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Flatbed.MDI.AvaloniaUI

MDI host built on AvaloniaUI and the Dock component

Windows.NET 8

Latest release v0.5.2 · 2026-05-03
Flatbed.MDI.AvaloniaUI_v0.5.2_net8.0-windows.zip 56.7 MB

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v0.5.1
v0.5.0

Flatbed.MDI.AvaloniaUI is a Windows desktop plugin host built with Avalonia UI, Dock.Avalonia, and SAL.Windows. It loads plugin assemblies from disk, lets the user choose a kernel plugin, and hosts plugin windows inside a dockable multi-document shell.

UI Screenshot

Overview

At startup, the host scans the plugin folder, loads available assemblies, selects an IPluginKernel, initializes settings providers, and then initializes the remaining plugins.

Features

Plugin host

  • File-based plugin discovery from the application base directory.
  • Kernel plugin selection through SelectPluginDlg when multiple kernel plugins are available.
  • Persisted default kernel plugin selection.
  • Session value cache exposed by the host.
  • Cleanup of plugin-owned windows and menu items when a plugin is unloaded.

Docking UI

  • Built on Dock.Avalonia.
  • Uses a document dock plus dynamically created tool docks for side-hosted panels.
  • Tool docks are created on demand for Left, Right, Top, and Bottom placement hints.
  • Built-in utility panels open as tool windows:
    • Output defaults to the bottom side,
    • Event List defaults to the left side.
  • Layout serialization and restore across runs.
  • Full dock tree restore from persisted layout state.
  • Restore of visible, hidden, and pinned dockables, including side placement.
  • User-driven docking layout is preserved across restarts instead of being remapped into fixed host areas.
  • Stable ContentId generation for plugin windows, including persisted settings arguments when available.

Hosted content

  • Avalonia controls can be hosted directly.
  • System.Windows.Forms.Control instances are wrapped and hosted through WinFormsHost.
  • Built-in dockable utility windows:
    • Output
    • Event List

Diagnostics

  • Console output is redirected into the Output panel.
  • Trace events are forwarded into the Output panel.
  • Non-fatal exceptions are collected in the Event List panel.
  • Error notifications are surfaced through in-window notifications.

User settings

  • Main window size, position, and state are persisted.
  • About dialog and plugin selection dialog sizes are persisted.
  • Default kernel plugin is persisted.
  • Options dialog stores authentication-related values and default kernel selection.

Target framework

  • .NET 8
  • net8.0-windows

Runtime behavior

Startup flow

  1. Program.cs starts the Avalonia desktop lifetime.
  2. App.axaml.cs registers tracing and creates MainWindow.
  3. MainWindow loads persisted settings and creates built-in panels.
  4. HostMdi loads plugins from disk.
  5. The kernel plugin is selected.
  6. Plugin settings providers are initialized.
  7. The dock layout is created and restored from disk.

Tray integration

The app defines a tray icon in App.axaml. The active kernel plugin can override the main window title, tray tooltip, and window icon through IKernelInfo.

Command line

  • /SAL_Kernel:PluginName - preselects the default kernel plugin.

Settings and persistence

Settings are stored under one of these locations:

  • the current working directory if Assembly.config exists there,
  • otherwise %AppData%\Company\Kernel.

The effective Company and Kernel values are taken from configuration and can be updated from the selected kernel plugin.

Persisted files include:

  • <AssemblyName>.settings - application settings stored as JSON,
  • <AssemblyName>.Forms.config - dock layout state.

Project structure

  • Flatbed.MDI.AvaloniaUI/Program.cs - application entry point.
  • Flatbed.MDI.AvaloniaUI/App.axaml - global styles and tray icon definition.
  • Flatbed.MDI.AvaloniaUI/App.axaml.cs - application bootstrap and tray commands.
  • Flatbed.MDI.AvaloniaUI/MainWindow.axaml - main shell UI.
  • Flatbed.MDI.AvaloniaUI/MainWindow.axaml.cs - plugin loading, menu handling, layout restore, and window persistence.
  • Flatbed.MDI.AvaloniaUI/Plugins/HostMdi.cs - plugin lifecycle management and host services.
  • Flatbed.MDI.AvaloniaUI/Windows/FlatbedDockFactory.cs - dock layout creation and layout restoration.
  • Flatbed.MDI.AvaloniaUI/Windows/WindowControl.cs - adapter between dockables and plugin UI.
  • Flatbed.MDI.AvaloniaUI/Dialogs/PanelOutput.axaml.cs - output viewer.
  • Flatbed.MDI.AvaloniaUI/Dialogs/PanelEventList.axaml.cs - exception/event viewer.
  • Flatbed.MDI.AvaloniaUI/Logging/HostTraceListener.cs - trace forwarding into the host UI.
  • Flatbed.MDI.AvaloniaUI/Logging/ConsoleReader.cs - redirects Console.Out to the Output panel.
  • SAL.Shared/ - shared configuration, plugin provider, settings, and utility code linked into the app.

Plugin development

This host is built around abstractions from SAL.Flatbed and SAL.Windows.

Typical plugin integration points:

  • implement IPlugin for a standard plugin,
  • implement IPluginKernel for a kernel plugin,
  • implement IKernelInfo to provide application name, icon, or logo metadata,
  • implement IPluginSettings for windows that need persisted arguments,
  • use IHostWindows, IWindows, IMenu, and IToolBarContainer to integrate with the host shell.

Drop plugin assemblies into the application base directory to make them available to the host.

Build

dotnet build .\Flatbed.MDI.AvaloniaUI\Flatbed.MDI.AvaloniaUI.csproj

Notes

  • This is a Windows-only desktop host because it targets net8.0-windows and enables WindowsForms interop.
  • The current implementation is an Avalonia-based shell, not a WPF shell.