fixed PropertyPanel fill background for flatlaf l&f

[DJ-Raven]

This PR I has fixed fill the PropertyPanel background color for flatlaf look and feel. Can you please review it, Thank you.

[neilcsmith-net]

What's the issue you're fixing here, exactly? The visual artefacts under Editor:. etc.?

-1 to any more checks for look and feel name (and is lowercase flatlaf correct anyway?)

[DJ-Raven]

What's the issue you're fixing here, exactly? The visual artefacts under Editor:. etc.?

Yes in editor, I see this issue with TableCustomizer class

-1 to any more checks for look and feel name (and is lowercase flatlaf correct anyway?)

flatlaf is the package name com.formdev.flatlaf.FlatDarkLaf I thing future netbean have com.formdev.flatlaf.IntelliJTheme

[DevCharly]

Better remove the isGtk field completely.
isGtk is only used in PropertyPanel.paint() to decide whether to fill the component background
and should be replaced with isOpaque() in that method.

Class PropertyPanel extends JComponent, which does not fill it background.
So when using setOpaque(true), which is done in constructor of PropertyPanel, it is required to fill its background.

Following comment should be also removed:

netbeans/platform/openide.explorer/src/org/openide/explorer/propertysheet/PropertyPanel.java

Lines 1155 to 1157 in 276a423

	* Overridden to fill in the background color, since Synth/GTKLookAndFeel ignores
	* setOpaque(true).
	* @see https://bz.apache.org/netbeans/show_bug.cgi?id=43024

[neilcsmith-net]

Was just writing the same comment as @DevCharly . +1 to taking that approach. Whoever wrote that comment misunderstood the use of setOpaque. It's possible this should have been a JPanel to start with, but safer not to change now.

Also, please make sure this is based on top of the delivery branch rather than master. I think this might be good to get into NB22.

[neilcsmith-net]

Please can you rebase the branch on top of delivery - eg. git rebase HEAD~1 --onto delivery? Would be good to get this fix in the next release, but needs to not bring in later commits from master.

[mbien]

@DJ-Raven also squash to one commit and push with -f to the remote branch. Then you can change the target here and everything will update.

[DJ-Raven]

@neilcsmith-net @mbien Sorry, I no experience with git rebase, I has try it but failed.

[mbien]

@DJ-Raven no worries, let me do this quickly.

[mbien]

@DJ-Raven could you check that the author information is correct? Patch file: https://github.com/apache/netbeans/pull/7332.patch (one commit had just raven, I took the header from the other commit)

also please note that your master branch is now in fact the delivery branch ;). I can fix this again once this PR is integrated if you want.

[DJ-Raven]

Yes raven

also please note that your master branch is now in fact the delivery branch ;). I can fix this again once this PR is integrated if you want.

I will check it

[mbien]

oh no you changed back :(

[DJ-Raven]

Ohh sorry that I have updated my master branch 😔.

[mbien]

going to force push again. don't touch anything please :D

[mbien]

@DJ-Raven congrats on your first contribution