[Development] QLibraryInfo::path(): to deprecate or not to deprecate?

[Volker Hilsheimer]

> On 28 Jul 2026, at 02:10, Thiago Macieira <thiago.macieira at intel.com> wrote:
> 
> On Monday, 27 July 2026 04:50:49 Pacific Daylight Time Volker Hilsheimer via 
> Development wrote:
>> Ok; it then seems reasonable for the next step to be a cleaning up of
>> in-tree code, see what we can learn from that (if anything; tests can
>> perhaps get away with s/path()/paths().first()?), and only deprecate once
>> we have a clean source tree ourselves and a good porting guideline.
> 
> The libraries are already all free of it.
> 
> The problem are examples and tests. I asked the question because I noticed 
> just how much there is of it and I don't intend to fix them all.


Getting the examples cleaned up is IMHO a precondition for deprecating, and the tests should disable the deprecation warning as otherwise we get -Werror build failures. The examples are a fairly overviewable list, but they should of course show the right pattern.

So the question is what the correct replacement for code like this is:

    // from qtbase/examples/corelib/mimetypes/mimetypebrowser/main.cpp
    QTranslator translator;
    if (translator.load(QLocale::system(), "qtbase"_L1, "_"_L1,
                        QLibraryInfo::path(QLibraryInfo::TranslationsPath))) {
        app.installTranslator(&translator);
    }


I assume the right pattern is using a while-loop until one of the loads succeeded, rather than loading them all in a for-loop.

Esp when looking at:

    // from qttools/examples/assistant/remotecontrol/remotecontrol.cpp
    QString app = QLibraryInfo::path(QLibraryInfo::BinariesPath);
#if !defined(Q_OS_MACOS)
    app += "/assistant"_L1;
#else
    app += "/Assistant.app/Contents/MacOS/Assistant"_L1;
#endif

    process->start(app, {"-enableRemoteControl"_L1});
    if (!process->waitForStarted()) {
        QMessageBox::critical(this, tr("Remote Control"),
                tr("Could not start Qt Assistant from %1.").arg(QDir::toNativeSeparators(app)));
        return;
    }


Launching several assistants would be a surprise.

Perhaps a naive

    QString app = QLibraryInfo::paths(QLibraryInfo::BinariesPath).first();

is fine, as long as paths() guarantees that there is always at least one entry. But is it a practice we want to encourage?


Volker