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KWin moved to an own repository

As you might have read in Aleix’s blog post the kde-workspace repository got split into several repositories. KWin was also affected by this change. As the largest module in the old kde-workspace repository and given the fact that it has always been a rather stand alone part in kde-workspace it got moved into an own repository. If you want to clone it just run:

git clone kde:kwin

This change will hopefully make development easier, especially following all commits should be easier. A nice change is that KWin now does the dependency resolving itself which removes quite some quirks we had in the old setup. All of kde-workspace had X11 and a few other dependencies optional, but for KWin they were mandatory. Now all mandatory dependencies can clearly be stated.

The new KWin repository does not contain all source code as it used to. The Oxygen window decoration got moved together with other parts of Oxygen. But this doesn’t change anything for KWin: Oxygen is still the default window decoration, just the dependency is now at runtime. If Oxygen is not around KWin can fallback to the Plastik window decoration just as it used to be.

Furthermore the documentation for the configuration modules got moved into the new repository, so all the documentation is now also directly in KWin. And also the new kwin-compositing-kcm got imported into the new repository. This got initially developed in an own repository to ease the initial development (which started on Qt 5 when KWin was still on Qt 4), but we had the plan to merge it back into KWin once the repositories are split. Note for distributions: you can drop the package in case you packaged it already. Sorry if that created some extra work for you.

Bug fixes for the 4.11 release still need to happen from the old kde-workspace repository as that’s the one used to make the releases. Commits to this branch will get cherry-picked by me to the new repository.

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Desktop Effects Control Module in KWin5

One of the new features in KWin 5 is a completely rewritten configuration module for our Desktop Effects. In KWin 4 our module was based on KPluginSelector, which is a great widget for a small list of plugins, but it was never a really good solution for the needs of KWin.

Also we noticed that a QWidget based user interface is not flexible enough for what we would like to provide (e.g. preview videos). So when QtQuick came around we had the first experiments with reimplementing the selector with QtQuick, but with the lack of what today is QtQuick Controls it never left the prototype state. But it encouraged us to use one GSoC project on redesigning the control module from scratch and Antonis did a great job there to lay the foundation for what we have now in the upcoming alpha release.

The most noticeable change is that the new control module just focuses on the Desktop Effects. What we learned from our users is that they are only interested in configuring the effects and that the other options exposed in that control module bare the risk of users changing and breaking their system. Thus we decided to give the users what they need and move all other options into another control module.

In order to give the users the possibility to focus on the effects we also did some cleanup in the list and all effects which are not supported by the currently used compositing backend are hidden by default (e.g. OpenGL effects when using XRender). Also all internal or helper effects are hidden by default. These are effects which replace functionality from KWin Core or provide interaction with other elements of the desktop shell. Normally there is no reason for users to change that except if they want to break their system. That’s of course a valid use case and so there is a configuration button to modify the filtering of the list to show also those effects.

Last but not least our effects got extended by information on whether they are mutual exclusive to other effects. For example one would only want to activate the minimize or the magic lamp effect. Both at the same time result in broken animations. For effects in a mutual exclusive group the UI uses radio buttons and manages that only one of the effects can be activated. That’s the change I’m most happy about.

Check out the video to see the new configuration module in action and also see some of the new features I haven’t talked about. Please don’t tell me in the comments about padding issues and rendering problems. We can see those, too, and are quite aware of them. If you want to help iron out issues with Oxygen and QtQuick Controls check have a look to our wiki page.

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House Cleaning in KWin 5

We are currently approaching the release of the first alpha version of KWin 5. This is of course a significant milestone and we have put lots of work into the transition to ensure that it’s already working quite fine. With such a big migration it is also important to not only work on new cool stuff, but also to do lots of house cleaning.

For example last week the build option for disabling scripting support got removed as we consider scripting as an important and integrated part of KWin. Thus during the house cleaning the build option got removed.

And of course there are areas where we wanted to remove some legacy code for quite some time but never really dared to do. Two years ago I already discussed the costs of supporting the legacy OpenGL 1 compositing backend. Now it was time to re-evaluate the situation.

KWin 5 is a strong user of QtQuick 2. In fact almost all user interface code is written with this new framework – be it the close button in Present Windows, the window switcher or (since today) the outline shown when using quick tiling/maximization. QtQuick 2 uses an OpenGL (ES) 2 powered scene graph thus KWin already has a runtime dependency on OpenGL 2. And in opposite to our Compositor this is a required dependency. While it has always been possible to disable the Compositor (and that won’t change for X11), it is not (yet) possible to disable the OpenGL usage of QtQuick.

Thus we have to ask whether it’s still worth keeping a code path for legacy hardware, if we require newer hardware. Combined with all the problems mentioned in the above linked blog post from two years ago it becomes really questionable to keep the code.

After some preparation to ensure that we have a clean cut I pushed today the changes to remove the legacy OpenGL 1 compositor in order to have this change in Alpha 1. We encourage all users who used to run the OpenGL 1 compositor to try with the OpenGL 2 compositor and also with the still supported XRender based compositor. If you run into any severe issues please report a bug (or check whether one has already been reported) and provide the support information. This will help us to iron out any issues, like ensuring that no effects get loaded which are not suited for your hardware. After all the base OpenGL 2 compositor should not be an issue for most hardware. But some effects are more demanding than the compositor itself and those can be disabled automatically. Also we try to keep the impact low. If our logic recommended OpenGL 1 compositing for a specific set of hardware, it doesn’t enforce OpenGL 2 now, but uses the better suited XRender compositor.

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Laptop and BII window decorations want to be ported to KWin/5

At the moment the window decorations Laptop and BII are disabled from build in kde-workspace master branch. From the KWin development team side these two decorations had been unmaintained for a long time and this means I will not do the port and I don’t expect anyone else from the core team will port them.

This means it depends on YOU dear reader to make sure that those two decorations are also available in the next release. So if you are using one of the decorations and are able to program in C++ please step up and port them (also maintaining would be awesome).

If nothing happens till let’s say end of January I will git rm those two decorations.

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Quick Window Switchers in KWin 5

One of the oldest usages of QtQuick in KWin are the Window Switchers. During the design it was aimed for having them Plasma-styled just like the previous implementation. This was not as easy as one could hope, because back then we couldn’t use the Dialog component provided by PlasmaCore. So all the various Switcher styles implemented the Plasma styling themselves and the C++ side did some additional adjustments like guessing the blur region. As the Plasma theme recognized that the blur effect is active the FrameSvg used as a background was rendered in the blur-available translucency state. To have it readable it needs to be blurred.

For this we would the correct blur mask of the FrameSvg but that’s not available from the Qml bindings. The hack we went for was to just assume in the C++ side that the switcher is Plasma styled, created another FrameSvg of same size and extracted the blur mask from that. Sounds fragile, doesn’t it?

And of course there came the day when that broke. About a year ago we noticed that the shadow doesn’t work any more and we needed to bring in some more fixes to make that work. If we would have used a PlasmaCore Dialog this would not have been an issue at all.

Now after the Qt 5 port the blur and shadow was once again broken and once again I was about to start fixing it. But nowadays we use the Plasma Dialog in e.g. declarative KWin scripts (the desktop change OSD being a prominent example). So I took a step back and thought about instead of fixing the fragile code to re-think it and make it possible to use the Plasma Dialog or in general QtQuick Windows from inside the Qml code.

Given that this required to adjust all switchers anyway I decided to go a step further and also improve the API a little bit. So far all the important data was exposed as context properties. I’m not a huge fan of context properties as it’s kind of magic. Instead there is now a dedicated switcher item available, which is just a QObject exposing a few properties:

import org.kde.kwin 2.0 as KWin

KWin.Switcher {
    property QAbstractItemModel *model // The model with either the windows or the virtual desktops
    property QRect screenGeometry // The geometry of the active screen (as KWin thinks of active)
    property bool visible // Whether the switcher is currently visible or not, a Window should follow this
    property bool allDesktops // Whether the switcher includes windows from all desktops or only the current one
    property int currentIndex // The index of the selected window - this is controlled from KWin side
}

The model provides the following roles for Window Switchers:

  • caption – The caption of the window
  • desktopName – The name of the virtual desktop the window is on
  • minimized – Boolean whether the window is minimized or not
  • windowId – Window system specific identifier
  • closeable – Boolean whether the window can be closed
  • icon – QIcon containing the window’s icon

With that we can design a very simple thumbnails switcher:

import QtQuick 2.1
import org.kde.kwin 2.0 as KWin
import QtQuick.Window 2.1
 
KWin.Switcher {
    id: switcher
    currentIndex: listView.currentIndex
 
    Window {
        id: window
        flags: Qt.X11BypassWindowManagerHint // important, without it won't work
        visible: switcher.visible
        color: "white"
        x: switcher.screenGeometry.x + switcher.screenGeometry.width / 2 - window.width / 2
        y: switcher.screenGeometry.y + switcher.screenGeometry.height / 2 - window.height / 2
        width: switcher.screenGeometry.width - 100 // keep 50 px space to each side
        height: 200 * (switcher.screenGeometry.width/switcher.screenGeometry.height) + 20
 
        ListView {
            id: listView
            orientation: ListView.Horizontal
            model: switcher.model
            spacing: 10
            anchors.fill: parent
            anchors.leftMargin: 10
            anchors.rightMargin: 10
            delegate: KWin.ThumbnailItem {
                width: 200
                height: width * (switcher.screenGeometry.width/switcher.screenGeometry.height)
                wId: windowId
                brightness: ListView.isCurrentItem ? 1.0 : 0.5
                saturation: brightness
                MouseArea {
                    anchors.fill: parent
                    onClicked: {
                        listView.currentIndex = index;
                    }
                }
            }
            Connections {
                target: switcher
                onCurrentIndexChanged: {
                    // currentIndex is updated from KWin side - need to keep in sync
                    listView.currentIndex = switcher.currentIndex;
                }
            }
        }
    }
}

I wrote this code directly in the blog post without any testing at all (hey it found one bug in KWin and two in the systemsetting previewer. I should do such stuff more often 😉 ). So let’s see how it looks like:

Aus TabBox

Not a bad result for 50 lines of code. As one can also see from the code it does not do any Plasma styling at all any more. Which is a nice side-effect for the usage of KWin outside the Plasma workspaces. The changes to get Plasma styling is not difficult either. Just use PlasmaCore.Dialog instead of the Window and that’s it.

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KWin a solution for non-KDE based Desktop Environments?

Recently I have seen more comments about using KWin as a stand-alone window manager in other desktop environments. It looks like quite some users are looking for a replacement for Compiz nowadays. But of course especially among the users of the lightweight desktops there is the perception that one cannot use KWin because it is done by KDE.

So I thought I spent some time on explaining about what it actually means. Of course KWin is the window manager of the KDE Plasma workspaces. And this means it is part of the KDE source code module called “kde-workspace”. Most distributions provide one package or a set of packages which depend on each other for this workspace module. This means to install KWin one has to install what people consider to be “KDE”. But it doesn’t mean that one has to run any other part of the kde-workspaces. KWin is a standalone application which only depends on the kde libraries and requires a few runtime modules (e.g. the globalshortcuts daemon or kcmshell4). One does not have to run the Plasma desktop shell or systemsettings or any other application provided by the KDE community.

So installing KWin requires to install a few more applications, but all they will do is take up some space on your hard disk. I know that people are sometimes very concerned about it, so I run “du -h” on my kde install directory. This includes not just the kde-workspace module with its dependencies, but more or less everything we have in KDE’s git repository including things like an office suite, IDE, webbrowser, artwork and many other things one doesn’t need to run a window manager 😉 The result of all that is just 13 GB of disk usage. Given current storage costs (0.06 EUR/GB) this costs less than 1 EUR which is less than a cup of coffee where I live. And remember KWin will need less storage. The bare kde-window-manager package in Debian is just around 10 MB.

I understand that people care about the dependencies and think this is important. I just don’t think it’s of any importance in a world where a movie needs significantly more data storage. Still we care about the dependencies and we are working on breaking down the dependency chain as part of the frameworks modularization efforts. One of the results of this is that we have documented dependencies nowadays. And we are working on getting the dependency to the Plasma framework as a runtime-only dependency over QtQuick, so that people can put together themeing for KWin which does not pull in any bits of the Plasma dependency. Help on that is appreciated 🙂

A more relevant issue is the question of memory usage due to running KWin. Unlike disk storage, memory storage is still rather constraint. Unfortunately it’s very difficult to provide correct measurements on the memory usage of a single KDE application. KDE applications have many shared libraries (e.g. Qt). So if KWin is the only Qt application, the relative memory usage is higher than when using several Qt applications as for example in LXDE on Qt.

Now a few highly non-scientific numbers: according to KSysGuard my self-compiled KWin (Qt4) uses around 40 MB of private memory and 38 MB of shared libraries (Qt, kdelibs, XLib, xcb, etc.). The memory usage also depends on what you use. If you activate the desktop cube effect with a 10 MB wallpaper put in the background, you will see this in the memory usage 😉 Just as another value for comparison: the iceweasel instance I’m writing this blog post in has a private memory usage of more than 700 MB. Of course KWin is with that in a different league than the minimalistic window managers, but one has to see that KWin provides more features and is a window manager and compositor. If one needs to run two applications to get close to the same feature set, it’s quite likely that the same amount of memory is needed. KWin has many features and there is no such thing as free-lunch in IT. It’s certainly possible to trim KWin down by not loading the KWin effects and ensuring that no scripts are loaded and simplified graphics.

Given that I can only recommend to give KWin a try and not to discard it because it is from KDE and might pull in some dependencies. Evaluate by the features we provide and you want to use and not by some random number on your hard disk or your memory usage.

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KWin/5, QtQuick 2 and the caused changes for OpenGL

In the KWin/4 days our OpenGL implementation could be based on some assumptions. First of all only KWin creates an OpenGL context, none of the libraries, KWin depends on, uses OpenGL. From this it is possible to derive more assumptions, for example our compositing OpenGL context is always current. Which means that it’s possible to run any OpenGL code in any effect. No matter how the code path got triggered. Also we can link KWin against OpenGL or OpenGL ES. We don’t have to check with other libraries to prevent conflicts.

With KWin/5 these assumptions no longer hold. KWin uses QtQuick 2 and with that we pull in the Qt OpenGL module. One of the direct implications of this change is, that we are no longer able to provide kwin/OpenGL and kwin/OpenGLES at the same time. The compilation of KWin has to follow the compilation of the Qt OpenGL module. So compiling against OpenGLES is only possible if Qt is compiled for OpenGLES, which means that the option to run KWin on OpenGLES is probably non-existing on classic desktop computers and the option to run KWin on OpenGL is probably non-existing on ARM systems such as the Improv. Given that it’s no longer possible to compile both versions at the same time, the binary kwin_gles got removed. A kwin compiled against GLES is just called kwin.

With QtQuick also our assumption that only KWin creates an OpenGL context and makes it current doesn’t hold any more. In fact it could be that at any time Qt creates an OpenGL context and makes it current in the main GUI thread. Now people probably know that QtQuick 2 uses a rendering thread, so that should be fine, right? Well not quite. To decide whether QtQuick uses a rendering thread it creates a dummy context in the main gui thread and makes it current. So our assumption that our context is created once and then kept current, doesn’t hold any more. The first solution to this problem was to make our context current whenever we go into the repaint loop. That worked quite well, till I tested KWin/5 on my SandyBridge notebook.

The problem I stumbled upon is that Qt doesn’t use a rendering thread in all cases. For some hardware it prefers to use the main gui thread. One of them is SandyBridge Mobile, the hardware I am using on my notebook. This showed that the initial solution was not elaborated enough. With another context rendering in the same thread it showed that it’s quite likely that we hit conditions where our compositing context is not current. Resulting in e.g. not rendered window decorations, effects not able to load their textures, etc. etc.

These problems are hopefully solved, now. The effects API is extended by calls to make the context current and I tried to hunt down all effects which do OpenGL calls outside the repaint loop. Unfortunately given the large number of effects it’s still possible that some effects use it incorrectly. It will be difficult to track those down: so please test.

The case when QtQuick uses the main GUI thread for rendering illustrates that we in KWin are not the only ones having incorrect assumptions on OpenGL. QOpenGLContext assumes that every OpenGL context in a Qt application has been created through QOpenGLContext and that an OpenGL context is only made current on the current thread through the QOpenGLContext API. Especially if one uses glx or egl directly to make a context current QOpenGLContext doesn’t notice this and assumes that its own context is still current which can result in nastiness. This is circumvented in KWin now by making sure that QOpenGLContext has correct information once the compositing context is made current. Nevertheless we are still hitting a bug causing a crash. This one is also currently worked around in the development version by enforcing XRender based compositing on the hardware which uses the main GUI thread for rendering. On SandyBridge one can also use the environment variable QT_OPENGL_NO_SANITY_CHECK to force QtQuick to use a dedicated rendering thread as the problem why Qt uses the main gui thread is not relevant to KWin’s usage of QtQuick. KWin also checks for this environment variable and doesn’t force to XRender, if it is set.

Obviously one could question why we are not using QOpenGLContext given that this seems to conflict. We haven’t used Qt’s OpenGL module mostly for historic reasons. Of course I evaluated the option of using QOpenGLContext when investigating this issue and right now in Qt 5.2 it would not be an appropriate solution for the usage in KWin. It’s not possible to create a QOpenGLContext from a native context and even if it were possible our implementation is more flexible. KWin can be compiled against both egl and glx allowing to switch through an environment variable. Qt on the other hand supports either egl or glx, but not both at the same time. If I find time for this, I intend to improve the situation for Qt 5.3, so that we can consider the usage of QOpenGLContext once we depend on Qt 5.3. Switching to Qt’s OpenGL context wrapper would allow us to get rid of a considerable amount of code. I’m especially interested in the QOpenGLFunctions. Obviously that will only be a solution if KWin uses the same windowing system as Qt’s platform plugin. But that’s a problem for another day 😉

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Color Scheme syncing between window and it’s decoration

Some time ago I started Krita and I had the thought: well we can do better. The window decoration is just looking out of place. Everything is a nice dark color, but the window decoration isn’t. So I asked a few people what they think about making it better and the reaction was overall very positive and I started to investigate.

Right now I have a solution for KWin/5 which allows the window decoration to follow the color scheme of the window. Have a video:

At the moment it’s implemented mostly inside Oxygen, but I intend to move most of it to KColorScheme an KStyle directly, so that any KDE/Qt application can benefit from this new feature.

And of course I need to point out that all of that is possible without opening Pandora’s box of Client Side Window Decorations as Aaron said today.

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Next step: running

Last week I reported that KWin compiles and links against Qt 5 and KF 5. This week I’m glad to report that I got KWin also to run. The biggest issue was a PEBKAC – if you try to run anything build against frameworks make sure to not have KDE 4 libraries in your LD_LIBRARY_PATH.

Aus KWin

Before you are tempted to run KWin next in the new Project Neon setup a word of warning: it will dead lock. The current code base I use for testing depends on not yet upstreamed changes in frameworks and Qt. Obviously I have not yet pushed the KWin code needing these library adjustments but without them KWin will hit a dead lock – more to that explained later on.

Project Neon has been a huge help over the last days. Harald reported again and again build issues which we were not able to detect on our system because we also have Qt 4 installed. One example was a file being included which does not exist anymore in KF 5. As it was installed in /usr/include I was not able to detect such a problem, but with a clean setup like Project Neon it becomes immediately obvious.

So what is already working in KWin on 5? The most obviously visible one is the compositor. This doesn’t surprise me much, I didn’t expect any problems there. So far I have mostly tested the XRender compositor as I’m currently mostly working with Xephyr which only provides llvmpipe OpenGL and I rather spent my CPU cycles on compiling than drawing triangles. Since yesterday I have also Oxygen shadows working again which I had initially disabled as it needed XCB porting. But it just looked too strange without them, so I had to enable it 😉 I think Hugo ported Shadows in Oxygen for the same reason.

Related to the compositor is the effect system and our effects. This was rather surprising for me: they just worked out of the box. The only major problem is that global shortcuts are not yet supported so I have problems triggering them. For some effects I solved this problem by just adding a DBus interface – might be an idea to keep this; some users might appreciate it. Only the scripted effects were not loaded because I did one mistake during the initial porting – this is fixed since today as you can see by the dialog parent effect being applied in the screen shot above.

Also window decorations work, though there is still quite some work to be done. For example the QML based Aurorae does not like to work which is the reason why I ported Oxygen over. It’s overall nice to see that it works, but it seems to be only working with compositing enabled. Not so surprising as this hits areas which changed a lot inside Qt.

The window manager seems also to be working, though obviously I have not tested all features and are using only a minimal sub set of the available functionality. Due to missing global shortcuts support it’s difficult to test all features and due to missing port of the configuration interfaces I cannot even adjust the configuration (well I could just edit the config file, but…).

Nevertheless there are still quite some issues which need investigation and fixing before I can start to consider using KWin 5 in production. The biggest problem at the moment is that all windows present at startup get unmapped and are kind of lost to the window manager. So far I have not yet been able to figure out why this is happening. That is for example a show stopper if you would want to use it in a neon setup. (Update: This issue is fixed as of 3bddd1100aa)

The biggest change for KWin is the port of the event filter from XLib to XCB and this is still causing some headaches to me. With XLib one was able to look into the future by inspecting the XEvent queue or to the extreme wait till a specific event has arrived. With XCB the event queue doesn’t allow to be inspected which makes porting properly a non-trivial task. KWin was using this functionality at three places (at least that’s what I found so far). During move/resize operations we only process the last mouse motion event currently in the event queue to limit the resizes. This functionality should be possible to emulate with a more async event handling approach. The second usage is that we do not deactivate a window on focus out event if there is also a focus in event following. The documentation says this is to prevent flickering. In a composited world it doesn’t really matter as the compositor should prevent the flicker, but also here a more async approach should be able to handle it.

The big problem though is the third usage: updating the current xTime. KWin needs to have the most recent X time to be able to properly compare timestamps. This is done by changing a property and waiting for the event which contains the timestamp. In addition KWin does some more tricks like looking at the first event in the queue containing a timestamp, to get it really correct. Now with XCB event queue not being available to us this is a sever issue as without this functionality KWin doesn’t function properly. While looking at how to solve the problem I discovered that the XCB QPA internally uses a method providing this functionality of getting a current timestamp. Not with all the bells and whistles as we used to have in KWin, but good enough for a start. So my solution at the moment is to have my local Qt copy to make this function available and by that solve the problem. That’s the change I talked about in the beginning of this blog post.

As you can see there has been quite some progress and I hope to get KWin in a dogfoodable state quite soon. And that’s something where you can help. There are many easy tasks available which just need you to be able to compile KWin and with Project Neon this just became easier. So drop by the Trello board and claim your task. This week I was already able to push one first time KDE commit with a small cleanup for our code base 🙂 So who wants to be next?

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Help porting KWin to Frameworks 5

With Akademy behind me and the situation about “what is master” in kde-workspace resolved I decided to switch my work away from Wayland towards getting KWin on top of Qt 5 and KDE Frameworks 5. After a few days of hacking the compilation of KWin is re-enabled in the frameworks-scratch branch of the kde-workspace git repository.

This means that KWin compiles, links and installs when compiling against KF5. A quite important step and only very few code areas got ifdefed. The preparation work of the last months showed it values as for example the compile errors due to QPixmap were extremely easy to resolve (just delete the code) without loss in functionality.

But of course at the moment KWin does not work yet when compiled against KF5 as the event filter is not yet ported to xcb. This is what I will focus on next so that we can soon start testing a KWin on 5 and start to adjust the areas which need to be tested against a running KWin, where “ship it, it compiles” is not enough.

Of course getting KWin to KF5 is still a long road and we need help for this. There are many, many tasks which are rather easy and do not need a working KWin. It’s just a matter of changing for example KPushButton into QPushButton and verify that it still compiles. This means that right now is a perfect time to get started with KWin hacking.

And obviously I started to prepare for that and created a wiki page for KWin on Frameworks. I plan to update this page whenever new information becomes available like how to run KWin on 5. Most important I created a Trello board listing the tasks which can be done to help the porting. I will add tasks as I notice them. So if you want to get involved, just ping me, tell me your trello username and I’ll add you to the board and start hacking. If you look at the list you will notice that some tasks are really simple. Let’s rock to get KWin working on Qt 5 as fast as possible to get an awesome next release.