Tag Archives: glibmm

gtkmm 4 started

We (the gtkmm developers) have started work on an ABI-breaking gtkmm-4.0, as well as an ABI-breaking glibmm, target GTK+ 4, and letting us clean up some cruft that has gathered over the years. These install in parallel with the existing gtkmm-3.0 and glibmm-2.4 APIs/ABIs.

A couple of days ago I released first versions of glibmm (2.51.1) and gtkmm (3.89.1), as well as accompanying pangomm and atkmm releases.

This also lets us use my rewrite of libsigc++ for libsigc++-3.0, bringing us more fully into the world of “modern C++”. We might use this opportunity to make other fundamental changes, so now is the time to make suggestions.

We did a parallel-installing ABI-breaking glibmm even though glib isn’t doing that. That’s because, now that GTK+ is forcing us to do it for gtkmm, this seems like as good a time as any to do it for glibmm too. It’s generally harder to maintain C++ ABIs than C ABIs, largely because C++ is just more complicated and its types are more exactly specified. For instance we’d never have been able to switch to libsigc++-3.0 without breaking ABI.


libsigc++: std::function-style syntax.

Yesterday I released version 2.99.2 of libsigc++-3.0. This changes the declaration syntax for sigc::slot and sigc::signal to use the same style as std::function, which was added in C++11. We don’t want to be arbitrarily and unnecessarily different.

We’ve also simplified sigc::mem_fun() to always take a reference, instead of either a reference or a pointer.

So, where you might do this for libsigc++-2.0:

sigc::slot<void, int, A> slot = sigc::mem_fun(this, &Thing::on_something);
signal<void, int, A> m_signal;

You would now do this for libsigc++-3.0.

sigc::slot<void(int, A)> slot = sigc::mem_fun(*this, &Thing::on_something);
signal<void(int, A)> m_signal;

Actually, as of version 2.9.1 of libsigc++-2.0, you can use both syntaxes with libsigc++-2.0, allowing you some time to adapt to the new API before one day moving to libsigc++-3.0.

glibmm: Deprecated Glib::Threads

As of glibmm 2.47 (currently unstable), we have deprecated the glibmm threads API, which wrapped the glib threads API. That’s because C++11 finally has its own standard threading API, and in C++14 its complete enough to replace all of Glib::Threads.

Here’s what replaces what:

We’ve replaced use of Glib::Threads in our example code and tests, such as the example in our multithreading chapter in the gtkmm book.

This is quite a relief because we never wanted to be in the concurrency API business anyway, and having a standard C++ concurrency API makes it far easier to write cross-platform code. Now if we could just have a standard C++ network IO API and maybe a file structure API, that would be nice.


gtkmm now uses C++11

Switching to C++11

All the *mm projects now require C++11. Current versions of g++ require you to use the –std=c++11 option for this, but the next version will probably use C++11 by default. We might have done this sooner if it  had been clearer that g++ (and libstdc++) really really supported C++11 fully.

I had expected that switching to C++11 would require an ABI break, but that has not happened, so already-built applications will not be affected. But our API now requires C++11 so this is a minor API change that you will notice when rebuilding your application.

Some distros, such as Fedora, are breaking the libstdc++ ABI slightly and requiring a rebuild of all applications, but that would have happened even without the *mm projects moving to C++11. It looks like Ubuntu might be doing this too, so I am still considering taking advantage of a forced (not gtkmm’s fault) widespread ABI break to make some ABI-breaking changes in gtkmm.

C++11 with autotools

You can use C++11 in your autotools-based project by calling AX_CXX_COMPILE_STDCXX_11() in your configure.ac after copying that m4 macro into your source tree. For instance, I used AX_CXX_COMPILE_STDCXX_11() in glom. The *mm projects use the MM_AX_CXX_COMPILE_STDCXX_11() macro that we added to mm-common, to avoid copying the .m4 file into every project. You may use that in your application instead. For instance, we used MM_AX_CXX_COMPILE_STDCXX_11() in the gtkmm-documentation module.

C++11 features

So far, the use of C++11 in gtkmm doesn’t provide much benefit to application developers and you can already use C++11 in applications that use older versions of gtkmm. But it makes life nicer for the gtkmm developers themselves. I’m enjoying learning about the new C++11 features (particularly move constructors) and enjoying our discussions about how best to use them.

I’m reading and re-reading Scott Meyer’s Effective Modern C++ book.  C++11’s rvalue references alone require great care and understanding.

For now, we’ve just made these changes to the **mm projects:

  • Using auto to simplify the code.
    For instance,
    auto builder = Gtk::Builder::create();
  • Using range-based for-loops.
    For instance,
    for(const auto& row : model->children()) { … }
  • Using nullptr instead of 0 or (void*)0.
    For instance,
    Gtk::Widget* widget = nullptr;
  • Using the override keyword when we override a virtual method.
    For instance,
    bool on_draw(const Cairo::RefPtr<Cairo::Context>& cr) override;
  • Using noexcept instead of throw().
    For instance,
    virtual ~Exception() noexcept;
  • Using “= delete” instead of private unimplemented copy constructors and operator=().
  • Using C++11 lambdas, instead of sigc::slots, for small callback methods.
    See below.

libsigc++ with C+11

libsigc++ has also moved to C++11 and we are gradually trying to replace as much as possible of its internals with C++11. Although C++11 has std::function, there’s still no C++11 equivalent for libsigc++ signals and object tracking

You can use C++11 lambda functions with libsigc++. For instance, with glibmm/gtkmm signals:

  [] () {
    std::cout << "clicked" << std::endl;

And now you don’t need the awkard SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE macro if the signal/slot returns a value. For instance:

  [this] (const Gtk::TreeModel::const_iterator& iter) -> bool
    auto row = *iter;
    return row[m_columns.m_col_show];

With C++14 that should be even nicer:

  [this] (auto iter) -> decltype(auto)
    auto row = *iter;
    return row[m_columns.m_col_show];

These -> return type declarations are necessary in these examples just because of the unusual intermediate type returned by row[].

PrefixSuffix revived

In 2002 I released a little GNOME app to rename files by changing the start or end of the filename, using gtkmm and gnome-vfs(mm). It worked well enough and was even packaged for distros for a while before the dependencies became too awkward.

I’ve never heard of a single person using it, but I still need the app now and then so I just updated it and put it in github, changing it from gtkmm 2.4 to gtkmm 3, removing the bakery dependency, and changing from gnome-vfs to GIO. I also removed most signs of my 2002 code style.

It seems to work, but it really needs a set of test cases.

I’m sure that the performance could be vastly improved but I’m not greatly interested in that so far. Patches are welcome. In particular, I haven’t found an equivalent for the gnome_vfs_xfer_uri_list() function for renaming several files at once and I guess that repeated sequential calls to g_file_set_display_name_async() are probably not ideal.


cluttermm 1.18

cluttermm provides gtkmm-like C++ bindings for the Clutter API. It hasn’t had much attention over the last few years, while the Clutter API has moved on considerably.

I don’t have a great interest in Clutter, though I’d like cluttermm to be ready to inspire gtkmm if any future GTK+ 4 absorbs Clutter. However, Ian Martin has recently put lots of work into updating cluttermm and I’ve been helping him to get his changes upstream and I released some cluttermm-1.17.x tarballs. It’s in the cluttermm-1-18 branch.

This has involved deprecating a huge amount of API and adding (hopefully all of) the API that replaces it. I’ve already removed all this API in the parallel-installable cluttermm git master branch but I have some linker errors that stop that from building, and I’m not going to spend time on it until there are some releases from clutter’s git master (clutter-2.0).

This also means that the cluttermm-tutorial is even more wildly out of date. I’m not likely to spend my free time updating it.

I don’t want to be cluttermm maintainer again, but I didn’t want Ian’s work to be wasted and I hope he wants to keep at it.


glibmm 2.40 and gtkmm 3.12

Only a little late, we released stable glibmm 2.40.0 and gtkmm 3.12.0 versions.

This was only possible thanks to lots of work from Kjell Ahlstedt and  Juan Rafael García Blanco. For instance, Juan added the Gtk:::ActionBar, Gtk::FlowBox and Gtk::Popover classes,after having added Gtk::HeaderBar, Gtk::PlacesSidebar, Gtk::Revealer and Gtk::SearchBar in gtkmm 3.10. They also added example code in gtkmm-documentation.