<Swing Dev> RFR: 8247753: UIManager.getSytemLookAndFeelClassName() returns wrong value on Fedora 32

[Prasanta Sadhukhan]

Looks ok to me.

One observation is, in testcase you can remove line71 linux check as we 
already did the check in l54.

Regards
Prasanta
On 04-Aug-20 11:12 PM, Pankaj Bansal wrote:
>
> Hi All,
>
> Please review the following fix for jdk16.
>
> Bug : https://bugs.openjdk.java.net/browse/JDK-8247753
> webrev: http://cr.openjdk.java.net/~pbansal/8247753/webrev00 
> <http://cr.openjdk.java.net/%7Epbansal/8247753/webrev00>
>
> Bug: UIManager.getSytemLookAndFeelClassName() returns wrong value on 
> Fedora 32. It is returning the MetalLookAndFeel classname instead of 
> GTKLookAndFeel classname.
>
> Cause: Java uses a environment variable GNOME_DESKTOP_SESSION_ID to 
> verify if the system is gnome (which is set by gnome) and then checks 
> for GTKLookAndFeel support. If both conditions are satisfied, then 
> GTKLookAndFeel classname is returned, else cross platform 
> MetalLookAndFeel is selected.
>
> The GNOME_DESKTOP_SESSION_ID environment has been |deprecated| for a 
> long time and the value is set to "|this-is-deprecated|" by gnome. In 
> java, the actual value of variable is not being verified. As long as 
> the value is not null (it has been set to something by gnome), things 
> have been working fine though the value  set by gnome is 
> "|this-is-deprecated|". Now, gnome has removed the variable completely 
> and this is causing issues in Fedora 32. As the variable is not set at 
> all, java is returning the cross platform MetalLookAndFeel classname 
> for the SystemLookAndFeelClassName instead of GTKLookAndFeel.
>
> More information on this in JBS. Right now the issue is seen only on 
> Fedora 32, but this can very well come in future releases of RHEL, 
> CentOS, Oracle Linux etc.
>
> Fix: We should check XDG_CURRENT_DESKTOP also along with 
> GNOME_DESKTOP_SESSION_ID to verify gnome based linux. 
> XDG_CURRENT_DESKTOP is set by gnome based platforms to some string 
> containing "gnome" substring. So, this can be used to verify the gnome 
> based desktop. For backward compatibility, we need to continue 
> checking GNOME_DESKTOP_SESSION_ID as well because for some linux 
> platforms, XDG_CURRENT_DESKTOP may be set to something else as they 
> are not gnome based, but have been returning GTKL&F as 
> GNOME_DESKTOP_SESSION_ID was set by them. so, we dont want to change 
> anything for them.
>
> Other solution could have been to just make GTKL&F default on all 
> linux, but that would result in GTKL&F being selected on some new 
> platfoms like KDE based platforms where currently Metal L&F is selected.
>
> I have modified the test case 
> test/jdk/javax/swing/LookAndFeel/SystemLookAndFeel/SystemLookAndFeelTest.java. 
> The test fails on Fedora 32 without fix and passes with the fix. I 
> have run the required mach5 tests and this fix is not breaking 
> anything. Link in JBS.
>
>
> Regards,
>
> Pankaj Bansal
>
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