Add a last resort font for missing glyphs

Author: QuLogic

LICENSE/LICENSE_LAST_RESORT_FONT

@@ -0,0 +1,97 @@
+Last Resort High-Efficiency Font License
+========================================
+
+This Font Software is licensed under the SIL Open Font License,
+Version 1.1.
+
+This license is copied below, and is also available with a FAQ at:
+http://scripts.sil.org/OFL
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font
+creation efforts of academic and linguistic communities, and to
+provide a free and open framework in which fonts may be shared and
+improved in partnership with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded,
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply to
+any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software
+components as distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to,
+deleting, or substituting -- in part or in whole -- any of the
+components of the Original Version, by changing formats or by porting
+the Font Software to a new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed,
+modify, redistribute, and sell modified and unmodified copies of the
+Font Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components, in
+Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the
+corresponding Copyright Holder. This restriction only applies to the
+primary font name as presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created using
+the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.
+
+SPDX-License-Identifier: OFL-1.1

lib/matplotlib/font_manager.py

@@ -1552,17 +1552,26 @@ def is_opentype_cff_font(filename):
 
 
 @lru_cache(64)
-def _get_font(font_filepaths, hinting_factor, *, _kerning_factor, thread_id):
+def _get_font(font_filepaths, hinting_factor, *, _kerning_factor, thread_id,
+              enable_last_resort):
     first_fontpath, *rest = font_filepaths
+    fallback_list = [
+        ft2font.FT2Font(fpath, hinting_factor, _kerning_factor=_kerning_factor)
+        for fpath in rest
+    ]
+    # Add Last Resort font so we always have glyphs regardless of font.
+    if enable_last_resort:
+        path = _cached_realpath(
+            cbook._get_data_path('fonts', 'ttf', 'LastResortHE-Regular.ttf'))
+        last_resort = ft2font.FT2Font(path, hinting_factor,
+                                      _kerning_factor=_kerning_factor)
+        # Ensure we are using the right charmap; FreeType picks the Unicode one
+        # by default, but this exists only for Windows, and is empty.
+        last_resort.set_charmap(0)
+        fallback_list.append(last_resort)
     return ft2font.FT2Font(
         first_fontpath, hinting_factor,
-        _fallback_list=[
-            ft2font.FT2Font(
-                fpath, hinting_factor,
-                _kerning_factor=_kerning_factor
-            )
-            for fpath in rest
-        ],
+        _fallback_list=fallback_list,
         _kerning_factor=_kerning_factor
     )
 
@@ -1618,7 +1627,8 @@ def get_font(font_filepaths, hinting_factor=None):
         hinting_factor,
         _kerning_factor=mpl.rcParams['text.kerning_factor'],
         # also key on the thread ID to prevent segfaults with multi-threading
-        thread_id=threading.get_ident()
+        thread_id=threading.get_ident(),
+        enable_last_resort=mpl.rcParams['font.enable_last_resort'],
     )
 
 

lib/matplotlib/mpl-data/fonts/ttf/LastResortHE-Regular.ttf

@@ -278,6 +278,11 @@
 #font.fantasy:    Chicago, Charcoal, Impact, Western, xkcd script, fantasy
 #font.monospace:  DejaVu Sans Mono, Bitstream Vera Sans Mono, Computer Modern Typewriter, Andale Mono, Nimbus Mono L, Courier New, Courier, Fixed, Terminal, monospace
 
+## If font.enable_last_resort is True, then Unicode Consortium's Last Resort
+## font will be appended to all font selections. This ensures that there will
+## always be a glyph displayed.
+#font.enable_last_resort: true
+
 
 ## ***************************************************************************
 ## * TEXT                                                                    *

lib/matplotlib/mpl-data/matplotlibrc

@@ -1002,6 +1002,7 @@ def _convert_validator_spec(key, conv):
     "boxplot.meanprops.linewidth":       validate_float,
 
     ## font props
+    "font.enable_last_resort":     validate_bool,
     "font.family":     validate_stringlist,  # used by text object
     "font.style":      validate_string,
     "font.variant":    validate_string,

lib/matplotlib/rcsetup.py

@@ -823,6 +823,7 @@ def test_pdf_kerning():
 
 
 def test_unsupported_script(recwarn):
+    plt.rcParams['font.enable_last_resort'] = False
     fig = plt.figure()
     t = fig.text(.5, .5, "\N{BENGALI DIGIT ZERO}")
     fig.canvas.draw()