Add minimal support for GTK4

Co-authored-by: Muhammad Murad <[email protected]>

.github/workflows/ci.yml

@@ -235,8 +235,9 @@ jobs:
         - "macOS-x86_64"
         - "macOS-arm64"
         - "windows"
-        - "linux-x11"
-        - "linux-wayland"
+        - "linux-x11-gtk3"
+        - "linux-wayland-gtk3"
+        - "linux-wayland-gtk4"
         - "android"
         - "iOS"
         - "textual-linux"
@@ -261,7 +262,7 @@ jobs:
         # We use a fixed Ubuntu version rather than `-latest` because at some point,
         # `-latest` will be updated, but it will be a soft changeover, which would cause
         # the system Python version to become inconsistent from run to run.
-        - backend: "linux-x11"
+        - backend: "linux-x11-gtk3"
           platform: "linux"
           runs-on: "ubuntu-24.04"
           # The package list should be the same as in unix-prerequisites.rst, and the BeeWare
@@ -290,7 +291,7 @@ jobs:
           setup-python: false  # Use the system Python packages
           app-user-data-path: "$HOME/.local/share/testbed"
 
-        - backend: "linux-wayland"
+        - backend: "linux-wayland-gtk3"
           platform: "linux"
           runs-on: "ubuntu-24.04"
           # The package list should be the same as in unix-prerequisites.rst, and the BeeWare
@@ -309,14 +310,45 @@ jobs:
             # Start Window Manager
             echo "Start window manager..."
             # mutter is being run inside a virtual X server because mutter's headless
-            # mode is not compatible with Gtk
+            # mode does not provide a Gdk.Display
             DISPLAY=:99 MUTTER_DEBUG_DUMMY_MODE_SPECS=2048x1536 \
               mutter --nested --wayland --no-x11 --wayland-display toga &
             sleep 1
           briefcase-run-prefix: "WAYLAND_DISPLAY=toga"
           setup-python: false  # Use the system Python packages
           app-user-data-path: "$HOME/.local/share/testbed"
 
+        - backend: "linux-wayland-gtk4"
+          platform: "linux"
+          runs-on: "ubuntu-24.04"
+          env:
+            XDG_RUNTIME_DIR: "/tmp"
+          # The package list should be the same as in unix-prerequisites.rst, and the BeeWare
+          # tutorial, plus mutter to provide a window manager.
+          pre-command: |
+            sudo apt update -y
+            sudo apt install -y --no-install-recommends \
+              mutter pkg-config python3-dev libgirepository1.0-dev libcairo2-dev \
+              gir1.2-webkit2-4.1 gir1.2-xapp-1.0 gir1.2-geoclue-2.0 gir1.2-flatpak-1.0 \
+              gir1.2-gtk-4.0
+
+            # Start Virtual X Server
+            echo "Start X server..."
+            Xvfb :99 -screen 0 2048x1536x24 &
+            sleep 1
+
+            # Start Window Manager
+            echo "Start window manager..."
+            # mutter is being run inside a virtual X server because mutter's headless
+            # mode does not provide a Gdk.Display
+            DISPLAY=:99 MUTTER_DEBUG_DUMMY_MODE_SPECS=2048x1536 \
+              mutter --nested --wayland --no-x11 --wayland-display toga &
+            sleep 1
+          briefcase-run-prefix: "WAYLAND_DISPLAY=toga TOGA_GTK=4"
+          briefcase-test-args: -k 'test_window or test_desktop or test_app and not test_app_icon'
+          setup-python: false  # Use the system Python packages
+          app-user-data-path: "$HOME/.local/share/testbed"
+
         - backend: "textual-linux"
           platform: "linux"
           runs-on: "ubuntu-latest"
@@ -397,7 +429,8 @@ jobs:
       timeout-minutes: 15
       run: |
         ${{ matrix.briefcase-run-prefix }} \
-          briefcase run ${{ matrix.platform }} --log --test ${{ matrix.briefcase-run-args }} -- --ci
+          briefcase run ${{ matrix.platform }} --log --test ${{ matrix.briefcase-run-args }} \
+          -- ${{ matrix.briefcase-test-args }} --ci
 
     - name: Upload Logs
       uses: actions/[email protected]

changes/3087.feature.rst

@@ -0,0 +1 @@
+Toga GTK now supports GTK4 for BeeWare Tutorial 1 by setting `TOGA_GTK=4`.

cocoa/tests_backend/window.py

@@ -16,6 +16,7 @@ class WindowProbe(BaseProbe, DialogsMixin):
     supports_unminimize = True
     supports_minimize = True
     supports_placement = True
+    supports_as_image = True
 
     def __init__(self, app, window):
         super().__init__()

gtk/src/toga_gtk/app.py

@@ -6,6 +6,7 @@
 
 from .keys import gtk_accel
 from .libs import (
+    GTK_VERSION,
     IS_WAYLAND,
     TOGA_DEFAULT_STYLES,
     Gdk,
@@ -34,7 +35,7 @@ def __init__(self, interface):
         # Stimulate the build of the app
         self.native = Gtk.Application(
             application_id=self.interface.app_id,
-            flags=Gio.ApplicationFlags.FLAGS_NONE,
+            flags=Gio.ApplicationFlags.DEFAULT_FLAGS,
         )
         self.native_about_dialog = None
 
@@ -53,12 +54,22 @@ def gtk_startup(self, data=None):
 
         # Set any custom styles
         css_provider = Gtk.CssProvider()
-        css_provider.load_from_data(TOGA_DEFAULT_STYLES)
 
-        context = Gtk.StyleContext()
-        context.add_provider_for_screen(
-            Gdk.Screen.get_default(), css_provider, Gtk.STYLE_PROVIDER_PRIORITY_USER
-        )
+        if GTK_VERSION < (4, 0, 0):
+            css_provider.load_from_data(TOGA_DEFAULT_STYLES)
+            context = Gtk.StyleContext()
+            context.add_provider_for_screen(
+                Gdk.Screen.get_default(), css_provider, Gtk.STYLE_PROVIDER_PRIORITY_USER
+            )
+        else:
+            if Gtk.get_minor_version() >= 12:
+                css_provider.load_from_string(TOGA_DEFAULT_STYLES)
+            elif Gtk.get_minor_version() > 8:
+                css_provider.load_from_data(
+                    TOGA_DEFAULT_STYLES, len(TOGA_DEFAULT_STYLES)
+                )
+            else:
+                css_provider.load_from_data(TOGA_DEFAULT_STYLES.encode("utf-8"))
 
     ######################################################################
     # Commands and menus
@@ -173,20 +184,24 @@ def set_main_window(self, window):
 
     def get_screens(self):
         display = Gdk.Display.get_default()
-        if IS_WAYLAND:  # pragma: no-cover-if-linux-x
-            # `get_primary_monitor()` doesn't work on wayland, so return as it is.
-            return [
-                ScreenImpl(native=display.get_monitor(i))
-                for i in range(display.get_n_monitors())
-            ]
-        else:  # pragma: no-cover-if-linux-wayland
-            primary_screen = ScreenImpl(display.get_primary_monitor())
-            screen_list = [primary_screen] + [
-                ScreenImpl(native=display.get_monitor(i))
-                for i in range(display.get_n_monitors())
-                if display.get_monitor(i) != primary_screen.native
-            ]
-            return screen_list
+        if GTK_VERSION < (4, 0, 0):
+            if IS_WAYLAND:  # pragma: no-cover-if-linux-x
+                # `get_primary_monitor()` doesn't work on wayland, so return as it is.
+                return [
+                    ScreenImpl(native=display.get_monitor(i))
+                    for i in range(display.get_n_monitors())
+                ]
+
+            else:  # pragma: no-cover-if-linux-wayland
+                primary_screen = ScreenImpl(display.get_primary_monitor())
+                screen_list = [primary_screen] + [
+                    ScreenImpl(native=display.get_monitor(i))
+                    for i in range(display.get_n_monitors())
+                    if display.get_monitor(i) != primary_screen.native
+                ]
+                return screen_list
+        else:
+            return [ScreenImpl(native=monitor) for monitor in display.get_monitors()]
 
     ######################################################################
     # App state
@@ -201,7 +216,10 @@ def get_dark_mode_state(self):
     ######################################################################
 
     def beep(self):
-        Gdk.beep()
+        if GTK_VERSION < (4, 0, 0):
+            Gdk.beep()
+        else:
+            Gdk.Display.get_default().beep()
 
     def _close_about(self, dialog, *args, **kwargs):
         self.native_about_dialog.destroy()