QPainter's auto-scaling is prone to off-by-one rounding errors and draws on
fractional coordinates. With this change, we paint on a 1x DPR QPainter and
scale the shadow offset and strength manually based on DPR.
This resolves an issue with resulting in seams on the right and bottom
edges of a menu due to shadow boundaries being off-by-one.
BUG: 418166
v2: remove unrelated formatting changes
v3:
- move the DPR helper to ShadowHelper
- retrieve the DPR from the widget instead of the global QGuiApplication
- added BUG reference
Summary:
KWindowSystem cannot be used in the Qt 4 style plugin. On the other hand,
we need to use KWindowSystem to make QWidget-based internal clients in
KWin cast drop-shadows.
Another problem with the Qt 4 style plugin is that some distributions
have already dropped Qt 4, so one has to build it first in order to
verify that his or her change works with Qt 4.
Given maintenance burden and the fact that Qt 6 is around the corner,
this change drops the Qt 4 style plugin.
Reviewers: #kwin, #plasma, davidedmundson
Reviewed By: #kwin, #plasma, davidedmundson
Subscribers: davidedmundson, mart, plasma-devel
Tags: #plasma
Maniphest Tasks: T12496
Differential Revision: https://phabricator.kde.org/D26476
Summary: includes were incompatible.
Test Plan: Built it.
Reviewers: #breeze, zzag
Reviewed By: zzag
Subscribers: plasma-devel
Tags: #plasma
Differential Revision: https://phabricator.kde.org/D16459
Summary:
Creation of shadows (especially for "Large" and "Very large" sizes) is
a computation expensive task because we have to blur alpha channel of a
shadow texture (which then will be tinted with desired shadow color).
Currently, we use the following approach:
* for blur radius less than 64, use naive 2-pass algorithm;
* for blur radius greater than or equal to 64, use FFT.
Even though the FFT approach is doing its the best, it still takes
impresive amount of time to blur the alpha channel.
What makes things even worse is that while we're blurring the alpha
channel, we're blocking the main thread of KWin (decorations are not
rendered in their own thread). This can result in frame drops (2 or 3
frames, something like that).
So, the only viable alternative is to use an approximation of the Gaussian
blur. As such an approximation, I picked the box blur because it's quite
simple, it's fast, and it takes small amount of iterations to have something
similar to the true Gaussian blur.
In general, there are no big differences between true gaussian shadows
and approximated shadows:
Before:
{F6312610}
After:
{F6312613}
Before:
{F6280935}
After:
{F6312608}
As a win, it takes much less time to generate decoration shadows.
Reviewers: #kwin, #plasma, #breeze, #vdg, ngraham
Reviewed By: #breeze, #vdg, ngraham
Subscribers: cfeck, ngraham, abetts, plasma-devel
Tags: #plasma
Differential Revision: https://phabricator.kde.org/D15514
Alexander Lohnau
Tatsuyuki Ishi
David Redondo
Vlad Zahorodnii
Vlad Zahorodnii
Noah Davis
Fabian Vogt