sqlbrowser example: use idiomatic Qt [2/3]: use button-box / override accept()

- The old code used two QPushButtons in a QHBoxLayout to provide
  Ok/Cancel buttons. This hard-codes the positions and text (and
  icons) of these buttons, instead of adapting to the platform style.

  The new code simply uses QDialogButtonBox, which is designed for
  this purpose.

- Also, the old code connected the Ok button's clicked() signal to a
  custom slot that then called QDialog::accept(). This means that the
  code in the custom slot is not executed when the dialog is accepted
  by other means (e.g. return press in one of the line edits
  ("auto-default"), though I'm not sure here).

  The new code uses the idiomatic Qt way of overriding
  QDialog::accept() instead, and connects the button-box's accepted()
  signal to it. This is done in the .ui file, so it already works in
  Designer preview.

- Finally, the old code made a manual connection from the Cancel
  button to QDialog::reject().

  The new code uses the Qt idiom of connecting in the .ui file
  directly, using QDialogButtonBox::rejected() as the signal.

Amends 2690822428deec4f0c08f4d118d69a7c6036369e, which, however,
inherited all of the above from even older code.

Pick-to: 6.8
Change-Id: I83afd6156a0811e0c0f99f2480625ea6b69ff78b
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 3419c299369ac1da94ba5710aaf5f5f65c38c33c)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

examples/sql/sqlbrowser/qsqlconnectiondialog.cpp

@@ -21,11 +21,6 @@ QSqlConnectionDialog::QSqlConnectionDialog(QWidget *parent)
         m_ui->dbCheckBox->setEnabled(false);
 
     m_ui->comboDriver->addItems(drivers);
-
-    connect(m_ui->okButton, &QPushButton::clicked,
-            this, &QSqlConnectionDialog::onOkButton);
-    connect(m_ui->cancelButton, &QPushButton::clicked,
-            this, &QSqlConnectionDialog::reject);
 }
 
 QSqlConnectionDialog::~QSqlConnectionDialog()
@@ -68,13 +63,13 @@ bool QSqlConnectionDialog::useInMemoryDatabase() const
     return m_ui->dbCheckBox->isChecked();
 }
 
-void QSqlConnectionDialog::onOkButton()
+void QSqlConnectionDialog::accept()
 {
     if (m_ui->comboDriver->currentText().isEmpty()) {
         QMessageBox::information(this, tr("No database driver selected"),
                                  tr("Please select a database driver"));
         m_ui->comboDriver->setFocus();
     } else {
-        accept();
+        QDialog::accept();
     }
 }

examples/sql/sqlbrowser/qsqlconnectiondialog.h

@@ -28,8 +28,7 @@ public:
     int port() const;
     bool useInMemoryDatabase() const;
 
-private slots:
+    void accept() override;
-    void onOkButton();
 
 private:
     Ui::QSqlConnectionDialogUi *m_ui;

examples/sql/sqlbrowser/qsqlconnectiondialog.ui

@@ -163,47 +163,11 @@
     </layout>
    </item>
    <item>
-    <layout class="QHBoxLayout" >
+    <widget class="QDialogButtonBox" name="buttonBox">
-     <property name="margin" >
+     <property name="standardButtons">
-      <number>0</number>
+      <set>QDialogButtonBox::StandardButton::Cancel|QDialogButtonBox::StandardButton::Ok</set>
      </property>
-     <property name="spacing" >
+    </widget>
-      <number>6</number>
-     </property>
-     <item>
-      <spacer>
-       <property name="orientation" >
-        <enum>Qt::Horizontal</enum>
-       </property>
-       <property name="sizeType" >
-        <enum>QSizePolicy::Expanding</enum>
-       </property>
-       <property name="sizeHint" >
-        <size>
-         <width>20</width>
-         <height>20</height>
-        </size>
-       </property>
-      </spacer>
-     </item>
-     <item>
-      <widget class="QPushButton" name="okButton" >
-       <property name="text" >
-        <string>&amp;OK</string>
-       </property>
-       <property name="default" >
-        <bool>true</bool>
-       </property>
-      </widget>
-     </item>
-     <item>
-      <widget class="QPushButton" name="cancelButton" >
-       <property name="text" >
-        <string>&amp;Cancel</string>
-       </property>
-      </widget>
-     </item>
-    </layout>
    </item>
   </layout>
  </widget>
@@ -216,8 +180,6 @@
   <tabstop>editHostname</tabstop>
   <tabstop>portSpinBox</tabstop>
   <tabstop>dbCheckBox</tabstop>
-  <tabstop>okButton</tabstop>
-  <tabstop>cancelButton</tabstop>
  </tabstops>
  <resources/>
  <connections>
@@ -237,5 +199,37 @@
     </hint>
    </hints>
   </connection>
+  <connection>
+   <sender>buttonBox</sender>
+   <signal>accepted()</signal>
+   <receiver>QSqlConnectionDialogUi</receiver>
+   <slot>accept()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>19</x>
+     <y>278</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>20</x>
+     <y>244</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>buttonBox</sender>
+   <signal>rejected()</signal>
+   <receiver>QSqlConnectionDialogUi</receiver>
+   <slot>reject()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>58</x>
+     <y>276</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>58</x>
+     <y>258</y>
+    </hint>
+   </hints>
+  </connection>
  </connections>
 </ui>