RFR: 8304831: TextFlow.hitTest.insertionIndex incorrect with surrogate pairs [v2]

[Andy Goryachev]

On Mon, 8 May 2023 12:22:17 GMT, Karthik P K <kpk at openjdk.org> wrote:

>> Since surrogate pairs are internally considered as 2 characters and text field is null in `HitInfo` when `getInsertionIndex` is invoked from `TextFlow`, wrong insertion index was returned.
>> 
>> Updated code to calculate insertion index in `getHitInfo` method of `PrismTextLayout` class when `hitTest` of trailing side of surrogate pair is requested. Since text runs are processed in this method already, calculating the insertion index in this method looks better than calculating in `getInsertionIndex` of `HitInfo` method.
>> The latter approach also requires the text to be sent to `HitInfo` as parameter from the `hitTest` method of `TextFlow`. If the number of `Text` nodes in `TextFlow` are very large, processing all the `Text` nodes on each `hitTest` method invocation might cause performance issue. Hence implemented first approach.
>> 
>> Added system test to validate the fix.
>
> Karthik P K has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix insertion index calculation issue with emojis. Add additional test cases

minor changes requested

modules/javafx.graphics/src/main/java/com/sun/javafx/text/PrismTextLayout.java line 456:

> 454: 
> 455:                 insertionIndex = charIndex;
> 456:                 String txt = new String(getText());

possible NPE: looks like getText() might return null, in which case this line will throw an NPE.

modules/javafx.graphics/src/main/java/com/sun/javafx/text/PrismTextLayout.java line 458:

> 456:                 String txt = new String(getText());
> 457:                 if (!leading) {
> 458:                     if (txt != null) {

This check should be done earlier for getText()

modules/javafx.graphics/src/main/java/com/sun/javafx/text/PrismTextLayout.java line 461:

> 459:                         int next;
> 460:                         BreakIterator charIterator = BreakIterator.getCharacterInstance();
> 461:                         synchronized(charIterator) {

question: why do we need to synchronize on the instance here?  BreakIterator.get*Instance() creates a new instance each time, so synchronization is probably unnecessary.

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

Changes requested by angorya (Committer).

PR Review: https://git.openjdk.org/jfx/pull/1091#pullrequestreview-1417028467
PR Review Comment: https://git.openjdk.org/jfx/pull/1091#discussion_r1187585950
PR Review Comment: https://git.openjdk.org/jfx/pull/1091#discussion_r1187586532
PR Review Comment: https://git.openjdk.org/jfx/pull/1091#discussion_r1187595409