Getting font metrics without GUI (console mode)

Question

Let's say some images have to be generated by a Qt console program and that font metrics are needed by internal algorithms (they use the text width/height as input to compute the position where the drawing should occur). This program has to be runable on a Linux without any GUI (runlevel-3, basically a cluster without any display server).

Problem: QFontMetrics are only available when running a Qt application in GUI mode.
Any workaround to get string metrics without any display server ?

Answer 1

Ok after additional comments I think I understand your problem. Just do it like that:

include <QApplication>

int main(int argv, char **args)
{
    QApplication app(argv, args);
    QApplication::processEvents(); // this should allow `QApplication` to complete its initialization

    // do here whatever you need 

    return 0; // or some other value to report errors
}

You can also try use QGuiApplication this version doesn't require (doesn't use) widgets.

See also example in documentation how to handle none gui cases.

---

This code works perfectly on my Ubnutu with Qt 5.3

#include <QGuiApplication>
#include <QFontMetrics>
#include <QDebug>

int main(int argc, char *argv[])
{
    QGuiApplication a(argc, argv);

    QFont font("Times", 10, QFont::Bold);
    qDebug() << font;
    QFontMetrics metrics(font);

    qDebug() << metrics.boundingRect("test");

    return 0;
}

It also works with Qt 4.8 when QApplication is used.

Project file was quite simple

QT       += core
TARGET = MetricsNoGui
TEMPLATE = app
SOURCES += main.cpp