The first series of changes relate to modifying the way that SGraphNode* inheritants are created. Previously, NodeFactory was responsible of creating the SGraphNode* inheritants based on some runtime type checking (which basically means a series of if statements checking if the passed in pointer is of a certain child class type). Now, the UMaterialGraph* inheritants (the controller classes in the MVC paradigm of the material graph) are responsible for creating their own UI components (SGraphNode* inheritants). This just means that we now polymorphically create the proper SGraphNode* for the given UMaterialGraph* inheritant.
This refactor allows us to more flexibly create a variety of nodes types instead of relying on SGraphNodeMaterialBase as a one size fits all solution, leading to the new HLSL custom node. Previously, this node didn't support showing the syntax-highlighted code inline in the node itself. Because we now use polymorphism to create the nodes, it was very easy to create new UMaterialGraph* and SGraphNode* inheritants to support this new change.
Other changes which relate to propagating changes (to affect previews) in MaterialGraphNode.cpp are needed because there previously wasn't the mechanism to do so (which may have been a bug). For instance, suppose you had a constant vector3 feeding into a custom HLSL node which just outputs the color coming from that constant vector3 node. It would be obvious that changing the vector3, requires a preview update of the HLSL node. However, that wouldn't happen - the preview on the HLSL node just stayed the same. These changes addresses that issue.
There is one last series of changes which relates to collapsing the HLSL code in the node. We want to make sure that this change doesn't mess up the layouts of artists' already made material graphs which use the custom HLSL node. In order to address this, we added the ability to collapse the code in order to hide it. Furthermore, we had to make sure that projects which previously used a custom HLSL node, have the code collapsed by default (because it wasn't there before). However, creating a new HLSL node once this change comes in, would yield an uncollapsed node. The collapsing of nodes uses the "Advanced Pins" chevron/collapser which doesn't save its state after saving and exiting the material. It was crucial, in order to preserve the layout of the material graph, that the saving happens. However, previously, the only way to save state, was to go through a recompile/regeneration of the previews. Therefore, it was necessary to add a special function in the material editor utilities which would just mark the material as dirty such that states like whether the code was collapsed save throughout sessions.
#jira UE-146779
#rb jason.nadro
[CL 26677757 by luc rosenzweig in ue5-main branch]
Cloth Editor: fix for interactive tool starting when the user drags a node in the dataflow graph editor
#jira UE-190816
#rb daren.cheng alex.mcadams
[CL 26547957 by tyson brochu in ue5-main branch]
