Dear imgui node editor - example

[luca-heltai]

I asked codex 5.2 to write a minimal node editor in dear-imgui. This is the results of 1h of playing around.

I wanted to have something I could play with in c++. This is fully functional in the network creation, loading, and saving. The backend understands it and runs it. I love that we can swap frontends like this! It would be fantastic to be able to swap backends in the same way.

[luca-heltai]

The network file for this is:

{
  "author": "coral-editor",
  "date_time_utc": "2026-01-11T22:34:33.000Z",
  "version": 1,
  "workflow": {
    "edges": {
      "11": {
        "source": 15,
        "source_output": 0,
        "target": 12,
        "target_input": 0
      },
      "12": {
        "source": 16,
        "source_output": 0,
        "target": 13,
        "target_input": 0
      },
      "13": {
        "source": 12,
        "source_output": 0,
        "target": 13,
        "target_input": 1
      }
    },
    "nodes": {
      "12": {
        "name": "Cube",
        "position": {
          "x": 50.0,
          "y": -93.0
        },
        "type": "coral::Network",
        "value": "{\"author\":\"coral-editor\",\"date_time_utc\":\"2026-01-11T22:34:33.000Z\",\"version\":1,\"workflow\":{\"edges\":{\"0\":{\"source\":0,\"source_output\":0,\"target\":3,\"target_input\":0},\"1\":{\"source\":1,\"source_output\":0,\"target\":3,\"target_input\":1},\"2\":{\"source\":2,\"source_output\":0,\"target\":3,\"target_input\":2},\"3\":{\"source\":3,\"source_output\":0,\"target\":5,\"target_input\":0}},\"nodes\":{\"0\":{\"position\":{\"x\":128.0,\"y\":-27.0},\"type\":\"dealii::Triangulation<2, 2>\"},\"1\":{\"position\":{\"x\":128.0,\"y\":58.0},\"type\":\"std::string\",\"value\":\"hyper_cube\"},\"2\":{\"position\":{\"x\":123.0,\"y\":163.0},\"type\":\"std::string\",\"value\":\"0: 1: false\"},\"3\":{\"position\":{\"x\":618.0,\"y\":6.0},\"type\":\"GridGenerator::generate_from_name_and_arguments<2>\"},\"5\":{\"position\":{\"x\":765.0,\"y\":248.0},\"type\":\"Triangulation<2>::refine_global\"}}}}"
      },
      "13": {
        "name": "Vtk",
        "position": {
          "x": 455.0,
          "y": -230.0
        },
        "type": "coral::Network",
        "value": "{\"author\":\"coral-editor\",\"date_time_utc\":\"2026-01-11T22:34:33.000Z\",\"version\":1,\"workflow\":{\"edges\":{\"6\":{\"source\":8,\"source_output\":0,\"target\":9,\"target_input\":0},\"8\":{\"source\":7,\"source_output\":0,\"target\":9,\"target_input\":2}},\"nodes\":{\"7\":{\"position\":{\"x\":8.0,\"y\":98.0},\"type\":\"std::ofstream\"},\"8\":{\"position\":{\"x\":-68.0,\"y\":-206.0},\"type\":\"dealii::GridOut\"},\"9\":{\"position\":{\"x\":440.0,\"y\":-154.0},\"type\":\"GridOut::write_vtk<2>\"}}}}"
      },
      "15": {
        "name": "n_refinements",
        "position": {
          "x": -351.0,
          "y": -14.0
        },
        "type": "unsigned int",
        "value": "2"
      },
      "16": {
        "name": "file_name",
        "position": {
          "x": 114.0,
          "y": -366.0
        },
        "type": "std::string",
        "value": "grid-1.vtk"
      }
    }
  }
}

[luca-heltai]

Ps: I did not write a single line of node_editor_main.cc. Just a bit of prompt steering.

[luca-heltai]

@pogmat and @pcolt, this has a bit drifted from its original intent...

I have split coral project into

core/tools/gui/backends

and enabled plugin based backends, splitting core coral utilities (coral.h, coral_network.h) from the deal.II backend itself, so that we could in principle have other backends in place that can be loaded at run time.

No change in functionality here, just splitting sources in core/backend, with minimal dependencies in core (no deal.II, no boost, etc.) and deal.II dependencies only in backend.

I also did the same with the ImGui based node editor, and I started working on a mesh manipulator based on vtk.