If you are on mobile, here is the direct link to the repo: https://github.com/therecipe/widgets_playground
Sorry, the widgets playground isn't really meant to be used on mobile devices.
The next playground will be made with QML instead and should be better suited for mobile usage.
I think you can't simply reuse the rpi3 env, but you can use it as a template to how to get this working for the beaglebone black.
So you would need to get a cross compiler and then extract the sysroot to compile Qt on your own. After you got Qt compiled, you will also need to make some changes similar to these [1]
But I think the hardest part might be to get Qt compiled for the beaglebone black, because the info I found online seems to be a bit outdated.
The file size depends on the target and what modules you use, for dynamically linked projects I would guess it's around 50mb for an average project.
Maybe 20mb more on windows because of the icu libs, but those can be replaced with your own (much smaller) versions. Static projects may weight half of what the dynamic ones do, so maybe around 25mb.
But depending on how much you care about file size, you could also compile your own static Qt version and then strip everything that you don't need.
Here [1] are some infos about QML development and here [2] you can try out QML in the browser.
It depends on how much you want to embrace docker. In general you can use this binding without touching docker at all.
But if you want, you can use docker in every step of the process.
It starts with the minimal setup that just depends on Go + Docker.
Then continues during development, so if you would want for example test your application on android really quick, then you would just need to pull the android image instead of setting up the android SDK, NDK and JDK by yourself.
And then in the end you can use docker for your CI and CD processes as well.
For example by creating your own docker images on top of provided ones.
go-qml, like the name suggests allows you to use QML together with Go. This binding allows you to also use Qt's C++ API. And it contains some tools to simplify deployment and development processes.
qtdeploy is intended to be used for deploying and therefore will run qtrcc, qtmoc, qtminimal and do the actual bundling of your binary. the -fast flag re-uses the cached rcc_* moc_* minimal-* files and will also not re-run the actual bundling process. this works for the desktop targets but not for the mobile targets, therefore I made it optional.
it depends on the target [1] and which Qt version you use, the default "official" Qt version usually dynamically links against Qt's libs.
for windows for example you can use the msys2 version (on windows), which can also be statically linked or you could use the docker images with mxe to statically link your windows application.
but you could also build a static version of Qt yourself and use that version as well.
Did you tried to use QT_MISC_DIR (which should contains the "mkspecs" subfolder) and QT_DOC_DIR, which should contain for example (QtCore/qtcore.index)?
Or if you like, open an issue on github and we can try to sort this out :) edit: also if you use PKG_CONFIG=true, the QT_DIR will be ignored