Use the highlighted matching tags for Live CSS as a performance optimization

src/calibre/gui2/tweak_book/boss.py

@@ -1134,14 +1134,6 @@ class Boss(QObject):
             if name is not None and getattr(ed, 'syntax', None) == 'html':
                 self.gui.preview.sync_to_editor(name, ed.current_tag())
 
-    def sync_live_css_to_editor(self):
-        ' Sync the Live CSS panel to the current cursor position in the current editor '
-        ed = self.gui.central.current_editor
-        if ed is not None:
-            name = editor_name(ed)
-            if name is not None and getattr(ed, 'syntax', None) == 'html':
-                self.gui.live_css.sync_to_editor(name)
-
     def goto_style_declaration(self, data):
         name = data['name']
         editor = self.edit_file(name, syntax=data['syntax'])
@@ -1152,12 +1144,13 @@ class Boss(QObject):
         editor.data_changed.connect(self.editor_data_changed)
         editor.copy_available_state_changed.connect(self.editor_copy_available_state_changed)
         editor.cursor_position_changed.connect(self.sync_preview_to_editor)
-        editor.cursor_position_changed.connect(self.sync_live_css_to_editor)
         editor.cursor_position_changed.connect(self.update_cursor_position)
         if hasattr(editor, 'word_ignored'):
             editor.word_ignored.connect(self.word_ignored)
         if hasattr(editor, 'link_clicked'):
             editor.link_clicked.connect(self.editor_link_clicked)
+        if getattr(editor, 'syntax', None) == 'html':
+            editor.smart_highlighting_updated.connect(self.gui.live_css.sync_to_editor)
         if data is not None:
             if use_template:
                 editor.init_from_template(data)
@@ -1284,7 +1277,6 @@ class Boss(QObject):
                     # focused. This is not inefficient since multiple requests
                     # to sync are de-bounced with a 100 msec wait.
                     self.sync_preview_to_editor()
-                self.sync_live_css_to_editor()
             if name is not None:
                 self.gui.file_list.mark_name_as_current(name)
             if ed.has_line_numbers:

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

@@ -20,7 +20,7 @@ class NullSmarts(object):
     def verify_for_spellcheck(self, cursor, highlighter):
         return False
 
-    def cursor_position_with_sourceline(self, cursor):
+    def cursor_position_with_sourceline(self, cursor, for_position_sync=True):
         return None, None
 
     def goto_sourceline(self, editor, sourceline, tags, attribute=None):

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

@@ -270,6 +270,10 @@ def set_style_property(tag, property_name, value, editor):
 
 class HTMLSmarts(NullSmarts):
 
+    def __init__(self, *args, **kwargs):
+        NullSmarts.__init__(self, *args, **kwargs)
+        self.last_matched_tag = None
+
     def get_extra_selections(self, editor):
         ans = []
 
@@ -288,7 +292,7 @@ class HTMLSmarts(NullSmarts):
 
         c = editor.textCursor()
         block, offset = c.block(), c.positionInBlock()
-        tag = find_closest_containing_tag(block, offset, max_tags=2000)
+        tag = self.last_matched_tag = find_closest_containing_tag(block, offset, max_tags=2000)
         if tag is not None:
             add_tag(tag)
             tag = find_closing_tag(tag, max_tags=4000)
@@ -391,13 +395,14 @@ class HTMLSmarts(NullSmarts):
 
         return False
 
-    def cursor_position_with_sourceline(self, cursor, for_position_sync=True):
+    def cursor_position_with_sourceline(self, cursor, for_position_sync=True, use_matched_tag=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. If ``for_position_sync`` is False then the tag
         *containing* the cursor is returned instead of the tag just before the
-        cursor. Note that finding the containing tag is relative expensive, so
+        cursor. Note that finding the containing tag is expensive, so
-        use with care.'''
+        use with care. As an optimization, the last tag matched by
+        get_extra_selections is used, unless use_matched_tag is False. '''
         block, offset = cursor.block(), cursor.positionInBlock()
         if for_position_sync:
             nblock, boundary = next_tag_boundary(block, offset, forward=False)
@@ -417,6 +422,10 @@ class HTMLSmarts(NullSmarts):
                                 break
                     block, offset = block.previous(), sys.maxint
         else:
+            tag = None
+            if use_matched_tag:
+                tag = self.last_matched_tag
+            if tag is None:
                 tag = find_closest_containing_tag(block, offset, max_tags=2000)
             if tag is None:
                 return None, None

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

@@ -132,6 +132,7 @@ class PlainTextEdit(QPlainTextEdit):
 class TextEdit(PlainTextEdit):
 
     link_clicked = pyqtSignal(object)
+    smart_highlighting_updated = pyqtSignal()
 
     def __init__(self, parent=None, expected_geometry=(100, 50)):
         PlainTextEdit.__init__(self, parent)
@@ -274,6 +275,7 @@ class TextEdit(PlainTextEdit):
             sel.append(self.current_search_mark)
         if instant and not self.highlighter.has_requests:
             sel.extend(self.smarts.get_extra_selections(self))
+            self.smart_highlighting_updated.emit()
         else:
             self.smarts_highlight_timer.start()
         self.setExtraSelections(sel)

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

@@ -107,6 +107,7 @@ class Editor(QMainWindow):
     cursor_position_changed = pyqtSignal()
     word_ignored = pyqtSignal(object, object)
     link_clicked = pyqtSignal(object)
+    smart_highlighting_updated = pyqtSignal()
 
     def __init__(self, syntax, parent=None):
         QMainWindow.__init__(self, parent)
@@ -129,6 +130,7 @@ class Editor(QMainWindow):
         self.editor.copyAvailable.connect(self._copy_available)
         self.editor.cursorPositionChanged.connect(self._cursor_position_changed)
         self.editor.link_clicked.connect(self.link_clicked)
+        self.editor.smart_highlighting_updated.connect(self.smart_highlighting_updated)
 
     @dynamic_property
     def current_line(self):
@@ -328,7 +330,7 @@ class Editor(QMainWindow):
         self.restore_state()
 
     def break_cycles(self):
-        for x in ('modification_state_changed', 'word_ignored', 'link_clicked'):
+        for x in ('modification_state_changed', 'word_ignored', 'link_clicked', 'smart_highlighting_updated'):
             try:
                 getattr(self, x).disconnect()
             except TypeError:
@@ -344,6 +346,7 @@ class Editor(QMainWindow):
         self.editor.copyAvailable.disconnect()
         self.editor.cursorPositionChanged.disconnect()
         self.editor.link_clicked.disconnect()
+        self.editor.smart_highlighting_updated.disconnect()
         self.editor.setPlainText('')
         self.editor.smarts = None
 

src/calibre/gui2/tweak_book/live_css.py

@@ -470,8 +470,8 @@ class LiveCSS(QWidget):
         actions['auto-reload-preview'].setEnabled(True)
         return QWidget.showEvent(self, ev)
 
-    def sync_to_editor(self, name):
+    def sync_to_editor(self):
-        self.start_update_timer()
+        self.update_data()
 
     def update_data(self):
         if not self.is_visible or self.preview_is_refreshing: