René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: TTC font files containing CFF data result in (crashes or) broken PS and PDF files","articleBody":"### Bug summary\n\nSome font files have the .ttc extension (\"TrueType collection\") but actually contain CFF data (\"compact font format\") which is not supported by the PDF and PS backends (#2869). Currently ttc files cause a crash which is easily fixed with\r\n\r\n```patch\r\ndiff --git a/lib/matplotlib/backends/_backend_pdf_ps.py b/lib/matplotlib/backends/_backend_pdf_ps.py\r\nindex 3224fb90e3..eaf8c8c094 100644\r\n--- a/lib/matplotlib/backends/_backend_pdf_ps.py\r\n+++ b/lib/matplotlib/backends/_backend_pdf_ps.py\r\n@@ -39,6 +39,10 @@ def get_glyphs_subset(fontfile, characters):\r\n     # prevent subsetting FontForge Timestamp and other tables\r\n     options.drop_tables += ['FFTM', 'PfEd']\r\n\r\n+    if fontfile.endswith('ttc'):\r\n+        options.font_number = 0\r\n     with subset.load_font(fontfile, options) as font:\r\n         subsetter = subset.Subsetter(options=options)\r\n         subsetter.populate(text=characters)\r\n```\r\n\r\nbut with this fix, some ttc fonts result in broken output files if using font type 42 (type 3 seems to be fine).\r\n\r\nThe font manager lists fonts using `fc-list -f '%{file}\\n'` and selects based on file extensions. A better way might be `fc-list :fontformat=TrueType -f '%{file}\\n'` since fontconfig knows about the real font format. However, FreeType supports CFF fonts so we probably shouldn't exclude them from other backends or type 3 embedding.\r\n\r\n(The correct way to embed CFF fonts in PostScript is described in https://adobe-type-tools.github.io/font-tech-notes/pdfs/5176.CFF.pdf, and in PDF the font type needs to be Type1C, CIDFontType0C, or OpenType.)\n\n### Code for reproduction\n\n```python\n# this needs the patch above\r\n\r\nimport matplotlib\r\nfrom pathlib import Path\r\nmatplotlib.use('ps')\r\nfrom matplotlib import pyplot as plt\r\n\r\n# the following font is in CFF format on my Mac\r\nfont = Path('/System/Library/Fonts/AppleSDGothicNeo.ttc')\r\n\r\nfig = plt.figure()\r\nplt.axis((0,10,0,10))\r\nplt.text(3,3,'Glib jocks quiz nymph to vex dwarf.', font=font)\r\n\r\nmatplotlib.rc('ps', fonttype=42)\r\nplt.savefig('fmt42.ps')\r\n\r\nmatplotlib.rc('ps', fonttype=3)\r\nplt.savefig('fmt3.ps')\n```\n\n\n### Actual outcome\n\n`ps2pdf fmt42.ps` errors out with\r\n\r\n```\r\nError: /invalidfont in definefont\r\nOperand stack:\r\n   AppleSDGothicNeo-Regular   --dict:11/15(L)--   Font\r\nExecution stack:\r\n   %interp_exit   .runexec2   --nostringval--   definefont   --nostringval--   2   %stopped_push   --nostringval--   definefont   definefont   false   1   %stopped_push   1990   1   3   %oparray_pop   1989   1   3   %oparray_pop   1977   1   3   %oparray_pop   1833   1   3   %oparray_pop   --nostringval--   %errorexec_pop   .runexec2   --nostringval--   definefont   --nostringval--   2   %stopped_push   --nostringval--   1923   2   4   %oparray_pop\r\nDictionary stack:\r\n   --dict:729/1123(ro)(G)--   --dict:0/20(G)--   --dict:76/200(L)--   --dict:10/12(L)--\r\nCurrent allocation mode is local\r\nCurrent file position is 11851\r\nGPL Ghostscript 9.54.0: Unrecoverable error, exit code 1\r\n```\n\n### Expected outcome\n\n\u003cimg width=\"589\" alt=\"image\" src=\"https://user-images.githubusercontent.com/92814/130317552-7ceece63-7c05-4789-86e4-e48f897b0794.png\"\u003e\r\n\n\n### Operating system\n\nmacOS 11.5.2\n\n### Matplotlib Version\n\nmaster as of a4e81e7f + some of my local changes\n\n### Matplotlib Backend\n\n_No response_\n\n### Python version\n\n_No response_\n\n### Jupyter version\n\n_No response_\n\n### Other libraries\n\nfontTools 4.24.4\n\n### Installation\n\nsource\n\n### Conda channel\n\n_No response_","author":{"url":"https://github.com/jkseppan","@type":"Person","name":"jkseppan"},"datePublished":"2021-08-21T09:38:52.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/20870/matplotlib/issues/20870"}