[fedora-java] JAVA Native Splash Screen Guidance
There doesn't seem to be any official guidance on how to show splash
images for Java applications packaged for Fedora in
<http://fedoraproject.org/wiki/Packaging:Java> . I am hoping the
following with lead to discussion and ultimately to a standard approach.
In short, I believe the issue can be addressed through Fedora packaging
guidelines without violating canonical JPackage guidelines. Indeed, the
JPackage guidelines http://www.jpackage.org don't seem to address splash
images at all.
BACKGROUND:
According to
http://docs.oracle.com/javase/tutorial/uiswing/misc/splashscreen.html
"...the main purpose of a splash screen is to provide the user with
feedback about the application's startup, the delay between the
application's startup and the moment when the splash screen pops up
should be minimal" [1]
Currently, JAVA supports only the 2 following mechanisms to display such
a splash screen:
1) Command-line argument
2) Java™ Archive (JAR) file with the specified manifest option
For JAVA applications packaged in Fedora, 2) is not possible since
executable .jar files are not allowed according to guidelines
http://fedoraproject.org/wiki/Packaging:Java. In Fedora, the
/usr/share/java-utils/java-functions are used. In contrast, for 1) to
work, a path to an image file residing on the file system must be given.
This differs sharply from 2) where the splash image must be a resource
packaged in the application jar file and indicated as the
SplashScreen-Image in the jar's manifest.
PROPOSAL:
The following work-around convention is suggested and is open for
discussion:
Fedora Java packages that wish to show a splash screen prior to their
package's main class running, should place an image in the directory
/usr/share/splash following the convention <fedora-package-name>.<ext>
where ext is one of the standard splash image file types (e.g. .png,
.gif, .jpg).
For applications wishing to show a splash screen, package maintainers
should then put a line in the package's JPackage launch script similar to:
BASE_FLAGS="-splash:/usr/share/splash/<fedora-package-name>.<ext>"
RPM/SPEC CONSIDERATIONS:
A reasonably common situation will be that a jar resource spash image
will already exist within the sources of JAVA applications wanting to
show a splash image. Fedora package maintainers can easily use maven or
ant build tactics to 1) copy the image from RPM sources or 2) extract
image resource from the packaged jar file and rename to
/usr/share/splash/<fedora-package-name>.<ext> during Fedora package
%build and/or %install etc.
[1] Some applications currently packaged in Fedora (e.g. Jabref) go to
some lengths to circumvent the issue altogether and use custom
undecorated JFrame or Window class instances to programmatically show a
"splash screen" followed by a timed delay prior to making their main
application window visible to the user. However such forced "splash
screens" are only shown after the JVM has already fully started and must
then impose a further delay by showing the splash for some predetermined
time (e.g. 2 seconds). This circumvents the "main purpose of a splash
screen" mentioned in
http://docs.oracle.com/javase/tutorial/uiswing/misc/splashscreen.html
--
Dan Dougherty