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

[Alexey Ivanov]

On Wed, 11 Jun 2025 03:09:16 GMT, Prasanta Sadhukhan <psadhukhan at openjdk.org> wrote:

> > 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.
> 
> If we create a new MediaTracker in ImageIcon and start anew with id of zero, then if application is having its own MediaTracker to track then when it calls for tracker.checkID(0) or tracker.statusID(0) then it will be confusing to which image it is referring to

Why is it? `ImageIcon` has its own instance of `MediaTracker`. Yes, technically, it's possible to get this instance from `AppContext` but no application should do it.

If an application needs to load images, it has to create its own instance of `MediaTracker`. Since `MediaTracker` API requires a caller provided id, the instance of `MediaTracker` can't be shared, otherwise there's a clash in ids.

> …so I guess this current PR is more simpler in the sense it will notify ABORTED status for all images which overflows so that application can start anew with new ImageIcon and then use their MediaTracker to track this new ImageIcon.

Could you elaborate please?

The `mediaTrackerID` is a static field in `ImageIcon`; `MediaTracker` is also a static-like shared instance that's stored in `AppContext`.

This means if `mediaTrackerID` overflows, the application can't use `new ImageIcon` to load any more images — the application can no longer work. The application can do nothing about it.

> Other thing that can be done is to modify "int" to "long" for all ids to further the overflow goalpost whereby `MediaTracker.checkID,addImage, statusID` signature will be changed..I dont think it will break any application but it will require CSR and since this issue is earmarked as Enhancement, maybe submitter also wanted that but I am not sure of going that route unless there is consensus on it..

I thought about it, and using `long` instead of `int` was my first idea. Yet `MediaTracker` API needs to be modified.

But it won't solve the underlying problem: `long` can also wrap around into negative numbers. It'll take much longer, but `long` will wrap around.

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PR Comment: https://git.openjdk.org/jdk/pull/25666#issuecomment-2962253908