Add an option to use bold fonts on the spine

Specially for JSWolf

src/calibre/gui2/__init__.py

@@ -526,6 +526,7 @@ def create_defs():
     }
     defs['bookshelf_min_font_multiplier'] = 0.75
     defs['bookshelf_max_font_multiplier'] = 1.3
+    defs['bookshelf_bold_font'] = False
 
     # Migrate beta bookshelf_thumbnail
     if isinstance(btv := gprefs.get('bookshelf_thumbnail'), bool):

src/calibre/gui2/library/bookshelf_view.py

@@ -1538,7 +1538,7 @@ class BookshelfView(MomentumScrollMixin, QAbstractScrollArea):
         self.template_inited = False
         self.min_font_size = max(0.1, min(gprefs['bookshelf_min_font_multiplier'], 1)) * self.base_font_size_pts
         self.max_font_size = max(1, min(gprefs['bookshelf_max_font_multiplier'], 3)) * self.base_font_size_pts
-        _, fm, _ = self.get_sized_font(self.min_font_size)
+        _, fm, _ = self.get_sized_font(self.min_font_size, bold=gprefs['bookshelf_bold_font'])
         self.min_line_height = math.ceil(fm.height())
         self.calculate_shelf_geometry()
         self.palette_changed()
@@ -2086,11 +2086,12 @@ class BookshelfView(MomentumScrollMixin, QAbstractScrollArea):
         first_rect, second_rect = calculate_rects(bool(second_line))
 
         nfl, nsl, font, was_wrapped = self.get_text_metrics(
-            first_line, second_line, first_rect.transposed().size(), allow_wrap=True)
+            first_line, second_line, first_rect.transposed().size(), allow_wrap=True, bold=gprefs['bookshelf_bold_font'])
         if not nfl and not nsl:  # two lines dont fit
             second_line = ''
             first_rect = QRect(rect.left(), first_rect.top(), rect.width(), first_rect.height())
-            nfl, nsl, font, _ = self.get_text_metrics(first_line, second_line, first_rect.transposed().size())
+            nfl, nsl, font, _ = self.get_text_metrics(
+                first_line, second_line, first_rect.transposed().size(), bold=gprefs['bookshelf_bold_font'])
         elif was_wrapped:
             first_rect, second_rect = calculate_rects(True)
         first_line, second_line, = nfl, nsl

src/calibre/gui2/preferences/look_feel_tabs/bookshelf_view.py

@@ -80,6 +80,7 @@ class BookshelfTab(QTabWidget, LazyConfigWidgetBase, Ui_Form):
         r('bookshelf_make_space_for_second_line', gprefs)
         r('bookshelf_min_font_multiplier', gprefs)
         r('bookshelf_max_font_multiplier', gprefs)
+        r('bookshelf_bold_font', gprefs)
 
         r('bookshelf_divider_text_right', gprefs)
         r('bookshelf_start_with_divider', gprefs)

src/calibre/gui2/preferences/look_feel_tabs/bookshelf_view.ui

@@ -458,6 +458,16 @@
            </property>
           </widget>
          </item>
+         <item>
+          <widget class="QCheckBox" name="opt_bookshelf_bold_font">
+           <property name="toolTip">
+            <string>&lt;p&gt;Use a bold font to draw text on the book spine</string>
+           </property>
+           <property name="text">
+            <string>Use &amp;bold font</string>
+           </property>
+          </widget>
+         </item>
          <item>
           <spacer name="horizontalSpacer_2">
            <property name="orientation">