tools: port to GTK4

[dbartolini]

Depends on: #195

• Changes that need to be done at the time of the switch
  • Larger changes
  • Stop using GdkScreen
  • Stop using the root window
  • Stop using GdkVisual
  • Stop using GdkDeviceManager
  • Adapt to GdkWindow API changes
  • The "iconified" window state has been renamed to "minimized"
  • Adapt to GdkEvent API changes
  • Stop using grabs
  • Adapt to coordinate API changes
  • Adapt to GdkKeymap API changes
  • Adapt to changes in keyboard modifier handling
  • Replace GtkClipboard with GdkClipboard
  • Stop using gtk_get_current_... APIs
  • Convert your UI files
  • Adapt to GtkBuilder API changes
  • Adapt to event controller API changes
  • Focus handling changes
  • Use the new apis for keyboard shortcuts
  • Stop using GtkEventBox
  • Stop using GtkButtonBox
  • Adapt to GtkBox API changes
  • Adapt to GtkWindow API changes
  • Adapt to GtkHeaderBar and GtkActionBar API changes
  • Adapt to GtkStack, GtkAssistant and GtkNotebook API changes
  • Adapt to button class hierarchy changes
  • Adapt to GtkScrolledWindow API changes
  • Adapt to GtkBin removal
  • Adapt to GtkContainer removal
  • Stop using GtkContainer::border-width
  • Adapt to gtk_widget_destroy() removal
  • Adapt to coordinate API changes
  • Adapt to GtkStyleContext API changes
  • Adapt to GtkCssProvider API changes
  • Stop using GtkShadowType and GtkRelief properties
  • Adapt to GtkWidget's size request changes
  • Adapt to GtkWidget's size allocation changes
  • Switch to GtkWidget's children APIs
  • Don't use -gtk-gradient in your CSS
  • Don't use -gtk-icon-effect in your CSS
  • Don't use -gtk-icon-theme in your CSS
  • Don't use -gtk-outline-...-radius in your CSS
  • Adapt to drawing model changes
  • Stop using APIs to query GdkSurfaces
  • Widgets are now visible by default
  • Adapt to changes in animated hiding and showing of widgets
  • Stop passing commandline arguments to gtk_init
  • GdkPixbuf is deemphasized
  • GtkWidget event signals are removed
  • Invalidation handling has changed
  • Stop using GtkWidget::draw
  • Window content observation has changed
  • Monitor handling has changed
  • Adapt to monitor API changes
  • Adapt to cursor API changes
  • Adapt to icon size API changes
  • Adapt to changes in the GtkAssistant API
  • Adapt to changes in the API of GtkEntry, GtkSearchEntry and GtkSpinButton
  • Adapt to changes in GtkOverlay API
  • Use GtkFixed instead of GtkLayout
  • Adapt to search entry changes
  • Adapt to GtkScale changes
  • Stop using gtk_window_activate_default()
  • Stop using gtk_widget_grab_default()
  • Stop setting ::has-default and ::has-focus in .ui files
  • Stop using the GtkWidget::display-changed signal
  • GtkPopover::modal has been renamed to autohide
  • gtk_widget_get_surface has been removed
  • gtk_widget_is_toplevel has been removed
  • gtk_widget_get_toplevel has been removed
  • GtkEntryBuffer ::deleted-text has changed
  • GtkMenu, GtkMenuBar and GtkMenuItem are gone
  • GtkToolbar has been removed
  • GtkAspectFrame is no longer a frame
  • Stop using custom tooltip windows
  • Switch to the new Drag-and-Drop api
  • Adapt to GtkIconTheme API changes
  • Adapt to GtkImage changes
  • Update to GtkFileChooser API changes
  • Stop using blocking dialog functions
  • Stop using GtkBuildable API
  • Adapt to GtkAboutDialog API changes
  • Adapt to GtkTreeView and GtkIconView tooltip context changes
  • Adapt to GtkPopover changes
  • Stop using GtkFileChooserButton
  • Adapt to changed GtkSettings properties
• Changes to consider after the switch
  • Consider porting to the new list widgets