When creating the texture containing the window decorations, the drawing
code now directly handles the rotation for the left and right
decoration, instead of rotating the image after it has been drawn.
The padding, to prevent texture bleeding, is now a fixed value instead
of being scaled. With this change, there are no longer visual artifacts
for window decorations with rounded corners, when the scaling value is
fractional.
On X11, if buffer age is unsupported, kwin can do some quirks like
copying parts of the front buffer to back buffer to avoid repainting the
whole screen.
Currently, the copying is performed in the opengl scene, which is not
perfect because it makes the scene responsible not only for painting the
scene but also some low level platform specific shenanigans.
This change moves the copying step to the glx and egl backends. It
simplifies the opengl scene, makes it less overloaded and more open to
changes, but it also duplicates code, which is not ideal. However, given
the de-facto deprecated state of the X11 platform, it's sort of acceptable
as the main focus is now on wayland session and the things that are
needed to make it fly as expected.
Tracking AbstractOutput properties in Toplevel is not extensible. Since
DecorationItem is the only one who needs Toplevel::screenScale(), make
it track the output device pixel ratio.
EffectQuickScene is not used strictly by effects, aurorae decorations
use it too to render window decorations.
This change renames the EffectQuickView/Scene to
OffscreenQuickView/Scene to clear up the naming scheme.
The lanczos filter checks the screen size before rendering in
LanczosFilter::updateOffscreenSurfaces(), so this is not needed.
This simplifies lifetime handling of the lanczos filter, e.g. we
don't need to bother with opengl context anymore, and makes the
scene use less Screens' features.
With a persistent vbo, kwin will allocate one big enough buffer and
allocate memory out of it.
In order to prevent overwriting vertex buffer data that is currently
being accessed by the GPU, fences are inserted at the end of frame.
The signaled fences are destroyed after the buffer swap operation, which
seems a bit odd because the just inserted fence most likely won't be
signaled. Perhaps it's a historical artifact?
This change rearranges fence cleanup so it's performed right before
starting a new frame. With it, kwin will most likely re-use the
previously used memory chunk because there will be plenty of time for
the fence to become signaled.
Another motivation behind this change is to make refactoring SceneOpenGL
code easier. As is, m_backend->endFrame() is wrapped in
GLVertexBuffer::endOfFrame() and GLVertexBuffer::framePosted(). With
that, the Compositor can't call m_backend->endFrame(), which can be
desired for cleaning up render backend abstractions.
The main idea behind the render backend is to decouple low level bits
from scenes. The end goal is to make the render backend provide render
targets where the scene can render.
Design-wise, such a split is more flexible than the current state, for
example we could start experimenting with using qtquick (assuming that
the legacy scene is properly encapsulated) or creating multiple scenes,
for example for each output layer, etc.
So far, the RenderBackend class only contains one getter, more stuff will
be moved from the Scene as it makes sense.
The GlStrictBinding flag indicates whether it's okay not to re-bind the X11
pixmap to the OpenGL surface texture if the corresponding window is damaged.
It doesn't really affect the SceneOpenGL, only low level backend stuff.
Currently, the scene owns the renderer, which puts more
responsibilities on the scene other than painting windows and it also
puts some limitations on what we can do, for example, there can be only
one scene, etc.
This change decouples the scene and the renderer so the scene is more
swappable.
Scenes are no longer implemented as plugins because opengl backend
and scene creation needs to be wrapped in opengl safety points. We
could still create the render backend and then go through the list
of scene plugins, but accessing concrete scene implementation is
much much simpler. Besides that, having scenes implemented as plugins
is not worthwhile because there are only two scenes and each contributes
very small amount of binary size. On the other hand, we still need to
take into account how many times kwin accesses the hard drive to load
plugins in order to function as expected.
This allows using base opengl backends in libkwin, which can be useful
later on for the purpose of moving the ownership of render backends from
the Scene class to the Compositor class.
It has been disabled with Mesa for almost half a decade due to false
positives and even if it weren't disabled, it contributes to the startup
time.
The commit message that added the self test doesn't explain why it was
added, but if it was added to detect unstable drivers, it's not worth it.
