For the purpouse of people who might search for an find this forum post, I put in a request with QT support and received the following.
Hi Joe,
Thank you for contacting Qt Support and for providing your sample project.
There are 2 broad ways to specify the fragmentShader property, depending on which version of Qt you want to target:
The Qt 5 way is to specify the shader's source code as a string.
The Qt 6 way is to pre-compile your shader source code into a .qsb file, and specify a URL to that .qsb file
See:
https://doc.qt.io/qt-5/qml-qtquick-shadereffect.html#fragmentShader-prop
https://doc.qt.io/qt-6/qml-qtquick-shadereffect.html#fragmentShader-prop
To do it the Qt 5 way, the easiest approach is to copy the contents of your .frag file and paste it as a string literal (surrounded by quotation marks) to the RHS of the "fragmentShader" property.
To do it the Qt 6 way, run the QSB tool to compile your shader source code. Unfortunately, the code of colour_wheel.frag is too old to be supported by QSB (for example, the "varying" keyword was deprecated long ago, and even removed for ES profiles)
See:
https://doc.qt.io/qt-6/qtshadertools-overview.html
https://doc.qt.io/qt-6/qtshadertools-qsb.html
I hope this helps.
