GNodeGUI

GNodeGUI is a C++ graphical node editor library aimed at providing an interface for building and manipulating nodes in a graphical context. This library is currently used in the Hesiod GUI, a node-based system for heightmap generation.

Features

• Node-based graphical interface
• Supports custom node definitions

Build Instructions

1. Clone the repository:

   git clone --recurse-submodules https://github.com/otto-link/GNodeGUI.git

2. Build using CMake:

   mkdir build && cd build
   cmake ..
   make

Application-owned graph editing

GraphViewer can delegate connection and deletion gestures to an application editor. Override these protected methods:

void request_connection(const gngui::LinkEndpoints &link) override;
void request_deletion(const std::vector<std::string> &node_ids,
                      const std::vector<gngui::LinkEndpoints> &links) override;

Requests arrive before established graphics nodes or links are changed. Connection endpoints are ordered output to input, regardless of drag direction. The temporary drag line is removed before the request. An occupied input retains its existing link until the editor accepts a replacement. Delete and Ctrl + right-click use the same deletion request; deleting a selection produces one batch of IDs and explicitly selected links. Incident links need not be individually selected.

The override owns validation, model mutation, error handling and synchronization. It may reject a request by leaving the graph and scene unchanged. For accepted edits, use add_node / add_link and erase_node / erase_link to synchronize the scene. Erasing a node also erases its incident graphics links. The erase methods return whether an item existed and emit no node_deleted or connection_deleted signals. Selection notifications still work. Keep the model proxies valid until their graphics items have been removed. Request arguments are owned values, but an override must copy them if it retains a request after returning.

Do not call the base request implementation when the application owns the edit. The defaults preserve standalone editing and the legacy after-edit signals. Existing remove_node / remove_link methods also retain those signals for compatibility. These legacy signals are not a second command path for a controller using the request overrides.

Regression tests

cmake -S . -B build -DGNODEGUI_ENABLE_TESTS=ON
cmake --build build --target test_edit_requests
ctest --test-dir build --output-on-failure

Tests require Qt Test and run with the offscreen platform plugin. They cover accepted and rejected requests, input replacement, both drag directions, batched deletion, Ctrl + right-click and legacy notifications. The interactive example is built as graph_viewer_demo (test is reserved for CTest).

License

This project is licensed under the GPL-3.0 license.