Bug 434269

SUMMARY

I originally added this problem onto Bug 421376, but after trying to diagnose it better I see differences in that bug to what I'm experiencing, so I'm creating a separate report.

Krita stutters two or three seconds after I complete a pen or mouse stroke. If I start a new stroke right away, the stutter will happen while I'm drawing. If I move the cursor across the canvas without drawing, the cursor will stutter as it moves, and any brush stroke after that is normal. When I complete that brush stroke however, the stutter cycle begins all over again.

See video:
https://drive.google.com/file/d/11i-G1C847naJ7YajYXeq9ZuDN4SJ3b53/view?usp=sharing

This is not a memory issue. It occurs when there's well over 10 GB of memory free. It occurs with both pen tablet and mouse. It doesn't matter if Instant Preview is on or off. It also ONLY occurs in Krita. It doesn't happen in GIMP or any other program.

I'm experiencing this in the current beta, 4.4.3-beta1. It also occurred in 4.4.2.

I recently upgraded my Nvidia card from a Quadro 600 to a GeForce GTX 660. I'm not sure if the issue was happening before that, but it's become painfully more noticeable in the past couple of weeks, perhaps because I'm doing more detail work in Krita at the moment. The GeForce card, however, is the same card I used in my previous machine, and there were no problems with it up through November of last year when I switched computers. I updated the Nvidia drivers today and the problem still happens.

This stutter makes Krita rather annoying to work with. I've had to adjust my workflow to wait a few seconds after I complete a line before I start drawing another.

STEPS TO REPRODUCE
1. Draw a line.
2. Move the cursor after completing the line.

OBSERVED RESULT
The cursor stutters after two or three seconds.

EXPECTED RESULT
No stutter

SOFTWARE/OS VERSIONS
Krita

 Version: 4.4.3-beta1
 Languages: en_US, en
 Hidpi: true

Qt

  Version (compiled): 5.12.9
  Version (loaded): 5.12.9

OS Information

  Build ABI: x86_64-little_endian-lp64
  Build CPU: x86_64
  CPU: x86_64
  Kernel Type: linux
  Kernel Version: 5.10.21-200.fc33.x86_64
  Pretty Productname: Fedora 33 (Cinnamon)
  Product Type: fedora
  Product Version: 33
  Desktop: X-Cinnamon

OpenGL Info
 
  Vendor:  "NVIDIA Corporation" 
  Renderer:  "GeForce GTX 660/PCIe/SSE2" 
  Version:  "4.6.0 NVIDIA 460.56" 
  Shading language:  "4.60 NVIDIA" 
  Requested format:  QSurfaceFormat(version 3.0, options QFlags<QSurfaceFormat::FormatOption>(DeprecatedFunctions), depthBufferSize 24, redBufferSize 8, greenBufferSize 8, blueBufferSize 8, alphaBufferSize 8, stencilBufferSize 8, samples -1, swapBehavior QSurfaceFormat::DoubleBuffer, swapInterval 0, colorSpace QSurfaceFormat::DefaultColorSpace, profile  QSurfaceFormat::CompatibilityProfile) 
  Current format:    QSurfaceFormat(version 4.6, options QFlags<QSurfaceFormat::FormatOption>(DeprecatedFunctions), depthBufferSize 24, redBufferSize 8, greenBufferSize 8, blueBufferSize 8, alphaBufferSize 8, stencilBufferSize 8, samples -1, swapBehavior QSurfaceFormat::DoubleBuffer, swapInterval 0, colorSpace QSurfaceFormat::DefaultColorSpace, profile  QSurfaceFormat::CompatibilityProfile) 
     Version: 4.6
     Supports deprecated functions true 
     is OpenGL ES: false 

QPA OpenGL Detection Info 
  supportsDesktopGL: true 
  supportsOpenGLES: true 
  isQtPreferOpenGLES: false 

Hardware Information

  GPU Acceleration: auto
  Memory: 24034 Mb
  Number of Cores: 4
  Swap Location: /tmp

Current Settings

  Current Swap Location: /tmp
  Current Swap Location writable: true
  Undo Enabled: true
  Undo Stack Limit: 30
  Use OpenGL: true
  Use OpenGL Texture Buffer: true
  Use AMD Vectorization Workaround: false
  Canvas State: OPENGL_SUCCESS
  Autosave Interval: 900
  Use Backup Files: true
  Number of Backups Kept: 1
  Backup File Suffix: ~
  Backup Location: Same Folder as the File
  Backup Location writable: false
  Use Win8 Pointer Input: false
  Use RightMiddleTabletButton Workaround: false
  Levels of Detail Enabled: false
  Use Zip64: false


Display Information
Number of screens: 2
	Screen: 0
		Name: DVI-D-0
		Depth: 24
		Scale: 1
		Resolution in pixels: 1920x1080
		Manufacturer: HP Inc.
		Model: HP VH240a-
		Refresh Rate: 60
	Screen: 1
		Name: DP-0
		Depth: 24
		Scale: 1
		Resolution in pixels: 1920x1080
		Manufacturer: LG Electronics
		Model: LG IPS FULLHD
		Refresh Rate: 60