[Gui] Touch screen for iOS and Android support

[hwagent]

Hi,

I use your GUI Controls (MonoGame.Extended.Gui) for an iOS Game and have a problem with the GuiButton class.

My buttons are created like this:

btnHighscore = new GuiButton();
btnHighscore.Position = new Vector2(100, 270);
btnHighscore.Text = "Highscore";
btnHighscore.Font = bitmapFont;
btnHighscore.Color = Color.Red;
btnHighscore.Size = new Size2(200, 50);
btnHighscore.Origin = new Vector2(0, 0);
btnHighscore.Clicked += BtnHighscoreClicked;

When clicking the button for the first time, the BtnHighscoreClicked() method is not called, but every following click works as expected. This means that when a button is clicked for the first time, the user must always click twice.

As a workaround I’ve changed the method OnPointerDown() in GuiSystem.cs:

private void OnPointerDown(GuiPointerEventArgs args)
{
    if (Screen == null || !Screen.IsVisible)
        return;

    _preFocusedControl = FindControlAtPoint(Screen.Controls, args.Position);

    // _hoveredControl is usually set in OnPointerMoved(). If OnPointerMoved() 
    // was not called, _hoveredControl is still null and OnPointerDown() will
    // not be called.
    if (_hoveredControl == null)
    {
        _hoveredControl = _preFocusedControl;
    }

    _hoveredControl?.OnPointerDown(this, args);
}