RFR: 8231864: JavaFX Labels in Tab's VBox is not displayed until it is clicked

[Ambarish Rapte]

On Mon, 19 Dec 2022 15:50:19 GMT, Lukasz Kostyra <lkostyra at openjdk.org> wrote:

> Creating a not-displayed node and then modifying its contents caused JFX to not consume its old dirty region and thus not update it. When such node was displayed, its old dirty region was used for drawing, which in some cases (ex. new content taking more space - a Label having more text as in bug request) caused it to clip.
> 
> Resolved by always unionizing dirty regions with new bounds when calculating Node's transformed bounds.
> 
> Change was tested on macOS and Windows 10 and does not affect any tests.

The change looks good.
Verified the computed `dirtyBounds` with and without the change. They look as expected.
I shall test more with some apps(Ensemble).
Providing one minor suggestion.

modules/javafx.graphics/src/main/java/com/sun/javafx/sg/prism/NGNode.java line 335:

> 333:         } else {
> 334:             // TODO I think this is vestigial from Scenario and will never
> 335:             // actually occur in real life... (RT-23956)

The comments should be removed and updated to explain the scenario when flow enters the else block and I think RT-23956 can be closed with this fix.

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Changes requested by arapte (Reviewer).

PR: https://git.openjdk.org/jfx/pull/978