Every Drupal developer knows the following error message (maybe some by heart): The content has been modified by another user, changes cannot be saved. In Drupal 8 the message is even a bit longer: The content has either been modified by another user, or you have already submitted modifications. As a result, your changes cannot be saved. While this inbuilt mechanism is very useful to preserve data integrity, the only way to get rid of the message is to reload the form and then redo the changes you want to make. This can be (or should I say 'is') very frustrating for users, especially when they have no idea why this is happening. In an environment where multiple users modify the same content, there are solutions like the Content locking module to get overcome this nagging problem. But what if your content changes a lot by backend calls ?
On a big project I'm currently working on, Musescore.com (D6 to D8), members can upload their scores to the website. When their score is uploaded, the file is send to Amazon where it will be processed so you can play and listen to the music in your browser. Depending on the length of a score, the processing might take a couple of minutes before it's available. In the meantime, you can still edit the score because the user might want to update the title, body content, or add some new tags. While the edit form is open, the backend might be pinging back to our application notifying the score is now ready for playing and will update field values, thus saving the node. At this very moment, the changed time has been updated to the future, so when the user wants to save new values, Drupal will complain. This is just a simple example, in reality, the backend workers might be pinging a couple of times back on several occasions doing various operations and updating field values. And ironically, the user doesn't even have any permission to update one or more of these properties on the form itself. If you have ever uploaded a video to YouTube, you know that while your video is processing you can happily update your content and tags without any problem at all. That's what we want here too.
A native mobile application which can cache the data locally is a way to make content available offline. However, not everyone has the time and/or money to create a dedicated app, and frankly, it's not always an additional asset. What if browsers could work without network connection but still serve content: Application Cache and/or Service Workers to the rescue!
Only add the manifest attribute to all "offline" pages which are completely separate from "online pages", even though they might serve the same content. In other words, you create a sandboxed version of some content of your site which can live on its own. Another technique is a hidden iframe which loads a page which contains the html tag with the manifest attribute. You can embed this iframe on any page you like. This gives you the option to create a page where you link to as an opt-in to get a site offline. Both techniques give us full control and no side affects so that when network is available the site works normally.
Offline in the browser or on the homescreen
Go to the Offline homepage of Frontend United and wait until the 'The content is now available offline!' message appears, which means you just downloaded 672 kb of data - it is really really small, surprising no? Now switch off your network connection and reload the browser: still there! Click around and you'll be able to check the offline version at any time. If you're on a mobile device, the experience can be even sweeter: you can add this page to your homescreen, making it available as an 'app'. On iOS, you need to open the app once while still being connected to the network. We really do hope safari/iOS fixes this behavior since this is not necessary on Android. After that, turn off your network and launch the app again. Oh, and it works on a watch too if you have a browser on it. If that isn't cool, we don't know what else is! We have a little video to show you how it looks like. Watch (pun intended) and enjoy! Oh, in case we make changes to the pages, you will see a different notification telling you that the content has been updated - if your device has network of course.
We've created a new project on Drupal.org, called Offline App, available for Drupal 8. The project contains the necessary code and routes for generating the appcache, iframe, pages (nodes and views) and settings to manipulate the manifest content. 3 new regions are exposed in which you can place the content for offline use. Those regions are used in offline-app-page.html.twig - but any region is available if you want to customize. Two additional view modes are created for content types and the read more link can be made available in the 'Offline teaser' mode. Formatters are available for long texts to strip internal links and certain tags (e.g. embed and iframe) and for images that will make sure that 'Link to content' is pointing to the 'Offline path'. Last, but not least, an 'Offline' Views display is available for creating lists. We're still in the process in making everything even more flexible and less error-prone when configuring the application. However, the code that is currently available, is used as is on the Fronted United website right now.
This module does not pretend to be the ultimate solution for offline content, see it as an example to quickly expose a manifest containing URL's from an existing Drupal installation for an offline version of your website. Other Drupal projects are available trying to integrate with AppCache or Service workers, however, some are unsupported or in a very premature state, apart from https://www.drupal.org/project/pwa. Note that I've been in contact with Théodore already and we'll see how we combine our efforts for coming up with one single solution instead of having multiple ones.
What about service workers ?
Not all browsers support the API yet. Even though AppCache is marked deprecated, we wanted to make sure everyone could have the same offline experience. However, we'll start adding support for service workers soon using the same concept.
We're also planning to start experimenting with delivering personal content as well, since that's also possible, yet a little trickier.
This is not a post about caching for applications, but a different kind, the kind where people all over the world hide artifacts and you must search and log them. Welcome to the world of Geocaching!
I've been introduced to this recently and must admit I like the concept very much. It brings you to places you'll probably never end up otherwise, even in your own neighbourhood, and just recently while visiting Berlin. Anytime I see someone strolling around at the same spot for a while, I know what this person is doing now! You can also hide your own caches, so that's what I did. My first geocache called 'De dokwerker' has been published. So if you're ever in Gent (Belgium), go and find it! :)
Turning your smartphone into a hologram projector has become fairly popular nowadays, although it's technically called Pepper's ghost to create the illusion. Anyway, I had to try it myself too, right ? Building the pyramid isn't that hard and the first try-out is pretty cool to be honest.
So with that going fine, I opened up Blender to create my own animation just for fun. I took the Drupal 8 logo, ripped it apart and let it build itself up again. I quickly wrote an Android application that would just play 4 videos on a surface; and each video in a different rotation. The app is attached at the end if you want to try it out yourself (works well on Motorala, with Lollipop). If all goes well, I'll make it possible to select your own video and make the code public on GitHub. But for now, just enjoy the video. Or start building your own pyramid, it's really fun.
I've also created one with the Druplicon, based on on a model made by @berkes
Chosen is a jQuery plugin which makes select boxes more user-friendly. Currently, support is disabled on mobile devices for various reasons. Enabling the support requires a hack in the source code for now in the AbstractChosen.browser_is_supported function to return true when the userAgent finds Android or iPhone/iPad. You can download the patched version at the bottom (or detail) of the article. The current version is 1.1.0
My name is Kristof De Jaeger also known as swentel. I live in beautiful Gent, cofounded eps & kaas and currently trying to create an album, writing a play (done!) and a book. Besides that I hack on Drupal, Android, HTML 5 and iOS. Loving travel, art, books, music and Mpatshi.