RFR: 8303904: [macos]Transparent Windows Paint Wrong (Opaque, Pixelated) w/o Volatile Buffering

[anass baya]

8303904: [macos]Transparent Windows Paint Wrong (Opaque, Pixelated) w/o Volatile Buffering

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Commit messages:
 - fix for pixelated images
 - Add test for pixelated images at high resolution
 - Test for Mac platfotm
 - Unit Test to Verify Window Transparency and Black Border Presence
 - fix 1 : fix for non-transparency and black borders

Changes: https://git.openjdk.org/jdk/pull/23430/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23430&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303904
  Stats: 244 lines in 4 files changed: 237 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/23430.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23430/head:pull/23430

PR: https://git.openjdk.org/jdk/pull/23430