Use combobox for login username

src/widget/loginscreen.ui

@@ -162,6 +162,24 @@
    <property name="palette">
     <palette>
      <active>
+      <colorrole role="Button">
+       <brush brushstyle="SolidPattern">
+        <color alpha="255">
+         <red>255</red>
+         <green>255</green>
+         <blue>255</blue>
+        </color>
+       </brush>
+      </colorrole>
+      <colorrole role="ButtonText">
+       <brush brushstyle="SolidPattern">
+        <color alpha="255">
+         <red>0</red>
+         <green>0</green>
+         <blue>0</blue>
+        </color>
+       </brush>
+      </colorrole>
       <colorrole role="Base">
        <brush brushstyle="SolidPattern">
         <color alpha="255">
@@ -182,6 +200,24 @@
       </colorrole>
      </active>
      <inactive>
+      <colorrole role="Button">
+       <brush brushstyle="SolidPattern">
+        <color alpha="255">
+         <red>255</red>
+         <green>255</green>
+         <blue>255</blue>
+        </color>
+       </brush>
+      </colorrole>
+      <colorrole role="ButtonText">
+       <brush brushstyle="SolidPattern">
+        <color alpha="255">
+         <red>0</red>
+         <green>0</green>
+         <blue>0</blue>
+        </color>
+       </brush>
+      </colorrole>
       <colorrole role="Base">
        <brush brushstyle="SolidPattern">
         <color alpha="255">
@@ -202,6 +238,24 @@
       </colorrole>
      </inactive>
      <disabled>
+      <colorrole role="Button">
+       <brush brushstyle="SolidPattern">
+        <color alpha="255">
+         <red>255</red>
+         <green>255</green>
+         <blue>255</blue>
+        </color>
+       </brush>
+      </colorrole>
+      <colorrole role="ButtonText">
+       <brush brushstyle="SolidPattern">
+        <color alpha="255">
+         <red>128</red>
+         <green>128</green>
+         <blue>128</blue>
+        </color>
+       </brush>
+      </colorrole>
       <colorrole role="Base">
        <brush brushstyle="SolidPattern">
         <color alpha="255">
@@ -652,11 +706,7 @@ margin-bottom:5px;</string>
           </widget>
          </item>
          <item>
-          <widget class="QLineEdit" name="lineEdit_3">
-           <property name="maxLength">
-            <number>64</number>
-           </property>
-          </widget>
+          <widget class="QComboBox" name="comboBox"/>
          </item>
          <item>
           <widget class="QLabel" name="label_4">