._pswriter.write("% text\n")
 
-        if _is_transparent(gc.get_rgb()):
+        if self._is_transparent(gc.get_rgb()):
             return  # Special handling for fully transparent.
 
         if ismath == 'TeX':
@@ -723,10 +739,10 @@ def _draw_ps(self, ps, gc, rgbFace, fill=True, stroke=True, command=None):
         if debugPS and command:
             write("% "+command+"\n")
         mightstroke = (gc.get_linewidth() > 0
-                       and not _is_transparent(gc.get_rgb()))
+                       and not self._is_transparent(gc.get_rgb()))
         if not mightstroke:
             stroke = False
-        if _is_transparent(rgbFace):
+        if self._is_transparent(rgbFace):
             fill = False
         hatch = gc.get_hatch()
 
@@ -764,21 +780,6 @@ def _draw_ps(self, ps, gc, rgbFace, fill=True, stroke=True, command=None):
         write("grestore\n")
 
 
-def _is_transparent(rgb_or_rgba):
-    if rgb_or_rgba is None:
-        return True  # Consistent with rgbFace semantics.
-    elif len(rgb_or_rgba) == 4:
-        if rgb_or_rgba[3] == 0:
-            return True
-        if rgb_or_rgba[3] != 1:
-            _log.warning(
-                "The PostScript backend does not support transparency; "
-                "partially transparent artists will be rendered opaque.")
-        return False
-    else:  # len() == 3.
-        return False
-
-
 @_api.deprecated("3.4", alternative="GraphicsContextBase")
 class GraphicsContextPS(GraphicsContextBase):
     def get_capstyle(self):
diff --git a/lib/matplotlib/tests/test_backend_ps.py b/lib/matplotlib/tests/test_backend_ps.py
@@ -149,10 +149,11 @@ def test_failing_latex():
 @needs_usetex
 def test_partial_usetex(caplog):
     caplog.set_level("WARNING")
-    plt.figtext(.5, .5, "foo", usetex=True)
+    plt.figtext(.1, .1, "foo", usetex=True)
+    plt.figtext(.2, .2, "bar", usetex=True)
     plt.savefig(io.BytesIO(), format="ps")
-    assert caplog.records and all("as if usetex=False" in record.getMessage()
-                                  for record in caplog.records)
+    record, = caplog.records  # asserts there's a single record.
+    assert "as if usetex=False" in record.getMessage()
 
 
 @image_comparison(["useafm.eps"])
