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Alberto Mardegan

I just released PhotoTeleport 0.12, which includes the feature mentioned in the title of this blog post. Given that it took me some time to understand how this could work with Qt, I think it might be worth spending a couple of lines about how to implement it.

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Categories: english
Alberto Mardegan

Recently I've grown an interest to the indieweb: as big corporations are trying to dictate the way we live our digital life, I'm feeling the need to take a break from at least some of them and getting somehow more control over the technologies I use.

Some projects have been born which are very helpful with that (one above all: NextCloud), but there are also many older technologies which enable us to live the internet as a free distributed network with no owners: I'm referring here to protocols such as HTTP, IMAP, RSS, which I perceive to be under threat of being pushed aside in favor of newer, more convenient, but also more oppressive solutions.

Anyway. The indieweb community is promoting the empowerment of users, by teaching them how to regain control of their online presence: this pivots arund having one's own domain and use self-hosted or federated solutions as much as possible.

One of the lesser known technologies (yet widely used in the indieweb community) is webmentions: in simple terms, it's a way to reply to other people's blog posts by writing a reply in your own blog, and have it shown also on the original article you are replying to. The protocol behind this feature is an recommendation approved by the W3C, and it's actually one of the simplest protocol to implement. So, why not give it a try?

I already added support for comments in my blog (statically generated with Nikola) by deploying Isso, a self-hosted commenting system which can even run as a FastCGI application (hence, it can be deployed in a shared hosting with no support for long-running processes) — so I was looking for a solution to somehow convert webmentions into comments, in order hot to have to deal with two different commenting systems.

As expected, there was no ready solution for this; so I sat down and hacked up Bussator, a WSGI application which implements a webmention receiver and publishes the reply posts as Isso comments. The project is extensible, and Isso is only one of the possible commenting systems; sure, at the moment it's indeed the only one available, but there's no reason why a plugin for Static Man, Commento, Remark or others couldn't be written. I'll happily accept merge requests, don't be shy — or I can write it myself, if you convince me to (a nice Lego box would make me do anything

Categories: english
Alberto Mardegan

We live in strange times. People are so filled with hatred and prejudices that their brain becomes unable to parse the simplest sentences. I take this issue to heart, because it could happen to anyone — it has happened to me before (luckily, only in private online conversations), where an acquaintance of mine accused me of saying things I never said. And it happens to famous people all the time. Guys, just because you hate person X, you should not skip over parts of their speech or suppress context in order to make it look like they said something terrible or stupid, when they didn't.

Now it happend to Richard Stallman, with a whole wave of hateful people accusing him of saying something that he didn't say. Let's start with the VICE article, titled "Famed Computer Scientist Richard Stallman Described Epstein Victims As 'Entirely Willing'", which insists in quoting only two words out of Stallman's sentence:

Early in the thread, Stallman insists that the “most plausible scenario” is that Epstein’s underage victims were “entirely willing” while being trafficked.

Except that he didn't say that. Why not quote the whole sentence? It's not such a long sentence, really! Just follow the link to the source, which provides a complete excerpt of Stallman's words:

We can imagine many scenarios, but the most plausible scenario is that she presented herself to him as entirely willing. Assuming she was being coerced by Epstein, he would have had every reason to tell her to conceal that from most of his associates.

Now, English is not my native language, but I read it well enough to understand that “to present oneself as” and “to be” are different expressions having very different meanings (and, in most context, actually opposite ones!). You don't need to be Shakespeare to understand that. You only need to either stop hating or, if you really cannot help it, at least stop projecting your prejudices onto the people you hate. Hate makes you blind.

It's sad to see otherwise intelligent people take stupid decisions because of such misunderstandings.

I for one, stand in solidarity with Richard Stallman and with the English language.

(please note that this is not an endorsement of everything Stallman might have said in the past; I don't follow him that closely, and it may be that he also happened to say terrible things in this very thread. I'm only commenting this very specific issue, and I know that in this very specific issue he's being wrongly accused)

Categories: english
Alberto Mardegan

Migrating to a new Mastodon instance

2019-08-20 14:39 UTC  by  Alberto Mardegan
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The wonders of improvised Mastodon instances: one node disappears after an outage caused by a summer heatwave, leaving its users no way to migrate their data or to notify their followers.

After about one month of waiting for the node to come up or give some signals of life, I've decided to create a new account on another instance. If you use Mastodon and you were following me, please forgive me for the annoyance and follow me again here.

Categories: amicos
Alberto Mardegan

I was looking at TripAdvisor, some days ago. It's a very useful site, filled with user-generated advice and reviews, which has become almost a must for travellers. But I never like it when a private entity gets so much power over our lives (even if it's — currently — exercised in total fairness).

I would like to have a federated TripAdvisor-like network. I duckduckwent for a while, but I didn't find anything similar (if you know of some project of that kind, please let me know in the comments).

But thinking more about the issue, I realised that I probably wouldn't even bother to type my reviews into that site; I have a blog, so ideally I would like to have the option to write my review here, and then have the site import it. Technically, it could work with a webhook, or even a periodic check (real-time updates would not be a requirement here) over a URL I've linked to in my profile on that site. Then, in order for the posts to be imported, they would have to be entered in a standard format: maybe some keywords (or invisible HTML elements) could be used as markers for the content that need to be extracted from an otherwise ordinary blog post, or the relevant content could be replicated in a different format in the HTML headers (this, though, would require some additional work).

And while we are at it, why not extend this to other social networks? I use Mastodon, for example, and occasionally I send out a toot with a link to my latest blog post in there. But it would be much nicer if I could somehow set a special mark into my posts while composing them, to have them automatically tooted out on my account (this could probably be implemented as a standalone service, authorized to act on my Mastodon account — similarly to how the Mastodon-Twitter crossposter app works).

But I'm rather confident that I'm not the only one having this kind of needs, and that's why I'm writing this blog post: maybe someone out there has already found a solution, or has some more concrete ideas? If so, I'm all eyes!

Categories: english
Alberto Mardegan
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Categories: energia
Alberto Mardegan

Qbs and code coverage reports

2019-07-01 13:42 UTC  by  Alberto Mardegan
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You know that I'm not an early adopter. That's why it was only a couple of weeks ago when I decided to give Qbs a try, by using the good old Mappero (and its spin-off, Mappero Geotagger) as a test bench. Yes, I know that the Qt company is not going to maintain Qbs anymore in the future, but the little I knew about Qbs was enough to convince me that it's a project worth supporting. So, better late than never -- and hopefully the community (me included) will do a good job in keeping Qbs thriving.

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Categories: english
Alberto Mardegan

More than one year has passed since the initial announcement of my plan to investigate using a different backend for contact storage. If you want to get a better understanding of the plan, that mail is still a good read -- not much has changed since them, planning wise.

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Categories: english
Alberto Mardegan

A critical view on the blockchain

2019-04-24 19:59 UTC  by  Alberto Mardegan
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At the beginning of this month I participated to the foss-north conference, in Gothenburg, and took the stage to give a short presentation of the blockchain technology. Given that my talk was somehow critical of the blockchain (or rather, of the projects using it without due reason) I was prepared to receive a wave of negative remarks, assuming that all the hype surrounding this technology would have infected a good part of my audience as well. I was therefore positively surprised when several people came to me afterwords to express their appreciation for my speech, appreciation that now makes me confident enough to share the video of the presentation here too:

I want to publicly thank Johan Thelin and all the other foss-north staff and volunteers who organized such a successful conference. They also managed to get the video recordings out in a surprisingly short time. Indeed, the above video is taken from the foss-north YouTube channel, which I recommend you to visit as there were a lot of good talks at the conference; the topics were so varied, that I'm sure you'll find at least a couple of talks of your interest.

Categories: blockchain
Alberto Mardegan

Ubports at the LinuxPiter conference

2019-03-13 16:07 UTC  by  Alberto Mardegan
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Last November I was invited to talk at the LinuxPiter conference. I held a presentation of the Ubports project, to which I still contribute in my little spare time.

The video recording from the conference has finally been published:

(there's also a version in Russian)

There was not a big audience, to be honest, but those that were there expressed a lot of interest in the project.

Categories: english
Alberto Mardegan

Mappero: public source code, CLA, Qt5 port

2013-11-03 17:55 UTC  by  Alberto Mardegan
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Mappero has always been distributed under a GPL licence. However, since when I started selling Mappero Geotagger (which is built from the same source), I decided not to publish the source code in a public repository, but only to provide it to those who made an explicit request to obtain it.

I spent some time reconsidering the matter, and I've finally decided to let the source code live in a public repository. I also setup a mailing list for it. And indeed I welcome code contributions, however there's a small catch: a CLA. While Mappero is distributed under the GPLv3 licence, I request that all contributors send me an e-mail in which they give me the right to re-licence their contribution under any licence published by the Free Software Foundation.

Since I believe that the busiest time for my involvement with speculo has passed, I expect to be able to spend some more time developing Mappero. The qt5 port is more or less working, but most of the cool features are missing, so it's little more than a map viewer at the moment (Mappero Geotagger, however, is fully working under Qt5!).

Here you can see Mappero running on an Ubuntu Touch powered Nexus 4. Pinch zooming and GPS are not yet working, but I promise they'll be there in less than a week. Also I found a nasty bug which can cause the application to crash when downloading map tiles, and I'll fix it ASAP (I'm mentioning it just so that I won't be flooded with identical bug reports now :-) ).
Categories: english
Alberto Mardegan

speculo, or shared memory made easy

2013-11-02 15:41 UTC  by  Alberto Mardegan
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The last few months I've been dedicating most of my (very little) free time to a new project: speculo, a library which implements IPC (Inter-Process Communication) on top of shared memory. Since developers appreciate conciseness and minimalism, here's a description of speculo in a few bullet points:
  • written in C
  • POSIX (tested in Linux and FreeBSD)
  • small (~850 LOC)
  • well commented (~400 lines)
  • good test coverage
  • zerocopy
  • lockless
  • one writer, many readers
  • data is written and read in chunks of arbitrary size
  • a data chunk becomes visible to the readers as soon as the writer commits it
  • data chunks can have an expiration time
  • data chunks can be obsoleted by a newer copy
  • garbage collector
  • no file descriptors are permanently kept open
  • no change notification
But here I probably need to write some paragraphs to explain a couple of points.  Except for a few memory addresses which hold the state of the memory area and which are atomically updated and guarded with memory barriers, all the data written to the shared memory object is immutable. This in particular guarantees that readers have a consistent access to the data, which will not change under their eyes. Data chunks are only appended, which means that the shared memory object can only grow. However, data chunks can be marked as expired (if they have an expiration time associated with them) or obsoleted (if a new chunk is said to replace their contents), which means that not all of the data which is written in the SHM object is actually valid. The readers' functions know this, and skip over the invalid data.
At some point the garbage collector will kick in, when the conditions specified by the writer are met or when the SHM area is completely full. All the chunks which are still valid will be copied over to a new SHM object, and then the SHM objects will be atomically switched. Readers will be able to complete their ongoing reads, and transparently move on to the new SHM object as they request to read a new data chunk.
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Categories: D-Bus