Introducing WPEQt, a WPE API for Qt5

WPEQt provides a QML plugin implementing an API very similar to the QWebView API. This blog post explains the rationale behind this new project aimed for QtWebKit users.

Qt5 already provides multiple WebView APIs, one based on QtWebKit (deprecated) and one based on QWebEngine (aka Chromium). WPEQt aims to provide a viable alternative to the former. QtWebKit is being retired and has by now lagged a lot behind upstream WebKit in terms of features and security fixes. WPEQt can also be considered as an alternative to QWebEngine but bear in mind the underlying Chromium web-engine doesn’t support the same HTML5 features as WebKit.

WPEQt is included in WPEWebKit, starting from the 2.24 series. Bugs should be reported in WebKit’s Bugzilla. WPEQt’s code is published under the same licenses as WPEWebKit, the LGPL2 and BSD.

At Igalia we have compared WPEQt and QtWebKit using the BrowserBench tests. The JetStream1.1 results show that WPEQt completes all the tests twice as fast as QtWebKit. The Speedometer benchmark doesn’t even finish due to a crash in the QtWebKit DFG JIT. Although the memory consumption looks similar in both engines, the upstream WPEQt engine is well maintained and includes security bug-fixes. Another advantage of WPEQt compared to QtWebKit is that its multimedia support is much stronger, with specs such as MSE, EME and media-capabilities being covered. WebRTC support is coming along as well!

So to everybody still stuck with QtWebKit in their apps and not yet ready (or reluctant) to migrate to QtWebEngine, please have a look at WPEQt! The remaining of this post explains how to build it and test it.

Building WPEQt

For the time being, WPEQt only targets Linux platforms using graphics drivers compatible with wayland-egl. Therefore, the end-user Qt application has to use the wayland-egl Qt QPA plugin. Under certain circumstances the EGLFS QPA might also work, YMMV.

Using a SVN/git WebKit snapshot

If you have a SVN/git development checkout of upstream WebKit, then you can build WPEQt with the following commands on a Linux desktop platform:

$ Tools/wpe/install-dependencies
$ Tools/Scripts/webkit-flatpak --wpe --wpe-extension=qt update
$ Tools/Scripts/build-webkit --wpe --cmakeargs="-DENABLE_WPE_QT=ON"

The first command will install the main WPE host build dependencies. The second command will setup the remaining build dependencies (including Qt5) using Flatpak. The third command will build WPEWebKit along with WPEQt.

Using the WPEWebKit 2.24 source tarball

This procedure is already documented in the WPE Wiki page. The only change required is the new CMake option for WPEQt, which needs to be explicitly enabled as follows:

$ cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo -DENABLE_WPE_QT=ON -GNinja

Then, invoke ninja, as documented in the Wiki.

Using Yocto

At Igalia we’re maintaining a Yocto overlay for WPE (and WebKitGTK). It was tested for the rocko, sumo and thud Yocto releases. The target platform we tested so far is the Zodiac RDU2 board, which is based on the Freescale i.MX6 QuadPlus SoC. The backend we used is WPEBackend-fdo which fits very naturally in the Mesa open-source graphics environment, inside Weston 5. The underlying graphics driver is etnaviv. In addition to this platform, WPEQt should also run on Raspberry Pi (with the WPEBackend-rdk or -fdo). Please let us know how it goes!

To enable WPEQt in meta-webkit, the qtwpe option needs to be enabled in the wpewebkit recipe:

PACKAGECONFIG_append_pn-wpewebkit = " qtwpe"

The resulting OS image can also include WPEQt’s sample browser application:

IMAGE_INSTALL_append = " wpewebkit-qtwpe-qml-plugin qt-wpe-simple-browser"

Then, on device, the sample application can be executed either in Weston:

$ qt-wpe-simple-browser -platform wayland-egl https://wpewebkit.org

Or with the EGLFS QPA:

$ # stop weston
$ qt-wpe-simple-browser -platform eglfs https://wpewebkit.org

Using WPEQt in your application

A sample MiniBrowser application is included in WebKit, in the Tools/MiniBrowser/wpe/qt directory. If you have a desktop build of WPEQt you can launch it with the following command:

$ Tools/Scripts/run-qt-wpe-minibrowser -platform wayland <url>

Here’s the QML code used for the WPEQt MiniBrowser. As you can see it’s fairly straightforward!

import QtQuick 2.11
import QtQuick.Window 2.11
import org.wpewebkit.qtwpe 1.0

Window {
    id: main_window
    visible: true
    width: 1280
    height: 720
    title: qsTr("Hello WPE!")

    WPEView {
        url: initialUrl
        focus: true
        anchors.fill: parent
        onTitleChanged: {
            main_window.title = title;
        }
    }
}

As explained in this blog post, WPEQt is a simple alternative to QtWebKit. Migrating existing applications should be straightforward because the API provided by WPEQt is very similar to the QWebView API. We look forward to hearing your feedback or inquiries on the webkit-wpe mailing list and you are welcome to file bugs in Bugzilla.

I wouldn’t close this post without acknowledging the support of my company Igalia and Zodiac, many thanks to them!