Node graph visualization and editing with PySide.

Very WIP right now, the goal is to have a bunch of premade components that make it easy to implement a node graph to store and modify arbitrary data.

The UI part is coming along nicely, but no actual data handling is attached to it yet.

Although this graph makes no sense, it shows the current look and feel:

from PySide import QtGui
from qtnodes import (Header, Node, InputKnob,
                     OutputKnob, NodeGraphWidget)

class Multiply(Node):

    def __init__(self, *args, **kwargs):
        super(Multiply, self).__init__(*args, **kwargs)
        self.addHeader(Header(node=self, text=self.__class__.__name__))
        self.addKnob(InputKnob(name="x"))
        self.addKnob(InputKnob(name="y"))
        self.addKnob(OutputKnob(name="value"))

app = QtGui.QApplication([])
graph = NodeGraphWidget()
graph.registerNodeClass(Multiply)
graph.addNode(Multiply())
graph.show()
app.exec_()

To start a small demo:

$ python -m qtnodes

You can load example .json files from examples/.

• Pan the viewport: Hold the middle mousebutton and drag.
• Zoom the viewport: Use the mouse wheel.
• Save scene to file: Rightclick > Scene > Save As...
• Load scene from file: Rightclick > Scene > Open File...
• Merge scene from file: Rightclick > Scene > Merge File...
• Clear complete scene: Rightclick > Scene > Clear Scene
• Hold scene state: Rightclick > Scene > Hold
• Fetch scene state: Rightclick > Scene > Fetch
• Autolayout scene: Rightclick > Scene > Auto Layout

Please note: The automatic layout needs graphviz, which means its dot command must be on PATH.

• Select a node: Leftclick its header.
• Select multiple nodes: Leftclick and drag a rectangle over the nodes, release to select.
• Create a node: Rightclick > Nodes, choose a node type.
• Move a node: Leftclick and drag its header.
• Delete a node: Select it then press DELETE.
• Create a connection: Hover over a knob, then leftclick and drag to another knob. You can only connect inputs to outputs and vice versa.
• Remove a connection: Hold ALT (on Windows, use CTRL on Linux/MacOs), the connections turn red, click one to remove it.

This started as a port of the original Qt/C++ tool qnodeseditor by Stanislaw Adaszewski, see:

https://algoholic.eu/qnodeseditor-qt-nodesports-based-data-processing-flow-editor/

Additional sources and inspirations:

• https://austinjbaker.com/node-editor-prototype
• https://nukengine.com/blog/category/all/qt-node-editor/
• https://blog.interfacevision.com/design/design-visual-progarmming-languages-snapshots/
• https://github.com/Tillsten/qt-dataflow
• https://gist.github.com/dbr/1255776 (Nuke node layout with graphviz)

MIT, see LICENSE.txt