Imported from VektorNode/selva (AGENTS.md). Install upstream with npx skills add VektorNode/selva. Copyright stays with the author.

Agent Guidance

Read STRUCTURE.md before adding or moving files, and follow CONTRIBUTING.md for validation and pull-request requirements.

Cross-platform plugin UI

Selva's Grasshopper plugin targets Rhino on Windows and macOS. Use Eto.Forms for every Selva-owned window, dialog, table, and interactive control. Do not add WinForms forms or controls for plugin-owned UI.

Grasshopper APIs still expose a few required WinForms boundary types. Keep them when an override or event signature requires them, including ToolStripDropDown in component menus and MouseButtons in canvas mouse events. Contain those references at the host boundary; never use them as a reason to build the window they open with WinForms.

For modeless Eto windows:

• set Owner with RhinoEtoApp.MainWindowForDocument(...) when a Rhino document is available;
• call UseRhinoStyle();
• prevent duplicate instances;
• close and release the window when its owning Grasshopper component is removed;
• verify open, edit, refresh, close, reopen, document switching, and Rhino shutdown behavior.

After changing C# UI, run dotnet build and dotnet test from Plugin/. A Windows build is not enough to claim macOS verification; keep host-required WinForms signatures separate from the Eto UI and request an interactive Mac check for new or substantially changed windows.