View source for GTK+ 4 Migration

'''<big>A page to track the migration to Gtk4.</big>'''

See: https://docs.gtk.org/gtk4/migrating-3to4.html

== Preparation: ==

* ☑ Do not use GTK-specific command line arguments
* ☑ Do not use widget style properties (We don't appear to use any.)
* ☐ Review your window creation flags  (3x src/ui/widget/color-slider.cpp) DELAY UNTIL GTK4,
* ☐ Stop using direct access to GdkEvent structs (note: can use GtkEvent structures) '''BIG'''
* ☑ Stop using gdk_pointer_warp()
* ☑ Stop using non-RGBA visuals
* ☑ gtk_widget_set_app_paintable
* ☐ Stop using GtkBox padding, fill and expand child properties DELAY UNTIL GTK4
* ☐ Stop using the state argument of GtkStyleContext getters (deprecated in 4.10, gtk_style_context_get_property removed, ui/widget/ink-ruler.cpp, color-slider.cpp, dash-selector.cpp, ink-ruler.cpp, ink-spinscale.cpp; src/ui/util.cpp) DELAY UNTIL GTK4
* ☑ Stop using gdk_pixbuf_get_from_window() and gdk_cairo_set_source_window()
* ☐ Stop using GtkButton's image-related API DELAY UNTIL GTK4
* ☐ Stop using GtkWidget event signals (Convert to Controllers, '''BIG''') DELAY UNTIL GTK4 (Controllers mostly unusable in Gtk3.)
* ☑ Set a proper application ID
* ☑ Stop using gtk_main() and related APIs (2geom tests, autotrace, script)
* ☑ Reduce the use of gtk_widget_destroy() (Only used for message dialogs and for ComboBoxEnryToolItem which will disappear.)
* ☑ Stop using the GtkWidget.destroy vfunc (Not used)
* ☐ Reduce the use of generic container APIs DELAY UNTIL GTK4
* ☑ Review your use of icon resources

== At time of switch: ==
Some of these we maybe able to do earlier.

* ☐ Subclassing widgets
* ☐ Life-cycle handling
* ☐ Stop using GdkScreen
* ☐ Stop using the root window. Used in ege-color-prof-tracker.cpp.
* ☑ Stop using GdkVisual. Don't use.
* ☑ Stop using GdkDeviceManager. Don't use.
* ☐ 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. Don't use either.
* ☐ 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 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  Used in style.css, Minwaita-Inkscape.css
* ☑ Don't use -gtk-icon-theme in your CSS
* ☐ Don't use -gtk-outline-...-radius in your CSS  Used in style.css, Minwaita-Inkscape.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. Don't use changed api.
* ☑ Use GtkFixed instead of GtkLayout. Don't use.
* ☑ Adapt to search entry changes. Don't use changed api.
* ☐ 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

== After switch: ==
* ☐ Use new list widgets.