TXTZ format: Store type of text formatting in the metadata and use it automatically when converting from TXTZ

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

@@ -147,6 +147,7 @@ class TXTInput(InputFormatPlugin):
 
         # Extract content from zip archive.
         if file_ext == 'txtz':
+            options.input_encoding = 'utf-8'
             zf = ZipFile(stream)
             zf.extractall('.')
 
@@ -154,6 +155,23 @@ class TXTInput(InputFormatPlugin):
                 if os.path.splitext(x)[1].lower() in ('.txt', '.text'):
                     with open(x, 'rb') as tf:
                         txt += tf.read() + b'\n\n'
+            if os.path.exists('metadata.opf'):
+                from lxml import etree
+                with open('metadata.opf', 'rb') as mf:
+                    raw = mf.read()
+                try:
+                    root = etree.fromstring(raw)
+                except Exception:
+                    pass
+                else:
+                    txt_formatting = root.find('text-formatting')
+                    if txt_formatting is not None and txt_formatting.text:
+                        txt_formatting = txt_formatting.text.strip()
+                        if txt_formatting in ('plain', 'textile', 'markdown') and options.formatting_type == 'auto':
+                            log.info(f'Using metadata from TXTZ archive to set text formmating type to: {txt_formatting}')
+                            options.formatting_type = txt_formatting
+                            if txt_formatting != 'plain':
+                                options.paragraph_type = 'off'
         else:
             if getattr(stream, 'name', None):
                 base_dir = os.path.dirname(stream.name)

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

@@ -158,7 +158,11 @@ class TXTZOutput(TXTOutput):
 
             # Metadata
             with open(os.path.join(tdir, 'metadata.opf'), 'wb') as mdataf:
-                mdataf.write(xml2str(oeb_book.metadata.to_opf1(), pretty_print=True))
+                root = oeb_book.metadata.to_opf1()
+                elem = root.makeelement('text-formatting')
+                elem.text = opts.txt_output_formatting
+                root.append(elem)
+                mdataf.write(xml2str(root, pretty_print=True))
 
             txtz = ZipFile(output_path, 'w')
             txtz.add_dir(tdir)