The paint device's cache should be connected to the new device,
during the paint operation, not to the old one.

BUG:387698

Now layers are created in an asynchronous way using
KisProcessingApplicator. I also wanted to refactor the rest
of the methids, but the resulting code look too awful :)

Fix some Markdown formatting and try to clear up some Windows notes.

Add notes about the scripts we have now, and fix the double
set PATH instruction for Windows.

This fixes a bug causing the wrong DPI being used when moving the window
from a screen to another screen to the left. Using the top-left position
of the window to determine screen changes doesn't work well since the
device pixel ratio of a window does not change until the window is
roughly halfway across.

Maniphest Tasks: T2299
Differential Revision: https://phabricator.kde.org/D20171

Opacity and Blending mode are now changed using a stroke. Therefore,
opacity change will arrive **after** the stroke has finished :)

BUG:405879

By ignoring a bunch of warnings that became errors
as Clang produces other unique warnings

TODO: we should still implement switching between Wintab and Winink
implementations in Qt.

The delay between tablet events and the corresponding mouse events
might be rather long on Windows. We should just accept that.

Qt 5.12 doesn't support QPainter::RasterOp_SourceXorDestination anymore.

Trying to paint with a painter that uses this while opengl is enabled
will lead to a crash. The only relevant place this enum value is still used
is in kis_tool.cc, where it is only painted on the regular non-accelerated canvas.

Anyhow, told the smartpatch to use this function instead of doing something itself.

The whole thing is a little bizar.

This obviates the need for manually copying the necessary executables.

Before this change, Colorize Mask asserted after flattening
or merging with another layer when the image was smaller than 1024px
wide and long. After this commit, it shouldn't happen.

It was caused by setting the parent dirty just before the parent gets
deleted. The request was linked to refreshing area outside the image
boundaries; since Colorize Mask didn't and doesn't work outside of the
image boundaries, it isn't necessary.

NOTE: In case of providing support for Colorize Mask working outside of
the canvas boundaries, the decision in this commit might need
reevaluation (in case of a need to update the mask there).

BUG:402494

This is a little slow on certain sizes, but it'll do for now.

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

CCBUG:399190

It looks like one of the users managed to catch such a case,
when the node has been deleted while the updates were still
holding a pointer to it. I don't know how it was reproduced,
and, technically, our system should not allow such cases.

Therefore, this patch just converts the node pointer into a
weak pointer and adds a sanity check assert into KisAsyncMerger.

I hope we'll catch this assert one day and get better report
about what triggered it.

CCBUG:405879

Summary:
Before Quick Brush engine (roundmarker) was crashing
because Sequential Iterator throwed out asserts
when the rectangle was not "empty" according to Qt
but  still not valid (for example has intmin value on
width or height). This commit fixes that behaviour by
providing additional checks.
Commit includes also benchmarks for roundmarker.

BUG:404179

Test Plan:
- benchmarks included in the commit
- painting with Quick Brush (i.e. b) Basic-1)
with size <1 px

Reviewers: dkazakov, #krita

Reviewed By: dkazakov, #krita

Subscribers: rempt

Tags: #krita

Differential Revision: https://phabricator.kde.org/D19881

BUG:404935
BUG:405540

glBlendFunc doesn't support correct alpha blending (alpha channel
value should be calculated separately), so we must ensure that the
calculated alpha value is just dropped entirely.

BUG:404935
BUG:405540

PyQt5 started requiring a private copy of the sip module, so we have to
build sip as a private sip module for PyQt5.

BUG: 405796

Basically, the patch mimics this Qt's patch that has been
added in Qt 5.12.0 only:
https://codereview.qt-project.org/#/c/239918/

BUG:399696