[OpenJDK 2D-Dev] RFR: 8266159: macOS ARM + Metal pipeline shows artifacts on Swing Menu with Java L&F [v2]

[Ajit Ghaisas]

> This PR fixes an issue exclusively seen on Apple M1 systems when SwingSet2 demo is run with uiScale=1.0.
> 
> **Issue :**
> SwingSet2 Demo - As reported in JBS description
> J2DDemo - As reported in a comment on JBS
> 
> **Root Cause :** 
> DrawPixel path is used only with uiScale=1.0. 
> MTLPrimitiveTypePoint is used to draw a pixel while encoding a render command.
> As mentioned in the documentation -
> https://developer.apple.com/documentation/metal/mtlprimitivetype/mtlprimitivetypepoint?language=objc
> 
> "The vertex shader must provide [[point_size]], or the point size is undefined."
> 
> In our shader functions, we do not define this point size. It is harmless on x86_64 based mac systems, but causes visual artifacts on M1 mac systems.
> 
> **Solution :**
>  Explicitly define point size in shader functions that draw MTLPrimitiveTypePoint.

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

  add automated test

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4356/files
  - new: https://git.openjdk.java.net/jdk/pull/4356/files/b61e512e..751c85cf

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4356&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4356&range=00-01

  Stats: 92 lines in 1 file changed: 92 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4356.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4356/head:pull/4356

PR: https://git.openjdk.java.net/jdk/pull/4356