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

1 files changed, 2 insertions, 1 deletions

diff --git a/source/blender/compositor/intern/COM_NodeGraph.cc b/source/blender/compositor/intern/COM_NodeGraph.cc
index f932acfa49e..d8220099f1f 100644
--- a/source/blender/compositor/intern/COM_NodeGraph.cc
+++ b/source/blender/compositor/intern/COM_NodeGraph.cc
@@ -188,7 +188,8 @@ void NodeGraph::add_bNodeLink(const NodeRange &node_range, bNodeLink *b_nodelink
   if (!(b_nodelink->flag & NODE_LINK_VALID)) {
     return;
   }
-  if ((b_nodelink->fromsock->flag & SOCK_UNAVAIL) || (b_nodelink->tosock->flag & SOCK_UNAVAIL)) {
+  if ((b_nodelink->fromsock->flag & SOCK_UNAVAIL) || (b_nodelink->tosock->flag & SOCK_UNAVAIL) ||
+      (b_nodelink->flag & NODE_LINK_MUTED)) {
     return;
   }