* Make compact mode switch work for both GTK 3 and 4
* Implement GTK 4-specific view gesture handling
* Fix torrents view context menu on GTK 4
* Explicitly show/hide menubar on startup/teardown
* Switch from `Gtk::Pixbuf` to `Gio::Icon` for views
* Support GTK 4 exceptions based on `std::exception`
* Fix options menu setup with GTK 4
* Use `delete-event` (GTK 3) and `close-request` (GTK 4) signals to handle window clousure
* Add custom file chooser button implementation
GTK 4 drops FileChooserButton widget and suggests implementing it using
Button.
* Add helpers to set X11 hints with GTK 4
* Remove `HigWorkarea` class that's no longer used
* Make main menu shortcuts work with GTK 4
* Make drops work in main window and make dialog with GTK 4
* Remove unused `gtr_action_get_widget()` helper
* Fix text direction mark setup with GTK 4 (due to switch to enum class)
* Fix file tree font size calculation with GTK 4
* Fix crash during shutdown with GTK 4
* Switch from `RadioButton` to `CheckButton` for compatibility with GTK 4
* Fix opening files with GTK 4
* Rework torrent cell renderer to support both GTK 3 and 4
* Disable system tray icon support with GTK 4
* Fix windows positioning with GTK 4
* Fix focus event handling with GTK 4
* Adapt to tree model row/iterator changes in GTK 4
* Adapt to toplevel/root window changes in GTK 4
* Adapt to clipboard changes in GTK 4
* Adapt to icon/theme changes in GTK 4
* Adapt to file/path changes in GTK 4
* Random leftover fixes for GTK 4 compatibility
* Clean up unused code
* Move GTK 3 *.ui files into a subdirectory
* Add GTK 4 *.ui files
* Search for both GTK 3 and 4 during configuration
* Move CSS definitions to resources
* Add Gtk::Builder helpers
* Switch StatsDialog to Gtk::Builder
* Switch RelocateDialog to Gtk::Builder
* Switch OptionsDialog to Gtk::Builder
* Switch MakeDialog to Gtk::Builder
* Switch FilterBar to Gtk::Builder
* Switch MainWindow to Gtk::Builder
* Switch MessageLogWindow to Gtk::Builder
* Switch DetailsDialog to Gtk::Builder
* Switch PrefsDialog to Gtk::Builder
* Fixup translatable strings
Since this branch was brewing for a while, changes happened in the meantime.
There is a fallback mechanism in GTK: when looking for an icon named
foo-a-b-c, it'll also try to find foo-a-b, foo-a, and foo, so the only
icon necessary (if all of them default to the same one) is foo. Given
that we're also installing this icon, including it in resources doesn't
make a lot of sense, by I'm leaving it just in case anyway (useful when
debugging without installing).
