Edit book: Preview: Support displaying mathematics

src/calibre/gui2/tweak_book/preview.py

@@ -27,7 +27,7 @@ from calibre.ebooks.oeb.polish.parsing import parse
 from calibre.gui2 import NO_URL_FORMATTING, error_dialog, open_url
 from calibre.gui2.tweak_book import TOP, actions, current_container, editors, tprefs
 from calibre.gui2.tweak_book.file_list import OpenWithHandler
-from calibre.gui2.viewer.web_view import send_reply
+from calibre.gui2.viewer.web_view import handle_mathjax_request, send_reply
 from calibre.gui2.webengine import (
     Bridge, RestartingWebEngineView, create_script, from_js, insert_scripts,
     secure_webengine, to_js
@@ -176,6 +176,9 @@ class UrlSchemeHandler(QWebEngineUrlSchemeHandler):
             return
         name = url.path()[1:]
         try:
+            if name.startswith('calibre_internal-mathjax/'):
+                handle_mathjax_request(rq, name.partition('-')[-1])
+                return
             c = current_container()
             if not c.has_name(name):
                 rq.fail(rq.UrlNotFound)

src/calibre/utils/rapydscript.py

@@ -387,7 +387,10 @@ def compile_editor():
     rapydscript_dir = os.path.join(base, 'src', 'pyj')
     fname = os.path.join(rapydscript_dir, 'editor.pyj')
     with lopen(fname, 'rb') as f:
-        js = compile_fast(f.read(), fname).replace('__SPECIAL_TITLE__', special_title, 1)
+        js = compile_fast(f.read(), fname).replace(
+            '__SPECIAL_TITLE__', special_title, 1).replace(
+            '__FAKE_PROTOCOL__', FAKE_PROTOCOL, 1).replace(
+            '__FAKE_HOST__', FAKE_HOST, 1)
     base = os.path.join(base, 'resources')
     atomic_write(base, 'editor.js', js)
 

src/pyj/editor.pyj

@@ -9,6 +9,10 @@ from live_css import get_matched_css, get_sourceline_address
 from qt import from_python, to_python
 
 
+FAKE_HOST = '__FAKE_HOST__'
+FAKE_PROTOCOL = '__FAKE_PROTOCOL__'
+
+
 def is_hidden(elem):
     while elem:
         if (elem.style and (elem.style.visibility is 'hidden' or elem.style.display is 'none')):
@@ -168,6 +172,22 @@ def live_css(editor_name, sourceline, tags):
         to_python.live_css_data(ans)
 
 
+def check_for_maths():
+    if document.body.getElementsByTagNameNS('http://www.w3.org/1998/Math/MathML', 'math').length > 0:
+        return True
+    for s in document.scripts:
+        if s.type is 'text/x-mathjax-config':
+            return True
+    return False
+
+
+def load_mathjax():
+    script = E.script(type='text/javascript')
+    script.async = True
+    script.src = f'{FAKE_PROTOCOL}://{FAKE_HOST}/calibre_internal-mathjax/startup.js'
+    document.head.appendChild(script)
+
+
 document.body.addEventListener('click', onclick, True)
 document.documentElement.appendChild(E.style(
     type='text/css',
@@ -175,3 +195,5 @@ document.documentElement.appendChild(E.style(
 ))
 
 fix_fullscreen_svg_images()
+if check_for_maths():
+    load_mathjax()