QTabWidget, setting colour of tab itself ?

[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.

[SPlatten]

@JoeCFD , @JonB , @J-Hilk , I've progressed this to the point where it gets all the way to:

opt.palette.setColor(QPalette::Button, color);

I output the color to the log file and its valid and the name() returns #ff0000. But still the colour of the tab doesn't change, again in my standard alone test project it does the same and in this it works...so why doesn't it work here?

[JoeCFD]

@SPlatten Make sure the same tabs are painted. Assign object names to the tabs when they are created. Check if the names are the same when they are painted.

[SPlatten]

@JoeCFD , I can see in the ui / XML file that each widget / tab has a name attribute. How do I go about checking if the names are the same when painted?

[JoeCFD]

@SPlatten it is object name. https://doc.qt.io/qt-5/qobject.html#objectName-prop

[SPlatten]

@JoeCFD , thank you, I realise that but I was expecting the QStyleOptionTab to have some member that represents the tab object name, it doesn't, the only way I can think of doing this is to make the object name the same as the tab text ?

[JoeCFD]

@SPlatten The better way to check it is to make sure the pointer addresses of your tabs are the same as the ones when they are created. Changing object names can not help anything. It is only one way for debug.

[SPlatten]

@JoeCFD , I'm not sure how this is going to help as only one set of tabs is displayed. I could try changing the text of any tab to see if that updates...if it does it doesn't explain why the colour doesn't change.

[JoeCFD]

@SPlatten Good idea. Try to change the texts to see if it works.

[SPlatten]

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

@SPlatten Good idea. Try to change the texts to see if it works.

I've modified the code where it sets the colour to also change the tab text:

setTabText(intTab, "modified: " + tabText(intTab));

[Edit] With this code in place I can see that no tab text is modified, which makes me wonder what is going on, the tabs show the same as defined in the UI file, but it appears they aren't the same in that they cannot be modified???

[SPlatten]

@JoeCFD , so now I'm looking at why this is the case and what I can do to fix it.

[Edit] I removed this:

<header location="global">ws_status_page.h</header>

From the customWidget defining the class TabWidget and now the modified text is visible, although when I applied the modified text to the project that the colours work in, the colours don't work while the text is modified, so I'm now rebuilding and testing without modified text...

[Edit#2] Sadly having removed the code that modified the text the colour still isn't set. But this does still work in the other project when I removed the modified text.

[SPlatten]

@JonB , @JoeCFD , @J-Hilk I'm still working on this and trying to find a solution, in the test project I created I've added to the end the TabBar::paintEvent function:

QPen objPen(QColor("#ffff00"));
objPen.setWidth(3);
painter.setPen(objPen);
painter.drawLine(0,0,100,100);

Having cleaned and rebuilt both projects I can see the thick yellow diagonal line drawn in both projects, but only the prototype I created has the tabs drawn with a red background.

[JoeCFD]

@SPlatten I still suspect that not the right tab is called. You do need to check their pointer addresses match exactly. Try to make only one tab in your project for testing. If this is confirmed, you need to dig into the source code to check what can block the change of color. There must be some flags for this.