Make the Main Window example use high-DPI toolbar icons

The Main Window example generates icons programmatically for its
toolbars. However, these icons are shown with low resolution in a
high-DPI display because the application is not enabling high-DPI
pixmap support.

Change-Id: Id763b707105d02f63162fff2efeb607eb5b59ed1
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

2 files changed, 20 insertions, 15 deletions

diff --git a/examples/widgets/mainwindows/mainwindow/main.cpp b/examples/widgets/mainwindows/mainwindow/main.cpp
index c78022e392..b82f67b361 100644
--- a/examples/widgets/mainwindows/mainwindow/main.cpp
+++ b/examples/widgets/mainwindows/mainwindow/main.cpp
@@ -175,6 +175,8 @@ static ParseCommandLineArgumentsResult
 
 int main(int argc, char **argv)
 {
+    QApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
+    QApplication::setAttribute(Qt::AA_UseHighDpiPixmaps);
     QApplication app(argc, argv);
     MainWindow::CustomSizeHintMap customSizeHints;
     switch (parseCustomSizeHints(QCoreApplication::arguments(), &customSizeHints)) {
diff --git a/examples/widgets/mainwindows/mainwindow/toolbar.cpp b/examples/widgets/mainwindows/mainwindow/toolbar.cpp
index baea124ae4..7c96f5b1be 100644
--- a/examples/widgets/mainwindows/mainwindow/toolbar.cpp
+++ b/examples/widgets/mainwindows/mainwindow/toolbar.cpp
@@ -62,10 +62,10 @@
 
 #include <stdlib.h>
 
-static QPixmap genIcon(const QSize &iconSize, const QString &, const QColor &color)
+static QPixmap genIcon(const QSize &iconSize, const QString &, const QColor &color, qreal pixelRatio)
 {
-    int w = iconSize.width();
-    int h = iconSize.height();
+    int w = qRound(iconSize.width() * pixelRatio);
+    int h = qRound(iconSize.height() * pixelRatio);
 
     QImage image(w, h, QImage::Format_ARGB32_Premultiplied);
     image.fill(0);
@@ -75,11 +75,13 @@ static QPixmap genIcon(const QSize &iconSize, const QString &, const QColor &col
     extern void render_qt_text(QPainter *, int, int, const QColor &);
     render_qt_text(&p, w, h, color);
 
-    return QPixmap::fromImage(image, Qt::DiffuseDither | Qt::DiffuseAlphaDither);
+    QPixmap pm = QPixmap::fromImage(image, Qt::DiffuseDither | Qt::DiffuseAlphaDither);
+    pm.setDevicePixelRatio(pixelRatio);
+    return pm;
 }
 
-static QPixmap genIcon(const QSize &iconSize, int number, const QColor &color)
-{ return genIcon(iconSize, QString::number(number), color); }
+static QPixmap genIcon(const QSize &iconSize, int number, const QColor &color, qreal pixelRatio)
+{ return genIcon(iconSize, QString::number(number), color, pixelRatio); }
 
 ToolBar::ToolBar(const QString &title, QWidget *parent)
     : QToolBar(parent)
@@ -91,22 +93,23 @@ ToolBar::ToolBar(const QString &title, QWidget *parent)
 
     setIconSize(QSize(32, 32));
 
+    qreal dpr = devicePixelRatioF();
     menu = new QMenu("One", this);
-    menu->setIcon(genIcon(iconSize(), 1, Qt::black));
-    menu->addAction(genIcon(iconSize(), "A", Qt::blue), "A");
-    menu->addAction(genIcon(iconSize(), "B", Qt::blue), "B");
-    menu->addAction(genIcon(iconSize(), "C", Qt::blue), "C");
+    menu->setIcon(genIcon(iconSize(), 1, Qt::black, dpr));
+    menu->addAction(genIcon(iconSize(), "A", Qt::blue, dpr), "A");
+    menu->addAction(genIcon(iconSize(), "B", Qt::blue, dpr), "B");
+    menu->addAction(genIcon(iconSize(), "C", Qt::blue, dpr), "C");
     addAction(menu->menuAction());
 
-    QAction *two = addAction(genIcon(iconSize(), 2, Qt::white), "Two");
+    QAction *two = addAction(genIcon(iconSize(), 2, Qt::white, dpr), "Two");
     QFont boldFont;
     boldFont.setBold(true);
     two->setFont(boldFont);
 
-    addAction(genIcon(iconSize(), 3, Qt::red), "Three");
-    addAction(genIcon(iconSize(), 4, Qt::green), "Four");
-    addAction(genIcon(iconSize(), 5, Qt::blue), "Five");
-    addAction(genIcon(iconSize(), 6, Qt::yellow), "Six");
+    addAction(genIcon(iconSize(), 3, Qt::red, dpr), "Three");
+    addAction(genIcon(iconSize(), 4, Qt::green, dpr), "Four");
+    addAction(genIcon(iconSize(), 5, Qt::blue, dpr), "Five");
+    addAction(genIcon(iconSize(), 6, Qt::yellow, dpr), "Six");
     orderAction = new QAction(this);
     orderAction->setText(tr("Order Items in Tool Bar"));
     connect(orderAction, &QAction::triggered, this, &ToolBar::order);