In the Mood

well, I failed at blagging each day of the User Experience hackfest, but mostly because of the sheer amount of discussions, designs and work done.

during the first common session on monday we all decided to split off into four groups:

  • file management
  • window and application management
  • widgets/gadgets/applets
  • effects and animations

I decided to work on effects and animations, along with Eve, Neil, Matthew and Andreas1. the wiki page of our group lists most of the stuff that came up in the group discussions and brain storming2. when not in the effects and animations group I was hanging around with the window and application management guys. since Tomas, Robert and Matthew have been working on a Clutter-based compositor for Metacity, I decided to give it a spin and work on some of the “animation tenets” that came up during the hackfest — like showing the direction of the workspace switching and provide a visual cue to the user that the windows are not going away forever, and are just being moved in another area of the screen. I know that Compiz is probably going to have these kind of effects some ten levels deep in the configuration manager, but the configuration UI always makes me want to carve my eyes out with a melon spoon while being bludgeoned to death, and the defaults are usually so bad that I develop seasickness after 15 minutes of continuous use — hence, the usage of the Clutter-powered Metacity.

the other groups did an awesome job as well: a lot of the ideas floating around will require hard work and time in order to be implemented, but they all contain a refreshing view of the desktop and challenge some of the fundamental tenets of the user interaction, based on the feedback from users and designers — and especially without resorting to something completely new or alien that will require years to get right for developers and to adjust the workflow for users, or just announcing new frameworks with the usual jingoistic tones common to open and closed software projects alike.

  1. who’s totally getting married — just as vuntz is expecting a baby []
  2. or idea showering []

Flying Teapot

final checks and the usual ohmygodwhycan’tIfindanything mode before I take the flight to Boston for the User Experience hackfest organized by Owen, Federico and Vincent. Neil and I will be talking about Clutter, what it does, and what it can do to enhance the user experience on a modern desktop.

then, it’s Boston Summit time! it’s going to be my first summit, but given the past editions and the people attending I just know it’s going to be awesome.

see you in Boston!

Sincerest Forms of Flattery

tidy: they say that imitation is the sincerest form of flattery:


the actual amount of code is quite small, and it’s already available in Tidy.

challenges: Luca dared me into making a Clutter-based coverflow-like plugin for Rhythmbox, but it was Iain that picked the challenge up and wrote some basic code for it. I, on the other hand, don’t like coverflow for browsing my music collection, so I finally decided to write something for the Eye of GNOME — a Ken Burns effect slide show. it’s not at all finished, and if nobody picks it up, I’ll try and do my best to have it ready for GNOME 2.24, if EOG maintainers want it, of course. it’s not the best display of Clutter features — except the animation framework — but if you have hardware acceleration it will make slideshows look a lot nicer.

json-glib: this weekend I released the first developers snapshot of JSON-GLib 0.6; the API is stable, the test suite is rocking and this release finally fixes the last bit needed for full RFC 4627 compliance (Unicode escaping). I’m probably going to release 0.6.0 in a couple of weeks.

Good Intentions/2

gtk+: I’ve been working again on the RecentManager and in trunk you’ll see some new stuff, namely:

  • use GIO to determine the MIME type of a URI, on every platform supported
  • use the file monitoring API to avoid polling the storage file
  • add a GtkSettings property for clamping the recently used resources list to a 30 days limit

more stuff I’d like to add is:

  • small parser changes to GBookmarkFile, to reflect changes in the spec
  • bulk addition, for applications storing multiple items when quitting
  • new API needed to follow the usability review in bug 349541
  • moving the RecentItem icon code to GIO, and add API to extract the thumbnail

twitter: I’ve been using Twitter a lot in the past two weeks; it’s nice, it makes it easier to copy and paste a quote or a thought, and the 160 characters limit is an interesting challenge. As it’s been ages since I last wrote an application1, I decided to start writing a Twitter reader/writer — using GTK+, Clutter and Tidy; without much thinking, I opened gvim and started writing code in C2 — so, the obvious thing that happened was that I ended up writing a library yet again in order to use Twitter’s web API. luckily for me, libsoup has now a really nice API to work with; all you need is GET and POST to their RESTful API, retrieve the result, parse it through JSON-GLib, hide everything inside a new GObject and you have a wrapper around a web service. the application, you say? oh, I was sure I forgot something. well, it’s coming along — it just needs some work still.

  1. lately all I’ve been doing was writing libraries []
  2. hey, that’s what I do for a living, it’s hard to switch off; plus, I could reuse some of the platform libraries []

Rhyme the rhyme well

Jason, it’s not just the canvas: writing a simple 2D canvas is trivial — that’s why a lot of applications end up writing their own homegrown one.

The hard bits are the animation framework, the event handling and down to the integration with the existing platform. A generic canvas is hard, and you probably don’t want it to be developed inside gtk+ (not even for 3.0) — just like Cairo is not developed inside gtk+ but supersedes part of gtk+’s API.

As for 3D acceleration — I’m obviously biased here, so everyone should take what I write with a graintruckload of salt — but I maintain my view that if GNOME (and Linux) started heavily pushing towards more support for OpenGL, then we could get more market share1, more visibility and thus more leverage to make the currently closed source drivers more open. Intel understood this; AMD is now getting it; I’m pretty sure nVidia will — or they will be simply pushed into irrelevance by the open drivers developed by the community2. Let’s face it: other platforms and toolkits are pushing heavily on hardware accelerated 3D effects.

Let’s start aggressively work to get the platform into the XXI century.

update@2008-10-11T12:21+0100 — just as a sidenote: if you have a good CPU, Mesa and software rendering, Clutter will work. It won’t be fast for some operations (like scaling and, possibly, rotating), but in that case you should probably start contributing to Mesa to make it fast (there’s a lot of room for improvement).

  1. think Compiz, and how many more users it brought home just with a spinning cube []
  2. unless you are a gamer, and need the very best card as soon as it’s out just to play Crisis []

Time to Build

Claudio did some interesting profiling (and patching) of the BookmarkFile implementation in GLib — so kudos to him and Felix.

one thing that he noted is:

However, I still have the feeling that letting ~\.recently-used.xbel grow without control is very, very wrong. In my laptop, this file is about 5MB, which accounts for ca. 9000 files(!).

this is very true, but I feel it needs some context. when I first wrote the RecentManager code I only had the EggRecent implementation as a comparison; the old EggRecentModel had an hardcoded limit of 500 items stored per file. limiting on the number, instead of the age of an item inside a recently used file list did not feel right, so I thought about hardcoding a limit of 30 days — but stopped short of doing it because I realized that hardcoding limits at the toolkit level was not a good idea:

  • application developers will not be able to change it in any way
  • users will not be able to change it in any way
  • system administrators will not be able to change it in any way

just to give a few examples: while I was still writing the RecentManager inside libegg, Alex Graveley was writing Gimmie. Gimmie had1 a local document and application history that could allow you to go back in time of months; had I hardcoded a limit, the Gimmie developers would have needed a new implementation, defeating the purpose of shipping the RecentManager inside GTK+ to cut down the amount of code replication.

hardcoding limits is also something that makes it hard, or even impossible, for users and administrators to control; I might want a 30 days limit, but other might want a 90 days, or a 7 days — or even a 1 day limit. some might not even want to save the recently used files at all (think kiosks).

I don’t believe in strictly hardcoding policies in the toolkit; providing fallbacks is perfectly fine, but preventing people from actually having different settings is akin to convince everyone that you’re right and they’re wrong.

still, this doesn’t solve the problem at hand, that is the current lack of policy.

what I’d like to see is some process taking care of purging the old entries, using some key inside gconf, at the end of the session; gnome-settings-daemon would fit the role for GNOME, and other desktop environments using GTK+ could provide the same functionality2. after all, gnome-settings-daemon should already flush the thumbnails cache — it wouldn’t be much of a complication.

  1. and might still have — I haven’t checked it for a while now []
  2. if you’re not using a GTK+ based desktop environment you’re either using the same spec used by GTK+ so you can provide your own way of purging the cache, or you’re using another way to store the recently used files, so the size of the file saved/read by the RecentManager will not bubble out of control so easily — and you can still flush it yourself []


last post of the Berlin Hackfest series, written on the last minutes of day 5

today was “wrap up” day. we got together in the room used for the presentations and summed up all our work during the various sessions of the week. it turned out that the amount of work, even though not reflected by the wiki page, was really enormous; the introspection guys worked a lot and now that they have received a lot of input, they are going to rework things and kick ass even more. apparently, Behdad decided that I would tackle the GL integration inside GDK — which, of course, I’d really like to do; the GL integration, and a GDK wrapper for the GLX_texture_from_pixmap (and the equivalent call for the other platforms) would obviously be the primary way to integrate Cairo 2D high quality drawing and GL 3D and hardware acceleration in a simple way. and this is a step forward the implementation of a scene graph inside GTK+.

in the meantime, I’m — as Ryan would put it — deeply recursing. it all started on tuesday, when I decided to start hacking on a real application with Vala using all the bits and pieces a modern GTK+ application requires: GtkUIManager, about dialogs, command-line switches. the application was supposedly going to read the new GTest framework reports, and allow comparing of multiple runs in a fast way. this, in turn, led to some bugs filed against Vala GTK+ bindings. working around these issues, I also found out that the libxml-2.0 bindings in Vala — which I need to parse the GTest report XML — require a lot of pointers usage and are, in general, quite sub-obtimal, due to the very C oriented API. while investigating on a substitute, I found out XmlReader — the cursor-based XML traversal API that .Net and other high-level languages implement1. Thus, today at a coffe shop2 I started hacking very quickly on a rough implementation of a XmlReader GObject class which, as of at this moment works quite nicely:

  XmlReader *reader = xml_reader_new ();
  GError *error = NULL;

  if (xml_reader_load_from_file (reader, "book.xml", &error))
    g_error ("Unable to parse book.xml: %s", error->message);

  xml_reader_read_start_element (reader, "book-info");

  xml_reader_read_start_element (reader, "author");
  author = g_strdup (xml_reader_get_element_value (reader));
  xml_reader_read_end_element (reader);

  xml_reader_read_start_element (reader, "title");
  title = g_strdup (xml_reader_get_element_value (reader));
  xml_reader_read_end_element (reader);

  xml_reader_read_end_element (reader);

  g_print ("The author of %s is %s\\n", title, author);

  g_free (title);
  g_free (author);
  g_object_unref (reader);

and you’re done. at this moment, I’m cleaning it up and adding the gtk-doc API reference to the build3. I’m probably going to add the generic read() method, so that:

  while (xml_reader_read (reader))

will work as expected. it’s, as usual, code replication — but I’m going to need it anyway, so it’s good code replication.

  1. Even libxml-2.0 implements it, even though it suffers from the same issues of its DOM API, and it’s still not GObject-based []
  2. Behdad is right: a coffee shop without any Internet connectivity makes wonders with your productivity levels []
  3. When I write new libraries, I usually stub out the API and document it at the same time; now I started to add the GTest units before I even implement the API []


second and third day of the hackfest, edited on day five

on tuesday, Behdad and I started working on OpenGL integration inside GTK+. as stated multiple times on the Bugzilla entry, what we both would like is a Cairo-like integration of GL inside the available drawing systems in GTK+. in short: not a specialized widget like GtkGLArea, which would make it difficult — or plainly impossible without jumping through a long series of hoops. in flames. tied. and blindfolded — to integrate GL inside existsing projects; and not the incredible API dump that GtkGLExt is.

the design we mostly agreed on was a shared object inside GTK+, containing the GL context abstraction object, and two simple calls to delimit the drawing code, wait for vblank and swap the GL buffers. plus, an easy to use wrapper around the texture_from_pixmap extension, to allow drawing with cairo on a Pixmap and then have it pushed into the GL pipeline.

Carl arrived on wednesday, and partecipated at the scene graph BoF we held. the BoF itself was pretty straightforward: we read the slides that Havoc sent on the mailing list and discussed the various points. we all agreed on a lot of points — and we tried to define the problem space more deeply1. being there, I could bring to the table my experience in the past two years2 with the design and implementation of Clutter. some of the attendees were already familiar with it — something very satisfying — and I could expand some points in Havoc’s slides about Clutter that have been recently fixed or are going to be fixed in this cycle. the biggest point is that the scene graph should integrate with Cairo, in order to allow applications and people to gently merge both the 2D drawing of surfaces into a full 3D environment; I’ll leave to Carl to explain the Cairo side, because he’s obviously better at this than I am. :-)

the operative result of the scene graph discussion was that Clutter emerged as an already powerful and established solution for this problem space, and given that it already nicely integrates with GTK+, we can work towards the common goal of making it “the GTK+ canvas”, outside the actual library so that it can grow unrestrained and experiment in new directions.

  1. We did not always succeed in this, but the issue at hand is quite large and it’s understandable []
  2. It’s really two years? holy crap! The time really flew… []

Helm, set a course… for love

a GNOME cruise? I already have the theme song…

GNOME-Love Boat, love exciting and new,
Come aboard, we're expecting you.

The GNOME-Love Boat soon will be making another release,
The GNOME-Love Boat promises something for everyone.

Set a course for adventure,
Your box's on a new romance.

And GNOME-Love
Won't hurt anymore,
It's an open source,
On a userfriendly shore.

it's GNOME-Love
Welcome aboard it's GNOME-love