Bug 399190

Summary:	Instant Preview causes severe canvas slowdown with non-painting tools on large documents
Product:	[Applications] krita	Reporter:	Tyson Tan <tysontanx>
Component:	Instant Preview	Assignee:	Dmitry Kazakov <dimula73>
Status:	ASSIGNED ---
Severity:	normal	CC:	halla, sti-naus
Priority:	NOR
Version First Reported In:	unspecified
Target Milestone:	---
Platform:	Other
OS:	Linux
Latest Commit:		Version Fixed/Implemented In:
Sentry Crash Report:

Description Tyson Tan 2018-09-28 17:43:13 UTC

SUMMARY
Instant Preview causes severe canvas slowdown with non-painting tools on large documents. Tested on Manjato 17.1.2 with krita-4.2.0-pre-alpha-4f31265-x86_64.appimage, i7-6567U+16GB+Iris550 (Turboburst and Framebuffer Compression disabled)

STEPS TO REPRODUCE
1. Create a A3 600 dpi document
2. Draw something
3. Compare the performance between Instant Preview ON/FF when using tools like Zoom / Selection Add-Subtract / Transform / Undo-Redo

OBSERVED RESULT
When I was working with a 14000x14000 document with only 2 layers (one of them is lineart and the other is white), Instant Preview caused severe slowdown all the time. Krita needs 1-3 seconds to respond to any action (Zoom / Selection Add-Subtract / Transform / Undo-Redo) on the canvas when Instant Preview is ON. Only drawing is usable. Everything else is extremely slow and choppy. When Instant Preview was turned OFF, everything went back to normal.

EXPECTED RESULT
Instant Preview should not cause any slowdown, or should be set to OFF by default. Since the majority of users would not use crazy big brushes, leaving such a function that causes constant, huge slowdowns is not wise.

At least from my experience, I gave it a chance every time when a new Krita version was released, but never once did it worked sufficiently fast on A4 300 dpi. It made drawing unpleasant at its best, and it made Krita totally unusable at its worst, like this reported instance. And for what reason this time it actually affected tools that does not paint.

Of all the questions I was asked by other artists about Krita's slow performance, more than a half of them were caused by Instant Preview. Artists are very sensitive to even small slowdowns, not to mention slowdowns at such level. Many new users told me they just gave up Krita the moment when the first few strokes were drawn. I suggest keep Instant Preview OFF by default and let people enable it on demand when they want to use it with a huge brush.

SOFTWARE VERSIONS
(available in About System)
KDE Plasma Version:
KDE Frameworks Version:
Qt Version:

ADDITIONAL INFORMATION

Comment 1 Dmitry Kazakov 2019-03-27 16:51:03 UTC

Git commit 0f736a3d2e36abc52db52a4b2c6c324dc5ca31cd by Dmitry Kazakov.
Committed on 27/03/2019 at 16:50.
Pushed by dkazakov into branch 'master'.

Clean-up system-wide default kritarc settings

These defaults are set in KisConfig. The patch fixes Instant
Preview being enabled on all the user systems by default. It
shouldn't be.

M  +0    -107  krita/data/kritarc

https://commits.kde.org/krita/0f736a3d2e36abc52db52a4b2c6c324dc5ca31cd

Comment 2 Halla Rempt 2019-06-17 07:47:08 UTC

Git commit 78576ea028120e8e30eb4c145b88711713aec059 by Boudewijn Rempt.
Committed on 17/06/2019 at 07:43.
Pushed by rempt into branch 'master'.

Set the defaults for the favorite composite ops

This got lost in

commit 0f736a3d2e36abc52db52a4b2c6c324dc5ca31cd
Author: Dmitry Kazakov <dimula73@gmail.com>
Date:   Wed Mar 27 19:50:08 2019 +0300

    Clean-up system-wide default kritarc settings

    These defaults are set in KisConfig. The patch fixes Instant
    Preview being enabled on all the user systems by default. It
    shouldn't be.
Related: bug 408753

However, the favorite composite ops were not set in KisConfig, so
they were empty. Unless you happened to have a an old install dir
which had a kritarc which still contained the defaults, so they
would still be present.

M  +2    -1    libs/ui/kis_config.cc

https://invent.kde.org/kde/krita/commit/78576ea028120e8e30eb4c145b88711713aec059

Comment 3 Halla Rempt 2019-06-17 08:18:08 UTC

Git commit 489ca961ce41187a264fb2a5123ab1c933d36efa by Boudewijn Rempt.
Committed on 17/06/2019 at 08:17.
Pushed by rempt into branch 'krita/4.2'.

Set the defaults for the favorite composite ops

This got lost in

commit 0f736a3d2e36abc52db52a4b2c6c324dc5ca31cd
Author: Dmitry Kazakov <dimula73@gmail.com>
Date:   Wed Mar 27 19:50:08 2019 +0300

    Clean-up system-wide default kritarc settings

    These defaults are set in KisConfig. The patch fixes Instant
    Preview being enabled on all the user systems by default. It
    shouldn't be.
Related: bug 408753

However, the favorite composite ops were not set in KisConfig, so
they were empty. Unless you happened to have a an old install dir
which had a kritarc which still contained the defaults, so they
would still be present.

M  +2    -1    libs/ui/kis_config.cc

https://invent.kde.org/kde/krita/commit/489ca961ce41187a264fb2a5123ab1c933d36efa

Comment 4 Stig (Rakurri) 2019-12-02 12:34:17 UTC

This happens to me too. Zooming is extremely slow when I am working on an animation with Instant Preview Mode turned on, while zooming is buttery smooth when it is turned off. Using Krita 4.2.8 on Windows 10