code examples: improve qt hello world

examples/qt/BUILD

@@ -1,11 +1,9 @@
-cc_library(
-    name = "lib",
-    srcs = ["hello.cpp"],
-    hdrs = [
-        "hello.hpp",
-    ],
+cc_binary(
+    name = "bin",
+    srcs = ["main.cpp"],
     copts = [
         "-I/usr/include/x86_64-linux-gnu/qt5",
+        "-I/usr/include/x86_64-linux-gnu/qt5/QtGui",
         "-I/usr/include/x86_64-linux-gnu/qt5/QtWidgets",
         "-I/usr/include/x86_64-linux-gnu/qt5/QtCore",
     ],
@@ -15,16 +13,3 @@ cc_library(
         "-lQt5Gui",
     ],
 )
-
-cc_binary(
-    name = "bin",
-    srcs = ["main.cpp"],
-    copts = [
-        "-I/usr/include/x86_64-linux-gnu/qt5",
-        "-I/usr/include/x86_64-linux-gnu/qt5/QtWidgets",
-        "-I/usr/include/x86_64-linux-gnu/qt5/QtCore",
-    ],
-    deps = [
-        ":lib",
-    ],
-)

examples/qt/main.cpp

@@ -1,19 +1,59 @@
-#include <qapplication.h>
-
 #include <QApplication>
-#include <memory>
+#include <QFont>
+#include <QGridLayout>
+#include <QLCDNumber>
+#include <QPushButton>
+#include <QSlider>
+#include <QVBoxLayout>
+#include <QWidget>
+
+class LCDRange : public QWidget {
+   public:
+    explicit LCDRange(QWidget *parent = nullptr);
+};
 
-#include "hello.hpp"
+LCDRange::LCDRange(QWidget *parent) : QWidget(parent) {
+    QLCDNumber *lcd = new QLCDNumber(2);
+    lcd->setSegmentStyle(QLCDNumber::Filled);
 
-auto main(int argc, char **argv) -> int {
-    QApplication const app(argc, argv);
+    QSlider *slider = new QSlider(Qt::Horizontal);
+    slider->setRange(0, 99);
+    slider->setValue(0);
+    connect(slider, SIGNAL(valueChanged(int)), lcd, SLOT(display(int)));
+
+    QVBoxLayout *layout = new QVBoxLayout;
+    layout->addWidget(lcd);
+    layout->addWidget(slider);
+    setLayout(layout);
+}
 
-    const int WindowWidth = 600;
-    const int WindowHeight = 600;
+class MyWidget : public QWidget {
+   public:
+    explicit MyWidget(QWidget *parent = nullptr);
+};
 
-    auto mainWidget = std::make_unique<MyWidget>();
-    mainWidget->resize(WindowWidth, WindowHeight);
-    mainWidget->show();
+MyWidget::MyWidget(QWidget *parent) : QWidget(parent) {
+    QPushButton *quit = new QPushButton(tr("Quit"));
+    quit->setFont(QFont("Times", 18, QFont::Bold));
+    connect(quit, SIGNAL(clicked()), qApp, SLOT(quit()));
+
+    QGridLayout *grid = new QGridLayout;
+    for (int row = 0; row < 3; ++row) {
+        for (int column = 0; column < 3; ++column) {
+            auto *lcdRange = new LCDRange;
+            grid->addWidget(lcdRange, row, column);
+        }
+    }
+
+    QVBoxLayout *layout = new QVBoxLayout;
+    layout->addWidget(quit);
+    layout->addLayout(grid);
+    setLayout(layout);
+}
 
-    return QApplication::exec();
+auto main(int argc, char *argv[]) -> int {
+    QApplication app(argc, argv);
+    MyWidget widget;
+    widget.show();
+    return app.exec();
 }