Accessing and setting the snapping mode.

[davecoventry]

I want the user to pick the centre point of an arc in my script.

How can I save the current snapping point configuration, set the snapping to centre point only and then restore the snapping configuration to what it was?

[carlopav]

It can be done with the Snapper, but for a script maybe it's easier to get the center point from the curve, isn't it?

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s = Gui.Selection.getSelectionEx()[0]
o = s.SubObjects[0]
center = o.Curve.Center

[davecoventry]

Very likely.

However, the arc is part of a wire with multiple fillets.

I might just look at that approach, though.

Thanks for the help!

[davecoventry]

Does anyone know how to manipulate the snapping modes?

Thanks.

[carlopav]

However, the arc is part of a wire with multiple fillets.

Yup, if you select just the segment or the fillet you want to process, the code should work.

Anyway, I was pretty sure about knowing what to answer you until i started to write...
How does your script work? Does it setup a callback to trap mouse movement? if so you are on the right way to use Snapper, else perhaps I suggest to go back to my initial suggestion and use a script that process a subObject that would be far more easy.

The Snapper is part of the Draft module, in its Gui, so first you have to activate the Draft workbench.
When done, you can access the snapper trough:

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Gui.Snapper

this is the documentation vocx provided:

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    """Classes to manage snapping in Draft and Arch.

    The Snapper objects contains all the functionality used by draft
    and arch module to manage object snapping. It is responsible for
    finding snap points and displaying snap markers. Usually You
    only need to invoke it's snap() function, all the rest is taken
    care of.

    3 functions are useful for the scriptwriter: snap(), constrain()
    or getPoint() which is an all-in-one combo.

    The individual snapToXXX() functions return a snap definition in
    the form [real_point,marker_type,visual_point], and are not
    meant to be used directly, they are all called when necessary by
    the general snap() function.

    The Snapper lives inside FreeCADGui once the Draft module has been
    loaded.

    """

The main used function is:

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Gui.Snapper.getPoint(self, last=None, callback=None, movecallback=None, extradlg=None, title=None, mode="point")

this is how it works:

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        """
        getPoint([last],[callback],[movecallback],[extradlg],[title]) : gets a 3D point
        from the screen. You can provide an existing point, in that case additional
        snap options and a tracker are available.
        You can also pass a function as callback, which will get called
        with the resulting point as argument, when a point is clicked, and optionally
        another callback which gets called when the mouse is moved.

        If the operation gets cancelled (the user pressed Escape), no point is returned.

        Example:

        def cb(point):
            if point:
                print "got a 3D point: ",point

        FreeCADGui.Snapper.getPoint(callback=cb)

        If the callback function accepts more than one argument, it will also receive
        the last snapped object. Finally, a qt widget can be passed as an extra taskbox.
        title is the title of the point task box
        mode is the dialog box you want (default is point, you can also use wire and line)

        If getPoint() is invoked without any argument, nothing is done but the callbacks
        are removed, so it can be used as a cancel function.
        """

-------------------------------
Anyway. I suggest you to have a look at how Draft Tools implement Snap:
https://github.com/FreeCAD/FreeCAD/blob ... ls.py#L396

[davecoventry]

Thanks.

If I use the FreeCADGui.Snapper.snapToCenter() function, I need to provide the shape, I think?

It would be nice if the function could simply turn off the snaps except for the snapToCenter() one.

[carlopav]

Thanks.

If I use the FreeCADGui.Snapper.snapToCenter() function, I need to provide the shape, I think?

It would be nice if the function could simply turn off the snaps except for the snapToCenter() one.

I had in mind to implement this. I have a pending PR where I did some refactoring, perhaps in the near future we can think about it.
I was thinking about a special way to let you termporary enable just one snap and bring back the previous configuration after the user clicks a point. But I still do not have clear how to do it.

[davecoventry]

Thanks for your help.

I want the user to enter the points of the arc as a start point, centre of the arc and finish point and I thought a good way of doing this would be to enable the endpoint and centrepoint snapping.

Still, maybe in the future.

[onekk]

try to type in the Python console.

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dir(Part)

If Snapper if there are a decent python interface you will obtain like in the example above, the "exposed" method.

A way to inspect better the method, could be:

Supose you have the arc and the arc is in the object tree and it isi named say "arc0001"

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obj = FreeCAD.activeDocument.getObject("arc0001")
obj.

hitting the . (poin) will make a window appear and suggest the "completion", if you move the mouse over the method name in this window, sometimes appear a tooltip box with if you are lucky the "docstring" of the method, that sometimes is very useful.

Sadly there are many "sometimes, and if you are lucky enough", but better than nothing, is some case it is really useful, I have discovered many treasure in this way.

Regards

Carlo D.