Bug 394567

Please provide the output of qdbus org.kde.KWin /KWin supportInformation when the problem is visible.

~ ▶ qdbus org.kde.KWin /KWin supportInformation
KWin Support Information:
The following information should be used when requesting support on e.g. http://forum.kde.org.
It provides information about the currently running instance, which options are used,
what OpenGL driver and which effects are running.
Please post the information provided underneath this introductory text to a paste bin service
like http://paste.kde.org instead of pasting into support threads.

==========================

Version
=======
KWin version: 5.12.5
Qt Version: 5.11.0
Qt compile version: 5.11.0
XCB compile version: 1.13

Operation Mode: X11 only

Build Options
=============
KWIN_BUILD_DECORATIONS: yes
KWIN_BUILD_TABBOX: yes
KWIN_BUILD_ACTIVITIES: yes
HAVE_INPUT: yes
HAVE_DRM: yes
HAVE_GBM: yes
HAVE_X11_XCB: yes
HAVE_EPOXY_GLX: yes
HAVE_WAYLAND_EGL: yes

X11
===
Vendor: The X.Org Foundation
Vendor Release: 12000000
Protocol Version/Revision: 11/0
SHAPE: yes; Version: 0x11
RANDR: yes; Version: 0x14
DAMAGE: yes; Version: 0x11
Composite: yes; Version: 0x4
RENDER: yes; Version: 0xb
XFIXES: yes; Version: 0x50
SYNC: yes; Version: 0x31
GLX: yes; Version: 0x0

Decoration
==========
Plugin: org.kde.breeze
Theme: 
Blur: 0
onAllDesktopsAvailable: false
alphaChannelSupported: true
closeOnDoubleClickOnMenu: false
decorationButtonsLeft: 0, 2
decorationButtonsRight: 6, 3, 4, 5
borderSize: 3
gridUnit: 10
font: Noto Sans,10,-1,5,50,0,0,0,0,0,Regular
smallSpacing: 2
largeSpacing: 10

Platform
==========
Name: KWin::X11StandalonePlatform

Options
=======
focusPolicy: 0
nextFocusPrefersMouse: false
clickRaise: true
autoRaise: false
autoRaiseInterval: 0
delayFocusInterval: 0
shadeHover: false
shadeHoverInterval: 250
separateScreenFocus: false
placement: 4
focusPolicyIsReasonable: true
borderSnapZone: 0
windowSnapZone: 0
centerSnapZone: 0
snapOnlyWhenOverlapping: false
rollOverDesktops: true
focusStealingPreventionLevel: 1
legacyFullscreenSupport: false
operationTitlebarDblClick: 5000
operationMaxButtonLeftClick: 5000
operationMaxButtonMiddleClick: 5015
operationMaxButtonRightClick: 5014
commandActiveTitlebar1: 0
commandActiveTitlebar2: 20
commandActiveTitlebar3: 2
commandInactiveTitlebar1: 4
commandInactiveTitlebar2: 20
commandInactiveTitlebar3: 2
commandWindow1: 7
commandWindow2: 8
commandWindow3: 8
commandWindowWheel: 31
commandAll1: 12
commandAll2: 20
commandAll3: 14
keyCmdAllModKey: 16777250
showGeometryTip: false
condensedTitle: false
electricBorderMaximize: true
electricBorderTiling: true
electricBorderCornerRatio: 0.25
borderlessMaximizedWindows: false
killPingTimeout: 5000
hideUtilityWindowsForInactive: true
inactiveTabsSkipTaskbar: false
autogroupSimilarWindows: false
autogroupInForeground: true
compositingMode: 1
useCompositing: true
compositingInitialized: true
hiddenPreviews: 2
glSmoothScale: 2
xrenderSmoothScale: false
maxFpsInterval: 16666666
refreshRate: 0
vBlankTime: 6000000
glStrictBinding: true
glStrictBindingFollowsDriver: true
glCoreProfile: false
glPreferBufferSwap: 0
glPlatformInterface: 1
windowsBlockCompositing: false

Screen Edges
============
desktopSwitching: false
desktopSwitchingMovingClients: false
cursorPushBackDistance: 1x1
timeThreshold: 150
reActivateThreshold: 350
actionTopLeft: 0
actionTop: 0
actionTopRight: 0
actionRight: 0
actionBottomRight: 0
actionBottom: 0
actionBottomLeft: 0
actionLeft: 0

Screens
=======
Multi-Head: no
Active screen follows mouse:  no
Number of Screens: 1

Screen 0:
---------
Name: HDMI-A-0
Geometry: 0,0,2560x1080
Scale: 1
Refresh Rate: 59.9995


Compositing
===========
Compositing is active
Compositing Type: OpenGL
OpenGL vendor string: X.Org
OpenGL renderer string: Radeon RX 560 Series (POLARIS11, DRM 3.23.0, 4.16.10-1-ARCH, LLVM 6.0.0)
OpenGL version string: 3.1 Mesa 18.1.0
OpenGL platform interface: GLX
OpenGL shading language version string: 1.40
Driver: Unknown
GPU class: Unknown
OpenGL version: 3.1
GLSL version: 1.40
Mesa version: 18.1
X server version: 1.20
Linux kernel version: 4.16.10
Direct rendering: Requires strict binding: yes
GLSL shaders:  yes
Texture NPOT support:  yes
Virtual Machine:  no
OpenGL 2 Shaders are used
Painting blocks for vertical retrace:  no

Loaded Effects:
---------------
kwin4_effect_frozenapp
screenshot
coverswitch
colorpicker
highlightwindow
blur
contrast
startupfeedback
kscreen

Currently Active Effects:
-------------------------
blur
contrast

Effect Settings:
----------------
kwin4_effect_frozenapp:

screenshot:

coverswitch:
animationDuration: 1
animateSwitch: true
animateStart: true
animateStop: true
reflection: true
windowTitle: true
zPosition: 900
primaryTabBox: false
secondaryTabBox: false

colorpicker:

highlightwindow:

blur:
blurRadius: 14
cacheTexture: true

contrast:

startupfeedback:
type: 1

kscreen:

Could you please also attach your kwinrc?

[Compositing]
AnimationSpeed=0
Backend=OpenGL
Enabled=true
GLCore=false
GLPreferBufferSwap=n
GLTextureFilter=2
HiddenPreviews=6
OpenGLIsUnsafe=false
WindowsBlockCompositing=false
XRenderSmoothScale=false

[Desktops]
Number=1

[Effect-Blur]
BlurRadius=14

[Effect-CoverSwitch]
TabBox=false
TabBoxAlternative=false

[Effect-Cube]
BorderActivate=9
BorderActivateCylinder=9
BorderActivateSphere=9
TouchBorderActivate=9
TouchBorderActivateCylinder=9
TouchBorderActivateSphere=9

[Effect-DesktopGrid]
BorderActivate=9
TouchBorderActivate=9

[Effect-FlipSwitch]
TabBox=false
TabBoxAlternative=false

[Effect-PresentWindows]
BorderActivate=9
BorderActivateAll=9
BorderActivateClass=9
TouchBorderActivate=9
TouchBorderActivateAll=7
TouchBorderActivateClass=9

[ElectricBorders]
Bottom=None
BottomLeft=None
BottomRight=None
Left=None
Right=None
Top=None
TopLeft=None
TopRight=None

[MouseBindings]
CommandActiveTitlebar1=Raise
CommandActiveTitlebar2=Minimize
CommandActiveTitlebar3=Operations menu
CommandAll1=Activate, raise and move
CommandAll2=Minimize
CommandAll3=Resize
CommandAllKey=Meta
CommandAllWheel=Maximize/Restore
CommandInactiveTitlebar1=Activate and raise
CommandInactiveTitlebar2=Minimize
CommandInactiveTitlebar3=Operations menu
CommandTitlebarWheel=Maximize/Restore
CommandWindow1=Activate, raise and pass click
CommandWindow2=Activate and pass click
CommandWindow3=Activate and pass click
CommandWindowWheel=Scroll

[NightColor]
EveningBeginFixed=1600
Mode=Times
MorningBeginFixed=0600

[Plugins]
NoBorderFirefoxWhenMaximizedEnabled=true
blurEnabled=true
contrastEnabled=true
coverswitchEnabled=true
desktopgridEnabled=false
enforcedecoEnabled=true
highlightwindowEnabled=true
kwin4_effect_dialogparentEnabled=false
kwin4_effect_fadeEnabled=false
kwin4_effect_loginEnabled=false
kwin4_effect_logoutEnabled=false
kwin4_effect_maximizeEnabled=false
kwin4_effect_morphingpopupsEnabled=false
kwin4_effect_translucencyEnabled=false
kwin4_effect_windowapertureEnabled=false
minimizeallEnabled=false
minimizeanimationEnabled=false
presentwindowsEnabled=false
screenedgeEnabled=false
slideEnabled=false
slidingpopupsEnabled=false
synchronizeskipswitcherEnabled=false
videowallEnabled=false
windowgeometryEnabled=false
zoomEnabled=false

[Script-minimizeall]
BorderActivate=9
TouchBorderActivate=9

[TabBox]
ActivitiesMode=1
ApplicationsMode=0
BorderActivate=9
BorderAlternativeActivate=9
DesktopLayout=org.kde.breeze.desktop
DesktopListLayout=org.kde.breeze.desktop
DesktopMode=1
HighlightWindows=true
LayoutName=thumbnails
MinimizedMode=0
MultiScreenMode=0
ShowDesktopMode=0
ShowTabBox=true
SwitchingMode=0
TouchBorderActivate=9
TouchBorderAlternativeActivate=9

[TabBoxAlternative]
ActivitiesMode=1
ApplicationsMode=0
DesktopMode=1
HighlightWindows=true
LayoutName=org.kde.breeze.desktop
MinimizedMode=0
MultiScreenMode=0
ShowDesktopMode=0
ShowTabBox=true
SwitchingMode=0

[TouchEdges]
Bottom=None
Left=None
Right=None
Top=None

[Windows]
ActiveMouseScreen=false
AutoRaise=false
AutoRaiseInterval=750
AutogroupInForeground=true
AutogroupSimilarWindows=false
BorderSnapZone=0
CenterSnapZone=0
ClickRaise=true
DelayFocusInterval=300
ElectricBorderCooldown=350
ElectricBorderCornerRatio=0.25
ElectricBorderDelay=150
ElectricBorderMaximize=true
ElectricBorderTiling=true
ElectricBorders=0
FocusPolicy=ClickToFocus
FocusStealingPreventionLevel=1
GeometryTip=false
HideUtilityWindowsForInactive=true
InactiveTabsSkipTaskbar=false
MaximizeButtonLeftClickCommand=Maximize
MaximizeButtonMiddleClickCommand=Maximize (vertical only)
MaximizeButtonRightClickCommand=Maximize (horizontal only)
NextFocusPrefersMouse=false
Placement=Smart
SeparateScreenFocus=false
ShadeHover=false
ShadeHoverInterval=250
SnapOnlyWhenOverlapping=false
TitlebarDoubleClickCommand=Maximize
WindowSnapZone=0

[org.kde.kdecoration2]
BorderSize=Normal
ButtonsOnLeft=MS
ButtonsOnRight=HIAX
CloseOnDoubleClickOnMenu=false
library=org.kde.breeze

Please report against Qt that there is a regression.

https://bugreports.qt.io/browse/QTBUG-68441

Could that be related to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85822 which caused QtScript to think 1+1=0?

It's not looking good on the qt side of things, they're asking for a self contained example which I can't provide.