On Windows, changing a system preference such as the light/dark color mode can
crash an application that embeds JavaFX in SWT using `FXCanvas`.
`GlassApplication` receives the Java `WinApplication` instance as the local JNI
reference `jrefThis`. It passes this reference to `PlatformSupport` and
separately creates a global reference for `m_grefThis`:
GlassApplication::GlassApplication(jobject jrefThis) : BaseWnd(),
m_platformSupport(GetEnv(), jrefThis)
{
m_grefThis = GetEnv()->NewGlobalRef(jrefThis);
...
}
Creating `m_grefThis` does not promote the original reference. `NewGlobalRef`
returns a new handle, while the copy retained by `PlatformSupport` remains a
local JNI reference. That local reference becomes invalid when the native
method invocation returns.
Using an invalid JNI reference is undefined behavior. Depending on the state of
the reused local-reference slot, the result can be a `NullPointerException`
without Java frames or an access violation inside the JVM.
This change stores the application reference as a `JGlobalRef<jobject>`, which
creates an independent global JNI reference while the input local reference is
still valid.
---------
- [x] I confirm that I make this contribution in accordance with the [OpenJDK
Interim AI Policy](https://openjdk.org/legal/ai).
-------------
Commit messages:
- Use global reference to application instance
Changes: https://git.openjdk.org/jfx/pull/2226/files
Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=2226&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8388526
Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
Patch: https://git.openjdk.org/jfx/pull/2226.diff
Fetch: git fetch https://git.openjdk.org/jfx.git pull/2226/head:pull/2226
PR: https://git.openjdk.org/jfx/pull/2226
