/// <summary>
/// Begin drawing a new frame.<br/>
/// Calls to NanoVG drawing API should be wrapped in <see cref="BeginFrame(Vector2D{float}, float)"/> and <see cref="EndFrame()"/>.
/// <para><see cref="BeginFrame(Vector2D{float}, float)"/> defines the size of the window to render to in relation currently
/// set viewport (i.e. glViewport on GL backends). Device pixel ratio allows to
/// control the rendering on Hi-DPI devices.</para>
/// <para>For example, GLFW returns two dimension for an opened window: window size and
/// frame buffer size. In that case you would set windowWidth / Height to the window size,
/// devicePixelRatio to: <c>frameBufferWidth / windowWidth</c>.</para>
/// </summary>
public void BeginFrame(Vector2D <float> windowSize, float devicePixelRatio)
{
fontManager.Pack();
stateStack.Clear();
Save();
Reset();
pixelRatio.SetDevicePixelRatio(devicePixelRatio);
renderer.Viewport(windowSize, devicePixelRatio);
FrameMeta = default;
}
