Some Eclipse Foundation services are deprecated, or will be soon. Please ensure you've read this important communication.

Bug 572208

Summary:	SWT.EDGE constant for Browser overlaps with SWT.NO_BACKGROUND
Product:	[Eclipse Project] Platform	Reporter:	Mikael Sterner <mikaels>
Component:	SWT	Assignee:	Niraj Modi <niraj.modi>
Status:	VERIFIED FIXED	QA Contact:
Severity:	normal
Priority:	P3	CC:	loskutov, nikita, niraj.modi
Version:	4.19
Target Milestone:	4.20 M1
Hardware:	PC
OS:	Windows 10
See Also:	https://bugs.eclipse.org/bugs/show_bug.cgi?id=538991 https://git.eclipse.org/r/c/platform/eclipse.platform.swt/+/178840 https://git.eclipse.org/c/platform/eclipse.platform.swt.git/commit/?id=13749c8685a91914b093fa8acab8759c3aa53f31
Whiteboard:
Bug Depends on:
Bug Blocks:	571909

Description Mikael Sterner

2021-03-23 03:54:16 EDT

I believe that the implementation for bug 538991 caused a regression for org.eclipse.swt.browser.Browser instances that use the SWT.NO_BACKGROUND style, since SWT.EDGE has the same value (1<<18, erroneously listed as 1<<16 in the javadoc).

This leads to e.g. the SpotBugs Bug Info view trying to use the experimental WebView2 on Windows, due to setting SWT.NO_BACKGROUND: https://github.com/spotbugs/spotbugs/blob/master/eclipsePlugin/src/de/tobject/findbugs/view/BugInfoView.java#L189

Which results in an exception "Not implemented [WebView2 runtime not found]" if WebView2 is not available.

Comment 1 Nikita Nemkin

2021-03-25 11:39:25 EDT

Oh, this is unfortunate. With this constant being part of a stable release I'm not sure if changing it is possible.

Anyway, SWT.NO_BACKGROUND isn't a valid style for the Browser widget, so an easy work-around is to simply remove it.

Comment 2 Mikael Sterner

2021-03-26 04:58:40 EDT

Thanks for the analysis. I filed https://github.com/spotbugs/spotbugs/issues/1477 downstream. The Composite documentation clearly says that using NO_BACKGROUND is undefined for other subclasses than Canvas, so I guess it could be considered a latent bug in the SpotBugs code to use it.

Comment 3 Niraj Modi

2021-04-05 06:18:22 EDT

(In reply to Mikael Sterner from comment #0)
> I believe that the implementation for bug 538991 caused a regression for
> org.eclipse.swt.browser.Browser instances that use the SWT.NO_BACKGROUND
> style, since SWT.EDGE has the same value (1<<18, erroneously listed as 1<<16
> in the javadoc).

Good catch, we need to fix this JavaDoc here.
Will submit gerrit shortly.

Comment 4 Eclipse Genie

2021-04-05 06:19:23 EDT

New Gerrit change created: https://git.eclipse.org/r/c/platform/eclipse.platform.swt/+/178840

Comment 5 Niraj Modi

2021-04-05 06:22:57 EDT

(In reply to Nikita Nemkin from comment #1)
> Oh, this is unfortunate. With this constant being part of a stable release
> I'm not sure if changing it is possible.
> 
> Anyway, SWT.NO_BACKGROUND isn't a valid style for the Browser widget, so an
> easy work-around is to simply remove it.

(In reply to Mikael Sterner from comment #2)
> Thanks for the analysis. I filed
> https://github.com/spotbugs/spotbugs/issues/1477 downstream. The Composite
> documentation clearly says that using NO_BACKGROUND is undefined for other
> subclasses than Canvas, so I guess it could be considered a latent bug in
> the SpotBugs code to use it.

Thanks Nikita/Mikael for sorting this part.

Comment 6 Eclipse Genie

2021-04-05 06:47:36 EDT

Gerrit change https://git.eclipse.org/r/c/platform/eclipse.platform.swt/+/178840 was merged to [master].
Commit: http://git.eclipse.org/c/platform/eclipse.platform.swt.git/commit/?id=13749c8685a91914b093fa8acab8759c3aa53f31

Comment 7 Niraj Modi

2021-04-05 06:50:27 EDT

NO more actions needed form SWT side on this bug, closing.

Comment 8 Niraj Modi

2021-04-07 06:08:02 EDT

Verified on master using Eclipse Build id: I20210406-1800