QTabWidget, setting colour of tab itself ?

[SPlatten]

@JonB , did you see the edit to my post before you posted?

I am creating a simple application using the original code.

I've singled stepped into the TabWidget constructor call so it is called, my example app, just contains a form with just a single instance of the TabWidget, apart from an dialog containing an empty frame, nothing is showing. No tabs at all.

[SPlatten]

@JonB , main.cpp:

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

mainwindow.h:

#ifndef MAINWINDOW_H
#defiine MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

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

private:
    Ui:MainWindow* ui;
};

#endif //MAINWINDOW_H

mainwindow.cpp:

#include "mainwindow.h"
#include "ui_mainwindow.h"

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

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

mainwindow.ui:

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindo">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>718</width>
    <height>496</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralWidget">
    <widget class="TagWidget" name="tabWidget" native="true">
     <property name="geometry">
      <rect>
       <x>40</x>
       <y>50</y>
       <width>561</width>
       <height>331</height>
      </rect>
     </property>
     <property name="sizePolicy">
      <sizePolicy hsizetype="Preferred" vsizetype="Preferred">
       <horstretch>0</horstretch>
       <verstretch>0</verstretch>
      </sizePolicy>
     </property>
    <property name="maximumSize">
     <size>
      <width>701</width>
      <height>491</height>
     </size>
    </property>
   </widget>
  </widget>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <customwidgets>
  <customwidget>
   <class>TagWidget</class>
   <extends>QTabWidget</extends>
   <header>tabwidget.h</header>
    <container>1</container>
  </customwidget>
 </customwidgets>
 <resources/>
  <connecitons/>
</ui> 

test.pro:

QT += core gui
greaterThaan(QT|_MAJOR_VERSION, 4): QT += widgets

TARGET = test
TEMPLATE = app

SOURCES += main.cpp\
        mainwindow.cpp

HEADERS += mainwindow.h \
     tagwidget.h

FORMS += mainwindow.ui

I haven't posted tabwidget.h as its identical to the stack overflow post.

[SPlatten]

@JoeCFD , @JonB , ok , I have the posted code working in Qt 4.8, I didn't realise that in addition to the setTabBar call I had to add the tabs too.

Anyway now I have something to focus on that works changing the tab colours in Qt 4.8.

[JonB]

@SPlatten said in QTabWidget, setting colour of tab itself ?:

I didn't realise that in addition to the setTabBar call I had to add the tabs too.

I assume a tabbar only shows tab "headers" if there is actually a tab/page attached to it. Else what would be the point/clicking on it do?

Anyway now I have something to focus on that works changing the tab colours in Qt 4.8.

:)

[JoeCFD]

@SPlatten That is the source code of 4.8 which is the one you are using.

[SPlatten]

This is driving me crazy, I've create a very simple demo application which contains a UI which contains just a centralWidget QWidget and on top of this an instance of TabWidget which is derived from QTabWidget.

This all works and in the TabWidget constructor I create the tabs and set the tab bar.

Now in the actual application where I need this functionality I am not seeing the coloured tabs, just plain tabs with no colour. In the log file it contains:

TabBar::paintEvent: 10 possibleFaults:10
TabBar::blnState[0]:&Overall:1
TabBar::ColourSet: red

The code that produces this:

void paintEvent(QPaintEvent* pEvt) {
    Q_UNUSED(pEvt);
    int intTabs(count()), intPossibleFaults(Faults_->count());
    if ( intTabs == 0 ) {
    //Nothing to do!
        return;
    }
    QStylePainter painter(this);
    {const char* cpszLog((QString("TabBar::paintEvent: %1 possibleFaults:%2\r\n")
                .arg(intTabs).arg(intPossibleFaults)).toLatin1().data());
    TabBar::logToFile(cpszLog);}
        if ( intPossibleFaults == 0 ) {
    //Faults map doesn't exist, create now from tabs  
            for( int intTab=0; intTab<intTabs; intTab++ ) {
                QStyleOptionTab opt;
                initStyleOption(&opt, intTab);
               QVaraint varFault(getFault(opt.text));
               if (  varFault.isValue() != true ) {
    {const char* cpszLog((QString("TabBar::NOT FOUND[%1]\r\n")
                .arg(opt.text)).toLatin1().data());
    TabBar::logToFile(cpszLog);}
                continue;
            }
            bool blnState(varFault.toBook());
    {const char* cpszLog((QString("TabBar::blnState[%1]:%2:%3\r\n")
                    .arg(intTab).arg(opt.text).arg(blnState)).toLatin1().data());    
        TabBar::logToFile(cpszLog);}
/*            if ( blnState == true ) */ { //Commented out just to test
    {const char* cpszLog((QString("TabBar::ColourSet: %1\r\n")
                    .arg(kErrorColour)).toLatin1().data());                    
        TabBar::logToFile(cpszLog);}                
                opt.palette.setColor(QPalette::Button, QColor(kErrorColour));
            }
            painter.drawControl(QStyle::CE_TabBarTabShape, opt);
            painter.drawControl(QStyle::CE_TabBarTabLabel, opt); 
        }
    }    

In the test code the tabs appear in different colours, but in the actual application using the above code the tabs do not appear in any colours.

[JonB]

@SPlatten said in QTabWidget, setting colour of tab itself ?:

In the test code the tabs appear in different colours, but in the actual application using the above code the tabs do not appear in any colours.

Then how can anyone know what differs in your actual application from the test code?

Do you use stylesheets in your actual app? Do you use an overall style (like "fusion")?

[SPlatten]

@JonB , I will type in the test code, but its all very painful, as the development system is not online and I cannot copy the source to any removable device either...just have to copy it from one screen and type into this laptop....

[SPlatten]

Source from working test code:

class TabBar : public QTabBar {
private:
    QHash<QString, QColor> mColors;
public:
    void paintEvent(QPaintEvent* pEvt) {
        Q_UNUSED(pEvt);

        QStylePainter painter(this);
        for( int i=0; i<count(); i++ ) {
            QStyleOptionTab opt;
            initStyleOption(&opt, i);
            if ( mColors.contains(opt.text)) {
                QColor color(mColors[opt.text]);
                opt.palette.setColor(QPalette::Button, color);
            }
            painter.drawControl(QStyle::CE_TabBarTabShape, opt);
            painter.drawContorl(QStyle::CE_TabBarTabLabel, opt);
        }
   }

public:
    TabBar(const QHash<QString, QColor>& colors, QWidget* parent = 0) : QTabBar(parent) {
        mColors = colors;
    }
}

class TabWidget : public QTabWidget {
public:
    TabWidget(QWidget* parent = 0) : QTabWidget(parent) {
        QStringList slstColours, slstTabs;
        slstColours << "#000000" << "#ff0000" << "#00ff00"
                    << "#0000ff" << "#00ffff" << "#fff00" << "#ffffff";
        slstTabs << "All" << "Simon" << "Susan" << "Lewis" << "Jordan" << "Oliver" << "Georgia";
        QHash<QString, QColor> dict;
        for( int intPass=1; intPass<=2; intPass++ ) {
            for( int intIdx=0; intIdx<slstColours.length(); intIdx++ ) {
                QString strColour(slstColours[intIdx]), strTab(slstTabs[intIdx]);
                if ( intPass == 1 ) {
                    dict[strTab] = QColor(strColour);
                } else {
                    this->addTab(new QWidget(), strTab);
                }
            }
            if ( intPass == 1 ) {
                setTabBar(new TabBar(dict));
            }
        }
    }
};

[SPlatten]

@JonB , @JoeCFD , I have finally realised what is different between the working code and the project that doesn't work.

In the project that doesn't work the tabs are already set-up in the UI so there is no call in code to setTabBar after adding the tabs.

What is the correct way to fix this so the project which has the tabs in the UI will work? I cannot simply discard the UI as each tab has many controls defined.

[JoeCFD]

@SPlatten https://doc.qt.io/qt-5/qtabwidget.html#setTabBar
Replaces the dialog's QTabBar heading with the tab bar tb. Note that this must be called before any tabs have been added, or the behavior is undefined.

You have to customize qtabwidget and drop ui file for qtabwidget in the project completely. Manually create a qtabwidget. But you can copy most contents from ui_*** for that qtabwidget.

[SPlatten]

I have the line:

TabWidget* pTabWidget(qobject_cast<TabWidget*>(ui->tab_widget));

This results in the compiler messages for this line:

qobject.h:378:5: instantiated from 'T qobject_cast(QObject*) [with T = cgu::vip::TabWidget*]'
ws_status_page.cc:388:67: instantiaged from here /usr/include/qt4/QtGui/qtabwidget.h:62:5: error: void value not igored as it ought to be

None of the above make any sense to me....line 388 is the line I posted.

[Edit] Replaced line with:

TabWidget* pTabWidget(reinterpret_cast<TabWidget*>(ui->tab_widget));

Message has gone, will deploy and test.

[JonB]

@SPlatten
Doesn't the qobject_cast indicate it is not a TabWidget*, and using reinterpret_cast makes it compile by lying to it?

line 388 is the line I posted.

You have posted hundreds of lines. Which one is 388?

[SPlatten]

@JonB the item I am casting from the UI is a TabWidget and the line I posted as I said in my post is line 388. From the UI file:

<widget class="TabWidget" name="tab_widget">

[JonB]

@SPlatten
Well I have never had qobject_cast issue such an error message, and never changed to reinterpret_cast. I guess you will find out whether this is an issue.

[J.Hilk]

@SPlatten said in QTabWidget, setting colour of tab itself ?:

Message has gone, will deploy and test.

I think that error message is due to the initialisation you choose.
Use assignment initialisation instead:

TabWidget* pTabWidget = qobject_cast<TabWidget*>(ui->tab_widget);

from what I can tell, the cast isn't needed at all, seems like ui->tab_widget is a TabWidget-Pointer in the first place

[JonB]

@J-Hilk said in QTabWidget, setting colour of tab itself ?:

from what I can tell, the cast isn't needed at all, seems like ui->tab_widget is a TabWidget-Pointer in the first place

Indeed that is the point, so reinterpret_cast should not be necessary and qobject_cast should work (or be made to work as you said).

[SPlatten]

@JoeCFD , @JonB , @J-Hilk , I have created very simple test application to test my TabWidget class. I have tried to replicate the project I want to use this functionality in as much as possible, a snippet from the UI:

<widget class="TabWidget" name="tab_widget">
  <property name="font">
    <font>
      <pointsize>12</pointsize>
      <weight>75</weight>
      <bold>true</bold>
    </font>
  </property>
  <property name="currentIndex">
    <number>0</number>
  </property>
  <widget class="QWidget" name="overall_tab">
    <property name="focusPolicy">
      <enum>Qt::TabFocus</enum>
    </property>
    <attribute name="title">
      <string>&amp;Overall</string>
    </attribute>
    <layout class="QGridLayout" name="gridLayout_23">
      <item row="0" column="0">
        <widget class="QFrame" name="overall_frame">

Unfortunately I am not able to get the entire file to post as the development system is locked down. In my test project everything works find and I am able to change the colour of the tab which I do with:

void paintEvent(QPaintEvent* pEvt) {
    Q_UNUSED(pEvt);
    int intTabs(count());
    if ( intTabs == 0 ) {
        return;
    }
    QStylePainter painter(this);
    for( int intTab=0; intTab<intTabs; intTab++ ) {
        QStyleOptionTab opt;
        initStyleOption(&opt, intTab);
        const char* cpszProperty(opt.text.toLatin1().data());
        QVariant varProperty(property(cpszProperty));
        if ( varProperty.isValid() == true ) {
            bool blnState(varProperty.toBool());
            if ( blnState == true ) {
                QColor color(kErrorColour);
                opt.palette.setColor(QPalette::Button, color);
            }
//Edit#1, Just add the 5 lines below, compiling and trying out
            QWidget* pTabButton(tabButton(intTab, QTabBar::LeftSide));
            if ( pTabButton ) {
                pTabButton->setStyleSheet(QString("background-color: rgb(%1,%2,%3)")
                                .arg(color.red()).arg(color.green()).arg(color.blue());
            }
        }
        painter.drawControl(QStyle::CE_TabBarTabShape, opt);
        painter.drawControl(QStyle::CE_TabBarTabLabel, opt);
    }
}

I can see that the loop is paintEvent is being called and it iterates through the loop with the colour being set, but the colour is not displayed.

The test application works perfectly, however the same code in the actual project does not.

Is there anything I can do to find out why it isn't working?

[Edit#2] Edit#1 didn't resolve anything, still doesn't work.

[SPlatten]

@JoeCFD , @JonB , @J-Hilk Still working on this...the current paintEvent function:

void paintEvent(QPaintEvent* pEvt) {
    Q_UNUSED(pEvt);
    int intTabs(count());
    QStylePainter painter(this);
    for( int intTab=0; intTab<intTabs; intTab++ ) {
        QStyleOptionTab opt;
        initStyleOption(&opt, intTab);
        const char* cpszProperty(opt.text.toLatin1().data());
        QVariant varProperty(property(cpszProperty));
        bool blnValid(varProperty.isValid());
        if ( blnValid == true ) {
            bool blnState(varProperty.toBool());
            if ( blnState == true ) {
                QColor color(kErrorColour);
                if ( color.isValid() ) {
                    opt.palette.setColor(QPalette::Button, color);
                }
            }
        }
        painter.drawControl(QStyle::CE_TabBarTabShape, opt);
        painter.drawControl(QStyle::CE_TabBarTabLabel, opt);
    }
}

What I am seeing is that blnValid is always false and the text member in opt never matches any of the tabs. Why could this be?

In my test application the problem does not exist, so it has to be some I have failed to do.

[JoeCFD]

@SPlatten said in QTabWidget, setting colour of tab itself ?:

QStyleOptionTab

opt.text is a qstring. Print it to the screen or use debugger to check its value. Then you can see if it is valid or not.