prompt: You will be provided with a partial code base and an issue statement explaining a problem to resolve.
  <issue>
  SceneGraph: HowTo view single scene in different viewboxes
  Using https://github.com/vispy/vispy/blob/master/examples/basics/scene/one_scene_four_cams.py to view a single scene in four different viewboxes doesn't work.
  
  The scene is actually generated four times, not only once. There are reminders of multi-parenting commented out in the example, but this won't work any more (since removal of multi-parenting).
  
  Is it possible to have one scene viewed from different angels (eg. top view, front view and side view) without recreating the scene four times?
  
  
  </issue>
  <code>
  [start of examples/basics/scene/one_scene_four_cams.py]
  1 # -*- coding: utf-8 -*-
  2 # -----------------------------------------------------------------------------
  3 # Copyright (c) Vispy Development Team. All Rights Reserved.
  4 # Distributed under the (new) BSD License. See LICENSE.txt for more info.
  5 # -----------------------------------------------------------------------------
  6 # vispy: gallery 2
  7 
  8 """
  9 Demonstrating a single scene that is shown in four different viewboxes,
  10 each with a different camera.
  11 """
  12 
  13 # todo: the panzoom camera sometimes work, sometimes not. Not sure why.
  14 # we should probably make iterating over children deterministic, so that
  15 # an error like this becomes easier to reproduce ...
  16 
  17 import sys
  18 
  19 from vispy import app, scene, io
  20 
  21 canvas = scene.SceneCanvas(keys='interactive')
  22 canvas.size = 800, 600
  23 canvas.show()
  24 
  25 # Create two ViewBoxes, place side-by-side
  26 vb1 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)
  27 vb2 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)
  28 vb3 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)
  29 vb4 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)
  30 scenes = vb1.scene, vb2.scene, vb3.scene, vb4.scene
  31 
  32 # Put viewboxes in a grid
  33 grid = canvas.central_widget.add_grid()
  34 grid.padding = 6
  35 grid.add_widget(vb1, 0, 0)
  36 grid.add_widget(vb2, 0, 1)
  37 grid.add_widget(vb3, 1, 0)
  38 grid.add_widget(vb4, 1, 1)
  39 
  40 # Create some visuals to show
  41 # AK: Ideally, we could just create one visual that is present in all
  42 # scenes, but that results in flicker for the PanZoomCamera, I suspect
  43 # due to errors in transform caching.
  44 im1 = io.load_crate().astype('float32') / 255
  45 #image1 = scene.visuals.Image(im1, grid=(20, 20), parent=scenes)
  46 for par in scenes:
  47     image = scene.visuals.Image(im1, grid=(20, 20), parent=par)
  48 
  49 #vol1 = np.load(io.load_data_file('volume/stent.npz'))['arr_0']
  50 #volume1 = scene.visuals.Volume(vol1, parent=scenes)
  51 #volume1.transform = scene.STTransform(translate=(0, 0, 10))
  52 
  53 # Assign cameras
  54 vb1.camera = scene.BaseCamera()
  55 vb2.camera = scene.PanZoomCamera()
  56 vb3.camera = scene.TurntableCamera()
  57 vb4.camera = scene.FlyCamera()
  58 
  59 
  60 # If True, show a cuboid at each camera
  61 if False:
  62     cube = scene.visuals.Cube((3, 3, 5))
  63     cube.transform = scene.STTransform(translate=(0, 0, 6))
  64     for vb in (vb1, vb2, vb3, vb4):
  65         vb.camera.parents = scenes
  66         cube.add_parent(vb.camera)
  67 
  68 if __name__ == '__main__':
  69     if sys.flags.interactive != 1:
  70         app.run()
  71
  [end of examples/basics/scene/one_scene_four_cams.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/examples/basics/scene/one_scene_four_cams.py b/examples/basics/scene/one_scene_four_cams.py
  --- a/examples/basics/scene/one_scene_four_cams.py
  +++ b/examples/basics/scene/one_scene_four_cams.py
  @@ -8,11 +8,12 @@
   """
   Demonstrating a single scene that is shown in four different viewboxes,
   each with a different camera.
  -"""
   
  -# todo: the panzoom camera sometimes work, sometimes not. Not sure why.
  -# we should probably make iterating over children deterministic, so that
  -# an error like this becomes easier to reproduce ...
  +Note:
  +    This example just creates four scenes using the same visual.
  +    Multiple views are currently not available. See #1124 how this could
  +    be achieved.
  +"""
   
   import sys
   
  @@ -22,7 +23,7 @@
   canvas.size = 800, 600
   canvas.show()
   
  -# Create two ViewBoxes, place side-by-side
  +# Create four ViewBoxes
   vb1 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)
   vb2 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)
   vb3 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)
  @@ -38,33 +39,16 @@
   grid.add_widget(vb4, 1, 1)
   
   # Create some visuals to show
  -# AK: Ideally, we could just create one visual that is present in all
  -# scenes, but that results in flicker for the PanZoomCamera, I suspect
  -# due to errors in transform caching.
   im1 = io.load_crate().astype('float32') / 255
  -#image1 = scene.visuals.Image(im1, grid=(20, 20), parent=scenes)
   for par in scenes:
       image = scene.visuals.Image(im1, grid=(20, 20), parent=par)
   
  -#vol1 = np.load(io.load_data_file('volume/stent.npz'))['arr_0']
  -#volume1 = scene.visuals.Volume(vol1, parent=scenes)
  -#volume1.transform = scene.STTransform(translate=(0, 0, 10))
  -
   # Assign cameras
   vb1.camera = scene.BaseCamera()
   vb2.camera = scene.PanZoomCamera()
   vb3.camera = scene.TurntableCamera()
   vb4.camera = scene.FlyCamera()
   
  -
  -# If True, show a cuboid at each camera
  -if False:
  -    cube = scene.visuals.Cube((3, 3, 5))
  -    cube.transform = scene.STTransform(translate=(0, 0, 6))
  -    for vb in (vb1, vb2, vb3, vb4):
  -        vb.camera.parents = scenes
  -        cube.add_parent(vb.camera)
  -
   if __name__ == '__main__':
       if sys.flags.interactive != 1:
           app.run()
  
verification_info: {"golden_diff": "diff --git a/examples/basics/scene/one_scene_four_cams.py b/examples/basics/scene/one_scene_four_cams.py\n--- a/examples/basics/scene/one_scene_four_cams.py\n+++ b/examples/basics/scene/one_scene_four_cams.py\n@@ -8,11 +8,12 @@\n \"\"\"\n Demonstrating a single scene that is shown in four different viewboxes,\n each with a different camera.\n-\"\"\"\n \n-# todo: the panzoom camera sometimes work, sometimes not. Not sure why.\n-# we should probably make iterating over children deterministic, so that\n-# an error like this becomes easier to reproduce ...\n+Note:\n+    This example just creates four scenes using the same visual.\n+    Multiple views are currently not available. See #1124 how this could\n+    be achieved.\n+\"\"\"\n \n import sys\n \n@@ -22,7 +23,7 @@\n canvas.size = 800, 600\n canvas.show()\n \n-# Create two ViewBoxes, place side-by-side\n+# Create four ViewBoxes\n vb1 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)\n vb2 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)\n vb3 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)\n@@ -38,33 +39,16 @@\n grid.add_widget(vb4, 1, 1)\n \n # Create some visuals to show\n-# AK: Ideally, we could just create one visual that is present in all\n-# scenes, but that results in flicker for the PanZoomCamera, I suspect\n-# due to errors in transform caching.\n im1 = io.load_crate().astype('float32') / 255\n-#image1 = scene.visuals.Image(im1, grid=(20, 20), parent=scenes)\n for par in scenes:\n     image = scene.visuals.Image(im1, grid=(20, 20), parent=par)\n \n-#vol1 = np.load(io.load_data_file('volume/stent.npz'))['arr_0']\n-#volume1 = scene.visuals.Volume(vol1, parent=scenes)\n-#volume1.transform = scene.STTransform(translate=(0, 0, 10))\n-\n # Assign cameras\n vb1.camera = scene.BaseCamera()\n vb2.camera = scene.PanZoomCamera()\n vb3.camera = scene.TurntableCamera()\n vb4.camera = scene.FlyCamera()\n \n-\n-# If True, show a cuboid at each camera\n-if False:\n-    cube = scene.visuals.Cube((3, 3, 5))\n-    cube.transform = scene.STTransform(translate=(0, 0, 6))\n-    for vb in (vb1, vb2, vb3, vb4):\n-        vb.camera.parents = scenes\n-        cube.add_parent(vb.camera)\n-\n if __name__ == '__main__':\n     if sys.flags.interactive != 1:\n         app.run()\n", "issue": "SceneGraph: HowTo view single scene in different viewboxes\nUsing https://github.com/vispy/vispy/blob/master/examples/basics/scene/one_scene_four_cams.py to view a single scene in four different viewboxes doesn't work.\n\nThe scene is actually generated four times, not only once. There are reminders of multi-parenting commented out in the example, but this won't work any more (since removal of multi-parenting).\n\nIs it possible to have one scene viewed from different angels (eg. top view, front view and side view) without recreating the scene four times?\n\n", "before_files": [{"content": "# -*- coding: utf-8 -*-\n# -----------------------------------------------------------------------------\n# Copyright (c) Vispy Development Team. All Rights Reserved.\n# Distributed under the (new) BSD License. See LICENSE.txt for more info.\n# -----------------------------------------------------------------------------\n# vispy: gallery 2\n\n\"\"\"\nDemonstrating a single scene that is shown in four different viewboxes,\neach with a different camera.\n\"\"\"\n\n# todo: the panzoom camera sometimes work, sometimes not. Not sure why.\n# we should probably make iterating over children deterministic, so that\n# an error like this becomes easier to reproduce ...\n\nimport sys\n\nfrom vispy import app, scene, io\n\ncanvas = scene.SceneCanvas(keys='interactive')\ncanvas.size = 800, 600\ncanvas.show()\n\n# Create two ViewBoxes, place side-by-side\nvb1 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)\nvb2 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)\nvb3 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)\nvb4 = scene.widgets.ViewBox(border_color='white', parent=canvas.scene)\nscenes = vb1.scene, vb2.scene, vb3.scene, vb4.scene\n\n# Put viewboxes in a grid\ngrid = canvas.central_widget.add_grid()\ngrid.padding = 6\ngrid.add_widget(vb1, 0, 0)\ngrid.add_widget(vb2, 0, 1)\ngrid.add_widget(vb3, 1, 0)\ngrid.add_widget(vb4, 1, 1)\n\n# Create some visuals to show\n# AK: Ideally, we could just create one visual that is present in all\n# scenes, but that results in flicker for the PanZoomCamera, I suspect\n# due to errors in transform caching.\nim1 = io.load_crate().astype('float32') / 255\n#image1 = scene.visuals.Image(im1, grid=(20, 20), parent=scenes)\nfor par in scenes:\n    image = scene.visuals.Image(im1, grid=(20, 20), parent=par)\n\n#vol1 = np.load(io.load_data_file('volume/stent.npz'))['arr_0']\n#volume1 = scene.visuals.Volume(vol1, parent=scenes)\n#volume1.transform = scene.STTransform(translate=(0, 0, 10))\n\n# Assign cameras\nvb1.camera = scene.BaseCamera()\nvb2.camera = scene.PanZoomCamera()\nvb3.camera = scene.TurntableCamera()\nvb4.camera = scene.FlyCamera()\n\n\n# If True, show a cuboid at each camera\nif False:\n    cube = scene.visuals.Cube((3, 3, 5))\n    cube.transform = scene.STTransform(translate=(0, 0, 6))\n    for vb in (vb1, vb2, vb3, vb4):\n        vb.camera.parents = scenes\n        cube.add_parent(vb.camera)\n\nif __name__ == '__main__':\n    if sys.flags.interactive != 1:\n        app.run()\n", "path": "examples/basics/scene/one_scene_four_cams.py"}]}