Actually, funnily enough, Qt.fontfamilies is an order of magnitude
faster than custom property wrapping the result of ::families. Dunno
why. 5s vs 500 ms for the sue case
Still, checking on .lncludes(name) in javascript is seemingly also an
order of magnitude slower than sending family name to c++ and
prematurely exiting from there. 500 ms vs <50ms
In 5.15 Qt.fontFamilies() is a JavaScript method on the 'Qt' member of
the JavaScript global object. It looks like this:
ReturnedValue QtObject::method_fontFamilies(const FunctionObject *b,
const Value *, const Value *, int argc)
{
QV4::Scope scope(b);
if (argc != 0)
THROW_GENERIC_ERROR("Qt.fontFamilies(): Invalid arguments");
return
scope.engine->fromVariant(QVariant(QQml_guiProvider()->fontFamilies()));
}
So, it wraps the QStringList into a QVariant and the QVaroamt into a JS
object. I'm really surprised that the wrapping is faster than anything
else, but I'm not surprised that access to its internals is slow.
In Qt6, this is a Q_INVOKABLE C++ method on the 'Qt' singleton. It
returns the QStringList as-is and lets the QML engine do with it
whatever it needs to do.
If this is a particularly hot code path, what you might try is create a
QJSValue that holds a JS array of font families in C++ and then expose
that instead of the QStringList. This way you tightly control the
JavaScript wrapping of the list. In turn, you lose any type information.
A QJSValue can be anything. However, in Qt5 you cannot use the type
information anyway.
best,
Ulf
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