As a xoder I want to explode patch nodes so that I can evolve quick-start nodes

[nkrkv]

Rationale

XOD has a convention of quick-start nodes for dealing with hardware. They are trivial combinations of the device and action nodes, but when a xoder wants to get more features out of his device, he has to step back: delete the quick-start node and re-create the existing functionality with new device and action nodes. This is cumbersome. Let’s make a shortcut allowing in-place patch node explosion.

User story

• I select a node
• I hit Edit → Explode Selection
• The node gets replaced with contents of its patch
• The program stays the same semantically: the links are preserved, the values bound to terminals are re-bound to the corresponding pins of internal nodes.
• The neighbor nodes are pushed to the right and bottom so that the explosion does not overlay other nodes on the patch

Acceptance criteria

• I can place and explode xod/math/log-bx, it is replaced with two log-e and a divide
• I can bind B and X to log-bx and they are re-bound to log-e inputs after explosion
• I can link the pins of log-bx to other nodes and they will be kept after the explosion
• The tabtest node is stripped out of the explosion result
• I can put a node to the right of log-bx and it will be pushed by 2 slots to the right on the explosion (1 slot margin)
• I can put a node to the bottom of log-bx and it will be pushed by 2 slots down on the explosion (1 slot margin)
• If I select several nodes and hit Explode Selections, the effect is the same as when exploding one by one (but grouped as a single undo/redo action)
• I can hit Undo once after an explosion and the patch state is reverted back to the pre-explosion state
• If I try to explode a C++ node an error message is shown¹
• If I try to explode a variadic with the arity level more than one, an error message is shown²

¹

C++ nodes don't explode
You may only explode nodes composed out of other nodes internally.
If you want to change the node implementation, make its local fork in your project.

²

Variadic nodes don't explode
You may only explode variadic nodes with the arity level of one. Exploding other
levels are not supported yet.