Allow the use of .NET Core 10

.github/workflows/ci.yml

@@ -43,13 +43,14 @@ jobs:
 
   package:
     name: Package Toga
+    runs-on: ubuntu-latest
     permissions:
       id-token: write
       contents: read
       attestations: write
     strategy:
       matrix:
-        subdir:
+        wheel:
         - "android"
         - "cocoa"
         - "core"
@@ -63,11 +64,60 @@ jobs:
         - "travertino"
         - "textual"
         - "web"
-        - "winforms"
-    uses: beeware/.github/.github/workflows/python-package-create.yml@main
-    with:
-      build-subdirectory: ${{ matrix.subdir }}
-      attest: ${{ inputs.attest-package }}
+        - "winforms-x64"
+        - "winforms-arm64"
+        include:
+          - subdir: ""
+
+          - wheel: "winforms-x64"
+            subdir: "winforms"
+            plat-name: "win_amd64"
+            exclude-runtime: "win-arm64"
+          - wheel: "winforms-arm64"
+            subdir: "winforms"
+            arch: "arm64"
+            plat-name: "win_arm64"
+            exclude-runtime: "win-x64"
+
+    # On Windows, we need to produce py3-none-win_arm64 and py3-none-win_amd64 wheels
+    # because the wheel includes a platform-specific binary to support WebView2. The
+    # existence of a `subdir` value is used as an indicator. However, this means we
+    # can't use the common BeeWare package building workflow. Reproduce the core parts here,
+    # with the extra pieces to support windows wheels.
+    #
+    # uses: beeware/.github/.github/workflows/python-package-create.yml@main
+    # with:
+    #   build-subdirectory: ${{ matrix.subdir || matrix.wheel }}
+    #   attest: ${{ inputs.attest-package }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6.0.2
+        with:
+          repository: ${{ github.repository }}
+          fetch-depth: 0  # Fetch all refs so setuptools_scm can generate the correct version number
+
+      # A tagged wheel is generated by writing a `bdist_wheel` section to pyproject.toml
+      - name: Configure platform tag
+        if: ${{ matrix.subdir }}
+        run: |
+          printf '[tool.distutils.bdist_wheel]\nplat-name = "${{ matrix.plat-name }}"\n' >> winforms/pyproject.toml
+
+      # To ensure the binary wheel only contains the binaries for that platform,
+      # delete content that is for the other architecture.
+      - name: Remove other-arch native DLL
+        if: ${{ matrix.subdir }}
+        run: |
+          rm -rf winforms/src/toga_winforms/libs/WebView2/runtimes/${{ matrix.exclude-runtime }}
+
+      - name: Build Package & Upload Artifact
+        id: package
+        uses: hynek/build-and-inspect-python-package@v2.15.0
+        with:
+          path: ${{ matrix.subdir || matrix.wheel }}
+          upload-name-suffix: ${{ format('-{0}', matrix.wheel) }}
+          attest-build-provenance-github: ${{ inputs.attest-package }}
+
 
   docs-lint:
     name: Documentation linting
@@ -143,7 +193,7 @@ jobs:
     - name: Get Packages
       uses: actions/download-artifact@v8.0.1
       with:
-        pattern: ${{ format('{0}-*', needs.package.outputs.artifact-basename) }}
+        pattern: "Packages-*"
         merge-multiple: true
         path: dist
 
@@ -232,7 +282,7 @@ jobs:
     - name: Get Package
       uses: actions/download-artifact@v8.0.1
       with:
-        pattern: ${{ format('{0}-*', needs.package.outputs.artifact-basename) }}
+        pattern: "Packages-travertino"
         merge-multiple: true
         path: dist
 
@@ -251,7 +301,9 @@ jobs:
         backend:
         - "macOS-x86_64"
         - "macOS-arm64"
-        - "windows"
+        - "windows-netfx-x86_64"
+        - "windows-netcore-x86_64"
+        - "windows-netcore-arm64"
         - "linux-x11-gtk3"
         - "linux-wayland-gtk3"
         - "linux-wayland-gtk4"
@@ -267,6 +319,7 @@ jobs:
         - pre-command: ""
           briefcase-run-prefix: ""
           briefcase-run-args: ""
+          briefcase-test-args: ""
           setup-python: true
           testbed-app: "testbed"
           copy-command: "cp -r"
@@ -489,10 +542,21 @@ jobs:
           briefcase-run-args: --config 'requires=["toga-core", "toga-textual"]' --config 'console_app=true'
           app-user-data-path: '$HOME\AppData\Local\Tiberius Yak\Toga Testbed\Data'
 
-        - backend: "windows"
+        - backend: "windows-netfx-x86_64"
           platform: "windows"
           runs-on: "windows-latest"
           app-user-data-path: '$HOME\AppData\Local\Tiberius Yak\Toga Testbed\Data'
+          briefcase-run-prefix: TOGA_WINFORMS_USE_NETFX=1
+
+        - backend: "windows-netcore-x86_64"
+          platform: "windows"
+          runs-on: "windows-latest"
+          app-user-data-path: '$HOME\AppData\Local\Tiberius Yak\Toga Testbed\Data'
+
+        - backend: "windows-netcore-arm64"
+          platform: "windows"
+          runs-on: "windows-11-arm"
+          app-user-data-path: '$HOME\AppData\Local\Tiberius Yak\Toga Testbed\Data'
 
         - backend: "iOS"
           platform: "iOS"
@@ -555,7 +619,7 @@ jobs:
     - name: Get Packages
       uses: actions/download-artifact@v8.0.1
       with:
-        pattern: ${{ format('{0}-*', needs.package.outputs.artifact-basename) }}
+        pattern: "Packages-*"
         merge-multiple: true
         path: dist
 
@@ -565,7 +629,7 @@ jobs:
       run: |
         ${{ matrix.briefcase-run-prefix }} \
           briefcase run ${{ matrix.platform }} --log --test \
-          ${{ matrix.briefcase-run-args }} --app ${{ matrix.testbed-app }} -- --ci
+          ${{ matrix.briefcase-run-args }} --app ${{ matrix.testbed-app }} -- --ci ${{ matrix.briefcase-test-args }}
 
     - name: Upload Logs
       uses: actions/upload-artifact@v7.0.1
@@ -634,7 +698,7 @@ jobs:
     - name: Get Packages
       uses: actions/download-artifact@v8.0.1
       with:
-        pattern: ${{ format('{0}-*', needs.package.outputs.artifact-basename) }}
+        pattern: "Packages-positron"
         merge-multiple: true
         path: dist
 

.github/workflows/release.yml

@@ -33,7 +33,7 @@ jobs:
       - name: Get Packages
         uses: actions/download-artifact@v8.0.1
         with:
-          pattern: ${{ format('{0}-*', needs.ci.outputs.artifact-basename) }}
+          pattern: "Packages-*"
           merge-multiple: true
           path: dist
 
@@ -79,7 +79,7 @@ jobs:
       - name: Get Packages
         uses: actions/download-artifact@v8.0.1
         with:
-          pattern: ${{ format('{0}-*', needs.ci.outputs.artifact-basename) }}
+          pattern: "Packages-*"
           merge-multiple: true
           path: staging_dist
 

changes/2782.feature.md

@@ -0,0 +1 @@
+Toga's WinForms backend can now be used on ARM64 machines with a native ARM64 Python interpreter.

docs/en/reference/platforms/windows.md

@@ -8,11 +8,13 @@ The Toga backend for Windows is [`toga-winforms`](https://github.com/beeware/tog
 
 `toga-winforms` requires Python 3.10+, and Windows 10 or newer.
 
-/// note | Note
+Toga requires the use of either .NET Framework 4.x, or .NET Core 10.
 
-Toga uses the [Python.NET](https://pythonnet.github.io) library to access the underlying Winforms GUI toolkit on Windows. Unfortunately, Python.NET doesn't always keep up with the release schedule of Python itself, and as a result, may not be compatible with recently-released versions of Python (i.e., a Python release with a version number of 3.X.0 or 3.X.1). If you experience problems installing Toga, and you're using a recently-released version of Python, try downgrading to the previous minor release (e.g. 3.13.9 instead of 3.14.0).
+If you're on an x86-64 machine, .NET Framework 4.x is installed by default on Windows 10 and 11. Toga will use .NET Core 10 if it is installed. If you explicitly *want* to use .NET Framework 4.x, set the `TOGA_WINFORMS_USE_NETFX` environment variable.
+
+If you're using an ARM64 machine, and you're using a native ARM64 Python interpreter, you *must* use .NET Core 10. The [.NET Desktop Runtime can be downloaded from the .NET website](https://dotnet.microsoft.com/en-us/download/dotnet/10.0). If you're using an x86-64 interpreter on an ARM64 machine, Toga can use the .NET Framework install that is provided by default.
 
-///
+Toga uses the [Python.NET](https://pythonnet.github.io) library to access the underlying Winforms GUI toolkit on Windows. Unfortunately, Python.NET doesn't always keep up with the release schedule of Python itself, and as a result, may not be compatible with recently-released versions of Python (i.e., a Python release with a version number of 3.X.0 or 3.X.1). If you experience problems installing Toga, and you're using a recently-released version of Python, try downgrading to the previous minor release (e.g. 3.13.9 instead of 3.14.0).
 
 If you are using Windows 10 and want to use a WebView to display web content, you will also need to install the [Edge WebView2 Evergreen Runtime.](https://developer.microsoft.com/en-us/microsoft-edge/webview2/#download) Windows 11 has this runtime installed by default.
 

testbed/src/testbed/app.py

@@ -238,6 +238,14 @@ async def on_running(self):
 
 
 def main(appname):
+    if toga.backend == "toga_winforms":
+        import toga_winforms
+
+        if toga_winforms._use_dotnet_core:
+            print("Running testbed using .NET Core")
+        else:
+            print("Running testbed using .NET Framework 4.x")
+
     return Testbed(
         app_name=appname,
         document_types=[ExampleDoc, ReadonlyDoc],

testbed/tests/app/test_desktop.py

@@ -786,6 +786,8 @@ def find_event(event_path, main_window_probe):
     from System import Array, Object
     from System.Reflection import BindingFlags
 
+    from toga_winforms import _use_dotnet_core
+
     event_class, event_name = event_path.split(".")
     if event_class == "Form":
         return getattr(main_window_probe.native, f"On{event_name}")
@@ -801,7 +803,9 @@ def find_event(event_path, main_window_probe):
         ][0]
 
         event_key = SystemEvents_type.GetField(
-            f"On{event_name}Event", binding_flags
+            # .NET Core 10 uses a different naming convention for system events.
+            (f"s_on{event_name}Event" if _use_dotnet_core else f"On{event_name}Event"),
+            binding_flags,
         ).GetValue(None)
 
         return lambda event_args: RaiseEvent.Invoke(

testbed/tests/testbed.py

@@ -1,4 +1,5 @@
 import os
+import platform
 import sys
 import tempfile
 import time
@@ -34,13 +35,25 @@ def run_tests(app, cov, args, report_coverage, run_slow, running_in_ci):
 
         print("ready.")
 
-        # Textual backend does not yet support testing.
-        # However, this will verify a Textual app can at least start.
+        # Some backends and platforms do not support interactive GUI testing.
+        # On those platforms, perform a basic app start test.
         import toga
 
-        if toga.backend == "toga_textual":
-            time.sleep(1)  # wait for the Textual app to start
-            app.returncode = 0 if app._impl.native.is_running else 1
+        if (
+            # Textual doesn't have a test probe
+            toga.backend == "toga_textual"
+            # On GitHub Actions, Windows/ARM64 runners don't have an interactive
+            # logon session, so you can't run most of the GUI tests.
+            or (
+                toga.backend == "toga_winforms"
+                and platform.machine() == "ARM64"
+                and running_in_ci
+            )
+        ):
+            time.sleep(1)  # wait for the app to start
+            print("Performing a basic app startup test...", end="")
+            app.returncode = 0 if app._impl.loop.is_running() else 1
+            print("done.")
             return
 
         # Control the run speed of the test app.
@@ -144,10 +157,12 @@ def main(main_package_name, backend_override=None):
     cov.set_option(
         "coverage_conditional_plugin:rules",
         {
+            # Linux X vs Wayland
             "no-cover-if-linux-wayland": "os_environ.get('WAYLAND_DISPLAY', '') != ''",
             "no-cover-if-linux-x": (
                 "os_environ.get('WAYLAND_DISPLAY', 'not-set') == 'not-set'"
             ),
+            # Linux GTK3/4 + Adwaita versions
             "no-cover-if-gtk4": "os_environ.get('TOGA_GTK', '') == '4'",
             "no-cover-if-gtk3": "os_environ.get('TOGA_GTK', '3') == '3'",
             "no-cover-unless-plain-gtk4": (
@@ -159,6 +174,11 @@ def main(main_package_name, backend_override=None):
                 "os_environ.get('TOGA_GTK', '') != '4' "
                 "or os_environ.get('TOGA_GTKLIB', '') != 'Adw'"
             ),
+            # Windows .NET usage
+            "no-cover-if-netfx": "os_environ.get('TOGA_WINFORMS_USE_NETFX', '') == '1'",
+            "no-cover-if-netcore": (
+                "os_environ.get('TOGA_WINFORMS_USE_NETFX', '') != '1'"
+            ),
         },
     )
     cov.start()

winforms/pyproject.toml

@@ -110,11 +110,6 @@ WebView = "toga_winforms.widgets.webview:WebView"
 MainWindow = "toga_winforms.window:MainWindow"
 Window = "toga_winforms.window:Window"
 
-[tool.distutils.bdist_wheel]
-# This backend needs to be tagged `py3-none-win_arm64`. All the code in this backend is
-# pure Python, *but* it contains pre-compiled binary libraries to support WebView2.
-plat-name = "win_amd64"
-
 [tool.setuptools_scm]
 root = ".."
 

winforms/src/toga_winforms/__init__.py

@@ -1,3 +1,66 @@
+import os
+import platform
+from pathlib import Path
+
+import clr_loader
+from pythonnet import set_runtime
+
+try:
+    ####################################################################################
+    # Toga Winforms requires the use of .NET; either .NET Framework 4.x, or .NET Core.
+    #
+    # .NET Framework 4.x is available by default on Windows 10 and 11. However, on
+    # Windows on ARM64, it is an x86-64 binary, so it can't be used by a native ARM64
+    # Python interpreter.
+    #
+    # However, it *can* be used on ARM64 if you have an x86-64 Python interpreter -
+    # which is what you get if you run `py install -3.13` or `py install -3.14`. This
+    # will apparently change in Python 3.15.
+    #
+    # Using .NET Core requires a separate install - but it will be present on a lot of
+    # systems.
+    #
+    # So - try to load .NET Core; if it succeeds, use it. If the load fails, fall back
+    # to .NET Framework. If we're on ARM64, check to see if the interpreter is running
+    # in emulation mode. If it is, we're OK; if we're not, stop the interpreter; the
+    # .NET gives instructions on how to install .NET.
+    #
+    # But: If TOGA_WINFORMS_USE_NETFX is defined in the environment, ignore .NET Core
+    # and prefer .NET Framework 4.x
+    ####################################################################################
+    if os.environ.get("TOGA_WINFORMS_USE_NETFX", False):  # pragma: no-cover-if-netcore
+        raise RuntimeError("Explicitly requesting .NET Framework 4.x")
+    else:  # pragma: no-cover-if-netfx
+        # runtime.json defines the .NET version. .NET 10 is the current LTS release.
+        set_runtime(
+            clr_loader.get_coreclr(
+                runtime_config=Path(__file__).parent / "resources/runtime.json"
+            )
+        )
+
+        # .NET Core load succeeded
+        _use_dotnet_core = True
+except (clr_loader.util.clr_error.ClrError, RuntimeError):  # pragma: no cover
+    # .NET Core load failed. This whole branch is no-cover because we can't
+    # easily describe no-cover conditions for the failure modes.
+    if platform.machine() == "ARM64" and "ARM64" in platform.python_compiler():
+        # If you're on a native ARM64 machine running an ARM64 Python, .NET Framework
+        # 4.x isn't an option. On Python 3.10 and 3.11, an x86-64 Python running on
+        # ARM64 will return `platform.machine() == "AMD64"`, so it fails the first
+        # part of the test.
+        raise RuntimeError("""
+
+On Windows, Toga requires .NET Core 10. Please visit:
+
+    https://dotnet.microsoft.com/en-us/download/dotnet/10.0
+
+and install the .NET Desktop Runtime.""") from None
+    else:
+        # Either a native x86_64 machine, or an ARM64 machine with and x86_64 Python
+        # interpreter in emulation mode. We can use .NET Framework 4.x
+        _use_dotnet_core = False
+
+
 import clr
 import travertino
 
@@ -9,6 +72,13 @@
 # Add a reference to the Winforms assembly
 clr.AddReference("System.Windows.Forms")
 
+# .NET Core requires some other explicit assemblies
+if _use_dotnet_core:  # pragma: no-cover-if-netfx
+    clr.AddReference("Microsoft.Win32.SystemEvents")
+    clr.AddReference("System.Windows.Extensions")
+else:  # pragma: no-cover-if-netcore
+    pass
+
 # Add a reference to the WindowsBase assembly. This is needed to access
 # System.Windows.Threading.Dispatcher.
 #