QTabBar tab text painting?

[Matic Kukovec]

Hello Maurizio,

You are right about the superfluous stuff, I copy pasted from an actual working example.
The painter save/restore is still in there because I forgot to remove it in this example.
And yes, data is the PyQt5 package with all sub-packages, all of them in one namespace.

The reason stylesheets are not usable in my case, is that I need to switch between an
active and inactive mode, and when setting a new stylesheet, the scroll offset is not remembered
and the tabbar's view snaps to the right. This has been very annoying for users as when they switch
to an inactive QTabWidget that becomes active, the whole tabbar view changes. When you have
a lot of tabs, then the user sometimes doesn't know where the active tab "jumped" to.
That is why I'm using the overridden paintEvent.
Anyway, the main issue here is that you're probably using Windows, and the Windows QStyle does paint some things a bit differently, including possibly ignoring the palette of the style option (but, hey, that could also be a bug, unfortunately I cannot test it).
Yes, I'm on Windows.

Thanks for the help, I will investigate further.
If anyone can shed more light on where the problem could be, please let me know.

Regards,
Matic
________________________________
From: Maurizio Berti <maurizio.berti at gmail.com>
Sent: Friday, June 4, 2021 3:46 PM
To: Matic Kukovec <kukovecmatic at hotmail.com>
Cc: pyqt at riverbankcomputing.com <pyqt at riverbankcomputing.com>
Subject: Re: QTabBar tab text painting?

Hello Matic,

The whole resetting the palette in the for loop is completely unnecessary (especially if done every time in a for loop, you can create a palette the first time, and then overwrite opt.palette, but that would be unnecessary anyway since the palette should not change between tabs).
Also, the painter save/restore is completely pointless like that: the point of saving the state of the painter is that you can temporarily change painter settings and restore the previous state (which should also match the state level: it's not really clear since the formatting is not monospaced, but it seems that you're calling painter.restore() in the for loop, and if that's the case, you should not, as you'd have unmatched levels of saved states). Since you're not painting anything before or after that, there's no benefit.

Anyway, the main issue here is that you're probably using Windows, and the Windows QStyle does paint some things a bit differently, including possibly ignoring the palette of the style option (but, hey, that could also be a bug, unfortunately I cannot test it).

That said, if you only want to change the color of the tab text, subclassing and overriding the paintEvent is a bit too much (and also risky: your implementation doesn't take into account movable tabs, which is really tricky). I'd suggest a more simpler:

self.tabWidget.setStyleSheet('QTabBar { color: red; }')

Which should solve the whole problem on any platform.

Be aware that it's very important that you use the class selector (unless you set the stylesheet on the tab bar), if you use generic/universal properties you'll get unexpected results, especially for a container widget such a QTabWidget.
So, *never* do the following: it works, but it works very badly.

self.tabWidget.setStyleSheet('color: red') # NO!


Maurizio

PS: it took me a while to understand what "data" actually was; I'd strongly suggest you against that choice, "data" is a very generic word and doesn't reflect what it refers to in your code (and it's also very confusing to others reading your code): what happens whenever you have a function that *actually* uses some "data"? Why should you then choose another word instead of an obvious name, because you already used that name for a wrong reference and you cannot overwrite it because it's required in the function scope?

Il giorno ven 4 giu 2021 alle ore 10:26 Matic Kukovec <kukovecmatic at hotmail.com<mailto:kukovecmatic at hotmail.com>> ha scritto:
Hi guys,

I have a subclassed QTabBar which I want to manually change the color of each tab.
After a lot of trial-and-error, I tried this to make all the tabs red:
def paintEvent(self, event):
            painter = data.QStylePainter(self)
            opt = data.QStyleOptionTab()
            painter.save()

            for i in range(self.count()):
                self.initStyleOption(opt, i)
                items = (
                    data.QPalette.Window,
                    data.QPalette.Background,
                    data.QPalette.WindowText,
                    data.QPalette.Foreground,
                    data.QPalette.Base,
                    data.QPalette.AlternateBase,
                    data.QPalette.ToolTipBase,
                    data.QPalette.ToolTipText,
                    data.QPalette.PlaceholderText,
                    data.QPalette.Text,
                    data.QPalette.Button,
                    data.QPalette.ButtonText,
                    data.QPalette.BrightText,
                    data.QPalette.Light,
                    data.QPalette.Midlight,
                    data.QPalette.Dark,
                    data.QPalette.Mid,
                    data.QPalette.Shadow,
                    data.QPalette.Highlight,
                    data.QPalette.HighlightedText,
                    data.QPalette.Link,
                    data.QPalette.LinkVisited,
                )
                groups = (
                    data.QPalette.Disabled,
                    data.QPalette.Active,
                    data.QPalette.Inactive,
                    data.QPalette.Normal,
                )
                color = data.QColor(0xffff0000)
                for g in groups:
                    for p in items:
                        opt.palette.setColor(g, p, color)
                        opt.palette.setBrush(g, p, color)
                painter.setBrush(data.QBrush(data.QColor(color)))
                painter.setPen(data.QPen(data.QColor(color)))
                painter.drawControl(data.QStyle.CE_TabBarTabLabel, opt)

                           painter.restore()

Now this works, but only for the non-currently selected tabs, the selected tab ALWAYS has black text and I have no idea why.
Here is a screenshot: [cid:179d72f4ca7cb971f161]
The "string.h" tab is the currently selected one.

Any ideas what I'm doing wrong or missing?

Thanks,
Matic


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