<i18n dev> RFR: JDK-8303950: [macos]Translucent Windows Flicker on Repaint [v3]

[Jeremy]

> I'm confident about the new test case for this ticket, but the resolution is more invasive than I'd like. (It works, though.)
> 
> In short:
> This introduces a new RenderingHint (in SunHints) to bypass the call in Window to `gg2d.fillRect(0, 0, getWidth(), getHeight());`
> 
> I left more detailed notes here about the proposed resolution:
> https://github.com/openjdk/jdk/commit/1991fdac5dbf76ddaf73cc78a9f7c38370c9674c
> 
> I'm open to suggestions if anyone has a more elegant proposal to prevent the monitor from refreshing too soon?

Jeremy has updated the pull request incrementally with one additional commit since the last revision:

  8303950: addressing artifacts observed in RepaintManagerFPUIScaleTest
  
  When I resized the window in the RepaintManagerFPUIScaleTest: I saw lots of random patches of misplaced pixels.
  
  I assume this is because the RepaintManager could now call AWTPaintManager#paint(..) recursively, which means each invocation could grab the cached VolatileImage returned by getVolatileOffscreenBuffer. As a test: I tried making getVolatileOffscreenBuffer always return a new image, and that resolved the artifacts.
  
  This change avoids the recursion with a new helper method. This logic is similar to checking JComponent#getFlag(ANCESTOR_USING_BUFFER) , except that can't help identify recursion when the outermost call is coming from a Component like a Window.
  
  To my knowledge this recursion can only ever happen when the outermost call is a non-Swing component and the innermost call is a Swing component. (And there should only ever be one layer of recursion.)

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12993/files
  - new: https://git.openjdk.org/jdk/pull/12993/files/6a3a9b42..960fd176

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12993&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12993&range=01-02

  Stats: 70 lines in 2 files changed: 35 ins; 10 del; 25 mod
  Patch: https://git.openjdk.org/jdk/pull/12993.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/12993/head:pull/12993

PR: https://git.openjdk.org/jdk/pull/12993