Why the string on model of table view will be changed after adding application font.

[mrjj]

Hi
Sounds like something wrong with font.
Try testing if it really is added after calling QFontDatabase::addApplicationFont()

QFontDatabase fdb;
QStringList fam = fdb.families();

    qDebug() << "QFontDatabase::Any: available font families -> " << fam.count();
    for (int i = 0 ; i < fam.count() ; i++)
    {
            qDebug() << fam[i];
    }
}

[SGaist]

Hi,

To add to @mrjj, did you deploy the font on the device ? Or are you embedding it in the application through Qt's resources system ?

[Mihan]

@sgaist Hi,
I add AwesomeFont in the vritual keyboard I made, the vritual keyboard is a plugin. When it is shown, it will add the font in resource

    m_FontId = QFontDatabase::addApplicationFont(":/font/FontAwesome.otf");
    QString fontName = QFontDatabase::applicationFontFamilies(m_FontId).at(0);
    QFont iconFont(fontName);
    iconFont.setPixelSize(20);

At the same time, the string of table in main project will be changed to be squares. Also, if I don't set the font in data() of table model, this phenomenon will not happen.

[Mihan]

@mrjj Hi,
I'm sure it was added successfully. But it is added in plugin.

Also, I try adding this font in main()of the project but do not use it, This phenomenon appears.

[Mihan]

@sgaist @mrjj
Thank you so much.
I found there are only two fonts except I added in the system .

QFontDatabase::Any: available font families ->  3
"FontAwesome"
"WenQuanYi Micro Hei"
"WenQuanYi Micro Hei Mono"

So when I set font to be "Sans Serif". It can't find this font and will use the first font of family default, "WenQuanYi Micro Hei". And when I add Awesome font, the font of string in the table I had set will be "WenQuanYi Micro Hei" -> "FontAwesome" .
So I should add "Sans Serif" in the system or modify QFont font("Sans Serif", 12, QFont::Normal, true); -> QFont font("WenQuanYi Micro Hei", 12, QFont::Normal, true);

Is that right? Or can I know which font the system use default?

[Mihan]

@mrjj @SGaist
Hi
I found the project's default font is "Sans Serif" not "WenQuanYi Micro Hei".
But I set the font in data(),

QFont font = QApplication::font();

it's still will be changed when I add a font.

Could you please explain?

[SGaist]

Can your create a minimal compilable example that reproduces this ?

By the way, which version of Qt are young using ?
On which platform ?

[Mihan]

@sgaist
Sure. Here's an example. When you click the button ,it will add the font, then you should touch the table to make it updated , and you can see the phenomenon. If you don't add font, the phenomenon will not appear.

I'm using Qt5.5.0 for linux, Qt5.6.2 for Arm-linux. This phenomenon only appears on Arm-linux. The arm-linux system has only two font

uh....."you do not have enough privileges for this action.", I can't upload file. So....

#mainwindows.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QDebug>
#include <QStringList>
#include <QApplication>
#include <QFontDatabase>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    ui->tableView->horizontalHeader()->setSectionResizeMode(QHeaderView::Stretch);

    InitTableModel();
    ConnectSlots();
}

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

void MainWindow::InitTableModel()
{
    TestModel *model = new TestModel;
    ui->tableView->setModel(model);
}

void MainWindow::ConnectSlots()
{
    connect(ui->CteateBtn,SIGNAL(clicked(bool)),this,SLOT(CreateFont()));
}

void MainWindow::CreateFont()
{
    qDebug()<<"add awesome font";
    QFontDatabase::addApplicationFont(":/new/prefix1/FontAwesome.otf");
}


TestModel::TestModel(QObject *parent):
    QAbstractTableModel(parent)
{
    m_String.clear();
    m_String<<"test1"<<"test2"<<"test3"<<"test4"<<"test5"<<"test6"<<"test7";
}

TestModel::~TestModel()
{

}

int TestModel::columnCount(const QModelIndex &parent) const
{
    return 2;
}

int TestModel::rowCount(const QModelIndex &parent) const
{
    return m_String.count();
}

QVariant TestModel::data(const QModelIndex &index, int role) const
{
    if(!index.isValid())
           return QVariant();
    if(role == Qt::DisplayRole)
    {
        return m_String.at(index.row());
    }
    else if(role == Qt::FontRole)
    {
        QFont font = QApplication::font();
        font.setItalic(true);
        switch (index.column()) {
        case 0:
            return QVariant();
            break;
        case 1:
            return font;
            break;
        default:
            return QVariant();
            break;
        }
    }
    else
        return QVariant();
}

#mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QAbstractTableModel>

namespace Ui {
class MainWindow;
class TestModel;
}

class TestModel : public QAbstractTableModel
{
    Q_OBJECT
public:
    explicit TestModel(QObject *parent = 0);
    ~TestModel();

    int columnCount(const QModelIndex &parent = QModelIndex()) const;
    int rowCount(const QModelIndex &parent = QModelIndex()) const;
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const;

private:
    QStringList m_String;
};


class MainWindow : public QMainWindow
{
    Q_OBJECT

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

    void InitTableModel();
    void ConnectSlots();

public slots:
    void CreateFont();

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

There is a TableView and a Pushbutton in ui(mainwindow.ui)

[SGaist]

Then please, add the content of the UI file to that post.

[Mihan]

@sgaist sorry I forgot it.

#mainwindow.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>344</width>
    <height>469</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralWidget">
   <layout class="QGridLayout" name="gridLayout">
    <item row="0" column="0">
     <widget class="QTableView" name="tableView">
      <attribute name="horizontalHeaderVisible">
       <bool>false</bool>
      </attribute>
      <attribute name="verticalHeaderVisible">
       <bool>false</bool>
      </attribute>
     </widget>
    </item>
    <item row="1" column="0">
     <widget class="QPushButton" name="CteateBtn">
      <property name="text">
       <string>Create Font</string>
      </property>
     </widget>
    </item>
   </layout>
  </widget>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <resources/>
 <connections/>
</ui>

#main.cpp

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

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

# .pro

#-------------------------------------------------
#
# Project created by QtCreator 2019-08-15T08:51:22
#
#-------------------------------------------------

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = FontTest
TEMPLATE = app


SOURCES += main.cpp\
        mainwindow.cpp

HEADERS  += mainwindow.h

FORMS    += mainwindow.ui

RESOURCES += \
    font.qrc

[SGaist]

What is the content of font.qrc ?
Depending on that, where do you get the corresponding file(s) ?

[Mihan]

@sgaist I'm so sorry to reply to you after so long.
The font.qrc is a resource file I made, with the FontAwesome.otf .
It's found in a topic about making Qt virtual keyboard by BaiDu.
It is used to show some special symbols like circle, star and so on.
Maybe you can download the analogous from www.fontawesome.com.