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Virtual keyboard support in KWin/Wayland 5.7

Over the last weeks I worked on improved input device support in KWin/Wayland and support for virtual keyboard. KWin 5.7 will integrate the new QtVirtualKeyboard module which is now available under GPLv3. For us this means that we have access to a high quality QML based keyboard. For Qt it means that the virtual keyboard is exposed to more users and thanks to the open source nature it means that we can upstream fixes.

The virtual keyboard is integrated into KWin/Wayland making it part of our platform. To support it we implemented the text input interface in KWayland. If an application supports it, then the virtual keyboard can input text from the compositor side.

Video on youtube:

As you can see in the video the virtual keyboard is only enabled by default if no hardware keyboard is available. If a hardware keyboard gets plugged in the virtual keyboard gets disabled automatically. In addition there is a Status Notifier Item registered which allows to enable/disable the virtual keyboard independently of the hardware keyboard state. So on a notebook with a touch screen it’s possible to get the virtual keyboard even if there is (of course) a hardware keyboard.

Implementing support for the virtual keyboard was an interesting journey which required many unexpected changes and improvements all over the place. First of all wl_text_input interface needed to be implemented as that’s what is used in QtWayland 5.6. At one point I hit a wall and saw that the implementation in QtWayland is incomplete. So I checked how it looks like in QtWayland 5.7 and alas the complete implementation changed, it’s using zwp_text_input_unstable_v2, which is not even in wayland-protocols. I’m not happy about QtWayland using not standardized interfaces as I think that’s very bad for compatibility. Nevertheless I also added support for it in KWayland as otherwise we would not be able to communicate with applications using Qt 5.7. As the QtVirtualKeyboard will only be available with Qt 5.7, we need to support Qt 5.7’s interface as well. In KWayland this is implemented in a transparent way and KWin announces support for both interfaces.

Another area which needed lots of work is the support for input devices in KWin. We need to properly detect whether a real keyboard is available. We needed to add further support for touch events in KWin. So thanks to the integration of virtual keyboard KWin now supports touch much better on Wayland.

The improvements for input devices are also useful in other areas. E.g. today I landed a change to not show the cursor image if no pointer device (mouse or touchpad) is connected.

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KWayland joined KDE Frameworks

The current release 5.22 of KDE Frameworks gained a new framework: KWayland. So far KWayland got released together with Plasma. KWayland entered as tier 1/integration and is only available on Linux (and other Linux-like systems).

For us working on the Wayland stack in Plasma and KDE this is a very important step. Now we can use KWayland also in other frameworks. Also with KWayland in frameworks we expose it to a larger audience. We hope that it is a useful framework for anyone using Wayland with Qt. It’s not a replacement for QtWayland, rather an addition and way more flexible by being closer to the Wayland API.

This change is also important for distributions. Please note that this is only a logical move in the project structure. KWayland 5.22 is fully ABI compatible to the last release 5.6. You can just exchange the KWayland from Plasma with the one in frameworks. Plasma 5.6 of course works perfectly fine with KWayland 5.22.

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Improved input device support in KWin/Wayland

One of the areas I’m currently working on is improving our support for input devices in KWin. While general usage is already quite good in Plasma 5.6, we are not yet able to configure the input devices. This is something I’m working on to improve for Plasma 5.7.

Input devices are provided by libinput and KWin integrates with that for quite some time. What it didn’t do yet is to configure them and keep track of them.

So as a first step we created a Device wrapper class which encapsulates a libinput device in a way that we can easily use it from inside KWin. The Device allows us to gain knowledge about what it supports and also to configure it.

The used Devices and their states can be queried through KWin’s new Debug Console:
Input Devices in Debug console

The Debug Console is also new in Plasma 5.7 and allows us to have a deeper introspection into KWin. It can be opened through KRunner (Alt+Space) and then with the command “KWin”. The functionality set is inspired by tools like xprop (one tab allows to read all window properties), xwininfo -tree (one tab shows a (sub)surface tree), xev (input events).

Back to input devices. Once we had the Device wrapper class in place we could start making use of it to configure devices. And today I landed a series of commits in KWin master which bring us back many features from X11. From the configuration point of view it’s really easy for us as we can just reuse our existing configuration tools. For example the mouse configuration module writes to a config file which KWin can read. When the settings change the configuration module sends out a DBus signal which KWin uses to trigger a reconfigure.

So KWin now supports setting pointer devices (mouse) to left-handed usage and modifying the pointer acceleration.
Toggle Touchpad

In addition KWin started to integrate changes for touchpads. KWin listens to the global shortcut for touchpad toggle and uses this to enable/disable the touchpad. Of course this comes with triggering the new on-screen-display notification for enabling the touchpad. Next step will be to integrate more options for touchpads, but this will require writing a kwin-backend for our touchpad control module.

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Running Plasma-Wayland on KDE Neon

This morning I installed KDE Neon on my good old ExoPC as I need to test some touch functionality on Wayland. So here are the steps on how to switch Neon to use Wayland:

Install package plasma-workspace-wayland:

sudo apt install plasma-workspace-wayland

Log out and select in session drop down Plasma (Wayland), log in and enjoy your Wayland session.

If you want to verify that it truly is a Wayland session, just open any KDE application, open the “Help” Menu, go to “About <Application Name>”, click “Version” tab, it should say “The Wayland windowing system” is being used.