On Fri, 21 Mar 2025 21:30:28 GMT, Andy Goryachev <ango...@openjdk.org> wrote:
>> There is an undocumented limit on nesting calls to CFRunLoopRun (or the
>> equivalent wrapper NSRunLoop methods). When the limit is hit the OS
>> terminates the Java app. The situation arises when a JavaFX app creates too
>> many nested event loops from within Platform.runLater runnables.
>>
>> This PR doesn't change the limit (which is 250+ nested loops) but it does
>> throw an exception just before the limit is reached so a JavaFX developer
>> will get a useful Java stack trace instead of an OS crash log.
>>
>> On the Mac the nested event loop has two stages: first we ask the run loop
>> to run, then we pull an event out and process it. A Platform.runLater
>> runnable is executed in the first stage so if the runnable starts a new
>> nested event loop the system will re-enter CFRunLoopRun. The same isn't true
>> if an input event handler starts a new nested event loop; at that point
>> we're in stage two and are past the call to CFRunLoopRun.
>
> modules/javafx.graphics/src/main/native-glass/mac/GlassApplication.m line 778:
>
>> 776: beforeDate:[NSDate
>> dateWithTimeIntervalSinceNow:0.010]];
>> 777: nestedRunLoopRunCount -= 1;
>> 778: if (ran) {
>
> I could be wrong reading this code, but doesn't the `nestedRunLoopRunCount`
> value remain unchanged? L774 gets always cancelled by L777?
never mind, it's entering and exiting the loop there.
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PR Review Comment: https://git.openjdk.org/jfx/pull/1741#discussion_r2008390270
