Add dummy as a known platform, and use it in tests

.github/workflows/ci.yml

@@ -87,12 +87,12 @@ jobs:
           - runs-on: ubuntu-latest
           - python-version: "3.7"  # Should be env.min_python_version (https://github.com/actions/runner/issues/480)
           - pre-command:
-          - test-command: pytest
+          - test-command: pytest -v
           - backend: cocoa
             runs-on: macos-latest
           - backend: gtk
             pre-command: "sudo apt-get update -y && sudo apt-get install -y python3-gi python3-gi-cairo gir1.2-gtk-3.0 python3-dev libgirepository1.0-dev libcairo2-dev pkg-config"
-            test-command: "xvfb-run -a -s '-screen 0 2048x1536x24' pytest"
+            test-command: "xvfb-run -a -s '-screen 0 2048x1536x24' pytest -v"
           - backend: iOS
             runs-on: macos-latest
           - backend: winforms
@@ -124,4 +124,4 @@ jobs:
     - name: Test
       run: |
         cd src/${{ matrix.backend }}
-        ${{ matrix.test-command }}
+        TOGA_BACKEND=toga_${{ matrix.backend }} ${{ matrix.test-command }}

docs/conf.py

@@ -59,7 +59,7 @@
 version = '.'.join(release.split('.')[:2])
 
 # Fix the autodoc import issues
-os.environ['TOGA_PLATFORM'] = 'dummy'
+os.environ['TOGA_BACKEND'] = 'toga_dummy'
 
 autoclass_content = 'both'
 

docs/how-to/contribute.rst

@@ -364,7 +364,7 @@ Start by running the core test suite:
     .. code-block:: bash
 
       (venv) $ cd src/core
-      (venv) $ python setup.py test
+      (venv) $ TOGA_BACKEND=toga_dummy python setup.py test
       ...
       ----------------------------------------------------------------------
       Ran 181 tests in 0.343s
@@ -376,7 +376,7 @@ Start by running the core test suite:
     .. code-block:: bash
 
       (venv) $ cd src/core
-      (venv) $ python setup.py test
+      (venv) $ TOGA_BACKEND=toga_dummy python setup.py test
       ...
       ----------------------------------------------------------------------
       Ran 181 tests in 0.343s
@@ -388,20 +388,30 @@ Start by running the core test suite:
     .. code-block:: doscon
 
       (venv) C:\...>cd src/core
+      (venv) C:\...>set TOGA_BACKEND=toga_dummy
       (venv) C:\...>python setup.py test
+      (venv) C:\...>set TOGA_BACKEND=
       ...
       ----------------------------------------------------------------------
       Ran 181 tests in 0.343s
 
       OK (skipped=1)
 
-You should get some output indicating that tests have been run. You shouldn’t
+You should get some output indicating that tests have been run. You shouldn't
 ever get any FAIL or ERROR test results. We run our full test suite before
-merging every patch. If that process discovers any problems, we don’t merge
-the patch. If you do find a test error or failure, either there’s something
-odd in your test environment, or you’ve found an edge case that we haven’t
+merging every patch. If that process discovers any problems, we don't merge
+the patch. If you do find a test error or failure, either there's something
+odd in your test environment, or you've found an edge case that we haven't
 seen before - either way, let us know!
 
+Note that when we run the test suite, we set the environment variable
+``TOGA_BACKEND``. Under normal operation, Toga will automatically choose the
+appropriate backend for your platform. However, when running the tests for
+the core platform, we need to use a special "dummy" backend. This dummy backend
+satisfies the interface contract of a Toga backend, but doesn't acutally
+display any widgets. This allows us to test the behavior of the core library
+independent of the behavior of a specific backend.
+
 Although the tests should all pass, the test suite itself is still
 incomplete. There are many aspects of the Toga Core API that aren't currently
 tested (or aren't tested thoroughly). To work out what *isn't* tested, we're
@@ -421,7 +431,7 @@ ask coverage to generate a report of the data that was gathered:
     .. code-block:: bash
 
       (venv) $ pip install coverage
-      (venv) $ coverage run setup.py test
+      (venv) $ TOGA_BACKEND=toga_dummy coverage run setup.py test
       (venv) $ coverage report -m --include="toga/*"
       Name                                 Stmts   Miss  Cover   Missing
       ------------------------------------------------------------------
@@ -437,7 +447,7 @@ ask coverage to generate a report of the data that was gathered:
     .. code-block:: bash
 
       (venv) $ pip install coverage
-      (venv) $ coverage run setup.py test
+      (venv) $ TOGA_BACKEND=toga_dummy coverage run setup.py test
       (venv) $ coverage report -m --include="toga/*"
       Name                                 Stmts   Miss  Cover   Missing
       ------------------------------------------------------------------
@@ -453,7 +463,9 @@ ask coverage to generate a report of the data that was gathered:
     .. code-block:: doscon
 
       (venv) C:\...>pip install coverage
+      (venv) C:\...>set TOGA_BACKEND=toga_dummy
       (venv) C:\...>coverage run setup.py test
+      (venv) C:\...>set TOGA_BACKEND=
       (venv) C:\...>coverage report -m --include=toga/*
       Name                                 Stmts   Miss  Cover   Missing
       ------------------------------------------------------------------
@@ -488,7 +500,7 @@ expect to see something like:
 
     .. code-block:: bash
 
-      (venv) $ coverage run setup.py test
+      (venv) $ TOGA_BACKEND=toga_dummy coverage run setup.py test
       running test
       ...
       ----------------------------------------------------------------------
@@ -509,7 +521,7 @@ expect to see something like:
 
     .. code-block:: bash
 
-      (venv) $ coverage run setup.py test
+      (venv) $ TOGA_BACKEND=toga_dummy coverage run setup.py test
       running test
       ...
       ----------------------------------------------------------------------
@@ -530,7 +542,9 @@ expect to see something like:
 
     .. code-block:: doscon
 
+      (venv) C:\...>set TOGA_BACKEND=toga_dummy
       (venv) C:\...>coverage run setup.py test
+      (venv) C:\...>set TOGA_BACKEND=
       running test
       ...
       ----------------------------------------------------------------------
@@ -554,70 +568,6 @@ in the coverage results.
 Submit a pull request for your work, and you're done! Congratulations, you're
 a contributor to Toga!
 
-How does this all work?
-=======================
-
-Since you're writing tests for a GUI toolkit, you might be wondering why you
-haven't seen a GUI yet. The Toga Core package contains the API definitions for
-the Toga widget kit. This is completely platform agnostic - it just provides
-an interface, and defers actually drawing anything on the screen to the
-platform backends.
-
-When you run the test suite, the test runner uses a "dummy" backend - a
-platform backend that *implements* the full API, but doesn’t actually *do*
-anything (i.e., when you say display a button, it creates an object, but
-doesn’t actually display a button).
-
-In this way, it's possible to for the Toga Core tests to exercise every API
-entry point in the Toga Core package, verify that data is stored correctly on
-the interface layer, and sent through to the right endpoints in the Dummy
-backend. If the *dummy* backend is invoked correctly, then any other backend
-will be handled correctly, too.
-
-One error you might see...
---------------------------
-
-When you're running these tests - especially when you submit your PR, and the
-tests run on our continuous integration (CI) server - it's possible you might get
-an error that reads::
-
-    ModuleNotFoundError: No module named 'toga_gtk'.
-
-If this happens, you've found an bug in the way the widget you're testing
-has been constructed.
-
-The Core API is designed to be platform independent. When a widget is created,
-it calls upon a "factory" to instantiate the underlying platform-dependent
-implementation. When a Toga application starts running, it will try to guess
-the right factory to use based on the environment where the code is running.
-So, if you run your code on a Mac, it will use the Cocoa factory; if you're on
-a Linux box, it will use the GTK factory.
-
-However, when writing tests, we want to use the "dummy" factory. The Dummy
-factory isn't the "native" platform anywhere - it's just a placeholder. As a
-result, the  dummy factory won't be used unless you specifically request it -
-which means every widget has to honor that request.
-
-Most Toga widgets create their platform-specific implementation when they are
-created. As a result, most Toga widgets should accept a ``factory`` argument -
-and that factory should be used to instantiate any widget implementations or
-sub-widgets.
-
-However, *some* widgets - like Icon - are "late loaded" - the implementation
-isn't created until the widget is actually *used*. Late loaded widgets don't
-accept a ``factory`` when they're created - but they *do* have an `_impl()`
-method that accepts a factory.
-
-If these factory arguments aren't being passed around correctly, then a test
-suite will attempt to create a widget, but will fall back to the platform-
-default factory, rather than the "dummy" factory. If you've installed the
-appropriate platform default backend, you won't (necessarily) get an error,
-but your tests won't use the dummy backend. On our CI server, we deliberately
-don't install a platform backend so we can find these errors.
-
-If you get the ``ModuleNotFoundError``, you need to audit the code to find out
-where a widget is being created without a factory being specified.
-
 It's not just about coverage!
 =============================
 
@@ -629,8 +579,8 @@ purpose it was intended!
 
 As you develop tests and improve coverage, you should be checking that the
 core module is internally **consistent** as well. If you notice any method
-names that aren’t internally consistent (e.g., something called ``on_select``
-in one module, but called ``on_selected`` in another), or where the data isn’t
+names that aren't internally consistent (e.g., something called ``on_select``
+in one module, but called ``on_selected`` in another), or where the data isn't
 being handled consistently (one widget updates then refreshes, but another
 widget refreshes then updates), flag it and bring it to our attention by
 raising a ticket. Or, if you're confident that you know what needs to be done,

nursery/curses/setup.cfg

@@ -48,6 +48,10 @@ include =
     toga_curses
     toga_curses.*
 
+[options.entry_points]
+toga.backends =
+    terminal = toga_curses
+
 [flake8]
 exclude=\
     .eggs/*,\

nursery/qt/setup.cfg

@@ -47,6 +47,12 @@ include =
     toga_qt
     toga_qt.*
 
+[options.entry_points]
+toga.backends =
+    linux = toga_qt
+    macOS = toga_qt
+    windows = toga_qt
+
 [flake8]
 exclude=\
     .eggs/*,\

nursery/tvOS/setup.cfg

@@ -47,6 +47,10 @@ include =
     toga_tvOS
     toga_tvOS.*
 
+[options.entry_points]
+toga.backends =
+    tvOS = toga_tvOS
+
 [flake8]
 exclude=\
     .eggs/*,\

nursery/uwp/setup.cfg

@@ -48,6 +48,10 @@ include =
     toga_uwp
     toga_uwp.*
 
+[options.entry_points]
+toga.backends =
+    windows = toga_uwp
+
 [flake8]
 exclude=\
     .eggs/*,\

nursery/watchOS/setup.cfg

@@ -46,6 +46,10 @@ include =
     toga_watchOS
     toga_watchOS.*
 
+[options.entry_points]
+toga.backends =
+    watchOS = toga_watchOS
+
 [flake8]
 exclude=\
     .eggs/*,\

src/android/setup.cfg

@@ -44,6 +44,10 @@ package_dir =
 python_requires = >= 3.6
 zip_safe = False
 
+[options.entry_points]
+toga.backends =
+    android = toga_android
+
 [options.packages.find]
 where = src
 

src/android/src/toga_android/widgets/button.py

@@ -32,7 +32,7 @@ def set_enabled(self, value):
 
     def set_font(self, font):
         if font:
-            font_impl = font.bind(self.interface.factory)
+            font_impl = font.bind()
             self.native.setTextSize(TypedValue.COMPLEX_UNIT_SP, font_impl.get_size())
             self.native.setTypeface(font_impl.get_typeface(), font_impl.get_style())
 

src/android/src/toga_android/widgets/detailedlist.py

@@ -95,7 +95,7 @@ def _make_row(self, container, i):
         icon_image_view = ImageView(self._native_activity)
         icon = self.interface.data[i].icon
         if icon is not None:
-            icon.bind(self.interface.factory)
+            icon.bind()
             bitmap = BitmapFactory.decodeFile(str(icon._impl.path))
             icon_image_view.setImageBitmap(bitmap)
         icon_layout_params = RelativeLayout__LayoutParams(

src/android/src/toga_android/widgets/label.py

@@ -17,7 +17,7 @@ def set_text(self, value):
 
     def set_font(self, font):
         if font:
-            font_impl = font.bind(self.interface.factory)
+            font_impl = font.bind()
             self.native.setTextSize(TypedValue.COMPLEX_UNIT_SP, font_impl.get_size())
             self.native.setTypeface(font_impl.get_typeface(), font_impl.get_style())
 

src/android/src/toga_android/widgets/multilinetextinput.py

@@ -61,7 +61,7 @@ def set_color(self, color):
 
     def set_font(self, font):
         if font:
-            font_impl = font.bind(self.interface.factory)
+            font_impl = font.bind()
             self.native.setTextSize(TypedValue.COMPLEX_UNIT_SP, font_impl.get_size())
             self.native.setTypeface(font_impl.get_typeface(), font_impl.get_style())
 

src/android/src/toga_android/widgets/numberinput.py

@@ -69,7 +69,7 @@ def set_alignment(self, value):
 
     def set_font(self, font):
         if font:
-            font_impl = font.bind(self.interface.factory)
+            font_impl = font.bind()
             self.native.setTextSize(TypedValue.COMPLEX_UNIT_SP, font_impl.get_size())
             self.native.setTypeface(font_impl.get_typeface(), font_impl.get_style())
 

src/android/src/toga_android/widgets/switch.py

@@ -42,7 +42,7 @@ def get_value(self):
 
     def set_font(self, font):
         if font:
-            font_impl = font.bind(self.interface.factory)
+            font_impl = font.bind()
             self.native.setTextSize(TypedValue.COMPLEX_UNIT_SP, font_impl.get_size())
             self.native.setTypeface(font_impl.get_typeface(), font_impl.get_style())
 

src/android/src/toga_android/widgets/table.py

@@ -220,7 +220,7 @@ def remove_column(self, accessor):
 
     def set_font(self, font):
         if font:
-            self._font_impl = font.bind(self.interface.factory)
+            self._font_impl = font.bind()
         if self.interface.data is not None:
             self.change_source(self.interface.data)
 

src/android/src/toga_android/widgets/textinput.py

@@ -52,7 +52,7 @@ def set_alignment(self, value):
 
     def set_font(self, font):
         if font:
-            font_impl = font.bind(self.interface.factory)
+            font_impl = font.bind()
             self.native.setTextSize(TypedValue.COMPLEX_UNIT_SP, font_impl.get_size())
             self.native.setTypeface(font_impl.get_typeface(), font_impl.get_style())
 

src/cocoa/setup.cfg

@@ -45,6 +45,10 @@ package_dir =
 python_requires = >= 3.6
 zip_safe = False
 
+[options.entry_points]
+toga.backends =
+    macOS = toga_cocoa
+
 [options.packages.find]
 where = src
 

src/cocoa/src/toga_cocoa/app.py

@@ -124,7 +124,7 @@ def create(self):
         self.native = NSApplication.sharedApplication
         self.native.setActivationPolicy(NSApplicationActivationPolicyRegular)
 
-        icon = self.interface.icon.bind(self.interface.factory)
+        icon = self.interface.icon.bind()
         self.native.setApplicationIconImage_(icon.native)
 
         self.resource_path = os.path.dirname(os.path.dirname(NSBundle.mainBundle.bundlePath))
@@ -350,7 +350,7 @@ def set_main_window(self, window):
     def show_about_dialog(self):
         options = NSMutableDictionary.alloc().init()
 
-        options[NSAboutPanelOptionApplicationIcon] = self.interface.icon.bind(self.interface.factory).native
+        options[NSAboutPanelOptionApplicationIcon] = self.interface.icon.bind().native
 
         if self.interface.name is not None:
             options[NSAboutPanelOptionApplicationName] = self.interface.name

src/cocoa/src/toga_cocoa/widgets/button.py

@@ -40,7 +40,7 @@ def create(self):
 
     def set_font(self, font):
         if font:
-            self.native.font = font.bind(self.interface.factory).native
+            self.native.font = font.bind().native
 
     def set_text(self, text):
         self.native.title = self.interface.text