QTabWidget, setting colour of tab itself ?

SPlatten

@JoeCFD , at this point I'm out of ideas as to why it isn't working, at a guess I would say the paintEvent is not using the correct painter which means the "this" context isn't correct.

In "my" own project I created using the UI from the project that doesn't work, I have a working set of tabs where I can set the tab colours using flags and the paintEvent which is identical to the source in the project that doesn't work.

I've looked very carefully at everything I can and I just can't see where the issue is.

Project that works, mainwindow.ui contains:

centralWidget
    QFrame
        tab_widget
            overall_tab
            more tabs...

The bottom of the UI file contains:

<customwidgets>
  <customwidget>
    <class>TabWidget</class>
    <extends>QTabWidget</extends>
    <header>tabwidget.h</header>
    <container>1</container>
  </customwidget>
</customwidgets>

Project that doesn't work, has the same structure as the project that does work. Any suggestions welcome.

J.Hilk

@SPlatten suggestion,

make a backup :D
remove the not working class entirely, cpp, h and ui file
replace the removed files with the ones from your working example
adjust the api with dummy functions so it compiles
see if it works as expected
if it does add functionality from old file back in, and regular check if it still works

SPlatten

@J-Hilk , thank you, that's a massive job in itself...is there any tracing I can add to the paintEvent in the tabBar to see why one works and the other doesn't....

I'm going to compromise and try to use pre-processors to comment out sections of the CPP, rebuild and see if that works, commenting out almost everything to begin with.

SPlatten

@JoeCFD , @J-Hilk , its stranger and stranger, here is the paintEvent function:

void paintEvent(QPaintEvent* pEvt) {
        QStylePainter painter(this);
        int intTabs(count());
        for( int i=0; i<intTabs; i++ ) {
            QString strTabKey(strKey(i));
            QStyleOptionTab opt;
            initStyleOption(&opt, i);
            tFaultsMap::const_iterator citFound(mmpFaults.find(strTabKey));
            if ( citFound != mmpFaults.constEnd() ) {
                QColor color(citFound->value());
                const int cintBlue(color.blue());
                const int cintRed(color.red());
                color.setBlue(cintRed);
                color.setRed(cintBlue);
  //This only works in the project I've created not the original
                opt.palette.setColor(QPalette::Button, color);
  //Change tab text, this works
                opt.text = "HACK";
            }
            painter.drawControl(QStyle::CE_TabBarTabShape, opt);
            painter.drawContorl(QStyle::CE_TabBarTabLabel, opt);
        }
        Q_UNUSED(pEvt);
   }

Is there anything special I need to do in order to adjust the palette? As changing the text works.

[Edit] In searching for a solution on Google I found a suggestion to set the Fusion style:

QApplication::setStyle("Fusion");

I added this to the TabBar constructor, rebuilt and deployed, when the form is displayed the application now crashes.

[Edit#2] It wasn't this that caused the crash but another modification I made at the same time.

[Edit#3] I have read online that using the palette to set the colour isn't reliable and instead to use the style sheet. I would like to try this but:

QWidget* pobjTabButton(tabButton(i, QTabBar::LeftSide));

tabButton returns NULL, this is being called in a loop in the paintEvent where the iterations of the loop is determined by the count function. Why would tabButton return NULL when there are tabs set-up ?

Why is this so tricky? I can't get anything except NULL returned by tabButton, without the widget I cannot try setStyleSheet and the other just doesn't work (In one project at least).

JoeCFD

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

QStyleOptionTab

That is why I told you to check the pointers of tabs. When they are created, print their addresses to the screen. Then check their pointers here as well to make sure the same tabs are handled. Here, I mean tab buttons.

SPlatten

@JoeCFD , something funky is going on tho, as I posted earlier, if I use the structure to change the tab text, this works and is clearly visible. The issue is setting the colour doesn't work so this in itself tells me the pointers must be correct.

I was going to give using setStyleSheet a shot but I cannot get any button returned by using the function tabButton, it always returns NULL in both of the applications.

SPlatten

@JoeCFD , @J-Hilk , I'm comparing the UI from both projects in the form editor and looking for differences that could explain why one works and the other doesn't, so far:

In the project that works, the UI has a setting in the tab widget, palette which is set to Cusomized (3 roles), in the project that doesn't work this is set to inherited.

Looking at the XML for each files I cannot see anything that corresponds to this, so where is this specified?

It doesn't make any difference, I've now got them the same and it doesn't work in the same project.

[Edit] I've modified the paintEvent function adding more debug:

QColor color(citFound->value());
const int cintBlue(color.blue());
const int cintRed(color.red());
color.setBlue(cintRed);
color.setRed(cintBlue);
QColor before(opt.palette.color(QPalette::Button));
opt.palette.setColor(QPalette::Button, color);
QColor confirm(opt.palette.color(QPalette::Button));

I also log this data to a file and I can see that the output is:

Before: #d4d0c8, Colour:#ff0000, Confirm:#ff0000

However I'm not seeing the tabs with a red background, just the standard background colour.

[Edit#1] Looking into this as a possible solution:
https://stackoverflow.com/questions/54070408/change-color-of-single-qtabwidget-tab

SPlatten

Finally resolved, in the end I had to replace:

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

with:

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

Its still a mystery as to why the original code worked find in one project and not in the other, both using the same release of Qt.

JoeCFD

Great you made it. This was a heck of a lot work. This selection is actually obsolete. But it still works. Good for you.
QPalette::Background Window This value is obsolete. Use Window instead.
4.8 is too old for anyone here.

SPlatten

@JoeCFD , thank you, will do