Deprecate backend_ps.get_bbox_header, and split it for internal use.

It's clearly an internal helper, and the two parts (the actual bbox
header and the rotation command) don't really benefit from being smushed
together, so make the function private and split the two parts.

Author: anntzer

doc/api/next_api_changes/deprecations/26960-AL.rst

@@ -0,0 +1,3 @@
+``backend_ps.get_bbox_header``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+... is deprecated, as it is considered an internal helper.

lib/matplotlib/backends/backend_ps.py

@@ -9,6 +9,7 @@
 from io import StringIO
 import itertools
 import logging
+import math
 import os
 import pathlib
 import shutil
@@ -915,7 +916,7 @@ def print_figure_impl(fh):
             print(f"%%LanguageLevel: 3\n"
                   f"{dsc_comments}\n"
                   f"%%Orientation: {orientation.name}\n"
-                  f"{get_bbox_header(bbox)[0]}\n"
+                  f"{_get_bbox_header(bbox)}\n"
                   f"%%EndComments\n",
                   end="", file=fh)
 
@@ -1024,7 +1025,7 @@ def _print_figure_tex(
 %!PS-Adobe-3.0 EPSF-3.0
 %%LanguageLevel: 3
 {dsc_comments}
-{get_bbox_header(bbox)[0]}
+{_get_bbox_header(bbox)}
 %%EndComments
 %%BeginProlog
 /mpldict {len(_psDefs)} dict def
@@ -1219,21 +1220,26 @@ def xpdf_distill(tmpfile, eps=False, ptype='letter', bbox=None, rotated=False):
         pstoeps(tmpfile)
 
 
+@_api.deprecated("3.9")
 def get_bbox_header(lbrt, rotated=False):
     """
     Return a postscript header string for the given bbox lbrt=(l, b, r, t).
     Optionally, return rotate command.
     """
+    return _get_bbox_header(lbrt), (_get_rotate_command(lbrt) if rotated else "")
 
+
+def _get_bbox_header(lbrt):
+    """Return a PostScript header string for bounding box *lbrt*=(l, b, r, t)."""
     l, b, r, t = lbrt
-    if rotated:
-        rotate = f"{l+r:.2f} {0:.2f} translate\n90 rotate"
-    else:
-        rotate = ""
-    bbox_info = '%%%%BoundingBox: %d %d %d %d' % (l, b, np.ceil(r), np.ceil(t))
-    hires_bbox_info = f'%%HiResBoundingBox: {l:.6f} {b:.6f} {r:.6f} {t:.6f}'
+    return (f"%%BoundingBox: {int(l)} {int(b)} {math.ceil(r)} {math.ceil(t)}\n"
+            f"%%HiResBoundingBox: {l:.6f} {b:.6f} {r:.6f} {t:.6f}")
+
 
-    return '\n'.join([bbox_info, hires_bbox_info]), rotate
+def _get_rotate_command(lbrt):
+    """Return a PostScript 90° rotation command for bounding box *lbrt*=(l, b, r, t)."""
+    l, b, r, t = lbrt
+    return f"{l+r:.2f} {0:.2f} translate\n90 rotate"
 
 
 def pstoeps(tmpfile, bbox=None, rotated=False):
@@ -1243,12 +1249,6 @@ def pstoeps(tmpfile, bbox=None, rotated=False):
     None, original bbox will be used.
     """
 
-    # if rotated==True, the output eps file need to be rotated
-    if bbox:
-        bbox_info, rotate = get_bbox_header(bbox, rotated=rotated)
-    else:
-        bbox_info, rotate = None, None
-
     epsfile = tmpfile + '.eps'
     with open(epsfile, 'wb') as epsh, open(tmpfile, 'rb') as tmph:
         write = epsh.write
@@ -1257,7 +1257,7 @@ def pstoeps(tmpfile, bbox=None, rotated=False):
             if line.startswith(b'%!PS'):
                 write(b"%!PS-Adobe-3.0 EPSF-3.0\n")
                 if bbox:
-                    write(bbox_info.encode('ascii') + b'\n')
+                    write(_get_bbox_header(bbox).encode('ascii') + b'\n')
             elif line.startswith(b'%%EndComments'):
                 write(line)
                 write(b'%%BeginProlog\n'
@@ -1269,8 +1269,8 @@ def pstoeps(tmpfile, bbox=None, rotated=False):
                       b'/setpagedevice {pop} def\n'
                       b'%%EndProlog\n'
                       b'%%Page 1 1\n')
-                if rotate:
-                    write(rotate.encode('ascii') + b'\n')
+                if rotated:  # The output eps file need to be rotated.
+                    write(_get_rotate_command(bbox).encode('ascii') + b'\n')
                 break
             elif bbox and line.startswith((b'%%Bound', b'%%HiResBound',
                                            b'%%DocumentMedia', b'%%Pages')):