In 2012 I could pack a whole Python interpreter, Qt and various image-processing libraries into an InnoSetup installer that just-so scratched the 12 MB mark; I doubt this has changed significantly.
Contrary to what the linked (more interesting) survey article suggests, Qt is usually the answer to most issues when it comes to cross-platform UI.
Gtk is not bad, but Gtk is what it is: it was created because Qt couldn't be used for licensing concerns (at the time) by people unexperienced with the matter (compared to the Trolltech staff), and is maintained by people who, for the most part, care about Linux. Qt on the other hand is supported commercially, and puts far more effort into supporting more platforms better. [Also the tooling and docs are really nice].
Back when I did Win32 packaging of cross-platform applications, I never liked InnoSetup much, mostly because of the many levels of unpacking into temporary directories, but also because it was relatively slow and not as compact as it could be. Instead, I always preferred NSIS using the makensis command.
Among others, NSIS can be compiled on *nix systems, but still produces a Windows executable file (like a cross compiler), so you can put it in your cross compiling toolchain. That way, you can create your full Windows port including installer without ever having to touch a Windows.
InnoSetup was very easy to get started with and get the expected results, while NSIS looked more complex. I'm not particularly opinionated about installers as long as they install and uninstall things :)
While I agree about the respective qualities of the toolkits, if I remember correctly Gtk wasn't initially a replacement for Qt, but for Motif. The first version of Gimp was using that, and there was quite a bit of animosity against C++ back in those days.
They still could've tried to contribute to LessTif or at least created a new Xt-based toolkit instad of creating yet another overly verbose C OO system...
GTK was created for Gimp.The acronym was literally "Gimp ToolKit". It was adopted by the Gnome people, for the reasons you stated (KDE used Qt and the license issue was yet unresolved at the time). And for writing a PhotoShop-style program, at the time, it provided a lot that Qt couldn't.
In fact, Gimp stayed on GTK1 years after everyone else moved to GTK2.
Maybe, but what would be the point? I knew Qt already (although it's pretty easy to get started), and the UI of the application was quite complex and even with Qt had some custom, complex UI widgets (a node-graph editor, keyframing widgets etc.) -- although these were quite easy to implement on top of QGraphicsView. I'd expect that it would've been more effort to develop that with something like Tk.
Contrary to what the linked (more interesting) survey article suggests, Qt is usually the answer to most issues when it comes to cross-platform UI.
Gtk is not bad, but Gtk is what it is: it was created because Qt couldn't be used for licensing concerns (at the time) by people unexperienced with the matter (compared to the Trolltech staff), and is maintained by people who, for the most part, care about Linux. Qt on the other hand is supported commercially, and puts far more effort into supporting more platforms better. [Also the tooling and docs are really nice].