Update scaladoc demos to use JFXApp3

[jpsacha]

See for instance here: https://oss.sonatype.org/service/local/repositories/releases/archive/org/scalafx/scalafx_2.13/16.0.0-R23/scalafx_2.13-16.0.0-R23-javadoc.jar/!/index.html

[rom1dep]

➤ rg JFXApp -g "*.scala" scalafx-demos -c | wc -l
99
➤ rg JFXApp -g "*.scala" scalafx -c | wc -l     
22

I wonder how hard it is to write a source transformer from scalameta, seems justified in this case :)

[jpsacha]

Automatically transforming the code would be quite helpful. Would you be able to look into this?

[rom1dep]

I have no experience with that, but it sounds fun enough (based on the examples on https://scalameta.org/docs/trees/guide.html#transform-trees )

Would those two rules be relevant/enough, in your opinion:

• imports
  • transform scalafx.application.JFXApp into scalafx.application.JFXApp3
  • transform scalafx.application.JFXApp.PrimaryStage into scalafx.application.JFXApp3.PrimaryStage
• "main" object
  • transform object XYZ extends JFXApp into object XYZ extends JFXApp3
  • create new method start() for object XYZ: override def start(): Unit
  • move all members of object XYZ into start()

[jpsacha]

Those rule should work in most cases. There my be some corner cases that use declarations like private val, like in demo scalafx.controls.PaginationSample, but those could be fixed by removing private by hand.

[rom1dep]

so, I finally wrote a scalafix rule here: https://github.com/rom1dep/scalafx_scalafix_jfxapp3
and pushed the result there: #356

As it happens, scalafix doesn't make it practical to conserve formatting when implementing a rewrite rule, so I ran scalafmt before and after the rewrite, which makes this PR a bikeshed of its own (I tried to adapt .scalafmt.conf to minimize the diff, though).

The effect of the rewrite itself lies in this commit: 73f94c6 (before is just preparing the project and running scalafmt)

After the rewrite, some fine-tuning was needed for demos to compile: 68d1c99 (probably not everything is legit, the style of some demos was "not great" and I didn't want to spend too much time rewriting a lot of it)

I haven't tested most demos yet, that will be a task for another day

For the curious, the scalafix rewrite rule can be run by:

• cloning https://github.com/rom1dep/scalafx_scalafix_jfxapp3 at the root of the scalafx repo
• running scalafix --rules=file:scalafix/rules/src/main/scala/fix/JFXApp3Migration.scala in sbt with the patched build.sbt of the PR

[jpsacha]

@rom1dep Looks that we need a more consistent way of formatting the code. I will open issue for that and start with setup that you had in PR #356

[jpsacha]

I think all uses of JFXApp in ScalaFX project are now converted to JFXApp3