Nodes: Add support to mute node wires

This patch adds the ability to mute individual wires in the node editor.
This is invoked like the cut links operator but with a new shortcut.

Mute = Ctrl + Alt
Cut = Ctrl

Dragging over wires will toggle the mute state for that wire.
The muted wires are drawn in red with a bar across the center.
Red is used in the nodes context to indicate invalid links, muted links and internal links.

When a wire is muted it exposes the original node buttons which are normally hidden when a wire is connected.

Downstream and upstream links connected using reroute nodes are also muted.

Outside scope of patch:
- Add support for pynodes e.g. Animation Nodes
- Requires minor change to check for muted links using the `is_muted` link property or the `is_linked` socket property.

Maniphest Tasks: T52659

Differential Revision: https://developer.blender.org/D2807

release/scripts/presets/keyconfig/keymap_data/blender_default.py

@@ -1844,6 +1844,7 @@ def km_node_editor(params):
         ("node.resize", {"type": 'EVT_TWEAK_L', "value": 'ANY'}, None),
         ("node.add_reroute", {"type": 'EVT_TWEAK_L' if params.legacy else 'EVT_TWEAK_R', "value": 'ANY', "shift": True}, None),
         ("node.links_cut", {"type": 'EVT_TWEAK_L' if params.legacy else 'EVT_TWEAK_R', "value": 'ANY', "ctrl": True}, None),
+        ("node.links_mute", {"type": 'EVT_TWEAK_R', "value": 'ANY', "ctrl": True, "alt": True}, None),
         ("node.select_link_viewer", {"type": 'LEFTMOUSE', "value": 'PRESS', "shift": True, "ctrl": True}, None),
         ("node.backimage_move", {"type": 'MIDDLEMOUSE', "value": 'PRESS', "alt": True}, None),
         ("node.backimage_zoom", {"type": 'V', "value": 'PRESS', "repeat": True},

release/scripts/presets/keyconfig/keymap_data/industry_compatible_data.py

@@ -1113,6 +1113,7 @@ def km_node_editor(params):
         ("node.resize", {"type": 'EVT_TWEAK_L', "value": 'ANY'}, None),
         ("node.add_reroute", {"type": params.action_tweak, "value": 'ANY', "shift": True}, None),
         ("node.links_cut", {"type": params.action_tweak, "value": 'ANY', "ctrl": True}, None),
+        ("node.links_mute", {"type": params.action_tweak, "value": 'ANY', "ctrl": True, "alt": True}, None),
         ("node.select_link_viewer", {"type": 'LEFTMOUSE', "value": 'PRESS', "shift": True, "ctrl": True}, None),
         ("node.backimage_fit", {"type": 'A', "value": 'PRESS', "alt": True}, None),
         ("node.backimage_sample", {"type": 'LEFTMOUSE', "value": 'PRESS', "alt": True}, None),

release/scripts/startup/bl_ui/space_node.py

@@ -331,6 +331,7 @@ class NODE_MT_node(Menu):
         layout.operator("node.link_make", text="Make and Replace Links").replace = True
         layout.operator("node.links_cut")
         layout.operator("node.links_detach")
+        layout.operator("node.links_mute")
 
         layout.separator()