What's New in Qt 5: The QScreen Class
QScreen is a new class introduced in Qt 5.0.0 that returns information about screen properties, where screen here refers to a display, such as a monitor or LCD panel.
[Update: It was pointed out that Qt 4 has a class named QScreen. However, the QScreenclass in Qt 4 was entirely different from the one in Qt 5 with different APIs and used for a different purpose. So I really consider them to be different classes.]
It can be used to allow your application to handle different screen sizes, multiple screens, or calculate the physical size of items on the screen.
In Qt 4 you could get some of this information from the QX11Info and QDesktopWidgetclasses.
The QScreen class has 20 properties and a number of methods and signals. It is a subclass of QObject.
The QGuiApplication class (new in Qt 5) provides methods that will return the primary screen or a list of all screens as QScreen pointers.
The QWindow class can return the screen it was created on or let you set the screen it appears on using a method or in the constructor.
I'll show here a very simple text-based Qt example program that lists information for the display screens. While it is a non-graphical application, we do need to create aQGuiApplication object since it needs to exist in order to get the information about the screens.
Here is sample output on one system I ran it on:
Number of screens: 2 Primary screen: "VGA-0" Information for screen: "VGA-0" Available geometry: 0 0 1920 x 1165 Available size: 1920 x 1165 Available virtual geometry: 0 0 3520 x 1165 Available virtual size: 3520 x 1165 Depth: 24 bits Geometry: 0 0 1920 x 1200 Logical DPI: 94.1432 Logical DPI X: 93.0364 Logical DPI Y: 95.25 Orientation: "Landscape" Physical DPI: 94.1104 Physical DPI X: 94.1467 Physical DPI Y: 94.0741 Physical size: 518 x 324 mm Primary orientation: "Landscape" Refresh rate: 72 Hz Size: 1920 x 1200 Virtual geometry: 0 0 3520 x 1200 Virtual size: 3520 x 1200 Information for screen: "LVDS-0" Available geometry: 1920 0 1600 x 900 Available size: 1600 x 900 Available virtual geometry: 0 0 3520 x 1165 Available virtual size: 3520 x 1165 Depth: 24 bits Geometry: 1920 0 1600 x 900 Logical DPI: 94.1432 Logical DPI X: 93.0364 Logical DPI Y: 95.25 Orientation: "Landscape" Physical DPI: 117.987 Physical DPI X: 118.14 Physical DPI Y: 117.835 Physical size: 344 x 194 mm Primary orientation: "Landscape" Refresh rate: 72 Hz Size: 1600 x 900 Virtual geometry: 0 0 3520 x 1200 Virtual size: 3520 x 1200
Here is the complete source code for the example:
#include <QGuiApplication>
#include <QScreen>
#include <QDebug>
/*
Example of using Qt 5 QScreen class.
*/
// Helper function to return display orientation as a string.
QString Orientation(Qt::ScreenOrientation orientation)
{
switch (orientation) {
case Qt::PrimaryOrientation : return "Primary";
case Qt::LandscapeOrientation : return "Landscape";
case Qt::PortraitOrientation : return "Portrait";
case Qt::InvertedLandscapeOrientation : return "Inverted landscape";
case Qt::InvertedPortraitOrientation : return "Inverted portrait";
default : return "Unknown";
}
}
int main(int argc, char *argv[])
{
QGuiApplication a(argc, argv);
qDebug() << "Number of screens:" << QGuiApplication::screens().size();
qDebug() << "Primary screen:" << QGuiApplication::primaryScreen()->name();
foreach (QScreen *screen, QGuiApplication::screens()) {
qDebug() << "Information for screen:" << screen->name();
qDebug() << " Available geometry:" << screen->availableGeometry().x() << screen->availableGeometry().y() << screen->availableGeometry().width() << "x" << screen->availableGeometry().height();
qDebug() << " Available size:" << screen->availableSize().width() << "x" << screen->availableSize().height();
qDebug() << " Available virtual geometry:" << screen->availableVirtualGeometry().x() << screen->availableVirtualGeometry().y() << screen->availableVirtualGeometry().width() << "x" << screen->availableVirtualGeometry().height();
qDebug() << " Available virtual size:" << screen->availableVirtualSize().width() << "x" << screen->availableVirtualSize().height();
qDebug() << " Depth:" << screen->depth() << "bits";
qDebug() << " Geometry:" << screen->geometry().x() << screen->geometry().y() << screen->geometry().width() << "x" << screen->geometry().height();
qDebug() << " Logical DPI:" << screen->logicalDotsPerInch();
qDebug() << " Logical DPI X:" << screen->logicalDotsPerInchX();
qDebug() << " Logical DPI Y:" << screen->logicalDotsPerInchY();
qDebug() << " Orientation:" << Orientation(screen->orientation());
qDebug() << " Physical DPI:" << screen->physicalDotsPerInch();
qDebug() << " Physical DPI X:" << screen->physicalDotsPerInchX();
qDebug() << " Physical DPI Y:" << screen->physicalDotsPerInchY();
qDebug() << " Physical size:" << screen->physicalSize().width() << "x" << screen->physicalSize().height() << "mm";
qDebug() << " Primary orientation:" << Orientation(screen->primaryOrientation());
qDebug() << " Refresh rate:" << screen->refreshRate() << "Hz";
qDebug() << " Size:" << screen->size().width() << "x" << screen->size().height();
qDebug() << " Virtual geometry:" << screen->virtualGeometry().x() << screen->virtualGeometry().y() << screen->virtualGeometry().width() << "x" << screen->virtualGeometry().height();
qDebug() << " Virtual size:" << screen->virtualSize().width() << "x" << screen->virtualSize().height();
}
}
In summary, the new QScreen class in Qt 5 in a useful class for getting information about the properties of the display screens on a system in a portable manner. In addition to the properties demonstrated in this example, it also supports a number of methods and can emit signals when the display properties change.
You can download the source code for the example, at least for the next little while, fromhere.