[anmorgan]

This is geared towards qtquick (not widgets) applications, but to create a general theme you can use this pattern:

https://doc.qt.io/archives/qt-5.11/qtquickcontrols2-flatstyl...

Then before the engine is loaded in main.cpp call

qmlRegisterSingleton( QUrl(QStringLiteral("qrc:/Theme.qml")), "mycustomname.theme", 1, 0, "Theme");

Then in a qml file:

import mycustomname.theme 1.0

This allows you to do something like:

Rectangle { width: 100 height: 100 color: Theme.mainColor }

You can also do things like set the application font which would be done in main.cpp before the engine is loaded:

QFont appFont("NameOfLoadedFont); appFont.setPixelSize(16); QGuiApplication::setFont(appFont);

You would need to load the font, which you can do in the Theme.qml file:

property FontLoader someFont: FontLoader { source: "qrc:/locationOfFont/Font" name: "NameOfLoadedFont" }