Edit book: Auto-generate links to existing stylesheets when adding a new HTML file. Fixes #1733845 [[enhancement] editor, adding or importing a new hmtl page, add css](https://bugs.launchpad.net/calibre/+bug/1733845)

src/calibre/ebooks/oeb/polish/css.py

@@ -13,9 +13,9 @@
 from css_selectors import parse, SelectorSyntaxError
 
 from calibre import force_unicode
-from calibre.ebooks.oeb.base import OEB_STYLES, OEB_DOCS
+from calibre.ebooks.oeb.base import OEB_STYLES, OEB_DOCS, XHTML
 from calibre.ebooks.oeb.normalize_css import normalize_filter_css, normalizers
-from calibre.ebooks.oeb.polish.pretty import pretty_script_or_style
+from calibre.ebooks.oeb.polish.pretty import pretty_script_or_style, pretty_xml_tree, serialize
 from calibre.utils.icu import numeric_sort_key
 from css_selectors import Select, SelectorError
 
@@ -369,3 +369,19 @@ def rule_sort_key(rule):
         return primary, secondary, tertiary
     sheet.cssRules.sort(key=rule_sort_key)
     return sheet
+
+
+def add_stylesheet_links(container, name, text):
+    root = container.parse_xhtml(text, name)
+    head = root.xpath('//*[local-name() = "head"]')
+    if not head:
+        return
+    head = head[0]
+    sheets = tuple(container.manifest_items_of_type(lambda mt: mt in OEB_STYLES))
+    if not sheets:
+        return
+    for sname in sheets:
+        link = head.makeelement(XHTML('link'), type='text/css', rel='stylesheet', href=container.name_to_href(sname, name))
+        head.append(link)
+    pretty_xml_tree(head)
+    return serialize(root, 'text/html')

src/calibre/gui2/tweak_book/__init__.py

@@ -76,6 +76,7 @@
 d['insert_full_screen_image'] = False
 d['preserve_aspect_ratio_when_inserting_image'] = False
 d['file_list_shows_full_pathname'] = False
+d['auto_link_stylesheets'] = True
 del d
 
 ucase_map = {l:string.ascii_uppercase[i] for i, l in enumerate(string.ascii_lowercase)}

src/calibre/gui2/tweak_book/file_list.py

@@ -23,6 +23,7 @@
 from calibre.ebooks.oeb.polish.cover import (
     get_cover_page_name, get_raster_cover_name, is_raster_image
 )
+from calibre.ebooks.oeb.polish.css import add_stylesheet_links
 from calibre.ebooks.oeb.polish.replace import get_recommended_folders
 from calibre.gui2 import (
     choose_dir, choose_files, choose_save_file, elided_text, error_dialog,
@@ -827,6 +828,9 @@ def __init__(self, parent=None):
         self.name = n = QLineEdit(self)
         n.textChanged.connect(self.update_ok)
         l.addWidget(n)
+        self.link_css = lc = QCheckBox(_('Automatically add style-sheet links into new HTML files'))
+        lc.setChecked(tprefs['auto_link_stylesheets'])
+        l.addWidget(lc)
         self.err_label = la = QLabel('')
         la.setWordWrap(True)
         l.addWidget(la)
@@ -856,6 +860,7 @@ def import_file(self):
             self.do_import_file(path[0])
 
     def do_import_file(self, path, hide_button=False):
+        self.link_css.setVisible(False)
         with open(path, 'rb') as f:
             self.file_data = f.read()
         name = os.path.basename(path)
@@ -878,6 +883,7 @@ def accept(self):
         if not self.name_is_ok:
             return error_dialog(self, _('No name specified'), _(
                 'You must specify a name for the new file, with an extension, for example, chapter1.html'), show=True)
+        tprefs['auto_link_stylesheets'] = self.link_css.isChecked()
         name = unicode(self.name.text())
         name, ext = name.rpartition('.')[0::2]
         name = (name + '.' + ext.lower()).replace('\\', '/')
@@ -885,6 +891,10 @@ def accept(self):
         if not self.file_data:
             if mt in OEB_DOCS:
                 self.file_data = template_for('html').encode('utf-8')
+                if tprefs['auto_link_stylesheets']:
+                    data = add_stylesheet_links(current_container(), name, self.file_data)
+                    if data is not None:
+                        self.file_data = data
                 self.using_template = True
             elif mt in OEB_STYLES:
                 self.file_data = template_for('css').encode('utf-8')

src/calibre/gui2/tweak_book/templates.py

@@ -14,12 +14,13 @@
 '''\
 <?xml version='1.0' encoding='utf-8'?>
 <html xmlns="http://www.w3.org/1999/xhtml">
-    <head>
-        <title>{TITLE}</title>
-    </head>
-    <body>
-        %CURSOR%
-    </body>
+<head>
+    <title>{TITLE}</title>
+</head>
+
+<body>
+    %CURSOR%
+</body>
 </html>
 ''',
 
@@ -46,4 +47,3 @@ def template_for(syntax):
     }
     return raw_template_for(syntax).format(
         **{k:prepare_string_for_xml(v, True) for k, v in data.iteritems()})
-