Package: devhelp Version: 3.22.0-1+b1 After weeks of fighting this, I finally have the solution. For static HTML rendering its stupidly overcomplicated - the code involved in the failure goes devhelp (C) -> libwebkit (C++), including spawning 2 extra processes) -> libsoup (C) -> glib (C), which is why it took so long.
tldr: Its not a devhelp problem but libwebkit is a bit too restrictive in what it decides is content it can show. When libwebkit2gtk is deciding whether it can show the file requested or not, it checks Source/WebCore/platform/MIMETypeRegistry.cpp:MIMETypeRegistry::canShowMIMEType - if the MIME type determined for the requested resource doesn't start with 'text/', it is dropped immediately. The breaking documentation is XHTML rather than the usual HTML, which got me interested immediately. On this machine, the MIME type returned is 'application/x-extension-html' - the MIME type is determined in Source/WebCore/platform/network/soup/ResourceHandleSoup.cpp:sendRequestCallback, which calls libsoup soup_request_get_content_type, the result I think is set in libsoup/soup-request-file.c:soup_request_file_send, which runs g_file_query_info on the file, then g_file_info_get_content_type and finally g_content_type_get_mime_type. These functions are from glib, which call into functions maintained in the gio/xdgmime directory. So clearly something has registered this odd MIME type in the MIME type cache - to check for the dodgy MIME type: ======================================================================= grep -a 'application/x-extension-xhtml' ~/.local/share/mime/mime.cache /usr/local/share/mime/mime.cache /usr/share/mime/mime.cache ======================================================================= This brought up some clear WINE-related hit in '~/.local/share/mime/mime.cache' for me. The associated MIME type config XML is in '~/.local/share/mime/packages', 'user-extension-html.xml' was the culprit - killing this file then running: ======================================== update-mime-database ~/.local/share/mime ======================================== finally allowed the documentation to render.
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