#MessageBox

A MessageBox is a modal dialog with a title, an icon, a rich text message and buttons. ShowAsync returns the button the user chose:

var result = await MessageBox.ShowAsync(this, "Delete the layout?", "Confirm",
    MessageBoxButtons.YesNo, MessageBoxIcon.Question);
if (result == MessageBoxResult.Yes) DeleteLayout();

Build a box yourself for custom buttons:

var box = new MessageBox { Title = "File exists", Message = "<b>report.txt</b> exists.", Icon = MessageBoxIcon.Warning };
box.AddButton("Overwrite", MessageBoxResult.Yes);
box.DefaultButton = box.AddButton("Keep both", MessageBoxResult.No);
box.CancelResult = MessageBoxResult.Cancel;
var result = await box.ShowAsync(this);

A custom button has an id. A timeout closes the box when the user does not answer:

var box = new MessageBox { Message = "Join the match?", Timeout = 10, TimeoutResult = MessageBoxResult.No };
box.AddButton("Join", "join");
box.AddButton("Watch", "watch");
box.AddButton("No", MessageBoxResult.No);
if (await box.ShowAsync(this) == MessageBoxResult.Custom) Debug.Log(box.CustomResult); // "join" or "watch"

Ask before an action that deletes something. The Delete button shows in the danger color:

if (await MessageBox.ConfirmAsync(this, "Delete the save?", "<b>Slot 3</b> goes for good.", "Delete",
        MessageBoxIcon.Warning, destructive: true))
    DeleteSave();

• A blocking box takes every pointer press. Keys stop at the box, and the workspace shortcuts do nothing while it is open.
• A non-modal box stops only Escape, which closes it. The workspace keeps its shortcuts and keyboard navigation. A press on a button does not start a drag. The dialog stays inside the workspace.
• Tab and the arrow keys move between the buttons. Enter or Space chooses the focused button.
• If other code removes the box, the task completes with MessageBoxResult.None.
• The box fades and scales in and out when the workspace has AnimationsEnabled. The task completes when Close runs, before the exit animation ends. A ShowAsync during the exit keeps the box.
• While the box shows, it takes the classes of the nearest tb-style-scope (AnchoredPopup.STYLE_SCOPE_CLASS) above its UXML place, or above the anchor. So a box in a styled part of the UI keeps that style. See Style families and style scopes.
• A box declared in UXML stays hidden until ShowAsync. It moves to the workspace while it shows, then goes back to its place:

<tb:MessageBox name="declaredBox" title="Declared box" message="Save the layout?"
               icon="Question" buttons="YesNo" blocking="true" />

var result = await root.Q<MessageBox>("declaredBox").ShowAsync(this);

• UXML child buttons are not read. Use buttons, or AddButton in code. A blocking box does not drag.
• When the box closes, the focus goes back to the control that had it before the show. See Custom overlays (OverlayElement).

#Styling

The rules are in Assets/UIToolbox/Runtime/Resources/UIToolbox/Styles/Controls.uss.