RFR: 7124282: [macosx] Can't see table cell highlighter when the highlight border is the same color as the cell. [v11]

[Harshitha Onkar]

> Previously while tabbing through the JTable cell, the cell highlighter/focus ring was not visible against the selection background. 
> 
> Changes are made to Aqua LAF to derive a lighter focus ring color by changing saturation and setting brightness component to 100% of original focus ring color so that it is visible while tabbing through `JTable` cells. A new method is added for this purpose which takes in `focusRingColor`, does adjustment to saturation and brightness and returns a new focus ring color. There are edge cases where the HSB transformation does not yield the right focus ring color, for these cases a default color is returned.
> 
> **Edge Cases**
> ![image](https://user-images.githubusercontent.com/95945681/161360456-3929acf1-282b-4c2b-95d1-1d5707c1e238.png)
> 
> The edge case condition consists of two parts –
> To handle white/black colors - (hsbValues[0] == 0 && hsbValues[1] == 0) - representing hue and saturation of zero obtained for black, white or exactly grey (red=green=color) conditions
> To handle grayish colors - hsbValues[1] <= satGrayScale where satGrayScale <= 0.10 . For any given hue and brightness, a saturation of less than or equal to 10% represents grayish tint colors.
> (The second case was added to accommodate grayish focus ring color returned by system when Accent color = Graphite.  The returned color is not exactly gray but grayish (r=135, g=135, b=140)). 
> To accommodate a more generic case of grayish colors, the satGrayScale has a threshold or buffer of 0.10 or 10%. 
> 
> Used the following resources to test out different grayish colors and optimal saturation offsets used in  `deriveLighterFocusRing()`.
> 
> - [RapidTables](https://www.rapidtables.com/convert/color/rgb-to-hsl.html) 
> - [Colorizer](http://colorizer.org/).
> - [Chart Link](https://codepen.io/HunorMarton/details/eWvewo)
> 
> A test case is added to compare the RGB difference between the original focus ring color & selection background and the new focus ring color & selection background.
> 
> PS: The native L&F (Mac OS) and Swing L&F for JTable cell tabbing differs (on native tables the cell background turns white on focus with a cell focus ring). Since the background for Swing tables can be set by users and also overridden by subclassing `DefaultTableCellRenderer`, and to adhere to current implementation of Swing, the white cell background changes are not incorporated. Only the Focus Ring/ Cell Highlighter is made more prominent.

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

  added new color to CSystemColors.m - CELL_HIGHLIGHT_COLOR

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7768/files
  - new: https://git.openjdk.java.net/jdk/pull/7768/files/c796a99d..d13e37f8

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7768&range=10
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7768&range=09-10

  Stats: 51 lines in 6 files changed: 15 ins; 0 del; 36 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7768.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7768/head:pull/7768

PR: https://git.openjdk.java.net/jdk/pull/7768