It's not guaranteed that there will be current render target in
postPaintScreen() as all painting have been completed. Furthermore,
even the docs of the postPaintScreen() function indicate that no
painting should be done there, you can do only cleanup things, e.g.
schedule a repaint, etc. paintScreen() is a much safer place to
capture screenshot.
Having a render loop in the Platform has always been awkward. Another
way to interpret the platform not supporting per screen rendering would
be that all outputs share the same render loop.
On X11, Scene::painted_screen is going to correspond to the primary
screen, we should not rely on this assumption though!
This allows us to make the GLRenderTarget a bit nicer when using it to
wrap the default fbo as we don't know what the color attachment texture
is besides its size.
This means that the responsibility of ensuring that the color attachment
outlives the fbo is now up to the caller. However, most of kwin code
has been written that way, so it's not an issue.
Because the GLRenderTarget and the GLVertexBuffer use the global
coordinate system, they are not ergonomic in render layers.
Assigning the device pixel ratio to GLRenderTarget and GLVertexBuffer is
an interesting api design choice too. Scaling is a window system
abstraction, which is absent in OpenGL or Vulkan. For example, it's not
possible to create an OpenGL texture with a scale factor of 2. It only
works with device pixels.
This change makes the GLRenderTarget and the GLVertexBuffer more
ergonomic for usages other than rendering the workspace by removing all
the global coordinate system and scaling stuff. That's the
responsibility of the users of those two classes.
This reverts commit ac16bef409.
It causes crashes and color channels seem to be swapped.
GLTexture::toImage() needs more work before it can be used in the
screenshot effect, or maybe dropped.
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.
In general, on Wayland, there is no such a thing as "window scale factor"
because sub-surfaces can have different buffer scales. However, we know
the scale factor of the output where the window is considered to be on. So
we can use the screen's scale factor as the window's scale factor. In
most cases, it will produce the correct result.
For the scene redesign, window quads need to be removed from the effects
api. This change ports the screenshot effect away from quads.
In order to exclude the server-side decoration from the window
screenshot, the effect will render the contents of the client geometry
into the offscreen texture. If the window is client-side decorated, the
entire window will be rendered as before.
The good thing about this approach is that the screenshot effect will do
less work, it won't loop over window quads to compute the bounding rect
or filter out the deco quads.
With the new interface, the compositor sends raw image data instead of
encoding it as a png image, which causes a lot of overhead on Wayland.
In addition to that, the new interface is more extensible, for example
we can add new options or change the written image data format, however
the latter is less likely to happen.
BUG: 433776
On Wayland, when the compositor sends a screenshot to the requesting
app, it encodes the screenshot as a PNG image and sends the encoded data
over the pipe. The requesting app (Spectacle) then needs to decode the
data.
The issue is that encoding PNG images is not cheap. This is the main
reason why Spectacle is shown with a huge delay after you press the
PrtScr key.
In order to fix the latency issue, we need to transfer raw image data.
Unfortunately, the current dbus api of the screenshot is too cluttered
and the best option at the moment is to start with a clean slate.
This change prepares the screenshot effect for versioned dbus interface.
Most of existing dbus logic was moved out in a separate class. In order
to schedule screen shots, the screenshot effect got some new API.
QFuture<QImage> scheduleScreenShot(window, flags)
QFuture<QImage> scheduleScreenShot(area, flags)
QFuture<QImage> scheduleScreenShot(screen, flags)
If a dbus interface needs to take a screenshot, it needs to call one of
the overloaded scheduleScreenShot() functions. Every overload returns a
QFuture object that can be used for querying the result.
This change also introduces "sink" and "source" objects in the dbus api
implementation to simplify handling of QFuture objects.
Note that the QFutureInterface is undocumented, so if you use it, you do
it on your own risk. However, since Qt 5.15 is frozen for non-commercial
use and some other Plasma projects already use QFutureInterface, this
is not a big concern. For what it's worth, in Qt 6, there's the QPromise
class, which is equivalent to the QFutureInterface class.
CCBUG: 433776
CCBUG: 430869
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.
2021-02-10 15:31:43 +00:00
Renamed from effects/screenshot/screenshot.cpp (Browse further)
