Edit book: Fix highlighting for special characters not visible when t…

…he cursor is on the line with the special character

src/calibre/gui2/tweak_book/editor/syntax/base.py

@@ -4,14 +4,16 @@
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
 from collections import defaultdict, deque
+from qt.core import (
+    QTextBlock, QTextBlockUserData, QTextCursor, QTextFormat, QTextLayout, QTimer,
+)
 
-from qt.core import QTextCursor, QTextBlockUserData, QTextLayout, QTimer
-
-from ..themes import highlight_to_char_format
 from calibre.gui2.widgets import BusyCursor
 from calibre.utils.icu import utf16_length
 from polyglot.builtins import iteritems
 
+from ..themes import highlight_to_char_format
+
 
 def run_loop(user_data, state_map, formats, text):
     state = user_data.state
@@ -240,3 +242,11 @@ def apply_format_changes(self, block, formats):
                 elif r.start + r.length >= preedit_start:
                     r.length += preedit_length
         layout.setFormats(formats)
+
+    def formats_for_line(self, block: QTextBlock, start, length):
+        layout = block.layout()
+        start_in_block = start - block.position()
+        limit = start_in_block + length
+        for f in layout.formats():
+            if f.start >= start_in_block and f.start < limit and f.format.hasProperty(QTextFormat.Property.BackgroundBrush):
+                yield f

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

@@ -331,7 +331,7 @@ def go_to_line(self, lnum, col=None):
     def update_extra_selections(self, instant=True):
         sel = []
         if self.current_cursor_line is not None:
-            sel.append(self.current_cursor_line)
+            sel.extend(self.current_cursor_line)
         if self.current_search_mark is not None:
             sel.append(self.current_search_mark)
         if instant and not self.highlighter.has_requests and self.smarts is not None:
@@ -627,7 +627,24 @@ def highlight_cursor_line(self):
         sel.format.setProperty(QTextFormat.Property.FullWidthSelection, True)
         sel.cursor = self.textCursor()
         sel.cursor.clearSelection()
-        self.current_cursor_line = sel
+        self.current_cursor_line = [sel]
+
+        # apply any formats that have a backgroud over the cursor line format
+        # to ensure they are visible
+        c = self.textCursor()
+        block = c.block()
+        c.clearSelection()
+        c.select(QTextCursor.SelectionType.LineUnderCursor)
+        start = min(c.anchor(), c.position())
+        length = max(c.anchor(), c.position()) - start
+        for f in self.highlighter.formats_for_line(block, start, length):
+            sel = QTextEdit.ExtraSelection()
+            c = self.textCursor()
+            c.setPosition(f.start + block.position())
+            c.setPosition(c.position() + f.length, QTextCursor.MoveMode.KeepAnchor)
+            sel.cursor, sel.format = c, f.format
+            self.current_cursor_line.append(sel)
+
         self.update_extra_selections(instant=False)
         # Update the cursor line's line number in the line number area
         try:

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

@@ -66,7 +66,7 @@ def default_theme():
     Statement    fg={green} bold
     Keyword      fg={green}
     Special      fg={red}
-    SpecialCharacter bg={base02}
+    SpecialCharacter bg={base03}
 
     Error        us=wave uc={red}
     SpellError   us=wave uc={orange}
@@ -113,7 +113,7 @@ def default_theme():
     Special      fg={special}
     Error        us=wave uc=red
     SpellError   us=wave uc=orange
-    SpecialCharacter bg={cursor_loc}
+    SpecialCharacter bg=666666
     Link         fg=cyan
     BadLink      fg={string} us=wave uc=red
 
@@ -160,7 +160,7 @@ def default_theme():
     Statement    fg={keyword}
     Keyword      fg={keyword}
     Special      fg={special} italic
-    SpecialCharacter bg={cursor_loc}
+    SpecialCharacter bg=afafaf
     Error        us=wave uc=red
     SpellError   us=wave uc=magenta
     Link         fg=blue