Gallery/Gallery.Share/Resources/UI/AdaptedPage.cs

using System;
using Gallery.Services;
using Gallery.Util;
using Xamarin.Essentials;
using Xamarin.Forms;

namespace Gallery.Resources.UI
{
    public class AdaptedPage : ContentPage
    {
        public static readonly BindableProperty TopMarginProperty = BindableProperty.Create(nameof(TopMargin), typeof(Thickness), typeof(AdaptedPage));

        public Thickness TopMargin
        {
            get => (Thickness)GetValue(TopMarginProperty);
            set => SetValue(TopMarginProperty, value);
        }

        public event EventHandler Load;
        public event EventHandler Unload;

        protected static readonly bool isPhone = DeviceInfo.Idiom == DeviceIdiom.Phone;

        public AdaptedPage()
        {
            SetDynamicResource(Screen.StatusBarStyleProperty, Theme.Theme.StatusBarStyle);
            Shell.SetNavBarHasShadow(this, true);
        }

        public virtual void OnLoad() => Load?.Invoke(this, EventArgs.Empty);

        public virtual void OnUnload() => Unload?.Invoke(this, EventArgs.Empty);

        public virtual void OnOrientationChanged(bool landscape)
        {
            var old = TopMargin;
            Thickness @new;
            if (Definition.IsFullscreenDevice)
            {
                @new = landscape ?
                    AppShell.NavigationBarOffset :
                    AppShell.TotalBarOffset;
            }
            else if (isPhone)
            {
                @new = landscape ?
                    Definition.TopOffset32 :
                    AppShell.TotalBarOffset;
            }
            else
            {
                // iPad
                @new = AppShell.TotalBarOffset;
            }
            if (old != @new)
            {
                TopMargin = @new;
                OnTopMarginChanged(old, @new);
            }
        }

        protected virtual void OnTopMarginChanged(Thickness old, Thickness @new) { }

        protected override void OnSizeAllocated(double width, double height)
        {
            base.OnSizeAllocated(width, height);
            OnOrientationChanged(width > height);
        }

        protected void AnimateToMargin(View element, Thickness margin, bool animate = true)
        {
            var m = margin;
            var start = element.Margin.Top - m.Top;
            element.Margin = m;
            element.CancelAnimations();
            if (start > 0 && animate)
            {
                element.Animate("margin", top =>
                {
                    element.TranslationY = top;
                },
                start, 0,
#if DEBUG
                length: 500,
#else
                length: 300,
#endif
                easing: Easing.SinInOut,
                finished: (v, r) =>
                {
                    element.TranslationY = 0;
                });
            }
            else if (element.TranslationY != 0)
            {
                element.TranslationY = 0;
            }
        }

        protected void Start(Action action)
        {
            if (Tap.IsBusy)
            {
                Log.Error($"{GetType()}.tap", "gesture recognizer is now busy...");
                return;
            }
            using (Tap.Start())
            {
                action();
            }
        }

        private class Tap : IDisposable
        {
            public static bool IsBusy
            {
                get
                {
                    lock (sync)
                    {
                        return instance?.isBusy == true;
                    }
                }
            }

            private static readonly object sync = new();
            private static readonly Tap instance = new();

            private Tap() { }

            public static Tap Start()
            {
                lock (sync)
                {
                    instance.isBusy = true;
                }
                return instance;
            }

            private bool isBusy = false;

            public void Dispose()
            {
                isBusy = false;
            }
        }
    }
}