Control surface

ArionControlSurface puts a tree of drawn controls anywhere in a window — docked in a WinForms form, in a WPF panel, as the content of an Avalonia window — not only inside a grid. It is how ArionUI parts move into an existing application one panel at a time.

Preview One control per host, same members on all three: SetRoot, Host, Dispatch, VisualTheme, OpenPane. The WinForms host builds from source and is not a NuGet package yet.

WinForms

using ArionUI.Presentation;                  // ArionTheme
using ArionUI.Rendering.WinForms;            // ArionControlSurface
using Drawn = ArionUI.Presentation.Controls; // WinForms has its own Button and Label

var header = new ArionControlSurface
{
    Dock = DockStyle.Top,
    Height = 48,
    VisualTheme = ArionTheme.Light(),
};
header.SetRoot(new Drawn.StackPanel { Horizontal = true, Gap = 12, MainPadding = 12 }
    .Add(new Drawn.Label { Text = () => Text }, Drawn.StackPanel.Fill)
    .Add(new Drawn.Button { Id = "save", Text = () => "Save", Classes = ["primary"], Click = Save }, cross: 30));

Controls.Add(header);

On WinForms the surface draws its tree on the CPU into one bitmap and puts it on screen in one copy. It has no GL context of its own, so a form can dock many surfaces next to its grids without flicker. The control's BackColor — by default its parent's — is painted behind the tree.

WPF

using ArionUI.Presentation;                  // ArionTheme
using ArionUI.Rendering.Wpf;                 // ArionControlSurface
using Drawn = ArionUI.Presentation.Controls; // WPF has its own Button and Label

var surface = new ArionControlSurface { VisualTheme = ArionTheme.Light() };
surface.SetRoot(form, initialFocusId: "name");
formHost.Children.Add(surface);

The surface is a FrameworkElement, so it can also be declared in XAML and given its tree from code-behind. initialFocusId names the control that takes the keyboard first.

Avalonia

using ArionUI.Presentation;                  // ArionTheme
using ArionUI.Rendering.Avalonia;            // ArionControlSurface
using Drawn = ArionUI.Presentation.Controls; // Avalonia has its own Button and Label

var surface = new ArionControlSurface { VisualTheme = ArionTheme.Dark() };
surface.SetRoot(form);
window.Content = surface;

What the surface does

SetRoot(root, initialFocusId)

Shows a control — usually a StackPanel or a Board of controls — and lays it out in the surface's size.

Host

The hosted tree's ControlHost: focus, hover, pointer capture, the caret. Host.SetFocus(id) moves the keyboard to a control, Host.FindControl(id) finds one.

Dispatch

Keys, text, the clipboard and Tab into and out of the tree; also what a test or a screen reader uses to read and set values by id.

VisualTheme

The theme the surface draws with; null follows the current theme.

OpenPane(content, anchor, placement), ClosePanes(), HasOpenPane

Opens a pane — a menu, your own content — anchored to a rectangle, as on Controls.

MeasureText(text, style)

Measures text with the surface's renderer; menus take it to size themselves.

A surface shows controls. A board that holds view tiles — a data grid, a chart, a 3D scene in a tile — is shown by a grid control instead: grid.MainView = new BoardView(board) on ArionGrid (Avalonia, WPF) or ArionGridControl (WinForms). That path is virtualized in bands and runs on the GPU like a grid.

The WinForms showcase is built this way

Seen from the other side, this is the modernisation path: an ordinary Form whose panels are replaced, one after the other, by ArionUI surfaces and grids. The guide walks through it: Modernise a WinForms or WPF app.

Planned