RFR: 8301121: RichTextArea Control (Incubator) [v6]

[Andy Goryachev]

> Incubating a new feature - rich text control, **RichTextArea**, intended to bridge the functional gap with Swing and its StyledEditorKit/JEditorPane. The main design goal is to provide a control that is complete enough to be useful out-of-the box, as well as open to extension by the application developers.
> 
> This is a complex feature with a large API surface that would be nearly impossible to get right the first time, even after an extensive review. We are, therefore, introducing this in an incubating module, **jfx.incubator.richtext**. This will allow us to evolve the API in future releases without the strict compatibility constraints that other JavaFX modules have.
> 
> Please check out two manual test applications - one for RichTextArea (**RichTextAreaDemoApp**) and one for the CodeArea (**CodeAreaDemoApp**). Also, a small example provides a standalone rich text editor, see **RichEditorDemoApp**.
> 
> Because it's an incubating module, please focus on the public APIs rather than implementation.  There **will be** changes to the implementation once/if the module is promoted to the core by popular demand.  The goal of the incubator is to let the app developers try the new feature out. 
> 
> **References**
> 
> - Proposal: https://github.com/andy-goryachev-oracle/Test/blob/main/doc/RichTextArea/RichTextArea.md
> - Discussion points: https://github.com/andy-goryachev-oracle/Test/blob/main/doc/RichTextArea/RichTextAreaDiscussion.md
> - API specification (javadoc): https://cr.openjdk.org/~angorya/RichTextArea/javadoc
> - RichTextArea RFE: https://bugs.openjdk.org/browse/JDK-8301121
> - Behavior doc: https://github.com/andy-goryachev-oracle/jfx/blob/8301121.RichTextArea/doc-files/behavior/RichTextAreaBehavior.md
> - CSS Reference: https://cr.openjdk.org/~angorya/RichTextArea/javadoc/javafx.graphics/javafx/scene/doc-files/cssref.html
> - InputMap (v3): https://github.com/andy-goryachev-oracle/Test/blob/main/doc/InputMap/InputMapV3.md
> - Previous Draft PR: https://github.com/openjdk/jfx/pull/1374

Andy Goryachev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 10 additional commits since the last revision:

 - improved vertical scrolling
 - Merge remote-tracking branch 'origin/master' into 8301121.RichTextArea
 - cleanup
 - navigation
 - Merge remote-tracking branch 'origin/master' into 8301121.RichTextArea
 - whitespace
 - update + review comments
 - Merge remote-tracking branch 'origin/master' into 8301121.RichTextArea
 - whitespace
 - 8301121: RichTextArea Control (Incubator)

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1524/files
  - new: https://git.openjdk.org/jfx/pull/1524/files/09a1637c..e035c166

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1524&range=05
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1524&range=04-05

  Stats: 26362 lines in 566 files changed: 14023 ins; 7061 del; 5278 mod
  Patch: https://git.openjdk.org/jfx/pull/1524.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1524/head:pull/1524

PR: https://git.openjdk.org/jfx/pull/1524