Bug 416456

Summary:	Wobbly Windows does not respect Blur effect
Product:	[Plasma] kwin	Reporter:	Brennan Kinney <polarathene-signup>
Component:	effects-various	Assignee:	KWin default assignee <kwin-bugs-null>
Status:	RESOLVED DUPLICATE
Severity:	wishlist	CC:	kde, nate
Priority:	NOR
Version First Reported In:	5.17.5
Target Milestone:	---
Platform:	Manjaro
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Brennan Kinney 2020-01-19 13:15:25 UTC

SUMMARY

If the Blur effect is enabled, it is not applied on content being rendered via the Wobbly Window effect.


STEPS TO REPRODUCE
1. Enable Wobbly Windows and Blur effects.
2. Trigger the Wobbly Windows effect on content that also uses Blur, such as the Konsole(Konsole profile theme enabled blur and transparency).
3. Window shows transparency without blur effect applied.

OBSERVED RESULT

Blur effect is not present in combination with Wobbly Window effect.

EXPECTED RESULT

Blur effect and Wobbly Window effect should be compatible, or otherwise a checkbox in Wobbly Window effect settings to enable Blur support if there is notable overhead when the two effects are used together.

SOFTWARE/OS VERSIONS

Linux/KDE Plasma: Manjaro - Kernel 5.5
(available in About System)
KDE Plasma Version: 5.17.5
KDE Frameworks Version: 5.66
Qt Version: 5.14

ADDITIONAL INFORMATION

Intel Gen9 graphics(i3-10110U) with KMS modesetting driver.

Translucency effect disabled(also excludes applying blur, but does not appear to contribute to the Wobbly Window effect when enabled other than increasing transparency(defaults).

Comment 1 Brennan Kinney 2020-01-19 13:27:38 UTC

While filing this issue on behalf of another user that raised attention to it, a related one[1] did reveal itself(it'd be nice if the UI for the search could also toggle/query closed issues as I didn't notice those were excluded).

I also came across this issue[2] via google results. It showcases videos of several effects that use transforms with before/after of enabling blur. Scaling and translation transforms were shown as fine, but ones like Wobbly Windows were revealed as to why they're not compatible. While I was going through that and related info to understand the issue, another user shared the same Wobbly Window effect video directly on reddit[3].

While the reasoning for the closing [1] is clearly explained in [2], I would like to seek feedback from a developer with knowledge of the issue. Is the Wobbly Window effect not able to scale the blur texture to fit the bounds of the Wobbly Window effect and then use the distorted window as an alpha mask with glStencil or glScissor? I tried to go over the kwin effect code, but I'm not familiar with the codebase enough(or C++ and OpenGL)  to grok the flow/path of code for the effects.

[1] https://bugs.kde.org/show_bug.cgi?id=397329
[2] https://bugs.kde.org/show_bug.cgi?id=391819
[3] https://www.reddit.com/r/kde/comments/equisf/why_blur_is_off_when_using_wobbly_windows/

Comment 2 David Edmundson 2020-01-20 18:49:08 UTC


*** This bug has been marked as a duplicate of bug 397329 ***

Comment 3 David Edmundson 2020-01-20 18:52:39 UTC

In order for this to happen we would need:

Effects to have a virtual method to manipulate the vertex buffers for blur regions.

Blur to then push it's vertex buffer through the effects chain, wobbly windows would then take that manipulate the vertex buffer.

Then blur would render that..and only then do we continue the paintWindow chain to paint the window contents also manipulated by the wobbly window effect.