Conversion: Automatically set the page progression direction for books that do not have it set and have their primary language either Arabic or

Hebrew. Fixes #2592 (Automatically inserting page-progression-direction="rtl" in rtl languages ​​(Arabic and Hebrew))

src/calibre/ebooks/conversion/plugins/epub_output.py

@@ -205,6 +205,7 @@ class EPUBOutput(OutputFormatPlugin):
             from calibre.ebooks.oeb.transforms.filenames import UniqueFilenames
             UniqueFilenames()(oeb, opts)
 
+        self.oeb.set_page_progression_direction_if_needed()
         self.workaround_ade_quirks()
         self.workaround_webkit_quirks()
         self.upshift_markup()

src/calibre/ebooks/conversion/plugins/mobi_output.py

@@ -188,6 +188,7 @@ class MOBIOutput(OutputFormatPlugin):
             mobi_type = 'old'  # Amazon does not support KF8 periodicals
         create_kf8 = mobi_type in ('new', 'both')
 
+        self.oeb.set_page_progression_direction_if_needed()
         remove_html_cover(self.oeb, self.log)
         resources = Resources(oeb, opts, self.is_periodical,
                 add_fonts=create_kf8)
@@ -313,6 +314,7 @@ class AZW3Output(OutputFormatPlugin):
         self.oeb, self.opts, self.log = oeb, opts, log
         opts.mobi_periodical = self.is_periodical
         passthrough = getattr(opts, 'mobi_passthrough', False)
+        self.oeb.set_page_progression_direction_if_needed()
         remove_duplicate_anchors(oeb)
 
         resources = Resources(self.oeb, self.opts, self.is_periodical,

src/calibre/ebooks/oeb/base.py

@@ -27,7 +27,7 @@ from calibre.translations.dynamic import translate
 from calibre.utils.cleantext import clean_xml_chars
 from calibre.utils.icu import numeric_sort_key
 from calibre.utils.icu import title_case as icu_title
-from calibre.utils.localization import __
+from calibre.utils.localization import __, is_rtl_lang
 from calibre.utils.short_uuid import uuid4
 from calibre.utils.xml_parse import safe_xml_fromstring
 from polyglot.builtins import codepoint_to_chr, iteritems, itervalues, string_or_bytes
@@ -1823,6 +1823,16 @@ class OEBBook:
         self.auto_generated_toc = True
         self._temp_files = []
 
+    def set_page_progression_direction_if_needed(self):
+        if not self.spine.page_progression_direction:
+            try:
+                lang = self.metadata.language[0].value
+                if is_rtl_lang(lang):
+                    self.spine.page_progression_direction = 'rtl'
+            except Exception:
+                raise
+                pass
+
     def clean_temp_files(self):
         for path in self._temp_files:
             try:

src/calibre/utils/localization.py

@@ -610,3 +610,7 @@ def localize_website_link(url):
     parts = list(parts)
     parts[2] = path
     return urlunparse(parts)
+
+
+def is_rtl_lang(lang):
+    return lang[:2].lower() in ('ar', 'he')