Add GTK4 + libadwaita interface (GTK_BUILD_TYPE=GTK4)

[eaescob]

Summary

Adds a GTK4 + libadwaita port of the GTK GUI, selectable with
-DGTK_BUILD_TYPE=GTK4. GTK3 stays the default and is left completely
unchanged — the GTK4 interface is a parallel tree under
src/interfaces/gtk4/, so this change is purely additive.

Why now

GTK3 is in maintenance-only mode upstream, and recent GTK / glycin changes
have started to break the GTK3 interface in the field — see #1310, where
ettercap -G crashes after idle once glycin restarts its image loaders across
the privilege drop. This gives ettercap a modern, actively-supported toolkit
to move to. The move off GtkTreeView to GtkColumnView may also help with
long-standing rendering glitches some users hit on certain setups (#1231),
though that still needs confirmation from affected users on the new interface.

What's in it

A full modernization, not a mechanical port:

• Asynchronous dialogs everywhere. GTK4 removed gtk_dialog_run(); every
  dialog is now build → present → respond, with shared helpers in
  ec_gtk4_dialogs.c (AdwAlertDialog, GtkFileDialog, AdwToast).
• List views move from GtkTreeView/GtkListStore to GtkColumnView
  over a GListModel with a typed GObject item per view. This drops the
  hidden pointer column and the fragile GtkTreeIter-based deferred name
  resolution.
• libadwaita widgets: AdwApplicationWindow, AdwToolbarView /
  AdwHeaderBar, AdwTabView for the MDI pages, AdwAboutDialog,
  AdwToast, and AdwShortcutsDialog (with a plain AdwDialog fallback for
  libadwaita < 1.8).
• The keyboard-shortcuts window is generated from the accelerator table
  instead of the ~1370-line hand-written ec_gtk3_shortcuts.c.

Build wiring: a pkg-config-based FindGTK4.cmake, GTK_BUILD_TYPE=GTK4 in
EttercapLibCheck.cmake, HAVE_GTK4, and a 24.04-only entry in the CI matrix.

Requirements (for packagers)

• GTK ≥ 4.12 and libadwaita ≥ 1.5 (the latter is what provides
  AdwDialog/AdwAlertDialog). This gates the GTK4 build to Ubuntu ≥
  24.04 / Debian ≥ 13 / Fedora ≥ 39; older releases keep the GTK3 build.
• README.md and INSTALL document the dependencies and -DGTK_BUILD_TYPE=.

Validation

Built and driven in an Ubuntu 24.04 cloud sandbox via the included harness
(tests/gtk4/, see its README) — 5/5 checks pass: startup, the async
dialogs, the generated shortcuts window, the about dialog, and the sniffing UI
with its GtkColumnView list views populated from a fixture pcap, all with no
GTK criticals logged.

Screenshots from that run are attached below (setup screen, sniffing UI, the
connections and profiles GtkColumnViews with data, the generated shortcuts
window, and the AdwAboutDialog).

Notes for reviewers

• The GTK3 interface is untouched; nothing here changes existing behaviour.
• It also fixes a few latent GTK3 bugs picked up during the port: the
  tab-page accelerators that never fired (the GTK3 FIXME doesn't work yet),
  a duplicate <Primary>p binding, and a mislabelled OS in the profile
  detail view.
• This is a large diff. Happy to split it into smaller reviewable chunks
  (build wiring / dialog layer / individual views) if that's easier to land.

Related: #1310, #1231

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🤖 Generated with Claude Code

[LocutusOfBorg]

thank you! I tested and looks like working properly, but I have a question, on startup I can't see the "select interfaces", I don't know how to pass the interface properly, is it a bug?

[eaescob]

It's actually a bug. I'll be opening a PR to fix it.

[eaescob]

Follow-up (c4a8026): restored the network-interface picker on the setup
screen, which the initial port had dropped — there was no way to choose the
capture interface. It's rebuilt with libadwaita (an AdwPreferencesGroup
with AdwComboRow interface dropdowns and AdwSwitchRow toggles for "sniff
at startup" and "bridged sniffing"), plus the setup "Options" submenu
(Unoffensive / Promisc / Set Netmask) that GTK3 also exposed there.

I also diffed the GTK4 interface against GTK3 to make sure nothing else was
left behind: all 48 registered actions and all 38 sniffing-menu items match.
Still 5/5 on the sandbox harness. Updated setup-screen screenshot to follow.

[koeppea]

This is huge. But its good that you left GTK3 the default graphical UI variant.

When building, I get the following warnings:

[ 14%] Building C object src/interfaces/CMakeFiles/ec_interfaces.dir/gtk4/ec_gtk4_dialogs.c.o
/home/koeppea/dev/ettercap/src/interfaces/gtk4/ec_gtk4_dialogs.c:51:19: warning: redundant redeclaration of ‘toastoverlay’ [-Wredundant-decls]
   51 | extern GtkWidget *toastoverlay;
      |                   ^~~~~~~~~~~~
In file included from /home/koeppea/dev/ettercap/src/interfaces/gtk4/ec_gtk4_dialogs.c:48:
/home/koeppea/dev/ettercap/src/interfaces/gtk4/ec_gtk4.h:113:19: note: previous declaration of ‘toastoverlay’ with type ‘GtkWidget *’ {aka ‘struct _GtkWidget *’}
  113 | extern GtkWidget *toastoverlay;     /* AdwToastOverlay, replaces the infobar */
      |  

Has GTK4 also dropped the application menu, with Save, Open, Quit?
The Spider doesn't appear in the setup screen but a editable section below the selections (big white section and hovered cursor changes to text-marker).

When setup is finished and I try to open a list, the background picture isn't replaced:

When scanning (progress dialog), following messages appear on the terminal:

(ettercap:35975): Gtk-WARNING **: 15:26:01.017: Trying to measure GtkLabel 0x55e2518003a0 for width of 510, but it needs at least 756

(ettercap:35975): Gtk-WARNING **: 15:26:01.022: Trying to measure GtkLabel 0x55e2518003a0 for width of 510, but it needs at least 756

These are the main findings yet.

[eaescob]

Thanks for the thorough review, @koeppea — all four are real. The interface
picker that the merge was missing landed in #1320; these four fixes are in
#1329 (they were meant to ride along with #1320 but landed just after it was
merged).

• Redundant toastoverlay redeclaration — removed; it's only declared in
  ec_gtk4.h now, so the -Wredundant-decls warning is gone.

• Application menu (Open/Save/Quit) — not dropped. GTK4 removed
  gtk_application_set_app_menu(), so instead of the old GNOME app-menu slot
  it now lives in the primary "hamburger" menu (the ☰ button in the header
  bar), together with an Options submenu (Unoffensive / Promisc / Set Netmask)
  that the setup screen also exposed. Agreed it's less obvious there than the
  old app menu — open to moving individual items into the header if you'd
  prefer.

• Spider / editable white section on the setup screen — that white area
  was the message-log GtkTextView, which I had wrongly put on the setup
  screen; GTK3 shows the logo there and keeps the message log on the
  sniffing screen only. Fixed to match: the setup screen now shows the logo
  under the setup form, and the message log is created only on the sniffing
  screen.

• Background picture not replaced when opening a list — the logo was a
  sibling stacked above the tab view, so it never got replaced. It's now an
  overlay on the tab view, shown only while the view has no pages, so opening
  a list hides it.

• Trying to measure GtkLabel ... needs at least N during scan — the
  progress dialog set the title as both the AdwAlertDialog heading and a
  separate label; the duplicate, unwrapped label caused those warnings. The
  body is now just the progress bar and the heading carries the title.

All verified in the Cua sandbox harness (tests/gtk4/). A full GTK3-vs-GTK4
parity audit (menu actions, context menus, header buttons, accelerators) is on
#1320.