Edit Book: Live CSS: Improve detection of which tag the cursor is inside when there are multiple tags on the same line. See #1350495 (Private bug)

src/calibre/gui2/tweak_book/editor/smart/html.py

@@ -384,12 +384,14 @@ class HTMLSmarts(NullSmarts):
 
         return False
 
-    def cursor_position_with_sourceline(self, cursor):
-        ''' Return the tag containing the current cursor as a source line
+    def cursor_position_with_sourceline(self, cursor, for_position_sync=True):
+        ''' Return the tag just before the current cursor as a source line
         number and a list of tags defined on that line upto and including the
-        containing tag. '''
+        containing tag. If ``for_position_sync`` is False then the tag
+        *containing* the cursor is returned instead of the tag just before the
+        cursor. '''
         block = cursor.block()
-        offset = cursor.position() - block.position()
+        offset = cursor.positionInBlock()
         nblock, boundary = next_tag_boundary(block, offset, forward=False)
         if boundary is None:
             return None, None
@@ -412,8 +414,52 @@ class HTMLSmarts(NullSmarts):
         ud = start_block.userData()
         if ud is None:
             return None, None
-        all_tags = [t.name for t in ud.tags if (t.is_start and not t.closing and t.offset <= start_offset)]
-        return sourceline, all_tags
+        if for_position_sync:
+            return sourceline, [
+                t.name for t in ud.tags if (t.is_start and not t.closing and t.offset <= start_offset)]
+        # We discard self-closing as well as tags that are both opened and
+        # closed from the end of the list of tags as we want the tag that
+        # contains the cursor, not the last tag before the cursor
+        class Tag(object):
+            __slots__ = 'name', 'is_closed'
+            def __init__(self, name, is_closed):
+                self.name = name
+                self.is_closed = is_closed
+            def __repr__(self):
+                return '<%s%s>' % (self.name, ('/' if self.is_closed else ''))
+
+        if cursor.block().blockNumber() == start_block.blockNumber():
+            offset = cursor.positionInBlock()
+        tag_stack = []
+        in_tag = None
+        for t in ud.tags:
+            if t.offset < offset:
+                if t.is_start:
+                    if t.closing:
+                        # </tag
+                        for tag in reversed(tag_stack):
+                            is_match = not tag.is_closed and tag.name == t.name
+                            tag.is_closed = True
+                            if is_match:
+                                break
+                    else:
+                        # <tag
+                        in_tag = t.name
+                else:
+                    # tag>
+                    if in_tag is not None:
+                        tag_stack.append(Tag(in_tag, t.self_closing))
+                        in_tag = None
+
+        all_tags = []
+        found_open = False
+        for tag in reversed(tag_stack):
+            if not tag.is_closed:
+                found_open = True
+            if found_open:
+                all_tags.append(tag.name)
+
+        return sourceline, list(reversed(all_tags))
 
     def goto_sourceline(self, editor, sourceline, tags, attribute=None):
         ''' Move the cursor to the tag identified by sourceline and tags (a

src/calibre/gui2/tweak_book/editor/text.py

@@ -790,8 +790,8 @@ class TextEdit(PlainTextEdit):
         if hasattr(self.smarts, 'rename_block_tag'):
             self.smarts.rename_block_tag(self, new_name)
 
-    def current_tag(self):
-        return self.smarts.cursor_position_with_sourceline(self.textCursor())
+    def current_tag(self, for_position_sync=True):
+        return self.smarts.cursor_position_with_sourceline(self.textCursor(), for_position_sync=for_position_sync)
 
     def goto_sourceline(self, sourceline, tags, attribute=None):
         return self.smarts.goto_sourceline(self, sourceline, tags, attribute=attribute)

src/calibre/gui2/tweak_book/editor/widget.py

@@ -138,8 +138,8 @@ class Editor(QMainWindow):
             self.editor.go_to_line(val)
         return property(fget=fget, fset=fset)
 
-    def current_tag(self):
-        return self.editor.current_tag()
+    def current_tag(self, for_position_sync=True):
+        return self.editor.current_tag(for_position_sync=for_position_sync)
 
     @property
     def number_of_lines(self):

src/calibre/gui2/tweak_book/live_css.py

@@ -481,7 +481,7 @@ class LiveCSS(QWidget):
         if self.update_timer.isActive() or (ed is None and editor_name is not None):
             return QTimer.singleShot(100, self.update_data)
         if ed is not None:
-            sourceline, tags = ed.current_tag()
+            sourceline, tags = ed.current_tag(for_position_sync=False)
             if self.refresh_needed or self.now_showing != (editor_name, sourceline, tags):
                 self.show_data(editor_name, sourceline, tags)