8198549: Desktop.setOpenURIHandler() only receives event if application is already launched

[pabulaner]

Problem description

When You create a JavaFX native application with jpackage for macOS You will run into an issue when trying to handle URIs. When Your application isn’t running and You have it registered for handling certain types of URIs it won’t receive the first URI.

Here is a simple example:

If You have a JavaFX application that handles URIs for example of the form openurifx://your-content and You have it installed with jpackage for macOS and now You try to handle an URI by running the following command:

open openurifx://hello-world

The application will open, but it won’t receive the above URI. If You call the same command after the application is already running, everything will work fine and the application will receive the URI.

Problem cause

The cause of the problem is that when You build a JavaFX application and want to handle URIs You will have to combine JavaFX and AWT as AWT provides the URI handling capabilities. So the startup process is as follows:

1. JavaFX is initialized
2. JavaFX forwards the URI event to AWT
3. AWT is initialized
4. AWT is ready to handle URI events from JavaFX

The issue is that the URI event is delivered before AWT can handle it and therefore is simple dropped. That’s why later URIs will be received and are handled properly.

Fix

The fix is that JavaFX will wait until it receives a ready event from AWT so JavaFX knows that AWT is able to handle events now. After that it will forward all buffered URIs and therefore everything will be handled correctly. This means that the fix involves both the JFX and JDK repositories and needs to be integrated in both.

Note: In the case that a user has only a fix for the JFX part the URIs won’t be delivered at all, but there won’t be any error. This means that JavaFX applications won’t be able to handle any URIs so it might be an idea to add an environment variable to tell JavaFX to not wait for an AWT ready event. Then the first URI event would be lost, but at least all the following events would be handled properly.

Tests

To test the error and the fix You can clone this repository: https://github.com/pabulaner/openurifx and checkout the branch first-url. There You will find a README.md with further instructions.

PR inside JFX: openjdk/jfx#2203

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Issue

• JDK-8198549: Desktop.setOpenURIHandler() only receives event if application is already launched (Bug - P4)

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• 00: Full (20e9dd86)

[prrace]

I don't see any harm in AWT sending such a message, although perhaps a CSR is needed.
The impact seems to be on the FX side, I don't know that I like that you essentially force the JDK-baseline for FX to be one that has this fix. Perhaps some other way to determine that AWT is loaded can be used. Or there should be a "cap" on how long it waits. I'll post this comment in the FX PR too.