Linked sockets by Python has is_linked attribute as False #82390

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Sergey · 2020-11-04T05:39:40+01:00

Sergey commented

2020-11-04 05:39:40 +01:00

System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits

Blender Version
Broken: version: 2.91.0 Beta, branch: master, commit date: 2020-10-29 21:28, hash: 9e85812acc

Short description of error
If add link to a node tree in its update method linked sockets will still have is_linked attribute as False. I would expect that it should be True because what else should be expected if I explicitly saying that I what two sockets to be linked to each other.

Exact steps for others to reproduce the error
untitled.blend

Download file
Execute text script in the text editor
Look at prints in console

It is important to me because as I was told I have to replace sockets of reroute nodes in tree update method. https://developer.blender.org/T81701

I'm deleting old sockets with their links and create new one with new links. Then I'm passing running to update system which assumes that if socket has False in is_linked attribute then the socket is really unlinked what is not true anymore.

**System Information** Operating system: Windows-10-10.0.18362-SP0 64 Bits **Blender Version** Broken: version: 2.91.0 Beta, branch: master, commit date: 2020-10-29 21:28, hash: `9e85812acc` **Short description of error** If add link to a node tree in its update method linked sockets will still have `is_linked` attribute as False. I would expect that it should be True because what else should be expected if I explicitly saying that I what two sockets to be linked to each other. **Exact steps for others to reproduce the error** [untitled.blend](https://archive.blender.org/developer/F9189404/untitled.blend) 1. Download file 2. Execute text script in the text editor 3. Look at prints in console It is important to me because as I was told I have to replace sockets of reroute nodes in tree update method. https://developer.blender.org/T81701 ![reroutes.gif](https://archive.blender.org/developer/F9189483/reroutes.gif) I'm deleting old sockets with their links and create new one with new links. Then I'm passing running to update system which assumes that if socket has False in `is_linked` attribute then the socket is really unlinked what is not true anymore.

Sergey commented

2020-11-04 05:39:40 +01:00

Added subscriber: @randum

Sergey commented

2020-11-04 15:43:39 +01:00

Funny thing is that if I'm creating link outside of update tree event (via timer call) sockets are getting their actual status immediately. How this behaviour can be explained?

    tree = create_tree()

    def add_link():
        n1, n2 = tree.nodes[0], tree.nodes[1]
        in_s, out_s = n1.inputs[0], n2.outputs[0]
        tree.links.new(in_s, out_s)
        print('New link was created')
        print(f'Input socket is linked: {in_s.is_linked}')
        print(f'Output socket is linked: {out_s.is_linked}')
    
        
    bpy.app.timers.register(add_link, first_interval=0.1)
    print('TREE WAS ADDED')

TREE WAS ADDED
New link was created
Input socket is linked: True
Output socket is linked: True

untitled (1).blend

Funny thing is that if I'm creating link outside of update tree event (via timer call) sockets are getting their actual status immediately. How this behaviour can be explained? ``` tree = create_tree() def add_link(): n1, n2 = tree.nodes[0], tree.nodes[1] in_s, out_s = n1.inputs[0], n2.outputs[0] tree.links.new(in_s, out_s) print('New link was created') print(f'Input socket is linked: {in_s.is_linked}') print(f'Output socket is linked: {out_s.is_linked}') bpy.app.timers.register(add_link, first_interval=0.1) print('TREE WAS ADDED') ``` ``` TREE WAS ADDED New link was created Input socket is linked: True Output socket is linked: True ``` [untitled (1).blend](https://archive.blender.org/developer/F9195927/untitled__1_.blend)

Richard Antalik commented

2020-11-09 23:03:21 +01:00

Added subscriber: @iss

Richard Antalik commented

2020-11-09 23:03:21 +01:00

Changed status from 'Needs Triage' to: 'Archived'

Richard Antalik closed this issue

2020-11-09 23:03:21 +01:00

Richard Antalik self-assigned this 2020-11-09 23:03:22 +01:00

Richard Antalik commented

2020-11-09 23:03:22 +01:00

Looking at code, adding link will run update function on to_node and on tree itself. So this is potentially quite dangerous to do inside update function. I am not quite sure if these update function calls will be nested or queued. After adding debug print inside update function, it looks like they are queued...

It is not quite clear to me why you need to do this though.

I will just repeat, please use https://www.blender.org/community/ for technical support.

Looking at code, adding link will run update function on `to_node` and on tree itself. So this is potentially quite dangerous to do inside update function. I am not quite sure if these update function calls will be nested or queued. After adding debug print inside update function, it looks like they are queued... It is not quite clear to me why you need to do this though. I will just repeat, please use https://www.blender.org/community/ for technical support.

Sergey commented

2020-11-10 05:51:33 +01:00

Did you read your own message posted several weeks ago?

Color type socket is created by default by operator. In case of shader nodes, socket type is changed in node tree update, which is called by operator. So if you want this functionality, you will have to implement this in your node tree

And now you are talking that it is not the way and :

It is not quite clear to me why you need to do this though.

What is not clear? Why I would like to see my own sockets in reroute node, why I would like to see it linked when it linked or what?

Did you read your own message posted several weeks ago? > Color type socket is created by default by operator. In case of shader nodes, socket type is changed in node tree update, which is called by operator. So if you want this functionality, you will have to implement this in your node tree And now you are talking that it is not the way and : > It is not quite clear to me why you need to do this though. What is not clear? Why I would like to see my own sockets in reroute node, why I would like to see it linked when it linked or what?

Richard Antalik commented

2020-11-10 18:45:37 +01:00

In #82390#1051306, @randum wrote:
Did you read your own message posted several weeks ago?

Color type socket is created by default by operator. In case of shader nodes, socket type is changed in node tree update, which is called by operator. So if you want this functionality, you will have to implement this in your node tree

And now you are talking that it is not the way and

I am not talking about sockets here, I am saying what happens when you create a link. rna_NodeTree_link_new() is function that does this.

It is not quite clear to me why you need to do this though.

What is not clear? Why I would like to see my own sockets in reroute node, why I would like to see it linked when it linked or what?

Why do you need to add links from within update function. Perhaps custom operator woud be better here, I am not sure.

> In #82390#1051306, @randum wrote: > Did you read your own message posted several weeks ago? > >> Color type socket is created by default by operator. In case of shader nodes, socket type is changed in node tree update, which is called by operator. So if you want this functionality, you will have to implement this in your node tree > > And now you are talking that it is not the way and I am not talking about sockets here, I am saying what happens when you create a link. `rna_NodeTree_link_new()` is function that does this. >> It is not quite clear to me why you need to do this though. > > What is not clear? Why I would like to see my own sockets in reroute node, why I would like to see it linked when it linked or what? Why do you need to add links from within update function. Perhaps custom operator woud be better here, I am not sure.

Sergey commented

2020-11-11 05:25:40 +01:00

How custom operator will be notify that reroute node was connected then? What I need is that reroute always has sockets the same type as socket to which it is connected. In another topic you gave me advice to do this in update function.

Richard Antalik commented

2020-11-11 20:55:53 +01:00

What I need is that reroute always has sockets the same type as socket to which it is connected.

Then just change type? I don't see why you would need to create new links.

> What I need is that reroute always has sockets the same type as socket to which it is connected. Then just change type? I don't see why you would need to create new links.

Sergey commented

2020-11-12 05:09:50 +01:00

The type of a socket is its class. It impossible to change class of an instance. Change socket type means to create new socket instance from another class.

Richard Antalik commented

2020-11-12 05:52:47 +01:00

I was almost convinced, but I thought that before I reopen I will need some evidence. However this function seems to work pretty well:

    def update(self):
        nodes = self.nodes
        for node in nodes:
            if isinstance(node, bpy.types.NodeReroute):
                in_sock = node.inputs[0]
                - in_sock.display_shape = 'SQUARE_DOT'
                - in_sock.type = 'VECTOR'
                from_sock = in_sock.links[0].from_socket
                in_sock.type = from_sock.type

I see some glitches like when you add more reroutes, this doesn't work well. That looks like a bug on the surface, but you can probably bubble up chain up to the actual node as workaround.

I was almost convinced, but I thought that before I reopen I will need some evidence. However this function seems to work pretty well: ``` def update(self): nodes = self.nodes for node in nodes: if isinstance(node, bpy.types.NodeReroute): in_sock = node.inputs[0] - in_sock.display_shape = 'SQUARE_DOT' - in_sock.type = 'VECTOR' from_sock = in_sock.links[0].from_socket in_sock.type = from_sock.type ``` I see some glitches like when you add more reroutes, this doesn't work well. That looks like a bug on the surface, but you can probably bubble up chain up to the actual node as workaround.

Sergey commented

2020-11-12 06:47:23 +01:00

Here is the list of standard socket types:

To see type of socket you should use socket.bl_idname

Value of type attribute of a socket is not type of socket. It is type of its default value.

Here is the list of standard socket types: ![2020-11-12_09-36-16.png](https://archive.blender.org/developer/F9263472/2020-11-12_09-36-16.png) To see type of socket you should use `socket.bl_idname` Value of type attribute of a socket is not type of socket. It is type of its default value.

Richard Antalik commented

2020-11-12 21:21:23 +01:00

I added debug prints of in_sock.bl_idname to update function

    def update(self):
        nodes = self.nodes
        for node in nodes:
            if isinstance(node, bpy.types.NodeReroute):
                in_sock = node.inputs[0]
                from_sock = in_sock.links[0].from_socket
                print(in_sock.bl_idname)
                in_sock.type = from_sock.type
                print(in_sock.bl_idname)

After making reroute, the output was:

NodeSocketColor
NodeSocketVector

So you should rather change type member of NodeSocket class to change its instance. This looks like it's working as expected.
Maybe a bit weird from OOP perspective, but these data structures are in C and there you can change class without having to make new intance.

I added debug prints of `in_sock.bl_idname` to update function ``` def update(self): nodes = self.nodes for node in nodes: if isinstance(node, bpy.types.NodeReroute): in_sock = node.inputs[0] from_sock = in_sock.links[0].from_socket print(in_sock.bl_idname) in_sock.type = from_sock.type print(in_sock.bl_idname) ``` After making reroute, the output was: ``` NodeSocketColor NodeSocketVector ``` So you should rather change `type` member of `NodeSocket` class to change its instance. This looks like it's working as expected. Maybe a bit weird from OOP perspective, but these data structures are in C and there you can change class without having to make new intance.

Sergey commented

2020-11-13 05:25:41 +01:00

Okay. Here is MY socket. How can I switch type of socket of any other type to socket of mine?

class MyCustomSocket(NodeSocket):
    bl_idname = 'MyCustomSocket'
    bl_label = "My Custom Socket"

    def draw_color(self, context, node):
        return (0.0, 0.0, 0.0, 1)
    
    def draw(self, context, layout, node, text):
        layout.label(text=text)

Okay. Here is MY socket. How can I switch type of socket of any other type to socket of mine? ``` class MyCustomSocket(NodeSocket): bl_idname = 'MyCustomSocket' bl_label = "My Custom Socket" def draw_color(self, context, node): return (0.0, 0.0, 0.0, 1) def draw(self, context, layout, node, text): layout.label(text=text) ```

Richard Antalik commented

2020-11-13 06:49:14 +01:00

Changed status from 'Archived' to: 'Needs Triage'

Richard Antalik reopened this issue

2020-11-13 06:49:14 +01:00

Richard Antalik commented

2020-11-13 06:49:14 +01:00

Added subscriber: @JacquesLucke

Richard Antalik commented

2020-11-13 06:49:14 +01:00

That seems to be problematic. So to recapitulate this:

Issue is that Add Reroute operator always creates color socket.
Node socket type should be changed during node tree update function, which works fine for predefined types.
But for custom socket type defined in python, it seems that it is necessary to make new socket instance and rebuild links to and from socket.
However is_linked property of socket is not changed immediately, but in node update function if I remember this correctly. Also this will cause node tree function to be called. I am not sure if this is making this problem unsolvable, but id definitely doesn't sound nice.

@JacquesLucke Can you look at this comment and give your opinion if this could be a bug? or are we missing something?

That seems to be problematic. So to recapitulate this: Issue is that Add Reroute operator always creates color socket. Node socket type should be changed during node tree update function, which works fine for predefined types. But for custom socket type defined in python, it seems that it is necessary to make new socket instance and rebuild links to and from socket. However is_linked property of socket is not changed immediately, but in node update function if I remember this correctly. Also this will cause node tree function to be called. I am not sure if this is making this problem unsolvable, but id definitely doesn't sound nice. @JacquesLucke Can you look at this comment and give your opinion if this could be a bug? or are we missing something?

Philipp Oeser commented

2021-06-02 10:10:08 +02:00

Changed status from 'Needs Triage' to: 'Confirmed'

Richard Antalik was unassigned by Philipp Oeser

2021-06-02 10:10:08 +02:00

Joshua Knauber commented

2022-01-29 12:19:51 +01:00

Added subscriber: @JoshuaKnauber