Also use paper sizes widget in PDF output settings

src/calibre/gui2/convert/__init__.py

@@ -146,6 +146,8 @@ class Widget(QWidget):
         ret = self.get_value_handler(g)
         if ret != 'this is a dummy return value, xcswx1avcx4x':
             return ret
+        if hasattr(g, 'get_value_for_config'):
+            return g.get_value_for_config
         if isinstance(g, (QSpinBox, QDoubleSpinBox)):
             return g.value()
         elif isinstance(g, (QLineEdit, QTextEdit, QPlainTextEdit)):
@@ -218,6 +220,9 @@ class Widget(QWidget):
         from calibre.gui2.widgets import EncodingComboBox
         if self.set_value_handler(g, val):
             return
+        if hasattr(g, 'set_value_for_config'):
+            g.set_value_for_config = val
+            return
         if isinstance(g, (QSpinBox, QDoubleSpinBox)):
             g.setValue(val)
         elif isinstance(g, (QLineEdit, QTextEdit, QPlainTextEdit)):

src/calibre/gui2/convert/pdf_output.py

@@ -33,8 +33,7 @@ class PluginWidget(Widget, Ui_Form):
         except TypeError:
             pass  # link already localized
 
-        for x in get_option('paper_size').option.choices:
+        self.opt_paper_size.initialize(get_option('paper_size').option.choices)
-            self.opt_paper_size.addItem(x)
         for x in get_option('unit').option.choices:
             self.opt_unit.addItem(x)
         for x in get_option('pdf_standard_font').option.choices:

src/calibre/gui2/convert/pdf_output.ui

@@ -32,7 +32,7 @@
     </widget>
    </item>
    <item row="1" column="1">
-    <widget class="QComboBox" name="opt_paper_size"/>
+    <widget class="PaperSizes" name="opt_paper_size"/>
    </item>
    <item row="2" column="0">
     <widget class="QLabel" name="label_3">
@@ -300,6 +300,13 @@
    </item>
   </layout>
  </widget>
+ <customwidgets>
+  <customwidget>
+   <class>PaperSizes</class>
+   <extends>QComboBox</extends>
+   <header>calibre/gui2/widgets.h</header>
+  </customwidget>
+ </customwidgets>
  <resources/>
  <connections/>
 </ui>