Use the same gs process to convert all of the images from PDF to PS

lib/matplotlib/testing/compare.py

@@ -8,7 +8,7 @@
 
 import matplotlib
 from matplotlib.testing.noseclasses import ImageComparisonFailure
-from matplotlib.testing import image_util
+from matplotlib.testing import image_util, util
 from matplotlib import _png
 from matplotlib import _get_configdir
 from distutils import version
@@ -138,32 +138,29 @@ def convert(old, new):
 
    return convert
 
-try:
-   import ghostscript
-except ImportError:
-   if matplotlib.checkdep_ghostscript() is not None:
-      # FIXME: make checkdep_ghostscript return the command
-      if sys.platform == 'win32':
-         gs = 'gswin32c'
-      else:
-         gs = 'gs'
-      cmd = lambda old, new: \
-        [gs, '-q', '-sDEVICE=png16m', '-dNOPAUSE', '-dBATCH', '-dSAFER',
-         '-sOutputFile=' + new, old]
-      converter['pdf'] = make_external_conversion_command(cmd)
-      converter['eps'] = make_external_conversion_command(cmd)
-else:
-   def ghostscript_lib_converter(old, new):
-      args = [
-          'matplotlib', '-q', '-sDEVICE=png16m', '-dNOPAUSE', '-dBATCH',
-          '-dSAFER', '-sOutputFile=' + new, old]
-      try:
-         gs = ghostscript.Ghostscript(*args)
-      finally:
-         gs.exit()
-         ghostscript.cleanup()
-   converter['pdf'] = ghostscript_lib_converter
-   converter['eps'] = ghostscript_lib_converter
+if matplotlib.checkdep_ghostscript() is not None:
+    def make_ghostscript_conversion_command():
+        # FIXME: make checkdep_ghostscript return the command
+        if sys.platform == 'win32':
+            gs = 'gswin32c'
+        else:
+            gs = 'gs'
+        cmd = [gs, '-q', '-sDEVICE=png16m', '-sOutputFile=-']
+
+        process = util.MiniExpect(cmd)
+
+        def do_convert(old, new):
+            process.expect("GS>")
+            process.sendline("(%s) run" % old)
+            with open(new, 'wb') as fd:
+                process.expect(">>showpage, press <return> to continue<<", fd)
+            process.sendline('')
+
+        return do_convert
+
+    converter['pdf'] = make_ghostscript_conversion_command()
+    converter['eps'] = make_ghostscript_conversion_command()
+
 
 if matplotlib.checkdep_inkscape() is not None:
    cmd = lambda old, new: \

lib/matplotlib/testing/util.py

@@ -0,0 +1,67 @@
+import subprocess
+
+
+class MiniExpect:
+    """
+    This is a very basic version of pexpect, providing only the
+    functionality necessary for the testing framework, built on top of
+    `subprocess` rather than directly on lower-level calls.
+    """
+    def __init__(self, args):
+        """
+        Start the subprocess so it may start accepting commands.
+
+        *args* is a list of commandline arguments to pass to
+        `subprocess.Popen`.
+        """
+        self._name = args[0]
+        self._process = subprocess.Popen(
+            args,
+            stdin=subprocess.PIPE,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.STDOUT)
+
+    def check_alive(self):
+        """
+        Raises a RuntimeError if the process is no longer alive.
+        """
+        returncode = self._process.poll()
+        if returncode is not None:
+            raise RuntimeError("%s unexpectedly quit" % self._name)
+
+    def sendline(self, line):
+        """
+        Send a line to the process.
+        """
+        self.check_alive()
+        stdin = self._process.stdin
+        stdin.write(line)
+        stdin.write('\n')
+        stdin.flush()
+
+    def expect(self, s, output=None):
+        """
+        Wait for the string *s* to appear in the child process's output.
+
+        *output* (optional) is a writable file object where all of the
+        content preceding *s* will be written.
+        """
+        self.check_alive()
+        read = self._process.stdout.read
+        pos = 0
+        buf = ''
+        while True:
+            char = read(1)
+            if not char:
+                raise IOError("Unexpected end-of-file")
+            elif char == s[pos]:
+                buf += char
+                pos += 1
+                if pos == len(s):
+                    return
+            else:
+                if output is not None:
+                    output.write(buf)
+                    output.write(char)
+                buf = ''
+                pos = 0