Question re: drawing addon - correct way to clear view/scene/backend?

[bandtank]

Using the drawing addon, is there a built-in way to clear the scene/reset the view/unload the DXF file? When the example first loads without a CAD file, the scene is white and uninitialized. How would I return it to that state?

So far, I am using self._cad._backend.clear(), which seems to mostly work. However, the scene appears to still be loaded because the background is black instead of white, so I'm not sure if that is sufficient to fully reset the frontend and backend. In other words, I'm trying to figure out how to close a DXF file and return the program to the initial state.

[mozman]

You can follow the qtviewer.py example. Start at the CADWidget.set_document() method.

ezdxf/src/ezdxf/addons/drawing/qtviewer.py

Line 259 in 860dd34

def set_document(

The viewer creates a new backend for each new loaded DXF document. This seems to be the safest way to do it.

The CADWidget.draw_layout() method draws another layout of the same DXF document without creating a new backend, which also seems to work.

ezdxf/src/ezdxf/addons/drawing/qtviewer.py

Line 287 in 860dd34

def draw_layout(

[bandtank]

I added this to the CAD Widget:

  def reset(self):
    self._view.clear()
    self._bbox_cache = ezdxf.bbox.Cache()
    self._doc = None
    self._render_context = None
    self._visible_layers = set()
    self._current_layout = None
    self._reset_backend()

The goal was to set as many attributes in the widget as possible to the initial states. It is called from the CAD viewer like this:

  def unloadDXFFile(self):
    self._cad.reset()
    self._doc = None

However, the screen was still black instead of white. I then added the following code to the CAD Graphics View:

  def clear(self):
    self.setScene(qw.QGraphicsScene())

Now the screen is white. It seems like the replacement of the scene fixes the graphical aspect while everything else resets the internal state.

Thanks for the help.