Posts about programming (old posts, page 28)

2009-12-11 11:04

Making a unique application using python and DBUS

No, not unique in the sense "oh, this app is a special snowflake", but unique in the sense "you can only run one copy of this application".

I tried googling for it and I always found the same answer, "use dbus, try to own the name, if it exists already, then a copy is already running".

What I could not find is one working example of this, or at least not something conveniently labeled "here is how you do a unique application using dbus and python".

So, here is how you do a unique application using dbus and python:

Supposing your application is called uRSSus (mine is):

session_bus = dbus.SessionBus()
try:
    session_bus.get_object("org.urssus.service", "/uRSSus")
    # This is the second copy, make the first one show instead
    # TODO: implement
except dbus.DBusException: # No other copy running
    # This will 'take' the DBUS name
    name = dbus.service.BusName("org.urssus.service", bus=session_bus)
    # Now, start your app:
    window=MainWindow()
    object = UrssusServer(window,name)
    :
    :
    :
    etc, etc

And that's it. No, it's not hard, but since the DBUS docs seem to be... rather they seem almost not to be sometimes, every little bit may help.

2009-12-03 10:44

I knew not doing it was smarter, or how HTML5 and Qt do my work for me.

I wrote a while ago a RSS program called uRSSus. I expect I am the only user of it because it has some problems (all of them my fault ;-) but I really like it.

For a while now I have wanted it to have podcast support. The thing is... that always seemed like a lot of work. Sure, using phonon I can create an audio player and everything, but...

I am using a HTML widget to display the posts, so I would have to find a way to add the audio player to the UI and ... too much work.

So, today I woke up and thought... wait a minute... Qt's HTML widget is based on Webkit. And Webkit supports HTML5. And HTML5 has an "audio" tag.

So, if I fixed uRSSus to fetch the enclosure links, and added them in the database, and then added this to the post template:

<?py for enclosure in  post.enclosures: ?>
  <audio autobuffer="Yes" controls="controls" src=#{enclosure.href}></audio><br>
<?py #end ?>

Wouldn't that actually work? Well, yeah!

urssus26

So there you have it, I was right not to implement it, because the easiest way is to let Qt do it ;-)

2009-11-24 13:08

My first public python code works!

No, this is not a post announcing I just wrote my first public python code. This is a post about my first public python code... from 1996!

In 1996, the soon-to-be-here year of the Linux desktop was fueled by one of the marquee open source applications of the time: LyX.

LyX was (is) a sort of word processor where you wrote and generated LaTeX which then produced whatever you used to print. But I am digressing: LyX was cool because it used one of the first good free graphical toolkits: XForms.

Ok, it was not really free, because you couldn't distribute patches.

And it was not all that good either, but we were comparing it with Motif, so it was much more free and much better than that monstrosity.

BTW: The latest release of XForms is from august of 2009.

At the time, a 25-year-old me was in love with Python 1.3. Here's how I described it:

Python 1.3
It's a beautiful ,free, language. Get it from ftp://ftp.python.org http://www.python.org

Yes, Python 1.3. So, I wanted to use this C GUI toolkit used in this cool app, and this neat language I was learning and use them at the same time.

I ran (not walked) to my faithful Slackware 3.0 ELF in my 486DX2 PC and started hacking. In a weekend or so I had a working binding.

I even started writing the holy grail of desktop applications, a GUI version of Pine, using python and its IMAP module (python mailer, or PyM):

//ralsina.me/static/im1.jpg
//ralsina.me/static/im2.jpg

I released version 0.1 alpha in 1996, May 13 ... and a few months later Matthias Ettrich started KDE and I found Qt and never thought about XForms again.

Until this month.

For reasons that don't matter, I mentioned PyM in the PyAr mailing list the other day, and ... well, would pyxforms still work?

Why, pretty much, yeah!

I got the pyxforms-0.1-alpha sources from somewhere in the internet, installed XForms 1.0.92sp2 (yes, the latest release, from three months ago), of course I already had python 2.6.4 installed, added a setup.py, edited 10 lines of code and...

im1

Yes, it works. You can get this 0.2 version (codename "Cthulhu was here") here just 13 years after 0.1.

No, I don't understand the weird rounded corners, or why the cursor looks weird and old when it's inside the window.

It's a REALLY small and fast toolkit, though.

Honestly, is it useful for ayone? Almost certainly not. Am I amazed something I wrote in 1996 still works? Oh, yeah I am.

2009-11-17 21:45

I'll be speaking in Mar Del Plata

I will be doing a brand-new never seen introduction to PyQt programming at the "Jornadas de Software Libre y Open Source" in Mar del Plata tomorrow or the next day.

More info at http://softwarelibre.mdp.utn.edu.ar/

If you mention this blog and ask nicely, you get a can of cheap national beer tomorrow night (limit: 2 cans ;-)

2009-10-23 23:27

24-hour app #1: Die Schere, a video editor

I have long known that application development is an arduous process. I have also long suspected one of the reasons it's arduous is the developer. I should be more specific, I am one of the reasons.

That's because I don't know what I am doing, and I don't mean that in the "I am a lame programmer" sense (even if that's also true somewhat), but in the sense that I literally don't know what the app should look like, or what its feature set should be.

So, I have decided to embark on a series of experiments I will call 24-hour apps.

Here are the rules:

  • I shall create a neat application, stable, useful, usable and decent-looking.
  • I shall do it in no more than 24 hours. After that time, it should be at least good enough for a preview release, if not a beta.
  • Those 24 hours can be split in two or three sessions
  • Time spent doing icons, docs, etc, counts.
  • All development shall be public (I am using github)
  • I must have a use for the resulting application, and it should be at least an adequate solution for that problem.

So, what's the first project? I call it Die Schere (The Scissors in german) and it's a video editor.

It's not a kdenlive replacement, it's just the video editor I wish I had when I needed to glue a piece of one video with a piece of another.

In the old, pre-digital world, that was done using a cutter and scotch tape. I want Die Schere to be as useful and comprehensible as that was, but useful for clumsy people like myself.

Here is a video after today's session, which lasted 8 hours:

The basic functions are there, even if lots of work is still needed.

  • You can load clips to work with them
  • You can cut clips (like using a cutter!)
  • You can choose the cut points interactively or by editing a time
  • You can arrange them (like using scotch tape!)
  • You can generate the output video

As a backend it's using mencoder, but there's no reason it shouldn't work with ffmpeg or melt if someone writes 20 lines of code.

2009-10-19 11:30

rst2pdf 0.12.2: minor bugfix release

I just uploaded rst2pdf 0.12.2 to http://rst2pdf.googlecode.com Rst2pdf is a tool to generate PDF files directly from restructured text sources via reportlab.

This release fixes a major bug (incompatibility with reportlab 2.1) as well as several minor ones and adds a minor feature (better styling of list items).

For more details, you can see the changelog

2009-10-09 23:12

rst2pdf 0.12 released!

It's my pleasure to announce the release of rst2pdf version 0.12, available at http://code.google.com/p/rst2pdf/downloads/list

Rst2pdf is a tool to generate PDF files directly from restructured text sources via reportlab.

Rst2pdf aims to support the full restructured text feature set, and is very close to that goal, while also including some of the more experimental features, like a source code directive with syntax highlighting and math notation support with LaTeX-like syntax.

It supports embedding arbitrary fonts, both True Type and PS Type 1, both raster and vector images (including SVG and PDF), page transition effects, multiple, flexible page layouts, cascading styles, and much, much more.

This version includes many bugfixes and MANY new features compared to the previous 0.11 version, including but not limited to better styling, integration with sphinx, a very raw, preliminar graphical frontend called bookrest, kerning support (via wordaxe), and a much more powerful table implementation.

In fact, this release has so much new code it needs testers! I would consider it beta quality, and may (probably will) have some rough spots.

You can find more information about rst2pdf in its home page ( http://rst2pdf.googlecode.com), and ask anything you want in the rst2pdf-discuss mailing list (http://groups.google.com/group/rst2pdf-discuss)

A list of improvements and changes in this version is just too long, but is available at the changelog

I hope you enjoy this program!


In other news, Google just found me two nice things related to rst2pdf:

  1. A tutorial to use sphinx and rst2pdf for japanese texts: http://d.hatena.ne.jp/MiCHiLU/20091009/1255065687
  2. It looks like a rst2pdf 0.11 binary for windows is shipped by pythonxy here: http://code.google.com/p/pythonxy/downloads/detail?name=rst2pdf-0.11_py26.exe I will link to that!

I love when people do things like these :-)

Contents © 2000-2019 Roberto Alsina