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

using System.Collections.Generic;
using Unity.UIWidgets.async;
using Unity.UIWidgets.editor;
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;
using Rect = UnityEngine.Rect;

namespace Unity.UIWidgets.engine {
    public class UIWidgetWindowAdapter : WindowAdapter {
        readonly UIWidgetsPanel _uiWidgetsPanel;
        bool _needsPaint;

        protected override void updateSafeArea() {
            this._padding = new WindowPadding(
                Screen.safeArea.x,
                Screen.safeArea.y,
                Screen.width - Screen.safeArea.width,
                Screen.height - Screen.safeArea.height);
        }

        public override void scheduleFrame(bool regenerateLayerTree = true) {
            base.scheduleFrame(regenerateLayerTree);
            this._needsPaint = true;
        }

        public UIWidgetWindowAdapter(UIWidgetsPanel uiWidgetsPanel) {
            this._uiWidgetsPanel = uiWidgetsPanel;
        }


        public override void OnGUI(Event evt) {
            if (this.displayMetricsChanged()) {
                this._needsPaint = true;
            }

            if (evt.type == EventType.Repaint) {
                if (!this._needsPaint) {
                    return;
                }

                this._needsPaint = false;
            }

            base.OnGUI(evt);
        }

        protected override Surface createSurface() {
            return new EditorWindowSurface(this._uiWidgetsPanel.applyRenderTexture);
        }

        public override GUIContent titleContent {
            get { return new GUIContent(this._uiWidgetsPanel.gameObject.name); }
        }

        protected override float queryDevicePixelRatio() {
            return this._uiWidgetsPanel.devicePixelRatio;
        }

        protected override Vector2 queryWindowSize() {
            var rect = this._uiWidgetsPanel.rectTransform.rect;
            var size = new Vector2(rect.width,rect.height) * 
                       this._uiWidgetsPanel.canvas.scaleFactor / this._uiWidgetsPanel.devicePixelRatio;
            size.x = Mathf.Round(size.x);
            size.y = Mathf.Round(size.y);
            return size;
        }
    }

    [RequireComponent(typeof(RectTransform))]
    public class UIWidgetsPanel : RawImage, IPointerDownHandler, IPointerUpHandler, IDragHandler,
        IPointerEnterHandler, IPointerExitHandler {
        static Event _repaintEvent;

        [SerializeField] protected float devicePixelRatioOverride;
        WindowAdapter _windowAdapter;
        Texture _texture;
        Vector2 _lastMouseMove;

        HashSet<int> _enteredPointers;

        bool _mouseEntered {
            get { return !this._enteredPointers.isEmpty(); }
        }

        readonly ScrollInput _scrollInput = new ScrollInput();
        DisplayMetrics _displayMetrics;

        const int mouseButtonNum = 3;

        protected override void OnEnable() {
            base.OnEnable();

            //Disable the default touch -> mouse event conversion on mobile devices
            Input.simulateMouseWithTouches = false;

            this._displayMetrics = DisplayMetricsProvider.provider();

            if (_repaintEvent == null) {
                _repaintEvent = new Event {type = EventType.Repaint};
            }

            D.assert(this._windowAdapter == null);
            this._windowAdapter = new UIWidgetWindowAdapter(this);

            this._windowAdapter.OnEnable();

            Widget root;
            using (this._windowAdapter.getScope()) {
                root = this.createWidget();
            }
            this._windowAdapter.attachRootWidget(root);   
            this._lastMouseMove = Input.mousePosition;

            this._enteredPointers = new HashSet<int>();
        }

        public float devicePixelRatio {
            get {
                return this.devicePixelRatioOverride > 0
                    ? this.devicePixelRatioOverride
                    : this._displayMetrics.DevicePixelRatio;
            }
        }

        protected override void OnDisable() {
            D.assert(this._windowAdapter != null);
            this._windowAdapter.OnDisable();
            this._windowAdapter = null;
            base.OnDisable();
        }

        protected virtual Widget createWidget() {
            return null;
        }

        internal void applyRenderTexture(Rect screenRect, Texture texture, Material mat) {
            this.texture = texture;
            this.material = mat;
        }

        void Update() {
            this._displayMetrics.Update();
            if (EventSystem.current != null && EventSystem.current.currentSelectedGameObject != this.gameObject) {
                this.unfocusIfNeeded();
            }

            if (this._mouseEntered) {
                if (this._lastMouseMove.x != Input.mousePosition.x || this._lastMouseMove.y != Input.mousePosition.y) {
                    this.handleMouseMovement();
                }
            }

            this._lastMouseMove = Input.mousePosition;

            if (this._mouseEntered) {
                this.handleMouseScroll();
            }

            D.assert(this._windowAdapter != null);
            this._windowAdapter.Update();
            this._windowAdapter.OnGUI(_repaintEvent);
        }

        void OnGUI() {
            this._displayMetrics.OnGUI();
            if (Event.current.type == EventType.KeyDown || Event.current.type == EventType.KeyUp) {
                this._windowAdapter.OnGUI(Event.current);
            }
        }

        void handleMouseMovement() {
            var pos = this.getPointPosition(Input.mousePosition);
            this._windowAdapter.postPointerEvent(new PointerData(
                timeStamp: Timer.timespanSinceStartup,
                change: PointerChange.hover,
                kind: PointerDeviceKind.mouse,
                device: this.getMouseButtonDown(),
                physicalX: pos.x,
                physicalY: pos.y
            ));
        }

        void handleMouseScroll() {
            if (Input.mouseScrollDelta.y != 0 || Input.mouseScrollDelta.x != 0) {
                var scaleFactor = this.canvas.scaleFactor;
                var pos = this.getPointPosition(Input.mousePosition);
                this._scrollInput.onScroll(Input.mouseScrollDelta.x * scaleFactor,
                    Input.mouseScrollDelta.y * scaleFactor,
                    pos.x,
                    pos.y,
                    InputUtils.getScrollButtonKey());
            }

            var deltaScroll = this._scrollInput.getScrollDelta();
            if (deltaScroll != Vector2.zero) {
                this._windowAdapter.postPointerEvent(new ScrollData(
                    timeStamp: Timer.timespanSinceStartup,
                    change: PointerChange.scroll,
                    kind: PointerDeviceKind.mouse,
                    device: this._scrollInput.getDeviceId(),
                    physicalX: this._scrollInput.getPointerPosX(),
                    physicalY: this._scrollInput.getPointerPosY(),
                    scrollX: deltaScroll.x,
                    scrollY: deltaScroll.y
                ));
            }
        }

        int getMouseButtonDown() {
            for (int key = 0; key < mouseButtonNum; key++) {
                if (Input.GetMouseButton(key)) {
                    return InputUtils.getMouseButtonKey(key);
                }
            }

            return 0;
        }

        public void OnPointerDown(PointerEventData eventData) {
            EventSystem.current.SetSelectedGameObject(this.gameObject, eventData);
            var position = this.getPointPosition(eventData);
            this._windowAdapter.postPointerEvent(new PointerData(
                timeStamp: Timer.timespanSinceStartup,
                change: PointerChange.down,
                kind: InputUtils.getPointerDeviceKind(eventData),
                device: InputUtils.getPointerDeviceKey(eventData),
                physicalX: position.x,
                physicalY: position.y
            ));
        }

        public void OnPointerUp(PointerEventData eventData) {
            var position = this.getPointPosition(eventData);
            this._windowAdapter.postPointerEvent(new PointerData(
                timeStamp: Timer.timespanSinceStartup,
                change: PointerChange.up,
                kind: InputUtils.getPointerDeviceKind(eventData),
                device: InputUtils.getPointerDeviceKey(eventData),
                physicalX: position.x,
                physicalY: position.y
            ));
        }

        public Vector2 getPointPosition(PointerEventData eventData) {
            Vector2 localPoint;
            RectTransformUtility.ScreenPointToLocalPointInRectangle(this.rectTransform, eventData.position,
                eventData.enterEventCamera, out localPoint);
            var scaleFactor = this.canvas.scaleFactor;
            localPoint.x = (localPoint.x - this.rectTransform.rect.min.x) * scaleFactor;
            localPoint.y = (this.rectTransform.rect.max.y - localPoint.y) * scaleFactor;
            return localPoint;
        }

        public Vector2 getPointPosition(Vector2 position) {
            Vector2 localPoint;
            Camera eventCamera = null;

            if (this.canvas.renderMode != RenderMode.ScreenSpaceCamera) {
                eventCamera = this.canvas.GetComponent<GraphicRaycaster>().eventCamera;
            }


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

        public void OnDrag(PointerEventData eventData) {
            var position = this.getPointPosition(eventData);
            this._windowAdapter.postPointerEvent(new PointerData(
                timeStamp: Timer.timespanSinceStartup,
                change: PointerChange.move,
                kind: InputUtils.getPointerDeviceKind(eventData),
                device: InputUtils.getPointerDeviceKey(eventData),
                physicalX: position.x,
                physicalY: position.y
            ));
        }

        public void OnPointerEnter(PointerEventData eventData) {
            var pointerKey = InputUtils.getPointerDeviceKey(eventData);
            this._enteredPointers.Add(pointerKey);

            this._lastMouseMove = eventData.position;
            var position = this.getPointPosition(eventData);
            this._windowAdapter.postPointerEvent(new PointerData(
                timeStamp: Timer.timespanSinceStartup,
                change: PointerChange.hover,
                kind: InputUtils.getPointerDeviceKind(eventData),
                device: pointerKey,
                physicalX: position.x,
                physicalY: position.y
            ));
        }

        public void OnPointerExit(PointerEventData eventData) {
            var pointerKey = InputUtils.getPointerDeviceKey(eventData);
            this._enteredPointers.Remove(pointerKey);

            var position = this.getPointPosition(eventData);
            this._windowAdapter.postPointerEvent(new PointerData(
                timeStamp: Timer.timespanSinceStartup,
                change: PointerChange.hover,
                kind: InputUtils.getPointerDeviceKind(eventData),
                device: pointerKey,
                physicalX: position.x,
                physicalY: position.y
            ));
        }

        void unfocusIfNeeded() {
            using (this._windowAdapter.getScope()) {
                var focusNode = WidgetsBinding.instance.focusManager.currentFocus;
                if (focusNode != null) {
                    focusNode.unfocus();
                }
            }
        }
    }
}