Who Wrote GTK4

GTK 4 has been a colossal, multi-year development endeavor that started in October 2016 and ended in December 2020. Now that the 4.0 release is finally out, it’s time to look back to the incredible amount of work done by hundreds of contributors over these four years.

Back in 2016 we were definitely a bit optimistic on the time table, and thought we would be able to release 4.0 in three years, by the end of 2019. The plan was to start by changing the rendering pipeline of GTK, by moving it to a retained graph of operations that could be submitted to the GPU, as opposed to the immediate mode rendering that we had since the very beginning of the toolkit, and which survived two major API cycles—first by abstracting Xlib drawing commands, and then by moving to Cairo operations. Of course, we also knew we wanted to improve other sub-systems, like input and the windowing system API, to move away from X11-isms and towards a design more in line with the requirements of Wayland (and other windowing systems). What we got, after all was said and done, is a deep redesign of the internals of the toolkit, as well as a different programming model that favors more delegation through ancillary objects, and fewer leaky abstractions and deep type hierarchies; additionally, we pared down the exposed internals, to ensure that the toolkit, and the applications using it, will be more maintainable in the future. The downside is that GTK is less of a “meta toolkit”, whose internal state can be poked at from the outside while expecting to work across multiple releases; that approach was, in the long term, unsustainable given the available resources, and left us unable to optimise or improve the internals of GTK, to the detriment of every user.

We don’t expect the next major development cycle to take this much time, but you know as they say: no plan of operations extends with any certainty beyond the first contact with the main hostile force. The important thing, though, is that we still see potential for improvement; and while we want to celebrate the release of GTK4, as well as everyone who contributed to it, we also want to communicate that the plan outlined in 2016 is still very much in effect. We already started collecting items for a GTK5 development cycle in our GitLab project page, and we plan to have more discussions with various stakeholders for future work in that direction.

Some statistics

Starting from commit 4cce6104 on October 5th, 2016:

  • Total commits: 16852
  • Developers: 256
  • Employers: 10
  • Lines added: 1053492, removed: 1053542 (delta: -50)

The most interesting thing is that, for all that work, we ended up with a total of 50 lines of code removed from the existing code base, which includes tests and documentation.

Per year breakdown

Year Developers Commits Lines added Lines removed Delta
2016 50 1422 64014 152103 -88089
2017 84 3446 186024 166198 19826
2018 111 2332 129726 140526 -10800
2019 85 3244 200476 207623 -7147
2020 109 6384 470907 386761 84206

We only had a couple of months in 2016, and the largest effort between October and December was the removal of the deprecated API, and various changes to cope with the renaming from GTK3 to GTK4. Nevertheless, GSK initially landed in November/December. On November 21st, GTK 3.89.1 was released, the first development snapshot of the new GTK 4 API.

In 2017, GSK had with multiple iterations over its API: new render nodes were added to implement CSS drawing primitives, and widgets were moved to the GtkSnapshot API from the old Cairo rendering primitives. Additionally, the new clipboard API was introduced, with a stream-based implementation. On March 31st, GTK 3.90.0 was released, followed by 3.92.0 in October.

In 2018, things seem to slow down, but mostly because we moved to GitLab. Suddenly, we had access to a CI pipeline and merge requests, and we became progressively more confident in our development process; lots of work happened in development branches, especially large refactorings, like the renaming of GdkWindow to GdkSurface; the move to GtkGesture objects and the removal of per-widget event signals; or making leaf classes not derivable. GTK 3.94.0 was released in June.

In 2019, development pace picked up once again:

  • widget transformations
  • layout managers
  • constraint layouts
  • no more GtkMenu
  • scope object for GtkBuilder
  • GtkText widget
  • GtkNative and GtkRoot interfaces
  • per-widget actions
  • simplified GdkSurface sub-types

Plus, of course, lots of performance and functionality improvements in the rendering pipeline. GTK 3.96.0 was released in May.

Finally, we arrive at 2020:

  • new drag and drop API, based on event controllers
  • new macOS backend in GDK, replacing the old Quartz one
  • new accessibility API, dropping ATK
  • no more GtkContainer
  • no more GtkRadioButton
  • simplified GdkDevice API
  • new keyboard shortcuts API
  • new expressions and filter models
  • new model-based list and tree widgets

GTK 3.98.0 was released in February; and, finally, 3.99.0 in July, as the first true beta towards GTK 4.0.

 

Developers

Top 20 by commit
Matthias Clasen 6519 (38.7%)
Timm Bäder 3229 (19.2%)
Benjamin Otte 2596 (15.4%)
Emmanuele Bassi 1094 (6.0%)
Carlos Garnacho 494 (2.9%)
Daniel Boles 383 (2.3%)
Alexander Larsson 313 (1.9%)
Jonas Ådahl 167 (1.0%)
Chun-wei Fan 162 (1.0%)
Christian Hergert 158 (0.9%)
Jakub Steiner 134 (0.8%)
Piotr Drąg 132 (0.8%)
Руслан Ижбулатов 120 (0.7%)
Alexander Mikhaylenko 93 (0.6%)
Rico Tzschichholz 78 (0.5%)
nana-4 66 (0.4%)
Christoph Reiter 62 (0.4%)
Tim-Philipp Müller 60 (0.4%)
Mohammed Sadiq 57 (0.3%)
Olivier Fourdan 42 (0.2%)
Top 20 by changes
Matthias Clasen 620248 (36.8%)
Benjamin Otte 466996 (27.7%)
Timm Bäder 187516 (11.1%)
Emmanuele Bassi 165354 (9.8%)
Alexander Larsson 53065 (3.1%)
Carlos Garnacho 27227 (1.6%)
Christian Hergert 26964 (1.6%)
Руслан Ижбулатов 21760 (1.3%)
Jakub Steiner 18388 (1.1%)
Jonas Ådahl 12824 (0.8%)
Chun-wei Fan 12518 (0.7%)
Daniel Boles 12371 (0.7%)
Lapo Calamandrei 9995 (0.6%)
Christoph Reiter 8391 (0.5%)
Alexander Mikhaylenko 4936 (0.3%)
Tim-Philipp Müller 3932 (0.2%)
Rico Tzschichholz 3108 (0.2%)
William Hua 2900 (0.2%)
Jason Francis 1908 (0.1%)
Peter Bloomfield 1727 (0.1%)

As usual, Matthias towers over every other contributor, both in terms of sheer number of commits and in terms of code changes.

Employers

By commit
Red Hat 13706 (81.3%)
(Unknown) 1185 (7.0%)
GNOME Foundation 1095 (6.5%)
GNOME 571 (3.4%)
Purism 93 (0.6%)
Canonical 84 (0.5%)
Centricular 75 (0.4%)
Endless 20 (0.1%)
Collabora 14 (0.1%)
Intel 6 (0.0%)
Novell 3 (0.0%)
By changes
Red Hat 1415771 (84.0%)
GNOME Foundation 165355 (9.8%)
(Unknown) 58220 (3.5%)
GNOME 33442 (2.0%)
Purism 4936 (0.3%)
Centricular 4205 (0.2%)
Canonical 3347 (0.2%)
Novell 336 (0.0%)
Intel 222 (0.0%)
Collabora 208 (0.0%)
Endless 121 (0.0%)
By contributor
(Unknown) 199 (72.4%)
GNOME 32 (11.6%)
Red Hat 22 (8.0%)
Endless 6 (2.2%)
Collabora 4 (1.5%)
Centricular 3 (1.1%)
Novell 3 (1.1%)
GNOME Foundation 2 (0.7%)
Canonical 2 (0.7%)
Intel 1 (0.4%)
Purism 1 (0.4%)

While Red Hat employees affect the most changes, we still have a very large number of contributors from the community—both using their GNOME email address and using their work address even when contributing on a personal level. We also have multiple contributors from various companies in the GNOME and free software at large ecosystems, signalling a healthy community around the project.

Comparing numbers with GTK3 is a bit more tricky:

  • the GTK 2 → 3 development phase only took about a year and change, instead of four years
  • we were still using the old GNOME infrastructure, which meant fewer, larger patches, and a higher barrier to contribution in the form of Bugzilla

Nevertheless, the amount of contributors more than doubled compared to 2011, with almost three times the amount of unaffiliated contributors.

¹ – Paid staff of the GNOME Foundation.

² – Contributors using a gnome.org email address with no clear employment status.

GTK Hackfest 2020 — Roadmap and accessibility

Between January 28th and January 31st, the GTK team held what’s now the third hackfest in Brussels.

The main topics of the hackfest were:

  • the schedule for the next development snapshot of GTK4
  • the missing features blocking the release of GTK 4.0
  • the current state of the accessibility support in the toolkit

The first two items occupied the most of the first two days of the hackfest; you can read the GTK 3.98 release announcement for what we’ve been working on for the past 300 days since the 3.96 release. The missing features are:

  • Event controllers for keyboard shortcuts
  • Movable popovers on Wayland
  • Row-recycling list and grid views
  • Animation API

and all of them are being worked on in topic branches. The keyboard shortcuts branch has recently been rebased, and it’s in the process of being documented and cleaned up; the movable popovers is also being reviewed after a few iterations. The last two remaining branches are fairly sizeable, and will require some more iterations to get them right—with the animations API currently being mostly a prototype.

The final topic of the hackfest was the largest, and was a discussion long overdue.

GTK’s accessibility support was added as part of the GTK 2.0 release by the Sun Accessibility Team; it depends on the abstract data types provided by ATK (the Accessibility Tool Kit), which are then implemented concretely in GTK classes like GtkWidgetAccessible, or GtkEntryAccessible. Each widget has an “accessible” object associated to it, which is either automatically created by GTK, or can be provided by application code when subclassing a GTK widget. Non-widget types can also have accessible objects associated to them—the most notable case is the set of cell renderers for tree views and combo boxes. Underneath it all, sits AT-SPI, a protocol that is used by AT—Accessible Technologies, like a screen reader—to consume the data provided by applications. Typically, ATs will use a library like libatspi to deal with the protocol itself.

The main issues with the existing stack are:

  • there’s a lot of indirection caused by the existence of ATK; any new feature or bug fix needs to be defined inside ATK and then implemented into GTK and libatspi
  • ATK was written in a very different environment, and while it has seen a few deprecations, it shows its age in the assumptions it makes—like global coordinate spaces—and in its design
  • there’s a certain overlap between AT requirements and requirements for GUI testing that end up creating friction in the API design
  • the stack has fell in disrepair since the Sun accessibility team was disbanded; most of the ongoing work is still pretty much happening in the AT space (like Orca) and in web browsers
  • the entire stack was written when CORBA was a thing, and then ported to DBus in time for GNOME3; the protocol, though, is not really efficient and requires lots of roundtrips to move around small amounts of data, instead of having bulk operations and notifications

The last point is also the reason why we need a separate accessibility bus in order to avoid spamming the session bus, and making everything slower as soon as the accessibility support is enabled. A separate bus means that we need to poke an additional hole in any sandbox, and still lets everything that connects to the accessibility bus potentially snoop into what happens in every application.

Finally, GTK only supports accessibility on Linux; there is no support for macOS or Windows, which means applications written in GTK and ported to other platforms are not accessible to ATs there. As we expose ATK in our API, adding support for accessibility features on other platforms would require bridging ATK, creating further complexity.

As we want to redesign and update the accessibility features in GTK4, we need to understand what are the requirements for existing consumers of the accessibility stack, and what kind of use cases we need to target. For that, we asked Hypra, a company dedicated to the development of accessible solutions based on free and open source software, to help us.

Hypra developers are familiar with GNOME, and have been working on the Linux accessibility stack. Their clients cover a wide gamut of accessibility users, so they are in the best position to describe what kind of ATs are in actual use on a day to day basis.

There are a wide range of tools and functionality that have to be provided by different layers of the stack, from the toolkit to the compositor; application developers must also have access to the tools necessary to provide proper support to ATs, as they have a much better idea of what their applications should look and behave than the toolkit.

Over the course of two days we have identified a plan for moving forward:

  • drop ATK from the stack, and have GTK talk the AT-SPI protocol directly; this is similar to what Qt does from the toolkit side, and it makes it easier to both expand and verify eventual protocol changes
  • clean up the AT-SPI protocol itself, updating it where needed when it comes to using DBus more efficiently
  • drop the global accessibility bus, and have ATs negotiate a peer-to-peer connection to each application
  • make ATs ask the compositor to gather global state, like key shortcuts, instead of talking to applications that would then have to ask the windowing system—if that’s possible—or return invalid data when it isn’t
  • decouple GUI testing from accessibility
  • write widget and application authoring guides for application developers, and provide validation tools that can be used as part of the build and CI process to check if UI elements have the correct accessible description and links

There are more information available on the wiki for the notes and the roadmap, and we have already scheduled an additional check point meeting for this summer.

There’s a lot of work to be done, but we have now a much clearer idea of the scope and deliverables for such a redesign. If you want to help making things happen faster, feel free to join the effort; you can also make a donation to the GNOME Foundation.

The GTK team would like to thank the GNOME Foundation for the sponsorship for the venue and the attendees, and the fine folks at Hypra for joining the hackfest and explaining use cases and the current state of the accessibility stack, as well as helping out on the development side.

GTK BoF at Guadec

As every year, we had a GTK BoF at Guadec in Thessaloniki. This year, we had a pretty good turnout — everybody was interested in GTK4 plans.

But since Emmanuele was busy in the morning, we started the discussion with some other topics.

GLib

We collected a few suggestions for useful GLib additions from the room.

  • API for OS information (basically, the data that is in /etc/os-release). This seemed uncontrolversial; Robert is going to implement it
  • An ordered map. This is implemented ad-hoc in many places by combining a hash table with a list or array.  There seemed to be agreement that it would be worthwhile to provide this in GLib, if somebody does the work to propose an API

The discussion of ordered maps also touched on generic container interfaces; Philipp described how that could be done, see details here.

Still on the topic of containers, Alex described a problem with transfer annotations. We discussed various ideas, but there may not be a perfect solution.

Matthias pointed out that there is still some Unicode data in Pango. We briefly discussed how nice it would be to have an agreed-on, mmappable binary format for Unicode data, so that everybody could share it. Short of that, moving the last bits of data to GLib was uncontroversial.

Dark mode

Since the “dark mode” BoF joined us, we switched to discussing dark mode next. There was a more discussion of this topic in the vendor theme BoF the next day; the GTK discussion focused on technical details of how to implement dark mode.

There are various options:

  • Add extra metadata to theme index files to mark themes as dark
  • Add a “dark-theme-name” setting and treat dark and light themes as independent
  • Keep the existing convention of appending “-dark” to theme names to find the dark variant of a theme

The pragmatic solution of keeping the existing convention seemed to have support in the room. Matthias started exploring some application support APIs here.

GTK

Eventually we swiched to talking about the state of and progress towards GTK4. The high-level summary is that there is still a list of  features that need to be completed for GTK4:

  • A scalable list view that recycles row widgets. This includes a broader switch to using list models in more places. To make it complete, it should also include a grid view using the technologies. Benjamin is working on this
  • Infrastructure and APIs for animations. This will be similar to the way animations work in CSS, and part of the work is to port not just our existing CSS animation support, but also stack switching animations, the revealer, progress bars and spinners to the new framework. Emmanuele is working on this.
  • Complete the menu/popover rework. Some people tried the new popover menubar. The feedback was that we should probably go back to nesting submenus, at least for menubars, and push forward with dropping menus, since some of the ways in which menus are special (such as keep-up triangles, scrolling) are hard to keep working (or keep working well). Matthias is getting back to working on this after Guadec.
  • Shortcuts – replace mnemonics, accelerators, and key bindings with event controllers. There is a fairly complete branch with code and APIs that several people have worked on; help with reviewing and testing it would be appreciated.
  • The new Drag-and-Drop API needs to be completed.

The good news is that this list is fairly short and has names next to most items. The bad news is that each item is a considerable amount of work. Therefore, it is not a good idea to promise a tight timeline towards the 4.0 release before we have all of them merged. Thus, the following is tentative, but (we hope) somewhat realistic:

  • another GTK 3.9x snapshot before the end of this year
  • a feature-complete 3.99 release around the same time as GNOME 3.36 in spring 2020
  • a 4.0 release around the same time as GNOME 3.38 in fall  2020

Inevitably, we also discussed other things that would be nice to have. None of these are on the GTK4 roadmap; but if somebody shows up to do the work, they can happen:

  • A “widget repository” or “hig” library in order to not overload GTK with too specific or experimental widgets
  • A “UI designer” widget. This could live in a separate library as well
  • Better support for split headerbars and state transitions

We also discussed things outside GTK proper that will keep applications from porting to GTK4. This includes commonly used libraries such as GtkSourceView, vte and webkitgtk, which all will need GTK4 ports before applications that depend on them can be ported. Some of this work is already underway; but any help in this area is appreciated!

Another potential blocker for GTK4 porting is platform support. The GL renderer works well on Linux; the Vulkan renderer needs some fixups. On Windows we currently use cairo fallback, which may be good enough for 4.0. Alternatively, we could merge existing work for using the GL renderer with ANGLE. The situation is less pleasant on OS X, where we don’t have a working backend; if you want to help us here, the first still would be to adapt the GDK backend to changes in GDK.

Hacking time

In the afternoon, the room drifted from discussion to hacking, and various GTK-related works-in-progress could be spotted on peoples laptops: work to speed up GtkBuilder template loading, nested popover menus, a half-finished GtkSourceView port.

You will hopefully see these (and others) in GTK master soon.

Testing Discourse for GTK

For the past 20 years or so, GTK used IRC and mailing lists for discussions related to the project. Over the years, use of email for communication has declined, and the overhead of maintaining the infrastructure has increased; sending email to hundreds or thousands of people has become increasingly indistinguishable from spam, in the eyes of service providers, and GNOME had to try and ask for exceptions—which are not easy to get, and are quite easy to be revoked. On top of that, the infrastructure in use for managing mailing lists is quite old and crumbly, and it’s unnecessarily split into various sub-categories that make following discussions harder than necessary.

After discussions among the GTK team, with the GNOME infrastructure maintainers, and with the GTK community at large, we decided to start a trial run of Discourse as a replacement for mailing lists, first and foremost, and as a way to provide an official location for the GTK community to discuss the development of, and with, GTK—as well as the rest of the core GNOME platform: GLib, Pango, GdkPixbuf, etc.

You can find the Discourse instance on discourse.gnome.org. On it, you can use the Platform and Core categories for discussions about the core GNOME platform; you can use the appropriate tags for your topics, and subscribe to the ones you’re interested in.

We’re planning to move some of the pages on the wiki to Discourse as well, especially the ones where we expect feedback from the community.

We’re still working on how to migrate users of the various mailing lists related to GTK, in order to close the lists and have a single venue instead of splitting the community; in the meantime, if you’re subscribed to one or more of these lists:

  • gtk-devel-list
  • gtk-app-devel-list
  • gtk-list
  • gtk-i18n-list

then you may want to have a look at Discourse, and join the discussions there.

Report from the GTK hackfest in Brussels

Thanks to the GNOME Foundation, various GTK developers were able to meet in Brussels right after FOSDEM, for one of our yearly hackfests.

The main topics of the hackfest were:

  • recap the work that landed into the master branch in the past 6-12 months, in order to have everyone on the same page
  • discuss the features still in flight in separate branches, assess their state of completion, and identify blockers
  • figure out what are the blockers for the first release of GTK 4.0

Hackfests allow us to have this kind of discussions with a large bandwidth at our disposal, compared to online communication channels, so they are very important for the project.

You can see the full agenda on the wiki, and we’ll make sure to write articles on the biggest items on it.

The largest items of the discussion were the introduction of new list models and list/grid view widgets; a unified key handling API; the decoupling of layout management policies from containers, and the introduction of constraint layout management; the possibility of merging widgets from libhandy, to allow for writing applications responsive to form factor changes; the switch to a purely declarative menu description API, and the removal of public menu widgets; adding 2D and 3D transformations to GtkWidget; implementing an animation API that applications can consume.

  • list models and list/grid widgets — we’d really like to retire GtkTreeView and GtkIconView, but the existing replacements, GtkListBox and GtkFlowBox, are not performant enough when scaling to very large and dynamic data sets. We need better data storage types, that can be composed to perform operations such as mapping, filtering, and sorting, but can also avoid iterating over all the elements when sizing and drawing widgets. Benjamin Otte already added various models to GTK, and is working on a list and a grid view widgets that can efficiently display their contents. Benjamin and other GNOME application developers are in the process of identifying various stakeholders for  a separate hackfest specifically for gathering more requirements and getting feedback on the new API.
  • unified key handling API — now that we moved all our pointer and touch input handling away from events and towards gestures, we want to do the same for key handling, like key bindings, mnemonics, and accelerators. The overall design is based on triggering actions, and allow introspection of all the “shortcuts” currently available to the GTK inspector, for ease of debugging. There is a development branch already available.
  • layout managers — in GTK 3, layout is imposed by containers on their children; we want to be able to decouple that from widgets and move it into a separate delegate objects hierarchy. Layout managers allow us to reduce the complexity of writing new widgets; they keep the layout code in a separate, non-derivable type; and they allow us to simplify the toolkit internals to the point that we might even make GtkWidget and instantiable type in the future. Layout managers are the first step towards adding constraint-based layout management to GTK, which do away with nesting boxes to create complex UIs. There is a development branch already available. For more information on constraint layouts, you can see the Emeus experimental library for GTK 3.
  • merging widgets from libhandy — Adrien Plazas gave an overview of what’s currently provided by libhandy, and what would be useful to have straight from GTK4 in the future. We discussed reactive layouts, and the ability express sizing with percentages, as well as possibly using constraints to get similar results.
  • declarative menus — GTK has iterated over different menus API over the years; from building menus out of widgets, to GtkUIManager, to GtkBuilder, to GMenu; we also moved to declaring the behaviour of pop up menus, in order to have the windowing system display them more accurately without exposing global coordinates. There’s a lot of overlap, but no clear winner, mostly because we still allow using widgets to build application menus and context menus. Fully switching to declarative style menus, adding new API to make them more expressive, and making GtkMenu and friends private implementations for the toolkit, would allow us to get things like being able to inspect all menus, even out of process; menus manipulable by plugin systems without necessarily creating widgets and keeping track of them; avoiding positioning bugs. There is a full strawman proposal available on the wiki, and Matthias Clasen is working on switching context menus to GMenu in a development branch.
  • widget transformations — Sadly, Timm Bädert couldn’t make it to the hackfest, but we’ve been reviewing his development branch that adds 2D and 3D transformations to GTK widgets, and we’re very excited about it.
  • animations — one last thing we’d like to land for GTK4 is an animation framework for GTK widgets to replace the current generic “frame tick callback”. The model for it is the Clutter explicit animation API, which in turn was based on Core Animation and CSS3 transitions. This work is still in the design phase, but you can expect development branches for it to land soon.

Aside from the big topics, we also discussed various smaller ones:

  • improving performance and memory use; we want to expose the SysProf counters during the frame clock phases, so we can easily identify problems.
  • improving the test suite, especially when it comes to reporting failures; right now, we have to go through the CI failure log, but we’d like to publish proper reports using the GitLab CI infrastructure
  • replacing child properties with real GObject properties on ancillary objects, especially for layout managers; would make documentation, introspection, and usage clearer.
  • finishing the drag and drop rework, to get a more modern API.
  • adding a top-level interface for “window-like” objects—such as windows, dialogs, popovers, menus/popups—useful for establishing common behaviour, and removing hacks and complexity in GtkWindow.

And, finally, yes: we did remove the “plus” from GTK. 😉

A report from the Guadec GTK+ BoF

The GTK+ team had a full day planning session during the BoF days at Guadec, and we had a full room, including representatives from several downstreams, not just GNOME.

We had a pretty packed agenda, too.

GTK+ 3

We started out by reviewing the GTK+ 3 plans that we’ve outlined earlier.

In addition to what was mentioned there, we also plan to backport the new event controllers, to make porting to GTK+ 4 easier. We will also add meson build support to help with Windows builds.

The 3.24 releases will effectively be a continuation of the 3.22 branch and should be entirely safe to put out as stable updates in distributions.

We plan to release GTK+ 3.24.0 in time for GNOME 3.30.

GTK+ 4 leftovers

The bulk of the day was taken up by GTK+ 4 discussion. We’ve reviewed the list of leftover tasks on the roadmap:

  • Finish DND: Gestures on the GTK+ level, local shortcuts
  • Introduce GtkToplevel and cleanly support popovers
  • Add transformations
  • Create a shortcuts event controller to replace key bindings
  • Port GtkTextView to render nodes
  • Profile the cairo backend, make sure its performance is on par with GTK+ 3
  • Port various dependent libraries:
    • vte
    • webkit
    • libchamplain
    • gtk-vnc
    • gtk-spice

Most of these tasks have names next to them, but if you want to help with any of these tasks, by all means, contact us!

Noticeably absent from this list are a few things that were on the roadmap before:

  • Constraint-based layout (emeus)
  • Shader compiler and application provided shaders
  • Designer support

All of these can still happen if merge requests appear, but we don’t think that we should block on them. They can be developed externally to GTK+ 4, and become GTK+ 5 material.

GTK+ backends

We spent some time evaluating the state of GDK backends in GTK+ master.

The Windows backend is in OK shape. We have several people who help with maintenance and feature development for it, meson makes building it a lot easier, and we have ci for it.

The Quartz backend is in a much worse state. It has not been kept in buildable shape, nobody is providing fixes or feature development for it, and we don’t have ci. We had a macbook offered that could be used for ci, and it was suggested that we could use travis ci for the OS X.

GTK+ timeline

We spent a long time on this, and did not reach a 100% consensus, but it seems realistic to aim for a GTK+ 4 release in spring of 2019, if we keep making good progress on the outstanding leftovers.

When we release GTK+ 3.96, we will also announce a date for GTK+ 4.0. We hope to be able commit to release before GNOME 3.32, so GNOME application developers can switch their master branches to GTK+ 4 without worrying about whether that will disrupt other development for 3.32.

Application porting

We really want feedback from application ports at this point. But we are in a bit of a difficult position, since we can’t plausibly claim to be done with major API work until the GtkToplevel and shortcuts controller work is done.

Our recommendation to app authors at this point is:

  • If you are a bit adventurous, do a port to 3.94 on a branch. It should be possible to keep it working without too much work during the remainder of GTK+ 4 development.
  • If you are not quite as adventurous, wait until 3.24 is released, use it to prepare your port, and port to GTK+ 3.96.
  • Either way, please make your port available to users for testing, either as a regular release, or as a Flatpak with a bundled GTK+.

GLib diversion

In the afternoon, we spent a while talking about GLib. We went over a laundry list of larger and smaller items. Notable highlights: GProperty may happen for 2.60 and we may be able to use g_autoptr soon.

Other ideas

We discussed a great number of other things that we could and should do.

For example, it was suggested (and generally agreed to) that we should merge gsk into gdk, since it is small and the internals are somewhat intertwined. It was also suggested to create subdirectories in gtk/, for example for the css machinery.