RFR: 8325900: Emit a warning on macOS if AWT has set the NSAppearance

[Michael Strauß]

Platform preferences detection doesn't pick up effective macOS system preferences if AWT owns the NSApplication and has set its NSAppearance to a fixed value.

The workaround is to set the system property "apple.awt.application.appearance=system".

If this property is not set, the following warning will be emitted if a JavaFX application attempts to use the platform preferences API:


WARNING: Reported preferences may not reflect the macOS system preferences unless the sytem
property apple.awt.application.appearance=system is set. This warning can be disabled by
setting javafx.preferences.suppressAppleAwtWarning=true.

-------------

Commit messages:
 - Emit a warning on macOS if AWT has set the NSAppearance

Changes: https://git.openjdk.org/jfx/pull/1367/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1367&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325900
  Stats: 53 lines in 4 files changed: 48 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jfx/pull/1367.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1367/head:pull/1367

PR: https://git.openjdk.org/jfx/pull/1367