On Mon, 26 Jan 2026 17:17:44 GMT, Kevin Rushforth <[email protected]> wrote:
>> modules/javafx.graphics/src/main/java/com/sun/javafx/sg/prism/NGGroup.java
>> line 218:
>>
>>> 216: for (int i = (startPos == -1 ? 0 : startPos); i <
>>> orderedChildren.size(); i++) {
>>> 217: NGNode child = orderedChildren.get(i);
>>> 218: child.render(g);
>>
>> more on the concurrency here: if one would instrument the get(int) method in
>> `children` like so
>>
>>
>> private final List<NGNode> children = new ArrayList<>(1) {
>> public NGNode get(int ix) {
>> System.out.println(Thread.currentThread());
>> return super.get(ix);
>> }
>> };
>>
>>
>> the log will show accesses from two threads:
>>
>>
>> Thread[#33,JavaFX Application Thread,5,main]
>> ...
>> Thread[#28,QuantumRenderer-0,5,main]
>> ...
>> Thread[#33,JavaFX Application Thread,5,main]
>>
>>
>> The access pattern for `viewOrderChildren` seem to show only QuantumRenderer
>> thread, though I did not test extensively.
>>
>> Does anyone know if these two threads are allowed to run in parallel, or is
>> there a mechanism in place that ensures mutual exclusion?
>
> Yes, this is expected. No, the threads do not run in parallel. The renderLock
> mechanism prevents it. The only access from the JavaFX Application thread is
> while holding the render lock to update the render graph (NG* nodes) from the
> scene graph.
A bit unrelated, but what does the "NG" in "NGNode" stand for?
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PR Review Comment: https://git.openjdk.org/jfx/pull/2043#discussion_r2728827941
