QFont Object not recognized.

[eLancaster]

Hi everyone,
i want to make a program with a text field and two check boxes: bold and italics which adjust the font in the text field accordingly.
I made QFont a private member in Stuff.h and initialized it in Stuff.cpp - but there seems to be some problem there. I followed the documentation so i dont understand why theres a problem.
the code and errors are mentioned below

Stuff.h

#ifndef STUFF_H
#define STUFF_H
 
#include <QWidget>
#include <QFont>
 
 
namespace Ui {
    class Stuff;
}
 
class Stuff : public QWidget
{
    Q_OBJECT
 
public:
    explicit Stuff(QWidget *parent = 0);
    ~Stuff();
 
private slots:
    void adjustFont();
 
private:
    Ui::Stuff *ui;
    QFont *font;// font declared here!
};
 
#endif

#ifndef STUFF_H
#define STUFF_H

#include <QWidget>
#include <QFont>


namespace Ui {
    class Stuff;
}

class Stuff : public QWidget
{
    Q_OBJECT

public:
    explicit Stuff(QWidget *parent = 0);
    ~Stuff();

private slots:
    void adjustFont();

private:
    Ui::Stuff *ui;
    QFont *font;// font declared here!
};

#endif

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#include "stuff.h"
#include "ui_stuff.h"
#include <QButtonGroup>
#include <QFont>
 
Stuff::Stuff(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Stuff)
{
    ui->setupUi(this);
    font = new QFont("Times",12);
 
 
    QButtonGroup *group = new QButtonGroup(this);
    group->addButton(ui->SBoldButton);
    group->addButton(ui->SItalicButton);
    group->setExclusive(false);
 
    ui->SLineEdit->setText("this is a line");
    ui->SLineEdit->setFont(font);// /home/ubuntu/QtProjects/Stuff-build-desktop/../Stuff/stuff.cpp:23: error: no matching function for call to ‘QLineEdit::setFont(QFont*&)’
 
    connect(group,SIGNAL(buttonClicked(int)),this,SLOT(adjustFont()));
    connect(ui->SQuitButton,SIGNAL(clicked()),qApp,SLOT(quit()));
}
 
Stuff::~Stuff()
{
    delete ui;
}
 
void Stuff::adjustFont()
{
    Qt::CheckState boldState;
    Qt::CheckState italicState;
 
    boldState=ui->SBoldButton->checkState();
    italicState=ui->SBoldButton->checkState();
 
    if(boldState==Qt::Checked && italicState!=Qt::Checked)
    {
        ui->SLineEdit->setFont(font->setBold(true));///home/ubuntu/QtProjects/Stuff-build-desktop/../Stuff/stuff.cpp:44: error: invalid use of void expression
        ui->SLineEdit->setFont(font->setItalic(false));//same as above and applies for all similar lines of code below
    }
 
    else if(boldState!=Qt::Checked && italicState==Qt::Checked)
    {
        ui->SLineEdit->setFont(font->setBold(false));
        ui->SLineEdit->setFont(font->setItalic(true));
    }
 
    else if(boldState==Qt::Checked && italicState==Qt::Checked)
    {
        ui->SLineEdit->setFont(font->setBold(true));
        ui->SLineEdit->setFont(font->setItalic(true));
    }
 
    else
    {
        ui->SLineEdit->setFont(font->setBold(false));
        ui->SLineEdit->setFont(font->setItalic(false));
    }
}

#include "stuff.h"
#include "ui_stuff.h"
#include <QButtonGroup>
#include <QFont>

Stuff::Stuff(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Stuff)
{
    ui->setupUi(this);
    font = new QFont("Times",12);


    QButtonGroup *group = new QButtonGroup(this);
    group->addButton(ui->SBoldButton);
    group->addButton(ui->SItalicButton);
    group->setExclusive(false);

    ui->SLineEdit->setText("this is a line");
    ui->SLineEdit->setFont(font);// /home/ubuntu/QtProjects/Stuff-build-desktop/../Stuff/stuff.cpp:23: error: no matching function for call to ‘QLineEdit::setFont(QFont*&)’

    connect(group,SIGNAL(buttonClicked(int)),this,SLOT(adjustFont()));
    connect(ui->SQuitButton,SIGNAL(clicked()),qApp,SLOT(quit()));
}

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

void Stuff::adjustFont()
{
    Qt::CheckState boldState;
    Qt::CheckState italicState;

    boldState=ui->SBoldButton->checkState();
    italicState=ui->SBoldButton->checkState();

    if(boldState==Qt::Checked && italicState!=Qt::Checked)
    {
        ui->SLineEdit->setFont(font->setBold(true));///home/ubuntu/QtProjects/Stuff-build-desktop/../Stuff/stuff.cpp:44: error: invalid use of void expression
        ui->SLineEdit->setFont(font->setItalic(false));//same as above and applies for all similar lines of code below
    }

    else if(boldState!=Qt::Checked && italicState==Qt::Checked)
    {
        ui->SLineEdit->setFont(font->setBold(false));
        ui->SLineEdit->setFont(font->setItalic(true));
    }

    else if(boldState==Qt::Checked && italicState==Qt::Checked)
    {
        ui->SLineEdit->setFont(font->setBold(true));
        ui->SLineEdit->setFont(font->setItalic(true));
    }

    else
    {
        ui->SLineEdit->setFont(font->setBold(false));
        ui->SLineEdit->setFont(font->setItalic(false));
    }
}

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[stampede]

I followed the documentation...

Then read again here what is the type of expected "setFont()" parameter (its not QFont *)

[eLancaster]

Ok now i'm confused.
It says

void setFont ( const QFont & )

void setFont ( const QFont & )

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, which means the paramter needs a reference to the font. So i passed a pointer which stores the reference. :S

[FelixB]

Pointer != Reference

[eLancaster]

I'm really sorry to be such a dufus,
but could you illustrate this with an unrelated code example, please?

[MarekR22]

I would say that QFont shouldn't be created on heap. Use of this class is similar to QString (implicit data sharing).
Note also that QWidfet::setFont has specific way of working! What is returned from QWidfet::font is compilation of fonts set for this widget its parent widgets and QApplication.

Just do it like that.

setFont(QFont("Times",12));

setFont(QFont("Times",12));

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[FelixB]

QFont font("Times",12);
myWidget.setFont(font);

QFont font("Times",12);
myWidget.setFont(font);

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[eLancaster]

I still dont understand why you have to do that. I've never read of anything like that, i'm very sorry to say :$
also i still get the error "invalid use of void expression"

[stampede]

also i still get the error "invalid use of void expression"

Because code like this

ui->SLineEdit->setFont(font->setBold(false));

ui->SLineEdit->setFont(font->setBold(false));

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makes no sense: font->setBold() is a method that returns 'void', and "setFont()" requires 'const QFont&'.
Modify your font and then assign it to QLineEdits:

font->setBold(true);
font->...
ui->lineEdit->setFont( *font ); //!< if you dont know why its here ...

font->setBold(true);
font->...
ui->lineEdit->setFont( *font ); //!< if you dont know why its here ...

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... read this

[eLancaster]

OMG, Stampede - that makes perfect sense now. I wasn't seeing the whole picture. Thanks alot to everyone!

---

Added after 23 minutes:

QFont font("Times",12);
myWidget.setFont(font);

QFont font("Times",12);
myWidget.setFont(font);

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Pointer != Reference

could you also provide a link that explains this. I know its basic but i'm still a bit confused. Thanks alot!