Node Editor in ImGui

About

This is an implementaion of node editor with ImGui-like API.

Project purpose is to serve as a basis for more complex solutions like blueprint editors.

Project is a prototype. What that means in practise:

• API will break. Current API does not help user do the right things and require some head banging on the wall to understand it. Can be done much more better.
• Code is hacked to test ideas, not to pursue production quality
• Relies on modified version of ImGui. There is a goal to use vanila version of ImGui and provide hacked-in code as an extension.
• Keeping dependencies minimal is not a priority. In the long run C++14 without non ImGui dependencies should be a minimum. Currently you will find parts of C++17 and use of picojson.
• If you have issues with editor, please let me know. I'm not going to promise immediate fix but I for sure will take them into account while reworking code.

Code

Editor code is in NodeEditor directory alone. Project can be build with examples with help of CMake 3.8. macOS and Linux require GLFW3 to be installed on your system.

Windows:
    cmake -H. -BBuild -G "Visual Studio 15 2017 Win64"

macOS:
    cmake -H. -BBuild -G "Xcode"

Linux:
    cmake -H. -BBuild -G "Unix Makefiles"

Build:
    cd Build
    cmake --build Build --config Release

You will find examples in Build\Bin directory.

Source code target to be comatible with C++11. Due to last minute pulls it require C++17. This requirement will soon be removed. Sorry for inconvenience.

Note: Editor code has pending refactor. Since almost a year has passed without time to do it, please don't tell me code style is horrible. It was and still is a prototype.

Public API

Public API of node editor is located in NodeEditor.h. For an examples of usage, please see Examples.

Minimal example of simple node can be found in Simple.cpp. If you do not see any node, press 'F' in editor to focus on content.

# include "Application.h"
# include "NodeEditor.h"

namespace ed = ax::NodeEditor;

static ed::EditorContext* g_Context = nullptr;

void Application_Initialize()
{
    g_Context = ed::CreateEditor();
}

void Application_Finalize()
{
    ed::DestroyEditor(g_Context);
}

void Application_Frame()
{
    ed::SetCurrentEditor(g_Context);

    ed::Begin("My Editor");

    int uniqueId = 1;

    // Start drawing nodes.
    ed::BeginNode(uniqueId++);
        ImGui::Text("Node A");
        ed::BeginPin(uniqueId++, ed::PinKind::Target);
            ImGui::Text("-> In");
        ed::EndPin();
        ImGui::SameLine();
        ed::BeginPin(uniqueId++, ed::PinKind::Source);
            ImGui::Text("Out ->");
        ed::EndPin();
    ed::EndNode();

    ed::End();
}

Result:

Dependencies

Code is using own copy of ImGui v1.50 WIP with modifications:

• New: Stack Based Layout implementation
• New: Added option to disable creation of global context. That simplifies management of multi-context environment by removing issues with static initialization. Required in work derived from this project.
• New: Add ImMatrix for stacked transformation. This is pulled from derived project.
• Changed: Made ImGuiStyle shareable between contexts. Required in work derived from this project.
• Changed: Don't clamp negative mouse coordinates to 0. Clamping caused problems with dragging nodes and canvas scrolling. Also was inconsistent behaviod since right bottom edges of DisplaySide did not clamp.
• Changed: Ability to scale polygon AA fringe. This was needed to achieve nice looking zoomed contend.

As a backend modified imgui_impl_dx11 is used. Changes:

• Add: Add ability to create custom RGBA textures.
• Fixed: Return values of WndProc are now correct. (already fixed in main branch)
• Changed: Font atlas texture is gamma corrected and clamped
• Changed: ImGui cursors are mapped to native cursors. It was easy to get this wrong, and I did in first try. WinAPI is a funny thing.