Month: May 2007

Look at those cute little devices! All doing Push E-mail with a Tinymail based E-mail client. All at the same time! A Nokia N800, a Nokia 770, my Feisty desktop and a OLPC. Next on the list .. the iLiad and Openmoko?

Video demo, Youtube version

Just like with the OLPC build I have fixed the builds for GPE and the builds for Maemo with older distributions like Mistral and Gregale (the rootstraps in Scratchbox that’ll compile for your Nokia 770). The build for Maemo’s Bora rootstrap (for the Nokia N800) and the one for GNOME desktops were of course already functional.

On all these devices and platforms (N800, 770, OLPC, GPE) you can now out of the box compile yourself a Tinymail demo user interface with the latest features. I will bring a few such devices with me at LinuxTag. Although very unfinished, I can demo a recent development version of Modest running on my N800 too. Which, by the way, is becoming more and more useful as fine dog food. The GPE and GPEPhone folks told me they will bring some GPE devices too (it wont take long before we’ll have the Tinymail demo ui running on all of them).

~# apt-cache search empathy
~#

While preparing my OLPC laptop for LinuxTag, I noticed some glitches in the OLPC build of Tinymail. These have now all been fixed and the demo-ui will run and work as-is. You will of course need to edit your $HOME/.xinitrc to override the “exec sugar” with an “exec xterm”, start matchbox-windowmanager and then the Tinymail demoui binary.

You can also try to use the development console which is accessible when typing the [alt]+[=] key combination. But I found it quite hard to make the application usable this way (it gets pushed to the back by the Sugar window manager or something).

The demoui is indeed not suitable nor has already been made suitable as a typical Sugar application. I would of course welcome attempts at this.

To compile do this on any typical x86 computer:

./autogen.sh --with-platform=olpc --prefix=/opt/tinymail-olpc
make && sudo make install

Now tar /opt/tinymail-olpc and untar it into the same directory on your device’s root filesystem.

After deployment follow these instructions for creating an account and in the xterm just launch /opt/tinymail-olpc/bin/demoui.

It’ll ask you for the password each time. I haven’t yet found which password storage API is going to be used on the laptop, so the platform specific implementation is just going to call a GtkDialog box that will each time ask you for the password.

Hey Benjamin, good that you mention “creativity” and Mozilla in the same blog post.

I’m sure the people at Mozilla and the distributions have a slightly better solution to this current situation of having to do funny things in your configure.ac to figure absurd things out. Things like having to search which of the Mozilla development packages are available: a developer can choose between nss.pc, mozilla-nss.pc, firefox-nss.pc and xulrunner-nss.pc. I’m sure there are a few more too. Like nspr.pc, mozilla-nspr.pc, firefox-nspr.pc and xulrunner-nspr. And like xpcom.pc, mozilla-xpcom.pc, firefox-xpcom.pc and xulrunner-xpcom.pc. And of course also gtkmozembed.pc, mozilla-gtkmozembed.pc, firefox-gtkmozembed.pc and xulrunner-gtkmozembed. Just to make sure our configure.acs will be bloated like crap just for figuring out what the system actually has installed for those libraries.

I wonder what the use of pkg-config is if everybody starts doing that, Mozilla team?

For some fun reason they also decided to have -rpath in some of their “Libs: ” lines too. Making it totally fun for the maintainer to figure out why certain symbols can’t be found in a lot of circumstances (like when you used to have a function that was static, and now became a non-static, those rpath tricks will trick your linker into trying to use the installed libraries that are located in the prefix location if you once did a “make install”).

Awesome things if you don’t know that and expect sanity from pkg-config configuration files.

Tinymail’s camel-lite is still being developed extensively. While making changes, though, I made sure that the API that once got implemented by some existing custom Camel providers more or less stays the same. Myself, I added support for a bunch of Lemonade -and related features and improved the bandwidth consumption a lot in the IMAP provider, while adding support for summaries in the POP provider. These changes included a huge amount of bug fixing and other improvements too, of course. Especially on memory consumption. The majority of the changes, though, happened in the implementation, not so much Camel’s API.

Although an existing Camel provider usually needs a lot of bandwidth improvements before being acceptable for usage for Tinymail’s target audience (I looked at a lot of them, they do), you can very quickly make any such existing provider work with Tinymail. It comes down to rewriting one method: the CamelFolderSummary::message_info_load one. Noting that even the CamelFolderSummary::message_info_save stays the same. The load one needs to be rewritten because it’s in this method that in stead of read()-ing the data from the FILE*, you’ll have to implement getting the pointers from the mmap(). At entry of the method you’ll get the offset where the data that you wrote to the file using CamelFolderSummary::message_info_save starts. You are responsible for moving that offset further (for example += it).

The file I/O API of Camel has been modified to always do data padding, which is necessary for some architectures with mmap(), and to always end strings with a ‘\0’, which is of course important when pointing to offsets and using the pointer as a char pointer C string. You’ll always do it right if you use the standard Camel file I/O API.

I created a trac wiki page on the Tinymail documentation describing how to do this. It has some examples too. On bandwidth it’s of course vital to understand that a lot Tinymail based E-mail clients will be used on flaky networks like GPRS. Dealing with being offline (being very good at synchronization, while trusting that the connection will die at totally unexeptected locations in your code) and dealing well with timeout situations is of course very important. Compression and SSL are vital too.

Yes me shall.

Most E-mail clients want some sort of queuing mechanism. Not surprisingly every developer has the desire to implement his own queue thing. This by itself is not a big problem if only they create a wrapper for their queue that implements my interface.

After that, I have some guarantees about that implementation that I can use to develop higher level functionality. Guarantees like the availability of a specific certain API. I need to fine tune the Design By Contract clauses for this little bit more, but these queue interfaces are well documented and by-contract defined (or going to be even more strict).

A few months ago I announced this AsyncWorker thing. A normal person would maybe simply require that library and assume that all developers will bend over and let me put my AsyncWorker … where the sun doesn’t shine? That’s not Tinymail’s concept though: flexibility and being adaptive to Change is.

Although I added a libtinymail-asyncworker library that implements a default queue implementation, you can implement your own. I believe a lot E-mail clients will actually want to do that: maybe they want very tight integration with and a lot of control over their queue? I can imagine that.

The trick, though, is to build a bunch of standard queue functionalities yet make it possible that they all share the same top level queue. For that, I used the decorator design pattern. All the default queues, except the asyncworker one, implement the queue interface and will aggregate one too. Usually that will be a base queue implementation, like the asyncworker one, but it can also be any of the queues (nested situations, why not).

I’m starting with a queue that will in the background get full messages, one that will act right after a full message is received and one for sending messages.

The one that will act will for example (depending on your mua’s policy) share a top level queue with the one that gets full messages in the background. It will have tasks with a higher priority though: acting can for example mean “to display that message in the message view”. While perhaps messages are being queued for retrieval? While Push-Email events cause get-message tasks to get added to the queue?

The thing is, Push-Email right now will only get the summary info of a message. But if that Push E-mailed E-mail contains a calendar item, then you’ll need to fetch that if your application wants to do something interesting with the calendar content. Like playing a different ring-tone if it’s a calendar item coming from your boss? Your application can in that case use a queue that will act with something, right after the queued task received the full message.

You guys remember that Push E-mail events can be caught using a TnyFolderObserver, right? An implementation for your folder observer’s update method could be “put a task on the act queue that will add the calendar item in the E-mail to the device’s calendar” once the task finished receiving the message. That is already possible with Tinymail today, yes.

I’m writing documentation right now. A bunch of it is already available, but the best page to start is this one: TnyQueue and TnyQueueTask. I need to adapt my gtk-doc scripts to enable adding the API to the API reference manual of Tinymail. All of the API is already documented fully, though. The script just isn’t yet adding it to the gtk-doc build.

Note: that some other E-mail clients don’t have this amount of flexibility for queuing just means that they are too limited for mobile applications. Mobile applications need to cause events to wake the person up. I believe that Push E-mail is just the beginning of all this. Future will tell, of course.

And Tinymail will be ready for that.

It has a very interesting item in the Applications section!

I wrote this a few times already, but documentation is something that needs to be repeated over and over again. Until it bores you so hard that you will do it just so that the idiot who keeps repeating about it, would stop. Exactly.

For that reason I keep repeating it so often to myself, that I myself will get bored of hearing myself repeating that it’s extremely important. In the end it’s all about self-inducting psychological tricks, indeed. Forcing yourself, forcing myself.

Today I started cross-referencing Tinymail’s manuals and documentation. I for example created links to the API reference manual and started pages with some minimal documentation about types being mentioned in a manual.

My opinion is that any software is pure vaporware until it’s fully documented for at least its target audience. This means that Tinymail will be vaporware until its documentation is more than perfect (as my goal for the project is to get it better than the current best). Undocumented software by definition sucks in my opinion. Doing free software isn’t a valid reason for having no documentation.

Unit testing, though, has been slipping a little bit (luckily not completely). I’m hoping to see GNOME Buildbot becoming ready and integrated with GMAE so that this will psychologically force me and other contributors into making sure that it will never slip again.

Last few days together with Murray I have been working on for example the status infrastructure in the Tinymail framework.

We simplified how to internally deal with status callbacks, we made sure that they’ll happen in the right order and wont happen after the final callback happened.

I created two video demos this time. A first one is for most people. It will show you how much status you can get out of the framework in case you will create a client on top of Tinymail. The video shows you the demo user interface with its ‘glamorous’ :-) progress bar (which shows a lot more status than “some other” E-mail client’s progress user interface).

User video demo, Rescaled one on youtube

A second is a technical video demo for people who want to learn how Tinymail works. Although it’s mentioned, it doesn’t really try to illustrate how to use the API to for example update a progress bar and show a status bar. The technical video demo shows you how Tinymail deals with launching status callbacks internally.

Technical video demo

I did the technical one with a normal video camera. That’s why the quality isn’t ideal. After doing that one, while not being satisfied, I discovered xvidcap for making the user video demo. Its quality is excellent. Therefore I recommend xvidcap for screencasting and I’m probably going to use this tool more often indeed. Finally I use Cinelerra to glue audio to it, cut and paste the “eums”, “swallow” and “grrmm”s away.

It looks like Alexander is correctly making it possible in GVFS to have a GInputStream, a GOutputStream and a GSeekable that has nothing to do with a GFile. It’s therefore possible that while it being a major API and ABI breakage, I will remove TnyStream from Tinymail’s API and adopt GVFS’s types for this in a second Tinymail version. I’m indeed already planning those API breakages ahead of time.

I’ll clarify why I think this is important.

In Tinymail a stream can have any source and any destination. For example a TCP stream that represents a connection with a IMAP server. A converting stream that gets as input the encoded MIME part of a message and outputs it decoded. A file stream that gets as input for example a decoded MIME part and as output a file.

Making any assumption about streams like that a stream always either originates from or results in a file, would make any of above situations impossible. The API for a ‘stream’ type therefore shouldn’t assume a lot of the rest of the virtual file system layer or assume the availability of for example a file descriptor (although I’m perfectly okay with ‘the VFS layer’ as location for a stream – API). In the end I hope to share that stream API with for example the implementers of future HTML render components. Then I can ‘stream’ the decoded MIME part to that HTML renderer. That the HTML renderer component will ask for ‘stream instances’ to the inline embedded images (in case the HTML E-mail has attached images being used in the document).

The thing is, that efficient mobile E-mail clients will not first download the entire E-mail to for example /tmp, in stead they will actually stream the MIME part on-demand straight from the IMAP server to a converting stream that decodes the MIME part and then stream that output straight to the HTML renderer. In the process it’s possible that I’ll put a ‘locally caching stream’ somewhere in between, yes.

This makes it possible to not cache attachments on a device with few disk resources, yet to do make them available when the user is online, yet to have it perfectly transparent IF caching attachments locally is to be done and IF it was done in the past. ‘Streaming’ doesn’t necessarily have anything to do with files, yet often does (like when caching certain streamable things, like files, locally).

I hope this is being kept in mind while designing GVFS, though it looks like the current API indeed allows this (so that’s excellent!). I’m definitely looking forward to having GVFS. It’s great to finally see Java and .NET’s streaming APIs being put in place. Very exciting to soon have this.