[keyboard] Simplify back down to lambdas

- With debugging and untangling done, the lambdas are simple
  and short, so return to using them. One point of improvement
  might be to give the models suitable slots themselves,
  to avoid even this indirection.

src/modules/keyboard/KeyboardPage.cpp

@@ -84,49 +84,20 @@ KeyboardPage::KeyboardPage( Config* config, QWidget* parent )
 
     connect( ui->layoutSelector->selectionModel(),
              &QItemSelectionModel::currentChanged,
-             this,
-             &KeyboardPage::layoutChangedByUser );
-    connect( config->keyboardLayouts(),
-             &KeyboardLayoutModel::currentIndexChanged,
-             this,
-             &KeyboardPage::layoutChangedByConfig );
+             [this]( const QModelIndex& current ) { m_config->keyboardLayouts()->setCurrentIndex( current.row() ); } );
+    connect( config->keyboardLayouts(), &KeyboardLayoutModel::currentIndexChanged, [this]( int index ) {
+        ui->layoutSelector->setCurrentIndex( m_config->keyboardLayouts()->index( index ) );
+    } );
 
     connect( ui->variantSelector->selectionModel(),
              &QItemSelectionModel::currentChanged,
-             this,
-             &KeyboardPage::variantChangedByUser );
-    connect( config->keyboardVariants(),
-             &KeyboardVariantsModel::currentIndexChanged,
-             this,
-             &KeyboardPage::variantChangedByConfig );
-
+             [this]( const QModelIndex& current ) { m_config->keyboardVariants()->setCurrentIndex( current.row() ); } );
+    connect( config->keyboardVariants(), &KeyboardVariantsModel::currentIndexChanged, [this]( int index ) {
+        ui->variantSelector->setCurrentIndex( m_config->keyboardVariants()->index( index ) );
+    } );
     CALAMARES_RETRANSLATE( ui->retranslateUi( this ); )
 }
 
-void
-KeyboardPage::layoutChangedByUser( const QModelIndex& current, const QModelIndex& previous )
-{
-    m_config->keyboardLayouts()->setCurrentIndex( current.row() );
-}
-
-void
-KeyboardPage::layoutChangedByConfig( int index )
-{
-    ui->layoutSelector->setCurrentIndex( m_config->keyboardLayouts()->index( index ) );
-}
-
-void
-KeyboardPage::variantChangedByUser( const QModelIndex& current, const QModelIndex& previous )
-{
-    m_config->keyboardVariants()->setCurrentIndex( current.row() );
-}
-
-void
-KeyboardPage::variantChangedByConfig( int index )
-{
-    ui->variantSelector->setCurrentIndex( m_config->keyboardVariants()->index( index ) );
-}
-
 KeyboardPage::~KeyboardPage()
 {
     delete ui;

src/modules/keyboard/KeyboardPage.h

@@ -37,13 +37,6 @@ public:
     explicit KeyboardPage( Config* config, QWidget* parent = nullptr );
     ~KeyboardPage() override;
 
-protected slots:
-    void layoutChangedByUser( const QModelIndex& current, const QModelIndex& previous );
-    void layoutChangedByConfig( int index );
-
-    void variantChangedByUser( const QModelIndex& current, const QModelIndex& previous );
-    void variantChangedByConfig( int index );
-
 private:
     Ui::Page_Keyboard* ui;
     KeyBoardPreview* m_keyboardPreview;