prompt: You will be provided with a partial code base and an issue statement explaining a problem to resolve.
  <issue>
  iOS app not showing content with Rubicon ObjC 0.4.4
  ### Describe the bug
  
  When running an iOS app with Toga 0.3.0dev39 and Rubicon 0.4.4, the app isn't successfully started, and the main app content is never displayed. When the app runs, you'll see the following in the log:
   
  ```
  2023-01-24 12:14:13.871494+0800 Hello World[94057:4239245] Running app module: helloworld
  2023-01-24 12:14:14.399629+0800 Hello World[94057:4239245] /Users/rkm/Library/Developer/CoreSimulator/Devices/84FC86CA-1D89-46EF-9349-29DDCF840143/data/Containers/Bundle/Application/7038F3CE-2212-4C60-9067-1978A80DEC8D/Hello World.app/app_packages/toga_iOS/app.py:95: DeprecationWarning: There is no current event loop
  2023-01-24 12:14:14.399738+0800 Hello World[94057:4239245]   self.loop = asyncio.get_event_loop()
  ```
  
  This is a warning, not an error; the app will continue to run.
  
  ### Steps to reproduce
  
  1. Run `examples/tutorial0` on iOS
  2. See error
  
  The app won't crash; but the app window will remain black.
  
  ### Expected behavior
  
  The app should run and window content should be displayed.
  
  ### Screenshots
  
  _No response_
  
  ### Environment
  
  - Operating System: iOS
  - Python version: All
  - Software versions:
    - Briefcase: All
    - Toga: <=0.3.0.dev39
    - Rubicon-objc 0.4.4
  
  
  ### Logs
  
  N/A
  
  ### Additional context
  
  The error has been caused because Toga-iOS 0.3.0.dev39 [included a shim](https://github.com/beeware/toga/blob/v0.3.0.dev39/src/iOS/src/toga_iOS/app.py#L112) that reproduced the implementation of `run_forever_cooperatively()`. This was done when the iOS implementation was originally created, with the expectation that this shim would be replaced with the actual call once Rubicon 0.3 was released. This didn't happen, but the old shim continued to work as it matched the implementation in Rubicon.
  
  However, Rubicon 0.4.4 altered the implementation of `run_forever_cooperatively()`. As a result, the shim in Toga-iOS 0.3.0.dev39 no longer does everything it needs to in order to start the app. 
  
  The issue has already been [fixed in the main branch](https://github.com/beeware/toga/blob/main/iOS/src/toga_iOS/app.py#L117) - the shim has been replaced with the actual call to `run_forever_cooperatively()`.
  
  Two workarounds exist:
  1. Use the `main` branch of Toga in your app.
  2. Block the use of rubicon-objc 0.4.4. If you add `rubicon-objc!=0.4.4` to the requires list in your iOS configuration, this will prevent toga-iOS from using the new version.
  
  
  </issue>
  <code>
  [start of iOS/setup.py]
  1 #!/usr/bin/env python
  2 import re
  3 
  4 from setuptools import setup
  5 
  6 # Version handline needs to be programatic because
  7 # we can't import toga_iOS to compute the version;
  8 # and to support versioned subpackage dependencies
  9 with open("src/toga_iOS/__init__.py", encoding="utf8") as version_file:
  10     version_match = re.search(
  11         r"^__version__ = ['\"]([^'\"]*)['\"]", version_file.read(), re.M
  12     )
  13     if version_match:
  14         version = version_match.group(1)
  15     else:
  16         raise RuntimeError("Unable to find version string.")
  17 
  18 setup(
  19     version=version,
  20     install_requires=[
  21         "rubicon-objc>=0.4.4",
  22         f"toga-core=={version}",
  23     ],
  24 )
  25
  [end of iOS/setup.py]
  [start of cocoa/setup.py]
  1 #!/usr/bin/env python
  2 import re
  3 
  4 from setuptools import setup
  5 
  6 # Version handline needs to be programatic because
  7 # we can't import toga_cocoa to compute the version;
  8 # and to support versioned subpackage dependencies
  9 with open("src/toga_cocoa/__init__.py", encoding="utf8") as version_file:
  10     version_match = re.search(
  11         r"^__version__ = ['\"]([^'\"]*)['\"]", version_file.read(), re.M
  12     )
  13     if version_match:
  14         version = version_match.group(1)
  15     else:
  16         raise RuntimeError("Unable to find version string.")
  17 
  18 setup(
  19     version=version,
  20     install_requires=[
  21         "rubicon-objc>=0.4.4",
  22         f"toga-core=={version}",
  23     ],
  24 )
  25
  [end of cocoa/setup.py]
  </code>
  
  I need you to solve this issue by generating a single patch file that I can apply directly to this repository using git apply. Please respond with a single patch file in the following format.
  <patch>
  diff --git a/file.py b/file.py
  --- a/file.py
  +++ b/file.py
  @@ -1,27 +1,35 @@
   def euclidean(a, b):
  -    while b:
  -        a, b = b, a % b
  -    return a
  +    if b == 0:
  +        return a
  +    return euclidean(b, a % b)
   
   
   def bresenham(x0, y0, x1, y1):
       points = []
       dx = abs(x1 - x0)
       dy = abs(y1 - y0)
  -    sx = 1 if x0 < x1 else -1
  -    sy = 1 if y0 < y1 else -1
  -    err = dx - dy
  +    x, y = x0, y0
  +    sx = -1 if x0 > x1 else 1
  +    sy = -1 if y0 > y1 else 1
   
  -    while True:
  -        points.append((x0, y0))
  -        if x0 == x1 and y0 == y1:
  -            break
  -        e2 = 2 * err
  -        if e2 > -dy:
  -            err -= dy
  -            x0 += sx
  -        if e2 < dx:
  -            err += dx
  -            y0 += sy
  +    if dx > dy:
  +        err = dx / 2.0
  +        while x != x1:
  +            points.append((x, y))
  +            err -= dy
  +            if err < 0:
  +                y += sy
  +                err += dx
  +            x += sx
  +    else:
  +        err = dy / 2.0
  +        while y != y1:
  +            points.append((x, y))
  +            err -= dx
  +            if err < 0:
  +                x += sx
  +                err += dy
  +            y += sy
  +
  +    points.append((x, y))
       return points
  
  </patch>
golden_diff: diff --git a/cocoa/setup.py b/cocoa/setup.py
  --- a/cocoa/setup.py
  +++ b/cocoa/setup.py
  @@ -18,7 +18,7 @@
   setup(
       version=version,
       install_requires=[
  -        "rubicon-objc>=0.4.4",
  -        f"toga-core=={version}",
  +        "rubicon-objc >= 0.4.5rc1, < 0.5.0",
  +        f"toga-core == {version}",
       ],
   )
  diff --git a/iOS/setup.py b/iOS/setup.py
  --- a/iOS/setup.py
  +++ b/iOS/setup.py
  @@ -18,7 +18,7 @@
   setup(
       version=version,
       install_requires=[
  -        "rubicon-objc>=0.4.4",
  -        f"toga-core=={version}",
  +        "rubicon-objc >= 0.4.5rc1, < 0.5.0",
  +        f"toga-core == {version}",
       ],
   )
  
verification_info: {"golden_diff": "diff --git a/cocoa/setup.py b/cocoa/setup.py\n--- a/cocoa/setup.py\n+++ b/cocoa/setup.py\n@@ -18,7 +18,7 @@\n setup(\n     version=version,\n     install_requires=[\n-        \"rubicon-objc>=0.4.4\",\n-        f\"toga-core=={version}\",\n+        \"rubicon-objc >= 0.4.5rc1, < 0.5.0\",\n+        f\"toga-core == {version}\",\n     ],\n )\ndiff --git a/iOS/setup.py b/iOS/setup.py\n--- a/iOS/setup.py\n+++ b/iOS/setup.py\n@@ -18,7 +18,7 @@\n setup(\n     version=version,\n     install_requires=[\n-        \"rubicon-objc>=0.4.4\",\n-        f\"toga-core=={version}\",\n+        \"rubicon-objc >= 0.4.5rc1, < 0.5.0\",\n+        f\"toga-core == {version}\",\n     ],\n )\n", "issue": "iOS app not showing content with Rubicon ObjC 0.4.4\n### Describe the bug\r\n\r\nWhen running an iOS app with Toga 0.3.0dev39 and Rubicon 0.4.4, the app isn't successfully started, and the main app content is never displayed. When the app runs, you'll see the following in the log:\r\n \r\n```\r\n2023-01-24 12:14:13.871494+0800 Hello World[94057:4239245] Running app module: helloworld\r\n2023-01-24 12:14:14.399629+0800 Hello World[94057:4239245] /Users/rkm/Library/Developer/CoreSimulator/Devices/84FC86CA-1D89-46EF-9349-29DDCF840143/data/Containers/Bundle/Application/7038F3CE-2212-4C60-9067-1978A80DEC8D/Hello World.app/app_packages/toga_iOS/app.py:95: DeprecationWarning: There is no current event loop\r\n2023-01-24 12:14:14.399738+0800 Hello World[94057:4239245]   self.loop = asyncio.get_event_loop()\r\n```\r\n\r\nThis is a warning, not an error; the app will continue to run.\r\n\r\n### Steps to reproduce\r\n\r\n1. Run `examples/tutorial0` on iOS\r\n2. See error\r\n\r\nThe app won't crash; but the app window will remain black.\r\n\r\n### Expected behavior\r\n\r\nThe app should run and window content should be displayed.\r\n\r\n### Screenshots\r\n\r\n_No response_\r\n\r\n### Environment\r\n\r\n- Operating System: iOS\r\n- Python version: All\r\n- Software versions:\r\n  - Briefcase: All\r\n  - Toga: <=0.3.0.dev39\r\n  - Rubicon-objc 0.4.4\r\n\r\n\r\n### Logs\r\n\r\nN/A\r\n\r\n### Additional context\r\n\r\nThe error has been caused because Toga-iOS 0.3.0.dev39 [included a shim](https://github.com/beeware/toga/blob/v0.3.0.dev39/src/iOS/src/toga_iOS/app.py#L112) that reproduced the implementation of `run_forever_cooperatively()`. This was done when the iOS implementation was originally created, with the expectation that this shim would be replaced with the actual call once Rubicon 0.3 was released. This didn't happen, but the old shim continued to work as it matched the implementation in Rubicon.\r\n\r\nHowever, Rubicon 0.4.4 altered the implementation of `run_forever_cooperatively()`. As a result, the shim in Toga-iOS 0.3.0.dev39 no longer does everything it needs to in order to start the app. \r\n\r\nThe issue has already been [fixed in the main branch](https://github.com/beeware/toga/blob/main/iOS/src/toga_iOS/app.py#L117) - the shim has been replaced with the actual call to `run_forever_cooperatively()`.\r\n\r\nTwo workarounds exist:\r\n1. Use the `main` branch of Toga in your app.\r\n2. Block the use of rubicon-objc 0.4.4. If you add `rubicon-objc!=0.4.4` to the requires list in your iOS configuration, this will prevent toga-iOS from using the new version.\r\n\n", "before_files": [{"content": "#!/usr/bin/env python\nimport re\n\nfrom setuptools import setup\n\n# Version handline needs to be programatic because\n# we can't import toga_iOS to compute the version;\n# and to support versioned subpackage dependencies\nwith open(\"src/toga_iOS/__init__.py\", encoding=\"utf8\") as version_file:\n    version_match = re.search(\n        r\"^__version__ = ['\\\"]([^'\\\"]*)['\\\"]\", version_file.read(), re.M\n    )\n    if version_match:\n        version = version_match.group(1)\n    else:\n        raise RuntimeError(\"Unable to find version string.\")\n\nsetup(\n    version=version,\n    install_requires=[\n        \"rubicon-objc>=0.4.4\",\n        f\"toga-core=={version}\",\n    ],\n)\n", "path": "iOS/setup.py"}, {"content": "#!/usr/bin/env python\nimport re\n\nfrom setuptools import setup\n\n# Version handline needs to be programatic because\n# we can't import toga_cocoa to compute the version;\n# and to support versioned subpackage dependencies\nwith open(\"src/toga_cocoa/__init__.py\", encoding=\"utf8\") as version_file:\n    version_match = re.search(\n        r\"^__version__ = ['\\\"]([^'\\\"]*)['\\\"]\", version_file.read(), re.M\n    )\n    if version_match:\n        version = version_match.group(1)\n    else:\n        raise RuntimeError(\"Unable to find version string.\")\n\nsetup(\n    version=version,\n    install_requires=[\n        \"rubicon-objc>=0.4.4\",\n        f\"toga-core=={version}\",\n    ],\n)\n", "path": "cocoa/setup.py"}]}