The Xrender backend was added at the time when OpenGL drivers were not
particularly stable. Nowadays though, it's a totally different situation.
The OpenGL render backend has been the default one for many years. It's
quite stable, and it allows implementing many advanced features that
other render backends don't.
Many features are not tested with it during the development cycle; the
only time when it is noticed is when changes in other parts of kwin break
the build in the xrender backend. Effectively, the xrender backend is
unmaintained nowadays.
Given that the xrender backend is effectively unmaintained and our focus
being shifted towards wayland, this change drops the xrender backend in
favor of the opengl backend.
Besides being de-facto unmaintained, another issue is that QtQuick does
not support and most likely will never support the Xrender API. This
poses a problem as we want thumbnail items to be natively integrated in
the qtquick scene graph.
We used to get a weird line around the window decoration because the
clamping would hit the outside of the rendered decoration.
To make sure we fall inside take the displayPixelRatio into account.
Also on non-integer scales, make sure we are actually falling inside.
It was needed to work around visual glitches in the wobbly windows
effect. Since the wobbly windows effect renders the animated window into
an offscreen texture, we don't need this workaround anymore.
Furthermore, rather than using half-pixel correction, it is more
desirable to use an offscreen texture as it results in simpler design.
Performance-wise, it's not that bad that we need to start looking for
other ways to get rid of the seams between window contents and deco.
Currently, the implementation of the DecoratedClient and the decoration
renderer are strongly coupled. This poses a problem with the item based
design as the ultimate goal is to have scene items construct paint nodes
which are then fed to the renderer. The DecorationItem has to have
control over the decoration texture. Another issue is that the scene
cannot smoothly cross-fade between two window states if the decoration
is removed, e.g. from fullscreen mode to normal and vice versa.
This change moves the decoration renderer to the decoration item. With
the introduction of a generic scene texture atlas, we hope to get rid of
the decoration renderer altogether.
One of the scene redesign goals is to make wayland surface items
re-usable. So we have the same rendering path for drag-and-drop icons,
software cursors, and window surfaces.
The biggest issue at the moment is that window pixmaps are tightly
coupled with scene windows.
This change de-couples window pixmaps from scene windows. In order to
achieve that, some architecture changes were made.
The WindowPixmap class was replaced with the SurfacePixmap class. A
surface pixmap is created by a surface item.
Under the hood, a SurfacePixmap will create a PlatformSurfaceTexture
object, which contains all the information necessary for the renderer.
The SceneOpenGLTexture class was removed. However, the GLX and the EGL
on X11 backends still mess with GLTexture's internals.
QPainter::setWindow() doesn't work as we expect if the device pixel
ratio of the paint device is less than 1, for example 0.5 or 0.75.
QPainter only allows the effective device pixel ratios that are greater
than or equal to 1. This restriction probably has to be lifted.
For the time being, this change introduces a helper function that can be
used to determine the scale factor by which QPainter::window() must be
multiplied.
BUG: 432766
At the moment a streamed screen when the screen scale was differnt
buffer scale would render wrong. This change addresses it by
compensating it.
This change compensates it resizing the rendered viewport to their
difference.
BUG: 428594
With the introduction of stripped down window items, the WindowPixmap
objects no longer form a hierarchy. WindowPixmap::children() method was
removed.
Surprisingly, the removal of the children() method didn't result in a
compilation error because the QObject class has a method with the same
name.
Currently, a window pixmap will have no QObject children even if the
associated wayland surface has child sub-surfaces. This may result in
blank thumbnails of apps that use sub-surfaces, e.g. Firefox. In order
to fix that issue, we need to check if there are child items instead.
Currently, dealing with sub-surfaces is very difficult due to the scene
design being heavily influenced by X11 requirements.
The goal of this change is to re-work scene abstractions to make improving
the wayland support easier.
The Item class is based on the QQuickItem class. My hope is that one day
we will be able to transition to QtQuick for painting scene, but in
meanwhile it makes more sense to have a minimalistic internal item class.
The WindowItem class represents a window. The SurfaceItem class represents
the contents of either an X11, or a Wayland, or an internal surface. The
DecorationItem and the ShadowItem class represent the server-side deco and
drop-shadow, respectively.
At the moment, the SurfaceItem is bound to the scene window, but the long
term plan is to break that connection so we could re-use the SurfaceItem
for things such as software cursors and drag-and-drop additional icons.
One of the responsibilities of the Item is to schedule repaints as needed.
Ideally, there shouldn't be any addRepaint() calls in the core code. The
Item class schedules repaints on geometry updates. In the future, it also
has to request an update if its opacity or visibility changes.
This provides the compositor a way to indicate what output is being
rendered. The effects such as the screenshot can check the provided
screen object in order to function as expected.
Once in a while, we receive complaints from other fellow KDE developers
about the file organization of kwin. This change addresses some of those
complaints by moving all of source code in a separate directory, src/,
thus making the project structure more traditional. Things such as tests
are kept in their own toplevel directories.
This change may wreak havoc on merge requests that add new files to kwin,
but if a patch modifies an already existing file, git should be smart
enough to figure out that the file has been relocated.
We may potentially split the src/ directory further to make navigating
the source code easier, but hopefully this is good enough already.
