Currently, the EffectsHandler has two signals that are emitted when the
combined geometry of all outputs change - virtualScreenGeometryChanged()
and screenGeometryChanged(). Having two signals is most likely a
historical artifact.
This change untangles the screenGeometryChanged() signal from the
Workspace and makes it the same as the virtualScreenGeometryChanged()
signal.
Currently, thumbnail items are rendered by kwin. This means that qtquick
code cannot do things such as applying shader effects to window thumbnails
or simply draw custom controls on top of thumbnails.
With this change, task switchers and qml extensions will be able to
place their own contents on top of thumbnails and apply custom effects
to them.
In order to integrate window thumbnails, a window is rendered on kwin
side using its own opengl context. A fence is inserted in the command
stream to ensure that the qtquick machinery doesn't start using the
offscreen texture while there are still rendering commands being executed.
Thumbnails are rendered into offscreen textures as we don't have full
control over when qtquick windows render their contents and to work around
the fact that things such as VAOs can't be shared across OpenGL contexts.
WindowThumbnailItem and DesktopThumbnailItem act as texture providers.
It's unused and the advantages of keeping it are outweighed by the
disadvantages - the returned value is dependant on the window type.
If you need to draw a drop-shadow that matches the shape of the window
or something along that line, render the window into an offscreen
texture and sample the alpha channel in a fragment shader.
At the moment, we handle window quads inefficiently. Window quads from
all items are merged into a single list just to be broken up again.
This change removes window quads from libkwineffects. This allows us to
handle window quads efficiently. Furthermore, we could optimize methods
such as WindowVertex::left() and so on. KWin spends reasonable amount
of time in those methods when many windows have to be composited.
It's a necessary prerequisite for making wl_surface painting code role
agnostic.
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.
On X11, the lockscreen greeter is an override-redirect window so the
scale and the glide effect ignore it.
On Wayland, the lockscreen greeter is a regular window so both effects
try to animate it upon the screen being unlocked, which looks bad.
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.
