RFR: 8055461: getNextID in ImageIcon class can lead to overflow

[Alexey Ivanov]

On Fri, 6 Jun 2025 03:29:47 GMT, Prasanta Sadhukhan <psadhukhan at openjdk.org> wrote:

> ImageIcon.getNextID uses `mediaTrackerID ` which do not detect overflow.
> 
> Theoretically there is a possibility that there can be overflow in the long time run or for large number of created "imageIcon"
> 
> Made sure there is no overflow and treat that loadImage as ABORTED
> 
> No regression testcase as it addresses theoretical possibility..

I think a better solution is to create a new `MediaTracker`, and start anew with id of zero.

The `TRACKER_KEY` is used only by `ImageIcon`, so it shouldn't break any apps.

src/java.desktop/share/classes/javax/swing/ImageIcon.java line 304:

> 302:                 height = image.getHeight(imageObserver);
> 303:                 return;
> 304:             }

This means that the application won't be able to load images using `MediaTracker`.

Is it really a problem that the id becomes negative? Does anything stop working?

~~I can't see that anything breaks because of that. The id is just an id, and it's compared for equality. (Although having a negative id could look suspicious.)~~

It may break at `MediaEntry` insertion, although it would still work probably…

Another problem may occur if and when the id wraps around again to positive numbers and 0, 1… _are still being used_.

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Changes requested by aivanov (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25666#pullrequestreview-2913496159
PR Review Comment: https://git.openjdk.org/jdk/pull/25666#discussion_r2137855023