How to visually display a warning on a node

[wassimj]

My code does the following:

def processItem(cells):
    cellComplex = cells[0]
    for i in range(1,len(cells)):
        try:
            cellComplex = cellComplex.Merge(cells[i], False)
        except:
            raise Exception("Error: CellComplex.ByCells operation failed during processing the input Cells")
    if cellComplex.GetType() != 64: #64 is the type of a CellComplex
        warnings.warn("Warning: Input Cells do not form a CellComplex", UserWarning)
    return fixTopologyClass(cellComplex)

How can I display that warning visually in the GUI (perhaps by changing the colour of the node and/or display the warning text? Is there a standard way to do it?

[Durman]

There is no way to display warnings now, only errors. It could be useful to have such feature but I'm not sure about real example of using this feature.

[zeffii]

if it's vital to user friendliness there are still options using a few bpy features. One thing you could do in the meantime is:

• add a show_warning: StringProperty() property to the node
• in your warning state, you set node.show_warning = "your message", and else node.show_warning = '' (reset it to empty string if there is no warning message)
• add a tooltip operator to display this warning.

[zeffii]

here's a small demo a do_nothing node.

# demo do nothing node

import bpy
from bpy.props import StringProperty

from sverchok.node_tree import SverchCustomTreeNode
from sverchok.data_structure import node_id, updateNode

class WM_OT_svtopo_tooltip(bpy.types.Operator):
    bl_idname = "node.sv_topo_custom_warning_operator"
    bl_label = 'Warning:'
    arg: StringProperty()

    @classmethod
    def description(cls, context, properties):
        return properties.arg

class SvDoNothingNode(bpy.types.Node, SverchCustomTreeNode):
    bl_idname = 'SvDoNothingNode'
    bl_label = 'Do Nothing'
    bl_icon = 'VIEW_PAN'

    show_message: StringProperty()

    def sv_init(self, context):
        self.inputs.new('SvStringsSocket', 'A')
        self.inputs.new('SvStringsSocket', 'B')

    def draw_buttons(self, context, layout):
        row = layout.row(align=True)
        if self.show_message:
            row.alert = True
            row.enabled = False
            op = row.operator("node.sv_topo_custom_warning_operator", icon="QUESTION", text="")
            op.arg = self.show_message

    def process(self):
        self.show_message = ""

        if not all([s.is_linked for s in self.inputs]):
            self.show_message = "Socket A and B must be linked"

classes = [WM_OT_svtopo_tooltip, SvDoNothingNode]
register, unregister = bpy.utils.register_classes_factory(classes)

if __name__ == "__main__":
    register()

[zeffii]

the upside to using a tooltip are, to name a few:

• you can fit a lot of text into it
• it doesn't reshape the node significantly, as opposed to trying to cram a full message into the node ui
• uses available bpy layout API, it can be tweaked to some extent
• if we really wanted, this could be socket specific (so drawing the socket row by prepending the tooltip button before the socket name for input sockets, and appending it for output sockets),
  • like:

    |_________some node _______________________|
    |                         socket_name [?]  o
    o [?] some_name A                          |
    o [?] some_name B                          |
    |__________________________________________|

  • the box node already implements it. (hover with your mouse in the empty space between label and socket will produce a tooltip )
    • 
    • it does that by using

      self.outputs.new('SvVerticesSocket', "Vers").description = "Box vertices"

    • it's not very customizable yet... but it could be, given the right incentives.

downside,

• is not consistent with Exception messages, with draws the messages directly to the nodeview pixels.