gui-cs.Terminal.Gui/Terminal.Gui/App/Application.Screen.cs

#nullable enable

namespace Terminal.Gui.App;

public static partial class Application // Screen related stuff; intended to hide Driver details
{
    private static readonly object _lockScreen = new ();
    private static Rectangle? _screen;

    /// <summary>
    ///     Gets or sets the size of the screen. By default, this is the size of the screen as reported by the <see cref="IConsoleDriver"/>.
    /// </summary>
    /// <remarks>
    /// <para>
    ///     If the <see cref="IConsoleDriver"/> has not been initialized, this will return a default size of 2048x2048; useful for unit tests.
    /// </para>
    /// </remarks>
    public static Rectangle Screen
    {
        get
        {
            lock (_lockScreen)
            {
                if (_screen == null)
                {
                    _screen = Driver?.Screen ?? new (new (0, 0), new (2048, 2048));
                }

                return _screen.Value;
            }
        }
        set
        {
            if (value is {} && (value.X != 0 || value.Y != 0))
            {
                throw new NotImplementedException ($"Screen locations other than 0, 0 are not yet supported");
            }

            lock (_lockScreen)
            {
                _screen = value;
            }
        }
    }

    /// <summary>Invoked when the terminal's size changed. The new size of the terminal is provided.</summary>
    /// <remarks>
    ///     Event handlers can set <see cref="SizeChangedEventArgs.Cancel"/> to <see langword="true"/> to prevent
    ///     <see cref="Application"/> from changing it's size to match the new terminal size.
    /// </remarks>
    public static event EventHandler<SizeChangedEventArgs>? SizeChanging;

    /// <summary>
    ///     Called when the application's size changes. Sets the size of all <see cref="Toplevel"/>s and fires the
    ///     <see cref="SizeChanging"/> event.
    /// </summary>
    /// <param name="args">The new size.</param>
    /// <returns><see lanword="true"/>if the size was changed.</returns>
    public static bool OnSizeChanging (SizeChangedEventArgs args)
    {
        SizeChanging?.Invoke (null, args);

        if (args.Cancel || args.Size is null)
        {
            return false;
        }

        Screen = new (Point.Empty, args.Size.Value);

        foreach (Toplevel t in TopLevels)
        {
            t.OnSizeChanging (new (args.Size));
            t.SetNeedsLayout ();
        }

        LayoutAndDraw (true);

        return true;
    }

    /// <summary>
    ///     Gets or sets whether the screen will be cleared, and all Views redrawn, during the next Application iteration.
    /// </summary>
    /// <remarks>
    ///     This is typical set to true when a View's <see cref="View.Frame"/> changes and that view has no
    ///     SuperView (e.g. when <see cref="Application.Top"/> is moved or resized.
    /// </remarks>
    internal static bool ClearScreenNextIteration { get; set; }
}