AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |
Back to Blog
Qt sync tutorial1/6/2024 It is usually best to use a mutex with a QMutexLocker since this makes it easy to ensure that locking and unlocking are performed consistently. The purpose of a QMutex is to protect an object, data structure or section of code so that only one thread can access it at a time (synchronized). New QWebChannel(navigator.The QMutex class provides access serialization between threads. Furthermore, you can pass the navigator.qtWebChannelTransport object to your channel – more on this below. The callback function gets invoked when the initialization of the web channel succeeded. Then, in your JavaScript code, instantiate a QWebChannel object and pass it a callback function. First, include the client-side qwebchannel.js library via its Qt resource URL: I tried to minimize it as much as possible, and plan to improve this situation even further in the future. On the client side, a bit of boiler-plate code is still required. You can also create a WebChannel object externally and set it on multiple WebViews if necessary. Internally, this will use the WebKit IPC mechanism to transmit method calls, signals and property update notifications to the HTML clients. This single line is all you need to publish potentially multiple objects. Publishing the object to the HTML clients in your WebView is as simple asĮ: the identifier under which this object Now, let’s create an object that we want to publish to the HTML/JavaScript clients: On the QML server side, first import the Qt WebChannel module, as well as the Qt WebKit module and its experimental one: So, what is necessary to build a hybrid QML/HTML application in the upcoming Qt 5.4? The following shows how to use the new Qt WebChannel module. What is left now, is the inclusion of two already approved patches, which provide an easy-to-use integration of the Qt WebChannel functionality into Qt WebKit with a minimum of boiler-plate code. A few days ago now, Qt WebChannel was added as a new module for Qt 5.4. At this year’s Qt Contributor Summit the design was reviewed and approved for inclusion in Qt 5.4. The goal was to create a proper Qt module which can be used by hybrid QML/HTML applications. Over the last couple of months, I had the pleasure to work on Qt WebChannel exclusively, sponsored by KDAB. Still, it remained a Qt Labs project and as such awkward to use by others. Eventually, the codebase worked reliably and efficiently even on embedded devices. In the process, I essentially took up maintainership of the Qt WebChannel project. In this first real-world use-case, numerous bugs and missing functionality were found, fixed and upstreamed to the Qt Labs repository. Naturally, we chose Qt WebChannel as a foundation and started polishing it. But, contrary to the WebKit Bridge, the API provided by the WebChannel is completely asynchronous.ĭespite the huge interest in hybrid QML/HTML applications, Nokia and nowadays, Digia, did not prioritize work on this missing functionality. Priorities lay elsewhere and the Qt WebChannel project never left the proof-of-concept stage on Qt Labs.Īt the beginning of 2013, a customer approached KDAB and requested the development of a QML application with an HTML 5 application framework. For communication between the QML host and the HTML/JavaScript client, he chose WebSockets. His idea was simple and powerful at the same time: By leveraging Qt’s introspection system, he could create mock objects on the JavaScript client side which mirror the API of the server-side QML/QObject objects. In October 2011, Noam Rosenthal presented an alternative approach to the problem, which he called Qt WebChannel. Due to that, hybrid QML/HTML applications were notoriously hard to implement. The reason for that was the multi-process architecture at the core of WebKit2, which is used internally by WebView in such an environment, the synchronous API of the WebKit bridge cannot be supported, since inter-process communication is inherently asynchronous. Up until now though, WebView, the Qt Quick 2 integration of Qt WebKit, was missing this functionality. This is a crucial functionality for any application that uses Qt WebKit as the foundation for an HTML app framework or similar. In the single-process world of the C++ Qt WebKit API, it was easily possible to publish a QObject instance to the JavaScript client side, thanks the Qt WebKit Bridge. But how does one bridge the gap between C++/QML on one side, and HTML/JavaScript on the other side? A bit of history Qt WebKit makes it trivial to embed HTML content in any graphical application. In particular, something like an HTML 5 app framework is often requested by customers. Hybrid applications, which mix a UI built with Qt Widgets or Qt Quick with embedded HTML websites, are very popular.
0 Comments
Read More
Leave a Reply. |