Let's port inkscape to gtk4

inkscape-gtk4.md

Inkscape GTK 4 Port

What needs to be done?

GTK3 Backport Branch: https://gitlab.com/firox263/inkscape/-/tree/gtk4-prep-events GTK4 Transition Branch: https://gitlab.com/firox263/inkscape/-/tree/gtk4

Pre-Switch

• Replace all direct uses of GdkEvent
• Try move to event controllers where possible (not easy because GtkGestureClick doesn’t exist in GTK 3, which is basically all uses in Inkscape)
• Stop using generic containers (should be fine, only toolbars which currently use it)
• There are no deprecated structures in Inkscape!
  • Well, almost…
  • Need to migrate away from a few properties like use-stock

Switch

• Adapt to GdkEvent name/type changes
  • It is no longer a union, so changes needed
• Adapt to libsigc++ changes
  • Seems to be ridiculously more verbose for some uses
  • How to keep static type parameters while keeping it readable?
• Adapt to drag and drop changes
  • New API is much more sanely designed
  • How much does Inkscape use drag and drop?

Post-Switch

• Probably move from GtkEventControllerLegacy to the relevant event controllers like GtkGestureClick and what not
• Touch support for free!
• Move from deprecated GtkTreeView and friends to new fancy list widgets
• Enable OpenGL canvas drawing and/or use GtkSnapshot

Questions

• Platform support
  • GTK4 on Windows… rough (worse than GTK3, but seems pretty active)
  • GTK4 on macOS… great-ish (much better than GTK3, although see gtk!4523)
• Gtkmm is being deprecated (see: gtkmm#110)
  • Write more or less gtkmm code?
• libadwaita? 👀