QTabWidget, setting colour of tab itself ?

SPlatten

@JoeCFD , thank you

SPlatten

@JoeCFD , hello, I'm trying to do this today, but not sure quite where to start. I have code already existing which I didn't write, the existing code uses a QTabWidget in the UI. Each tab is defined in the UI as QWidget.

Do I replace the QWidget with my own implementation? Is there a tutorial that could help me or guide me through this process ?

I'm getting confused by the online documentation for QTabWidget and QTabBar:

https://doc.qt.io/qt-6/qtabwidget.html
QTabWidget Class
The QTabWidget class provides a stack of tabbed widgets.

https://doc.qt.io/qt-6/qtabbar.html
QTabBar Class
The QTabBar class provides a tab bar, e.g. for use in tabbed dialogs.

I want to implement a tab where I can set the background colour according to my own logic.

I found this:
https://stackoverflow.com/questions/46137500/qt-tabwidget-each-tab-title-background-color

I am trying to tailor it to my problem....the issue I'm having now is that the tabs are already defined in the UI. How can I apply this logic to the tabs that are already defined in the UI ?

SPlatten

@J-Hilk , @JonB , @JoeCFD , This is the current issue or at least one issue:

The UI contained an instance of QTabWidget. This was set-up to contain the following tabs:

&Overall
C&2
&CGU
&LMS
&PDLT
&NLA
P&GU
&HCU
&UPSD
&Sensors

In the XML file these tabs were defined with the class as QWidget I have edited the XML file and changed instances of QTabWidget to TabWidget and the tabs from QWidget to TabBar which matches the names of the new implementation I am trying to use.

However I'm not sure why or what I need to do in order to transfer the tabs from the UI into the class I am using so I can use the colours that the replacement class is going to allow?

SPlatten

@J-Hilk , @JonB , @JoeCFD , a snippet from the UI file:

<widget class="TabWidget" name="tab_widget">
  <property name="font">
    <font>
      <pointsize>12</pointsize>
      <weight>75</weight>
      <bold>true</bold>
    </font>
  </property>
  <property name="styleSheet">
    <string notr="true"/>
  </property>
  <property name="currentIndx">
    <number>0</number>
  </property>
  <widget class="TabBar" nam="overall_tab">
    <property name="focusPolicy">
      <enum>Qt::TabFocus</enum>
    </property>
    <attribute name="title">
      <string>&amp;Overall</string>
    </attribute>
    ....

I can see in my log output that the constructor for the TabBar is called for each instance of the TabBar in the UI file. Can I determine from the constructor call what the title attribute is ?

JonB

@SPlatten
Constructor of what?

As far as I can see code must call either QTabWidget::setTabText(int index, const QString &label), QTabWidget::addTab(QWidget *page, const QString &label) or QTabBar::setTabText(int index, const QString &text). These are all individual calls, there is no "constructor" which takes the tab text/title as a parameter. Nor are any of the methods virtual. I imagine an explicit call is made to one of these after whatever construction. So does that answer your question as "No"?

Meanwhile you can also look in the uic-generated ui_....h file for the actual code used to execute what it reads from the .ui file, if that helps clarify.

SPlatten

@JonB , the default constructor of the TabBar is being called I assume when the UI file is parsed?

class TabBar : public QTabBar {
private:
    QHash<QString, QColor> colors_;

protected:
    void paintEvent(QPaintEvent* evt) {
... 
    }

public:
    TabBar(QWidget* parent = 0) : QTabBar(parent) {
        ...
    }
...
}

JonB

@SPlatten
Like I said, look in the ui_...h file?

But I don't see that helps particularly. Doesn't the ui_...h show some explicit, separate call to one of the functions I pasted after the TabWidget/TabBar has been constructed?

SPlatten

@JonB , from ui_...h file:

overall_tab = new TabBar();
overall_tab->setObjectName(QString::fromUtf8("overall_tab"));

Some where nearer the end of file in the function retranslateUi there is a call to:

tab_widget->setTabText(tab_widget->indexOf(overall_tab), QApplication::translate("::wsStatusPage", "&Overall", 0, QApplication::UnicodeUTF8));

Its all a bit fragmented...is there anything I can do to the UI file that will help me to identify the tab when the constructor is called?

I'm reworking this code, as it isn't well written and doesn't follow the correct way of doing things, hopefully this will lead to a solution.

JonB

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

is there anything I can do to the UI file that will help me to identify the tab when the constructor is called?

Nope. As you can see, the tab text is not set until that tab_widget->setTabText() is called, much later than construction. That's how it implements the instructions from the .ui file.

At least in terms of the tab's text/title, which is what you say you want to know.

And once again anyway (not that it helps): "the constructor" of what are you asking about? QTabWidget? QTabBar? Tabs are not even constructed until after both of these anyway.

SPlatten

@JonB , I guess I could generate an index of the tabs and use its position to indicate what it is...

JonB

@SPlatten
So now you are saying you do not need to know about the text/title after all??

SPlatten

@JonB , if its available but I can do it using an index...

JonB

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

I have edited the XML file and changed instances of QTabWidget to TabWidget and the tabs from QWidget to TabBar

class TabBar : public QTabBar

BTW, what is going on here? You confuse me (not for the first time!). A QTabWidget is supposed to have one QTabBar and a number of QWidgets for the widgets/contents/tabs of each page; one page per item in the tab bar. You have changed so that your QTabWidget has a QTabBar as each of its widgets/pages/tabs??

SPlatten

@JonB , to be honest, I'm confused by the implementation I have downloaded, I was looking online for an implementation that allows me to set the colours of the tabs and I found the source I'm using, this does appear to use a TabBar for each tab, please take a look at the source I posted in my earlier posts.

I'm looking at it again as I may have goofed it up.

JonB

@SPlatten
Nothing in https://stackoverflow.com/questions/46137500/qt-tabwidget-each-tab-title-background-color creates multiple QTabBars or changes the QWidgets which are the content/pages of each tab to themselves be QTabBars!

SPlatten

@JonB , no as I said I goofed up, looking at it again now.

SPlatten

@J.Hilk, @JonB , @JoeCFD, so I've finally got everything the way it should be and in my debug output I can see that various bits are being called, but it doesn't do what it is supposed to do, I'm not seeing the tabs in a different colour.

The modified classes:

typedef QMap<QString, QVariant> mpFaults;

class TabBar : public QTabBar {
private:
    mpFault* Faults_;

protected:
    void paintEvent(QPaintEvent* evt) {
        int intTabs(count()), intPossibleFaults(Faults_->count());
        QStylePainter painter(this);
        QStyleOptionTab opt;
 const char* cpszLog((QString("TabBar::paintEvent: %1 possibleFaults:%2\r\n")
                          .arg(intTabs).arg(intPossibleFaults)).toLatin1().data());
TabBar::logToFile(cpszLog);
        if ( intTabs > 0 && intPossibleFaults == 0 ) {
            for ( int intTab=0; intTab<intTabs; intTab++ ) {
                QString strText(tabText(intTab));
                Faults_->insert(strText, QVariant(false));
            }
        }
        for( int intTab=0; intTab<intTabs; intTab++ ) {
            initStyleOption(&opt, intTab);
const char* cpszLog((QString("TabBar::tab: %1\r\n")
              .arg(opt.text)).toLatin1().data());
TabBar::logToFile(cpszLog);
            mpFaults::iterator itTab(Faults_->find(opt.text));
            if ( itTab != Faults_->end() ) {
                QVariant varValue(itTab.value());
                bool blnState(varValue.toBool());
const char* cpszLog((QString("TabBar::blnState: %1\r\n")
              .arg(blnState)).toLatin1().data());
TabBar::logToFile(cpszLog);
                if ( blnState == true ) {
const char* cpszLog((QString("TabBar::ColourSet: %1\r\n")
              . arg(kErrorColour)).toLatin1().data());
                    opt.palette.setColor(QPalette::Button, QColor(kErrorColour));
                }
            }
            painter.drawControl(QStyle::CE_TabBarTabShape, opt);
            painter.drawControl(QStyle::CE_TabBarTabLabel, opt);
        }
    }
public:
    static void logToFile(const char* cpszMsg) {
        FILE* fp(fopen("/usr/local/cgu/paint.txt", "at"));
        if ( fp ) {
            fputs(cpszMsg, fp);
            fclose(fp);
        }
    } 
    TabBar(QWidget* pParent = 0) : QTabBar(pParent) {
TabBar::logToFile("TabBar::TabBar!!\r\n");
        Faults_ = new mpFaults();
    }
    bool setFault (QString& strText, bool blnState) {
        mpFaults::iterator itTab(Faults_->find(strText));
const char* cpszLog((QString("TabBar::setFault(%1,%2)\r\n")
                .arg(strText).arg(blnState)).toLatin1().data());
TabBar::logToFile(cpszLog);
        if ( itTab != Faults_->end() ) {
            itTab.value() = QVariant(blnState);
            return true;
        }
        return false;
    }
};

class TabWidget : public QTabWidget {
public:
    TabWidget(QWidget* pParent = 0) : QTabWidget(pParent) {
        setTabBar(new TabBar());
    }
    bool setFault(QString& strText, bool blnState) {
        TabBar* pTabBar(dynamic_cast<TabBar*>(tabBar()));
        if ( pTabBar ) {
            return pTabBar->setFault(strText, blnState);
        }
        return false;
    }
};

I see all the various debug messages in the log file, but tab is not showing as red which is the string literal assigned to kErrorColour:

const char_t kErrorColour[] = "red";

Logged to file:

TabBar::paintEvent: 10 possibileFaults:10
TabBar::tab: &Overall
TabBar::blnState: 1
TabBar::ColourSet: red

JoeCFD

You really want to add flashing icons to the tabs or simply change their colors?

SPlatten

@JoeCFD , changing the colour of the tab is the intention but it isn't working.

JoeCFD

You can not change it with style sheet? My suggestion for you was to flash the icons on the tabs.