Qt, QFont for all Widget

[plevasse]

Hello world,

I want to changer the font for all the widgets of my project, so I have used qApp->setFont().

Only, the font the font of widgets dosen't change

But qApp->font() return the right font

Do you have a solution ?

Really sory if my English is not right :'(

Thanks you very much for your answer :)

[ChrisW67]

QGuiApplication::setFont() sets the default font for the application. If any widget sets another font then that will apply (to that widget, possibly children). If you use Designer and set a font other than the default one Designer offers, which is not related to the one set on the application object, then code to set a font is in the generated code as matter of routine.

[plevasse]

@ChrisW67
I tried that, but the font daesn't change
I'm looking for a method witch changes the font of all my widgets (I don't want to change the font of all my widgets manualy (there are plenty of widgets)

[hskoglund]

Hi, you could try looping through all your widgets and setting the font, say like this from your MainWindow.cpp:

for (auto pKid : findChildren<QWidget*>())
{
// do it only on your own (named) widgets
    QString sName = pKid->objectName();
    if (sName.isEmpty())
        continue;
    if (sName.startsWith("qt_"))
        continue;

    pKid->setFont(QFont("Your font"));
}

[ChrisW67]

@plevasse This does here, with the default font widgets changing every second:

main.cpp

#include "widget.h"
#include <QApplication>

int main(int argc, char *argv[]) {
    QApplication a(argc, argv);
    Widget w;
    w.show();
    return a.exec();
}

widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();

private slots:
    void toggleFont();

private:
    Ui::Widget *ui;
    bool m_state;
};
#endif // WIDGET_H

widget.cpp

#include "widget.h"
#include "ui_widget.h"

#include <QTimer>
#include <QFont>


Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
    , m_state(false)
{
    ui->setupUi(this);

    QTimer *timer = new QTimer(this);
    connect(timer, &QTimer::timeout, this, &Widget::toggleFont);
    timer->start(1000);
}

Widget::~Widget()
{
    delete ui;
}

void Widget::toggleFont()
{
    m_state = !m_state;
    if (m_state) {
        qApp->setFont(QFont("Sans Serif", 10));
    }
    else {
        qApp->setFont(QFont("Serif", 12));
    }

}

widget.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>Widget</class>
 <widget class="QWidget" name="Widget">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>400</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>Widget</string>
  </property>
  <layout class="QVBoxLayout" name="verticalLayout">
   <item>
    <widget class="QLabel" name="label">
     <property name="text">
      <string>A label with no font set in Designer</string>
     </property>
    </widget>
   </item>
   <item>
    <widget class="QLabel" name="label_2">
     <property name="font">
      <font>
       <family>Serif</family>
       <pointsize>12</pointsize>
       <italic>false</italic>
      </font>
     </property>
     <property name="text">
      <string>A label with a non-default font set in Designer</string>
     </property>
    </widget>
   </item>
   <item>
    <widget class="QGroupBox" name="groupBox">
     <property name="title">
      <string>GroupBox</string>
     </property>
     <layout class="QVBoxLayout" name="verticalLayout_2">
      <item>
       <widget class="QRadioButton" name="radioButton">
        <property name="text">
         <string>No font set</string>
        </property>
       </widget>
      </item>
      <item>
       <widget class="QRadioButton" name="radioButton_2">
        <property name="font">
         <font>
          <family>Serif</family>
          <pointsize>12</pointsize>
         </font>
        </property>
        <property name="text">
         <string>Non-default font set</string>
        </property>
       </widget>
      </item>
      <item>
       <widget class="QCheckBox" name="checkBox">
        <property name="text">
         <string>No font set</string>
        </property>
       </widget>
      </item>
     </layout>
    </widget>
   </item>
  </layout>
 </widget>
 <resources/>
 <connections/>
</ui>

[plevasse]

I have try and your technique work
Tank you for your answer !