Full widget label combobox

Author: NathanW2

src/ui/qgslabelingwidget.ui

@@ -14,13 +14,28 @@
    <property name="spacing">
     <number>6</number>
    </property>
-   <property name="margin">
+   <property name="leftMargin">
+    <number>0</number>
+   </property>
+   <property name="topMargin">
+    <number>0</number>
+   </property>
+   <property name="rightMargin">
+    <number>0</number>
+   </property>
+   <property name="bottomMargin">
     <number>0</number>
    </property>
    <item>
     <layout class="QHBoxLayout" name="horizontalLayout">
      <item>
       <widget class="QComboBox" name="mLabelModeComboBox">
+       <property name="sizePolicy">
+        <sizepolicy hsizetype="Expanding" vsizetype="Fixed">
+         <horstretch>0</horstretch>
+         <verstretch>0</verstretch>
+        </sizepolicy>
+       </property>
        <item>
         <property name="text">
          <string>No labels</string>
@@ -59,19 +74,6 @@
        </item>
       </widget>
      </item>
-     <item>
-      <spacer name="horizontalSpacer_5">
-       <property name="orientation">
-        <enum>Qt::Horizontal</enum>
-       </property>
-       <property name="sizeHint" stdset="0">
-        <size>
-         <width>12</width>
-         <height>20</height>
-        </size>
-       </property>
-      </spacer>
-     </item>
      <item>
       <widget class="QPushButton" name="mEngineSettingsButton">
        <property name="enabled">