com.unity.uiwidgets/com.unity.uiwidgets/Runtime/engine/UIWidgetsPanel.cs

using System;
using System.Collections;
using System.Collections.Generic;
using Unity.UIWidgets.engine;
using Unity.UIWidgets.engine;
using Unity.UIWidgets.external.simplejson;
using Unity.UIWidgets.foundation;
using Unity.UIWidgets.ui;
using Unity.UIWidgets.widgets;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
using RawImage = UnityEngine.UI.RawImage;

namespace Unity.UIWidgets.engine {
    public enum UIWidgetsWindowType {
        InvalidPanel = 0,
        GameObjectPanel = 1,
        EditorWindowPanel = 2
    }

    [Serializable]
    public struct Font {
        public string asset;
        public int weight;
    }

    [Serializable]
    public struct TextFont {
        public string family;
        [SerializeField] public Font[] fonts;
    }

    public interface IUIWidgetsWindow {
        Offset windowPosToScreenPos(Offset offset);

        void startCoroutine(IEnumerator routing);

        bool isActive();

        void mainEntry();

        void onNewFrameScheduled();

        UIWidgetsWindowType getWindowType();
    }
    public class Configurations {
        
        private Dictionary<string, TextFont> _textFonts = new Dictionary<string, TextFont>();

        public void Clear() {
            _textFonts.Clear();
        }
        public void AddFont(string family, TextFont font) {
           _textFonts[key: family] = font;
        }
        public object fontsToObject() {
            Dictionary<string, TextFont> settings = _textFonts;
            if (settings == null || settings.Count == 0) {
                return null;
            }

            var result = new object[settings.Count];
            var i = 0;
            foreach (var setting in settings) {
                var font = new Dictionary<string, object>();
                font.Add("family", value: setting.Key);
                var dic = new Dictionary<string, object>[setting.Value.fonts.Length];
                for (var j = 0; j < setting.Value.fonts.Length; j++) {
                    dic[j] = new Dictionary<string, object>();
                    if (setting.Value.fonts[j].asset.Length > 0) {
                        dic[j].Add("asset", value: setting.Value.fonts[j].asset);
                    }

                    if (setting.Value.fonts[j].weight > 0) {
                        dic[j].Add("weight", value: setting.Value.fonts[j].weight);
                    }
                }

                font.Add("fonts", value: dic);
                result[i] = font;
                i++;
            }

            return result;
        }
    }

    public partial class UIWidgetsPanel : RawImage, IUIWidgetsWindow {
        static List<UIWidgetsPanel> panels = new List<UIWidgetsPanel>();

        static public Isolate anyIsolate {
            get {
                if (panels.Count == 0) {
                    return null;
                }

                return panels[0]._wrapper.isolate;
            }
        }

        static void registerPanel(UIWidgetsPanel panel) {
            panels.Add(panel);
        }

        static void unregisterPanel(UIWidgetsPanel panel) {
            panels.Remove(panel);
        }

        float _devicePixelRatioOverride;

        public bool hardwareAntiAliasing;

        public TextFont[] fonts;

        Configurations _configurations;

        UIWidgetsPanelWrapper _wrapper;

        int _currentWidth {
            get { return Mathf.RoundToInt(rectTransform.rect.width * canvas.scaleFactor); }
        }

        int _currentHeight {
            get { return Mathf.RoundToInt(rectTransform.rect.height * canvas.scaleFactor); }
        }

        float _currentDevicePixelRatio {
            get {
#if !UNITY_EDITOR
                return _wrapper.displayMetrics.DevicePixelRatioByDefault;
#endif
                var currentDpi = Screen.dpi;
                if (currentDpi == 0) {
                    currentDpi = canvas.GetComponent<CanvasScaler>().fallbackScreenDPI;
                }

                return currentDpi / 96;
            }
        }

        bool _viewMetricsCallbackRegistered;

        void _handleViewMetricsChanged(string method, List<JSONNode> args) {
            using (Isolate.getScope(anyIsolate)) {
                _wrapper.displayMetrics.onViewMetricsChanged();
                Window.instance.updateSafeArea();
                Window.instance.onMetricsChanged?.Invoke();
            }
        }
        
        protected virtual void Update() {
            UIWidgetsMessageManager.ensureUIWidgetsMessageManagerIfNeeded();

            if (!_viewMetricsCallbackRegistered) {
                _viewMetricsCallbackRegistered = true;
                UIWidgetsMessageManager.instance?.AddChannelMessageDelegate("ViewportMetricsChanged",
                    _handleViewMetricsChanged);
            }

            Input_Update();
        }

#if !UNITY_EDITOR && UNITY_ANDROID
        bool AndroidInitialized = true;

        IEnumerator DoInitAndroid() {
            yield return new WaitForEndOfFrame();
            AndroidPlatformUtil.Init();
            yield return new WaitForEndOfFrame();
            enabled = true;
        }
        bool IsAndroidInitialized() {
            if (AndroidInitialized) {
                enabled = false;
                AndroidInitialized = false;
                startCoroutine(DoInitAndroid());
                return false;
            }
            return true;
        }
#endif

        protected void OnEnable() {
#if !UNITY_EDITOR && UNITY_ANDROID
            if (!IsAndroidInitialized()) {return ;}
#endif
#if !UNITY_EDITOR && UNITY_IOS
            //the hook API cannot be automatically called on IOS, so we need try hook it here
            Hooks.tryHook();
#endif
            base.OnEnable();
            
            D.assert(_wrapper == null);
            _configurations = new Configurations();
            _wrapper = new UIWidgetsPanelWrapper();
            onEnable();
            if (fonts != null && fonts.Length > 0) {
                foreach (var font in fonts) {
                    AddFont(family: font.family, font: font);
                }
            }
            _wrapper.Initiate(this, width: _currentWidth, height: _currentHeight, dpr: _currentDevicePixelRatio,
                _configurations: _configurations);
            _configurations.Clear();
            texture = _wrapper.renderTexture;
            Input_OnEnable();
            registerPanel(this);
        }

        protected override void OnDisable() {
            unregisterPanel(this);
            D.assert(_wrapper != null);
            _wrapper?.Destroy();
            _wrapper = null;
            texture = null;
            Input_OnDisable();
            base.OnDisable();
        }

        protected virtual void OnGUI() {
            Input_OnGUI();
        }

        protected override void OnRectTransformDimensionsChange() {
            if (_wrapper != null && _wrapper.didDisplayMetricsChanged(width: _currentWidth, height: _currentHeight,
                dpr: _currentDevicePixelRatio)) {
                _wrapper.OnDisplayMetricsChanged(width: _currentWidth, height: _currentHeight,
                    dpr: _currentDevicePixelRatio);
                texture = _wrapper.renderTexture;
            }
        }

        public UIWidgetsWindowType getWindowType() {
            return UIWidgetsWindowType.GameObjectPanel;
        }

        public bool isActive() {
            return IsActive();
        }

        public void startCoroutine(IEnumerator routing) {
            StartCoroutine(routine: routing);
        }

        public void onNewFrameScheduled() {
        }

        public Offset windowPosToScreenPos(Offset offset) {
            Camera camera = null;
            if (canvas.renderMode != RenderMode.ScreenSpaceCamera) {
                camera = canvas.GetComponent<GraphicRaycaster>().eventCamera;
            }

            var pos = new Vector2(x: offset.dx, y: offset.dy);
            pos = pos * _currentDevicePixelRatio / canvas.scaleFactor;
            var rect = rectTransform.rect;
            pos.x += rect.min.x;
            pos.y = rect.max.y - pos.y;
            var worldPos = rectTransform.TransformPoint(new Vector2(x: pos.x, y: pos.y));
            var screenPos = RectTransformUtility.WorldToScreenPoint(cam: camera, worldPoint: worldPos);
            return new Offset(dx: screenPos.x, Screen.height - screenPos.y);
        }

        public void mainEntry() {
            main();
        }

        protected virtual void onEnable() {
        }
        
        protected void AddFont(string family, TextFont font) {
            _configurations.AddFont(family,font);
        }

        protected void AddFont(string family, List<string> assets, List<int> weights) {
            if (assets.Count != weights.Count) {
                Debug.LogError($"The size of {family}‘s assets should be equal to the weights'.");
                return;
            }

            var textFont = new TextFont {family = family};
            var fonts = new Font[assets.Count];
            for (var j = 0; j < assets.Count; j++) {
                var font = new Font {asset = assets[index: j], weight = weights[index: j]};
                fonts[j] = font;
            }

            textFont.fonts = fonts;
            AddFont(family: family, font: textFont);
        }
        
        protected virtual void main() {
        }
    }

    enum UIWidgetsInputMode 
    {
        Mouse,
        Touch
    }

    public partial class UIWidgetsPanel : IPointerDownHandler, IPointerUpHandler,
        IPointerEnterHandler, IPointerExitHandler, IDragHandler {
        bool _isEntered;
        Vector2 _lastMousePosition;

        UIWidgetsInputMode _inputMode;

        void _convertPointerData(PointerEventData evt, out Vector2? position, out int pointerId) {
            position = _inputMode == UIWidgetsInputMode.Mouse
                ? _getPointerPosition(Input.mousePosition)
                : _getPointerPosition(evt);
            pointerId = _inputMode == UIWidgetsInputMode.Mouse ? evt.pointerId : (-1 - evt.pointerId);
        }

        Vector2? _getPointerPosition(Vector2 position) {
            var worldCamera = canvas.worldCamera;
            if (RectTransformUtility.ScreenPointToLocalPointInRectangle(
                rect: rectTransform, screenPoint: position, cam: worldCamera, out var localPoint)) {
                var scaleFactor = canvas.scaleFactor;
                localPoint.x = (localPoint.x - rectTransform.rect.min.x) * scaleFactor;
                localPoint.y = (rectTransform.rect.max.y - localPoint.y) * scaleFactor;
                return localPoint;
            }

            return null;
        }

        Vector2? _getPointerPosition(PointerEventData eventData) {
            //refer to: https://zhuanlan.zhihu.com/p/37127981
            Camera eventCamera = null;
            if (canvas.renderMode != RenderMode.ScreenSpaceOverlay) {
                eventCamera = canvas.GetComponent<GraphicRaycaster>().eventCamera;
            }

            Vector2 localPoint;
            RectTransformUtility.ScreenPointToLocalPointInRectangle(rectTransform, eventData.position,
                eventCamera, out localPoint);
            var scaleFactor = canvas.scaleFactor;
            localPoint.x = (localPoint.x - rectTransform.rect.min.x) * scaleFactor;
            localPoint.y = (rectTransform.rect.max.y - localPoint.y) * scaleFactor;
            return localPoint;
        }

        void Input_OnEnable() {
            _inputMode = Input.mousePresent ? UIWidgetsInputMode.Mouse : UIWidgetsInputMode.Touch;
        }

        void Input_OnDisable() {
        }

        void Input_Update() {
            //we only process hover events for desktop applications
            if (_inputMode == UIWidgetsInputMode.Mouse) {
                if (_isEntered) {
                    if (!Input.GetMouseButton(0) && !Input.GetMouseButton(1) && !Input.GetMouseButton(2)) {
                        if (_lastMousePosition.x != Input.mousePosition.x ||
                            _lastMousePosition.y != Input.mousePosition.y) {
                            _lastMousePosition = Input.mousePosition;
                            _onMouseMove();
                        }
                    }
                    else {
                        _lastMousePosition = Input.mousePosition;
                    }

                    if (Input.mouseScrollDelta.magnitude != 0) {
                        _onScroll();
                    }
                }
            }
        }

        void Input_OnGUI() {
            var e = Event.current;
            if (e.isKey) {
                _wrapper.OnKeyDown(e: e);
            }
        }

        void _onMouseMove() {
            if (_inputMode != UIWidgetsInputMode.Mouse) {
                return;
            }
            var pos = _getPointerPosition(Input.mousePosition);
            _wrapper.OnMouseMove(pos);
        }

        void _onScroll() {
            if (_inputMode != UIWidgetsInputMode.Mouse) {
                return;
            }
            var pos = _getPointerPosition(Input.mousePosition);
            _wrapper.OnMouseScroll(Input.mouseScrollDelta, pos);
        }

        public void OnPointerEnter(PointerEventData eventData) {
            if (_inputMode != UIWidgetsInputMode.Mouse) {
                return;
            }
            D.assert(eventData.pointerId < 0);
            _isEntered = true;
            _lastMousePosition = Input.mousePosition;
        }

        public void OnPointerExit(PointerEventData eventData) {
            if (_inputMode != UIWidgetsInputMode.Mouse) {
                return;
            }
            D.assert(eventData.pointerId < 0);
            _isEntered = false;
            _wrapper.OnPointerLeave();
        }

        public void OnPointerDown(PointerEventData eventData) {
            _convertPointerData(eventData, out var pos, out var pointerId);
            _wrapper.OnPointerDown(pos, pointerId);
        }

        public void OnPointerUp(PointerEventData eventData) {
            _convertPointerData(eventData, out var pos, out var pointerId);
            _wrapper.OnPointerUp(pos, pointerId);
        }

        public void OnDrag(PointerEventData eventData) {
            _convertPointerData(eventData, out var pos, out var pointerId);
            _wrapper.OnDrag(pos, pointerId);
        }
    }
}