Test Unicode support for "SplashScreen-Image" manifest attribute and potential clean up of some c code

[Philipp Kunz]

Hi,

When I tried to improve Unicode support in JAR manifests in [1],
independent of what will happen with that, I found that there are not
only Manifest and Attributes classes parsing manifests but also some c
code which parses "SplashScreen-Image" attribute and also used to parse
some other attributes such as "Main-Class" and others.

There already are tests for splash screen images but those existing
ones work with the "-splash" command line option and not with the
"SplashScreen-Image" manifest attribute. I found "SplashScreen-Image"
manifest attribute not yet covered with a test and extended the
existing UnicodeTest accordingly, see attached patch which confirmed
that the "SplashScreen-Image" manifest attribute already fully supports
Unicode.

Support for "JRE-Version" manifest attribute and "-jre-restrict-search" 
and "-jre-no-restrict-search" command line attributes has already been
removed earlier already and the relevant lines of code determining the
main class from the manifest when launching have already been moved to
or near LauncherHelper::getMainClassFromJar in earlier
versions, apparently leaving them with no use any longer in java.c,
java.h, manifest_info.h, and parse_manifest.c, I figure. Hence, I
propose to remove those parts as in the attached patch.

This leaves manifest_info.h and parse_manifest.c with "SplashScreen-
Image" as the only attribute parsed there. Certainly it would be a
different change but anyway it might be worth a consideration to move
the code opening the splash screen image to LauncherHelper or a similar
appropriate place in Java which would allow to remove quite a number of
some lines of c code, provided it could be acceptable to show the
splash screen image slightly later.

There is no existing related bug and I didn't find a new one. It would
be nice to have "SplashScreen-Image" manifest attribute covered with a
test and there is some potential for cleaning up unused code which
certainly is not urgent at all and I would not know how desirable this
really is. Also I'm not sure whether it's better or not to add
SPLASHSCREEN_IMAGE to Attributes.Name.KNOWN_NAMES.

Any opinion about to how to proceed with this, if at all or would
someone sponsor this patch?

Regards,
Philipp


[1] 
https://mail.openjdk.java.net/pipermail/core-libs-dev/2019-December/064149.html

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