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29 Jun 2018 : Going QML-Live #

In my spare time I've been developing a QT app called GetiPlay. It's a simple app that allows you to download audio and video from BBC iPlayer, for use on Sailfish OS phones. The traditional approach on Linux devices would be to use get_iplayer in a console, but for all of the progress that's been made on mobile devices in the last decade, console use still sucks. Given I spend so much time listening to or watching BBC content, slapping a simple UI over the command line get_iplayer was an obvious thing to do.

The app has been developing nicely, using the QT Creator for C++ and the UI written in QML. Historically I've not been a fan of QML, but as I grow more familiar with it, it's been growing on me. For all of the things that I find weird about it, it really does give great performance and helps build a consistent UI, as well as promoting loose coupling between the UI and underlying functional logic.

A big downside to QML is that there's no preview, so the development process follows a consistent cycle: adjust code, build code, deploy code, test, repeat. The build and deploy steps are loooong. This impacts things in three serious ways: it makes development slow, it makes me sleepy, and it incentivises against making minor tweaks or experimentation.

Is It Worth the Time?
 

Nevertheless, there's always a trade-off between configuring and learning new technologies, and just getting things done using those you're already using. The ever-relevant XKCD has more than one pertinent comics covering this topic.

 
Automation

The UI for GetiPlay is straightforward, so I was quite content to use this lengthy, but (crucially) working approach until yesterday. What prompted me to change was a feature request that needed some more subtle UI work, with animated transitions between elements that I knew would take a couple of hundred cycles round that development loop to get right. Doing the maths using Randall Munroe's automation matrix, I needed to find a more efficient approach.

So this morning I started out using QML Live. This is a pretty simple tool with an unnecessarily bulky UI that nevertheless does a great job of making the QML design approach more efficient. You build and run the app as usual, then any QML changes are directly copied over to the device (or emulator) and appear in the app immediately. Previously a build cycle took between 40 and 100 seconds. Now it's too quick to notice: less than a second.

QT Creator IDE and QML-Live

Using a quick back of the envelope calculation, I'll perform a UI tweak that would previously have required a rebuilt around 20 times a day, but probably only every-other day, so let's say 10 times a day for the next six months. So (10 * 365 * 0.5) / (60 * 24) = 1.27 days I can save. I spent about half a day configuring everything properly, so that leaves a saving of 0.77 days, or 18 hours. Not bad!

QML-Live certainly isn't perfect, but it's simple, neat and has made me far more likely to try out interesting and experimental UI designs. Time configuring it is time well spent, even if that extra 18 hours is just about the same amount of time I wasted dithering over the last two days!

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12 Jun 2018 : GetiPlay now actually plays, too #
For some time now I've been meaning to add a proper media player to GetiPlay. Why, you may well ask, bother to do this when Sailfish already has a perfectly good media player built in? Well, there are two reasons. First, for TV and radio programmes, one of the most important controls you can have is 'jump back a few seconds'. I need this when I'm watching something and get interrupted, or miss an important bit of the narrative, or whatever. It's such a useful button, it's worth writing a completely new media player for. Second, it's just far more seamless to have it all in one application.

So I finally got to adding it in. Here's the video player screen.
 

The QT framework really does make it easy to add media like this. It still took a good few days to code up of course, but it'd be a lot quicker for someone who knew what they were doing.

I'm also quite proud of the audio player, with the same, super-useful '10 seconds back' button. It also stays playing no matter where you move to in the app. Here it is, showing the controls at the bottom of the screen.
 


If you'd like to get these new features in your copy of GetiPlay, just download the latest version from OpenRepos, grab yourself the source from GitHub, or check out the GetiPlay page.
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6 Jun 2018 : Huge GetiPlay release 0.3-1 #
I'm really pleased to release version 0.3-1 of GetiPlay, the unofficial interface for accessing BBC iPlayer stuff on Sailfish OS. This latest version is a huge update compared to previous releases, with a completely new tab-based UI and a lovely download queue so you can download multiple programmes without interruption.

Immediate info about every one of the thousands and thousands of TV and radio programmes is also now just a tap away.

Install yourself a copy from OpenRepos, grab the MIT-licensed source from GitHub or visit the GetiPlay page on this site.
 
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30 May 2018 : My last teaching at Cambridge #
In 2016 I did my first teaching at Cambridge, and now I've just finished what is likely to be my last ever supervision at Cambridge. The course was Part IB security (the second course out of three the students study), and as with all of the Cambridge courses, the structure is lectures and small-group supervisions (tutorials with two or three students). This term I was teaching students from St John's and Peterhouse colleges. My experience this term was made particularly good by a set of diligent and engaged students. In large classes, if there are too many questions it can become overwhelming, but with small groups there's much more scope to cover questions more deeply. Security covers the breadth of topics, from those that are quite straightforward to those that are much more conceptual, and all of the students this year were on the ball both asking very sensible questions, and answering questions for each other. That makes for a much more enjoyable teaching experience (and if you're reading this: good job; I hope you enjoyed the supervisions too).

The Computer Lab, Cambridge

So, I didn't think I'd say this, but I'll miss this teaching. I've had the privilege to experience teaching across multiple HE institutions in the UK (Oxford, Birmingham, Liverpool John Moores, Cambridge). Living up to the high teaching standards of my colleagues and what the students' rightfully demand has been hard across all of these, but it's been great motivation and inspiration at the same time.

And, having grown up in a household of teachers, and after twenty years in the business, I think I've now seen enough of a spectrum to understand both the importance of teaching, but also its limitations. The attitude and aptitude of students plays such a crucial role in their learning. When you only get to interact with students in one small slice of their overall curriculum, there's a limit to how much you can affect this. That's not to downplay the importance of encouraging students in the right way, but rather to emphasise that teaching is a group activity. Students need good teachers across the board, and also need to bring an appetite.

It's great to teach good, enthusiastic students, and to see them grasp ideas as they're going along. But my ultimate conclusion is a rather selfish one: the best way to learn a practical subject is to do it; the best way to learn a theoretical subject is to teach it.
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8 May 2018 : Finally addressing gitweb's gitosis #

My life seems to move in cycles. Back in February 2014 I set up git on my home server to host bare repositories for my personal dev projects. Up until then I'd been using Subversion on the same machine, and since most of my projects are personal this worked fine. Inevitably git became a sensible shift to make, so I set up gitolite for administration and with the Web front-end served up using gitweb.

Unfortunately, back then I couldn't get access control for the Web frond-end to synchronise with gitolite. It's been a thorn ever since, and left me avoiding my own server in favour of others. There were two parts to the reason for this. First the inability to host truly private projects wsa an issue. I often start projects, such as research papers where I host the LaTeX source on git, in private but then want to make them public later, for example when the paper has been published. Second, I was just unhappy that I couldn't set things up the way I wanted. It was important for me that the access control of the Web front end should be managed through the same config approach as used by gitolate for the git repositories themselves. Anything else just seemed backwards.

Well, I've suddenly found myself with a bit of time to look at it, and it turned out to be far easier than I'd realised. With a few global configuration changes and some edits to the repository config, it's now working as it should.

So, this isn't intended as a tutorial, but in case anyone else is suffering from the same mismatched configuration approach between gitweb and gitolite, here's a summary of how I found to set things up in a coherent way.

First, the gitweb configuration. On the server git is set up with its own user (called 'git') and with the repositories stored in the project root folder /srv/git/repositories. The gitweb configuration file is /etc/gitweb.conf. In this file, I had to add the following lines:

$projects_list = $projectroot . "/../projects.list";
$strict_export = 1;

The first tells gitweb that the Web interface should only list the project shown in the /srv/git/projects.list file. The second tells gitweb not to allow access to any sub-project that's not listed, even if someone knows (or can guess) the direct URL for accessing it.

However, that projects.list file has to be populated somehow. For this, I had to edit the gitolite config file at /srv/git/.gitolite.rc. This was already set up mostly correctly (probably with info I put in it four years ago), apart from the following line, which I had to add:

$GL_GITCONFIG_KEYS = "gitweb.owner|gitweb.description|gitweb.category";

This tells gitolite that any of these three keys can be validly added to the overall gitolote configuration files, for them to be propagated on to the repositories. The three values are used to display owner, description and category in the Web interface served by gitweb. However, even more importantly, any project that appears in the gitolite file with one of these variables, will also be added to the projects.list file automatically.

That's great, because it means I can now add entries to my gitolite.conf that look like this:

repo    myproject
        RW+     =   flypig
        R       =   @all
        R       =   gitweb
        config gitweb.owner = flypig
        config gitweb.description = "A project which is publicly accessible"
        config gitweb.category = "Public stuff"

When these changes are pushed to the gitolite-conf repository, hey-presto! gitolite will automatically add the project to the projects.list file, and the project will be accessible through the Web interface. Remove the last four lines, and the project will go dark, hidden from external access.

It's a small change, but I'm really pleased that it's finally working properly after such a long time and I can get back to developing stuff using tools set up just the way I like them.

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