GTK4

[Antoine Martin]

Assuming that we don't jump ship by then (#1995, the python3 / gtk3 transition is hard enough: #1568), we'll need to handle ​Migrating from GTK+ 3.x to GTK+ 4, in particular:

• Stop using the root window - ouch?
• Stop using GdkScreen, GdkVisual, GdkDeviceManager
• Adapt to GdkWindow API changes: GdkWindow has been renamed to GdkSurface. The gdk_window_new() function has been replaced by a number of more specialized constructors: gdk_surface_new_toplevel(), gdk_surface_new_popup(), gdk_surface_new_temp(), gdk_surface_new_child(), gdk_surface_new_input(), gdk_wayland_surface_new_subsurface(). Use the appropriate ones to create your windows.

Native and foreign subwindows are no longer supported. These concepts were complicating the code and could not be supported across backends.
gdk_window_reparent() is no longer available.

• Adapt to drawing model changes: If you are using a GtkDrawingArea for custom drawing, you need to switch to using gtk_drawing_area_set_draw_func() to set a draw function instead of connnecting a handler to the “draw” signal.
• Invalidation handling has changed: Only gtk_widget_queue_draw() is left to mark a widget as needing redraw. Variations like gtk_widget_queue_draw_rectangle() or gtk_widget_queue_draw_region() are no longer available.
• Stop using GtkWidget::draw: The “draw” signal has been removed. Widgets need to implement the “snapshot” function now. Connecting draw signal handlers is no longer possible.
• Adapt to cursor API changes..
• Stop accessing GdkEvent fields: Direct access to GdkEvent structs is no longer possible in GTK+ 4. Some frequently-used fields already had accessors in GTK+ 3, and the remaining fields have gained accessors in GTK+ 4.

[Antoine Martin]

Milestone renamed