* 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
* (C++) Macros should not be used to define constants
* (C++) Memory should not be managed manually
* (C++) "void*" should not be used in typedefs, member variables, function parameters or return type
* (C++) When the "Rule-of-Zero" is not applicable, the "Rule-of-Five" should be followed
* (C++) "switch" statements should have "default" clauses
* (C++) "explicit" should be used on single-parameter constructors and conversiosn operators
* (C++) Non-const global variables should not be used
