Sincerest Forms of Flattery

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

TidyFingerToggle

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 application ((lately all I’ve been doing was writing libraries)), 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 C ((hey, that’s what I do for a living, it’s hard to switch off; plus, I could reuse some of the platform libraries)) — 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.

Good Intentions

unique: this morning I released version 0.9.4 of libunique, everyone (least) favourite library for writing single instance applications. it’s mostly a bug fixing release, and since I’ve decided to release 1.0.0 soon, this is also the first release candidate for the 1.0 milestone. I’ve also moved the git repository to github, so you can clone it with:

  git clone git://github.com/ebassi/unique.git

I plan to add back a new x11 backend for the 1.2 release, targeting small embedded environments were D-Bus might not be an option, and support for a --replace command line switch. after that, I’ll try to get the same functionalities into GLib/GTK+, as part of the future “desktop platform” module.

Clutter: I did a 0.6.2 release of both the core and the Python bindings, but things are afoot in trunk. we recently landed the multi-stage branch, which means that you’ll be able to create multiple windows and multiple GtkClutterEmbed widgets per application with Clutter 0.8. we’re also about to land the massive COGL rewrite that Ivan Leben of ShivaVG fame did — which will make the GL and GLES abstraction more powerful, will reduce the code duplication and in general will rock your world. Neil Roberts has been doing loads of work on the native Win32 backend: he not only made it possible to run Clutter on WGL, but also use the GtkClutterEmbed on Windows natively:

GtkClutter on win32

now, only the Quartz backend is missing the party — hint hint, nudge nudge.

OpenedHand: we’re hiring!

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

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 had ((and might still have — I haven’t checked it for a while now)) 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 functionality ((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)). after all, gnome-settings-daemon should already flush the thumbnails cache — it wouldn’t be much of a complication.

Berlin/Final

some final thoughts on the Hackfest: it has been a great opportunity for discussing with all the usual suspects and more, and on a very high bandwidth channel — unlike IRC or the mailing list. definitely, an experience that must be repeated next year, because the discussions we had and the work we started will keep us all busy at least until GUADEC — and from then on, towards a very bright future for GTK+ and the whole GNOME project.

thanks to Mathias and Openismus for being the local organization; thanks to Tim, Kris and the entire Imendio, for moderating the whole panels; thanks to Vincent and the GNOME Foundation, and obviously all the sponsors, for helping out in organizing and funding this gathering of hackers; and thanks to everyone that made these five days an incredible experience for me: you all really rock the GNOME community.

Berlin/5

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 implement ((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)). Thus, today at a coffe shop ((Behdad is right: a coffee shop without any Internet connectivity makes wonders with your productivity levels)) 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 build ((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)). 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.

Berlin/3

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 deeply ((We did not always succeed in this, but the issue at hand is quite large and it’s understandable)). being there, I could bring to the table my experience in the past two years ((It’s really two years? holy crap! The time really flew…)) 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.

Berlin/1

day two of the gtk+ hackfest.

yesterday was devoted to the Imendio vision of a better toolkit, and how to get out of the hole we dug for ourselves with the current API/ABI contract – but others have written about it better than I could possibly do.

today was introspection day; Johan Dahlin showed the current state of the GObject introspection code by using a Vala widget, subclassing a GtkDrawingArea, from a Perl script — which was beyond cool. kudos to everyone that has been working on it.

today it’s also six years since the gtk+ 2.0.0 release, so happy birthday gtk+ 2.x!