Qt Designer/calculatorbuilder example: Remove the form class and its autoconnected slots

The autoconnection feature is considered error-prone and is warned
about by clazy. As this removes the need for a class, remove it entirely
and use a lambda for the slot.

As a drive-by, fix the documentation of the project files.

Task-number: QTBUG-110447
Change-Id: Idf78b58445a3f89399f7ae09065f145428ef83fe
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>
(cherry picked from commit 0e5a54f96dda1ea72fdc43026e3d9bb74886c61e)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

5 files changed, 62 insertions, 102 deletions

diff --git a/examples/designer/calculatorbuilder/CMakeLists.txt b/examples/designer/calculatorbuilder/CMakeLists.txt
index 293df3453..30a32c089 100644
--- a/examples/designer/calculatorbuilder/CMakeLists.txt
+++ b/examples/designer/calculatorbuilder/CMakeLists.txt
@@ -15,27 +15,28 @@ set(INSTALL_EXAMPLEDIR "${INSTALL_EXAMPLESDIR}/designer/calculatorbuilder")
 
 find_package(Qt6 REQUIRED COMPONENTS Core Gui UiTools Widgets)
 
-qt_add_executable(calculatorbuilder
-    calculatorform.cpp calculatorform.h
-    main.cpp
-)
+qt_add_executable(calculatorbuilder main.cpp)
 
 set_target_properties(calculatorbuilder PROPERTIES
     WIN32_EXECUTABLE TRUE
     MACOSX_BUNDLE TRUE
 )
 
+#! [0]
 target_link_libraries(calculatorbuilder PUBLIC
     Qt::Core
     Qt::Gui
     Qt::UiTools
     Qt::Widgets
 )
+#! [0]
 
 # Resources:
+#! [1]
 set(calculatorbuilder_resource_files
     "calculatorform.ui"
 )
+#! [1]
 
 qt6_add_resources(calculatorbuilder "calculatorbuilder"
     PREFIX
diff --git a/examples/designer/calculatorbuilder/calculatorbuilder.pro b/examples/designer/calculatorbuilder/calculatorbuilder.pro
index 052dbd38a..740c31a6c 100644
--- a/examples/designer/calculatorbuilder/calculatorbuilder.pro
+++ b/examples/designer/calculatorbuilder/calculatorbuilder.pro
@@ -1,8 +1,6 @@
 #! [0]
-HEADERS     = calculatorform.h
 RESOURCES   = calculatorbuilder.qrc
-SOURCES     = calculatorform.cpp \
-              main.cpp
+SOURCES     = main.cpp
 QT += widgets uitools
 #! [0]
 
diff --git a/examples/designer/calculatorbuilder/calculatorform.cpp b/examples/designer/calculatorbuilder/calculatorform.cpp
deleted file mode 100644
index 7af960f7e..000000000
--- a/examples/designer/calculatorbuilder/calculatorform.cpp
+++ /dev/null
@@ -1,59 +0,0 @@
-// Copyright (C) 2016 The Qt Company Ltd.
-// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
-
-#include "calculatorform.h"
-
-//! [0]
-#include <QtUiTools>
-//! [0]
-#include <QLabel>
-#include <QSpinBox>
-#include <QVBoxLayout>
-
-#include <QFile>
-
-using namespace Qt::StringLiterals;
-
-//! [1]
-CalculatorForm::CalculatorForm(QWidget *parent)
-    : QWidget(parent)
-{
-    QUiLoader loader;
-
-    QFile file(u":/forms/calculatorform.ui"_s);
-    file.open(QFile::ReadOnly);
-    QWidget *formWidget = loader.load(&file, this);
-    file.close();
-//! [1]
-
-//! [2]
-    ui_inputSpinBox1 = findChild<QSpinBox*>(u"inputSpinBox1"_s);
-    ui_inputSpinBox2 = findChild<QSpinBox*>(u"inputSpinBox2"_s);
-    ui_outputWidget = findChild<QLabel*>(u"outputWidget"_s);
-//! [2]
-
-//! [3]
-    QMetaObject::connectSlotsByName(this);
-//! [3]
-
-//! [4]
-    auto *layout = new QVBoxLayout(this);
-    layout->addWidget(formWidget);
-
-    setWindowTitle(tr("Calculator Builder"));
-}
-//! [4]
-
-//! [5]
-void CalculatorForm::on_inputSpinBox1_valueChanged(int value)
-{
-    ui_outputWidget->setText(QString::number(value + ui_inputSpinBox2->value()));
-}
-//! [5] //! [6]
-
-//! [6] //! [7]
-void CalculatorForm::on_inputSpinBox2_valueChanged(int value)
-{
-    ui_outputWidget->setText(QString::number(value + ui_inputSpinBox1->value()));
-}
-//! [7]
diff --git a/examples/designer/calculatorbuilder/calculatorform.h b/examples/designer/calculatorbuilder/calculatorform.h
deleted file mode 100644
index ca34f1acf..000000000
--- a/examples/designer/calculatorbuilder/calculatorform.h
+++ /dev/null
@@ -1,33 +0,0 @@
-// Copyright (C) 2016 The Qt Company Ltd.
-// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
-
-#ifndef CALCULATORFORM_H
-#define CALCULATORFORM_H
-
-#include <QWidget>
-
-QT_BEGIN_NAMESPACE
-class QLabel;
-class QSpinBox;
-QT_END_NAMESPACE
-
-//! [0]
-class CalculatorForm : public QWidget
-{
-    Q_OBJECT
-
-public:
-    explicit CalculatorForm(QWidget *parent = nullptr);
-
-private slots:
-    void on_inputSpinBox1_valueChanged(int value);
-    void on_inputSpinBox2_valueChanged(int value);
-
-private:
-    QSpinBox *ui_inputSpinBox1;
-    QSpinBox *ui_inputSpinBox2;
-    QLabel *ui_outputWidget;
-};
-//! [0]
-
-#endif // CALCULATORFORM_H
diff --git a/examples/designer/calculatorbuilder/main.cpp b/examples/designer/calculatorbuilder/main.cpp
index 54f091438..cfc146091 100644
--- a/examples/designer/calculatorbuilder/main.cpp
+++ b/examples/designer/calculatorbuilder/main.cpp
@@ -1,16 +1,69 @@
 // Copyright (C) 2016 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
 
-#include "calculatorform.h"
+//! [0]
+#include <QtUiTools>
+//! [0]
 
 #include <QApplication>
+#include <QLabel>
+#include <QSpinBox>
+#include <QVBoxLayout>
+
+#include <QFile>
+
+#include <memory>
+
+using namespace Qt::StringLiterals;
+
+//! [1]
+static QWidget *loadCalculatorForm(QWidget *parent = nullptr)
+{
+    QUiLoader loader;
+
+    QFile file(u":/forms/calculatorform.ui"_s);
+    if (!file.open(QFile::ReadOnly))
+        return nullptr;
+    QWidget *formWidget = loader.load(&file, parent);
+    file.close();
+    if (formWidget == nullptr)
+        return nullptr;
+//! [1]
+
+//! [2]
+    auto *inputSpinBox1 = formWidget->findChild<QSpinBox*>(u"inputSpinBox1"_s);
+    auto *inputSpinBox2 = formWidget->findChild<QSpinBox*>(u"inputSpinBox2"_s);
+    auto *outputWidget = formWidget->findChild<QLabel*>(u"outputWidget"_s);
+//! [2]
+
+//! [3]
+    auto updateResult = [inputSpinBox1, inputSpinBox2, outputWidget]()
+    {
+        const int sum = inputSpinBox1->value() + inputSpinBox2->value();
+        outputWidget->setText(QString::number(sum));
+    };
+    QObject::connect(inputSpinBox1, &QSpinBox::valueChanged, formWidget, updateResult);
+    QObject::connect(inputSpinBox2, &QSpinBox::valueChanged, formWidget, updateResult);
+//! [3]
+
+    return formWidget;
+}
 
 int main(int argc, char *argv[])
 {
     Q_INIT_RESOURCE(calculatorbuilder);
 
     QApplication app(argc, argv);
-    CalculatorForm calculator;
-    calculator.show();
+    QWidget w;
+    auto *formWidget = loadCalculatorForm(&w);
+    if (formWidget == nullptr)
+        return -1;
+    //! [4]
+    auto *layout = new QVBoxLayout(&w);
+    layout->addWidget(formWidget);
+    w.setWindowTitle(QCoreApplication::translate("CalculatorForm",
+                                                 "Calculator Builder"));
+    //! [4]
+    w.show();
     return app.exec();
 }