namespace AcDream.App.UI;

/// <summary>Renders a 3-D mini-scene into an off-screen buffer and returns the GL color-texture
/// handle. Called by the per-frame pre-UI hook (GameWindow), NOT from UiViewport.OnDraw. Implemented
/// by PaperdollViewportRenderer in AcDream.App.Rendering. Intra-App decoupling so the UI widget
/// doesn't depend on WbDrawDispatcher/GameWindow.</summary>
public interface IUiViewportRenderer
{
    /// <summary>Render at (width,height); return the color-texture GL handle, or 0 if nothing rendered.</summary>
    uint Render(int width, int height);

    /// <summary>
    /// Whether the produced texture's v=0 row is the BOTTOM of the rendered
    /// image.
    ///
    /// <para>Campaign V slice V6l. This is a property of the backend that made
    /// the texture, not of the widget that draws it. A GL framebuffer's origin is
    /// bottom-left, so its colour texture samples bottom-up and
    /// <see cref="UiViewport"/> has always flipped V to compensate. A Vulkan
    /// image's origin is top-left and the backend's negative viewport height
    /// stores the rendered image that way round, so the same flip would draw the
    /// doll on its head — which is exactly what the first Vulkan capture did, and
    /// what the comment on that line had predicted since V4a.</para>
    /// </summary>
    bool TextureIsBottomUp { get; }
}