citra-qt: Add option to configure the UI theme

src/citra_qt/configuration/configure_general.cpp

@@ -12,6 +12,11 @@ ConfigureGeneral::ConfigureGeneral(QWidget* parent)
     : QWidget(parent), ui(new Ui::ConfigureGeneral) {
 
     ui->setupUi(this);
+
+    for (auto theme : UISettings::themes) {
+        ui->theme_combobox->addItem(theme.first, theme.second);
+    }
+
     this->setConfiguration();
 
     ui->toggle_cpu_jit->setEnabled(!Core::System::GetInstance().IsPoweredOn());
@@ -26,11 +31,15 @@ void ConfigureGeneral::setConfiguration() {
 
     // The first item is "auto-select" with actual value -1, so plus one here will do the trick
     ui->region_combobox->setCurrentIndex(Settings::values.region_value + 1);
+
+    ui->theme_combobox->setCurrentIndex(ui->theme_combobox->findData(UISettings::values.theme));
 }
 
 void ConfigureGeneral::applyConfiguration() {
     UISettings::values.gamedir_deepscan = ui->toggle_deepscan->isChecked();
     UISettings::values.confirm_before_closing = ui->toggle_check_exit->isChecked();
+    UISettings::values.theme =
+        ui->theme_combobox->itemData(ui->theme_combobox->currentIndex()).toString();
     Settings::values.region_value = ui->region_combobox->currentIndex() - 1;
     Settings::values.use_cpu_jit = ui->toggle_cpu_jit->isChecked();
     Settings::Apply();

src/citra_qt/configuration/configure_general.ui

@@ -131,6 +131,34 @@
        </layout>
       </widget>
      </item>
+     <item>
+      <widget class="QGroupBox" name="theme_group_box">
+       <property name="title">
+        <string>Theme</string>
+       </property>
+       <layout class="QHBoxLayout" name="theme_qhbox_layout">
+        <item>
+         <layout class="QVBoxLayout" name="theme_qvbox_layout">
+          <item>
+           <layout class="QHBoxLayout" name="theme_qhbox_layout_2">
+            <item>
+             <widget class="QLabel" name="theme_label">
+              <property name="text">
+               <string>Theme:</string>
+              </property>
+             </widget>
+            </item>
+            <item>
+             <widget class="QComboBox" name="theme_combobox">
+             </widget>
+            </item>
+           </layout>
+          </item>
+         </layout>
+        </item>
+       </layout>
+      </widget>
+     </item>
      <item>
       <widget class="QGroupBox" name="groupBox_3">
        <property name="title">