com.unity.uiwidgets/Runtime/widgets/app.cs

using System.Collections.Generic;
using RSG;
using Unity.UIWidgets.foundation;
using Unity.UIWidgets.gestures;
using Unity.UIWidgets.painting;
using Unity.UIWidgets.ui;
using TextStyle = Unity.UIWidgets.painting.TextStyle;

namespace Unity.UIWidgets.widgets {
    public delegate PageRoute PageRouteFactory(RouteSettings settings, WidgetBuilder builder);

    public class WidgetsApp : StatefulWidget {
        public readonly TransitionBuilder builder;
        public readonly Widget home;
        public readonly string initialRoute;

        public readonly GlobalKey<NavigatorState> navigatorKey;
        public readonly List<NavigatorObserver> navigatorObservers;
        public readonly RouteFactory onGenerateRoute;
        public readonly RouteFactory onUnknownRoute;
        public readonly PageRouteFactory pageRouteBuilder;
        public readonly Dictionary<string, WidgetBuilder> routes;
        public readonly TextStyle textStyle;
        public readonly Window window;
        public readonly bool showPerformanceoverlay;

        public WidgetsApp(
            Key key = null,
            GlobalKey<NavigatorState> navigatorKey = null,
            RouteFactory onGenerateRoute = null,
            RouteFactory onUnknownRoute = null,
            PageRouteFactory pageRouteBuilder = null,
            List<NavigatorObserver> navigatorObservers = null,
            string initialRoute = null,
            Dictionary<string, WidgetBuilder> routes = null,
            TransitionBuilder builder = null,
            TextStyle textStyle = null,
            Widget home = null,
            bool showPerformanceOverlay = false
        ) : base(key) {
            routes = routes ?? new Dictionary<string, WidgetBuilder>();
            this.window = Window.instance;
            this.home = home;
            this.navigatorKey = navigatorKey;
            this.onGenerateRoute = onGenerateRoute;
            this.onUnknownRoute = onUnknownRoute;
            this.pageRouteBuilder = pageRouteBuilder;
            this.routes = routes;
            this.navigatorObservers = navigatorObservers ?? new List<NavigatorObserver>();
            this.initialRoute = initialRoute;
            this.builder = builder;
            this.textStyle = textStyle;
            this.showPerformanceoverlay = showPerformanceOverlay;

            D.assert(
                home == null ||
                !this.routes.ContainsKey(Navigator.defaultRouteName),
                "If the home property is specified, the routes table " +
                "cannot include an entry for \" / \", since it would be redundant."
            );

            D.assert(
                builder != null ||
                home != null ||
                this.routes.ContainsKey(Navigator.defaultRouteName) ||
                onGenerateRoute != null ||
                onUnknownRoute != null,
                "Either the home property must be specified, " +
                "or the routes table must include an entry for \"/\", " +
                "or there must be on onGenerateRoute callback specified, " +
                "or there must be an onUnknownRoute callback specified, " +
                "or the builder property must be specified, " +
                "because otherwise there is nothing to fall back on if the " +
                "app is started with an intent that specifies an unknown route."
            );

            D.assert(
                builder != null ||
                onGenerateRoute != null ||
                pageRouteBuilder != null,
                "If neither builder nor onGenerateRoute are provided, the " +
                "pageRouteBuilder must be specified so that the default handler " +
                "will know what kind of PageRoute transition to build."
            );
        }

        public override State createState() {
            return new _WidgetsAppState();
        }
    }

    public class WindowProvider : InheritedWidget {
        public readonly Window window;

        public WindowProvider(Key key = null, Window window = null, Widget child = null) :
            base(key, child) {
            D.assert(window != null);
            this.window = window;
        }

        public static Window of(BuildContext context) {
            var provider = (WindowProvider) context.inheritFromWidgetOfExactType(typeof(WindowProvider));
            if (provider == null) {
                throw new UIWidgetsError("WindowProvider is missing");
            }

            return provider.window;
        }

        public override bool updateShouldNotify(InheritedWidget oldWidget) {
            D.assert(this.window == ((WindowProvider) oldWidget).window);
            return false;
        }
    }

    class _WidgetsAppState : State<WidgetsApp>, WidgetsBindingObserver {
        GlobalKey<NavigatorState> _navigator;

        public IPromise<bool> didPopRoute() {
            D.assert(this.mounted);
            var navigator = this._navigator?.currentState;
            if (navigator == null) {
                return Promise<bool>.Resolved(false);
            }

            return navigator.maybePop();
        }

        public IPromise<bool> didPushRoute(string route) {
            D.assert(this.mounted);
            var navigator = this._navigator?.currentState;
            if (navigator == null) {
                return Promise<bool>.Resolved(false);
            }

            navigator.pushNamed(route);
            return Promise<bool>.Resolved(true);
        }

        public void didChangeMetrics() {
            this.setState();
        }

        public void didChangeTextScaleFactor() {
            this.setState();
        }

        public void didChangeLocales(List<Locale> locale) {
            // TODO: support locales.
        }

        public override void initState() {
            base.initState();
            this._updateNavigator();
            D.assert(() => {
                WidgetInspectorService.instance.inspectorShowCallback += this.inspectorShowChanged;
                return true;
            });

            WidgetsBinding.instance.addObserver(this);
        }

        public override void didUpdateWidget(StatefulWidget oldWidget) {
            base.didUpdateWidget(oldWidget);
            if (this.widget.navigatorKey != ((WidgetsApp) oldWidget).navigatorKey) {
                this._updateNavigator();
            }
        }

        public override void dispose() {
            WidgetsBinding.instance.removeObserver(this);

            D.assert(() => {
                WidgetInspectorService.instance.inspectorShowCallback -= this.inspectorShowChanged;
                return true;
            });
            base.dispose();
        }

        void _updateNavigator() {
            this._navigator = this.widget.navigatorKey ?? new GlobalObjectKey<NavigatorState>(this);
        }

        Route _onGenerateRoute(RouteSettings settings) {
            var name = settings.name;
            var pageContentBuilder = name == Navigator.defaultRouteName && this.widget.home != null
                ? context => this.widget.home
                : this.widget.routes[name];

            if (pageContentBuilder != null) {
                D.assert(this.widget.pageRouteBuilder != null,
                    "The default onGenerateRoute handler for WidgetsApp must have a " +
                    "pageRouteBuilder set if the home or routes properties are set.");
                var route = this.widget.pageRouteBuilder(
                    settings,
                    pageContentBuilder
                );
                D.assert(route != null,
                    "The pageRouteBuilder for WidgetsApp must return a valid non-null Route.");
                return route;
            }

            if (this.widget.onGenerateRoute != null) {
                return this.widget.onGenerateRoute(settings);
            }

            return null;
        }

        Route _onUnknownRoute(RouteSettings settings) {
            D.assert(() => {
                if (this.widget.onUnknownRoute == null) {
                    throw new UIWidgetsError(
                        $"Could not find a generator for route {settings} in the {this.GetType()}.\n" +
                        $"Generators for routes are searched for in the following order:\n" +
                        " 1. For the \"/\" route, the \"home\" property, if non-null, is used.\n" +
                        " 2. Otherwise, the \"routes\" table is used, if it has an entry for " +
                        "the route.\n" +
                        " 3. Otherwise, onGenerateRoute is called. It should return a " +
                        "non-null value for any valid route not handled by \"home\" and \"routes\".\n" +
                        " 4. Finally if all else fails onUnknownRoute is called.\n" +
                        "Unfortunately, onUnknownRoute was not set."
                    );
                }

                return true;
            });
            var result = this.widget.onUnknownRoute(settings);
            D.assert(() => {
                if (result == null) {
                    throw new UIWidgetsError(
                        "The onUnknownRoute callback returned null.\n" +
                        "When the $runtimeType requested the route $settings from its " +
                        "onUnknownRoute callback, the callback returned null. Such callbacks " +
                        "must never return null."
                    );
                }

                return true;
            });
            return result;
        }

        void inspectorShowChanged() {
            this.setState();
        }

        public override Widget build(BuildContext context) {
            Widget navigator = null;
            if (this._navigator != null) {
                navigator = new Navigator(
                    key: this._navigator,
                    initialRoute: this.widget.initialRoute ?? Navigator.defaultRouteName,
                    onGenerateRoute: this._onGenerateRoute,
                    onUnknownRoute: this._onUnknownRoute,
                    observers: this.widget.navigatorObservers
                );
            }


            Widget result;
            if (this.widget.builder != null) {
                result = new Builder(
                    builder: _context => { return this.widget.builder(_context, navigator); }
                );
            }
            else {
                D.assert(navigator != null);
                result = navigator;
            }

            if (this.widget.textStyle != null) {
                result = new DefaultTextStyle(
                    style: this.widget.textStyle,
                    child: result
                );
            }

            PerformanceOverlay performanceOverlay = null;
            if (this.widget.showPerformanceoverlay) {
                performanceOverlay = PerformanceOverlay.allEnabled();
            }

            if (performanceOverlay != null) {
                result = new Stack(
                    children: new List<Widget> {
                        result,
                        new Positioned(top: 0.0f,
                            left: 0.0f,
                            right: 0.0f,
                            child: performanceOverlay)
                    });
            }

            D.assert(() => {
                if (WidgetInspectorService.instance.debugShowInspector) {
                    result = new WidgetInspector(null, result, this._InspectorSelectButtonBuilder);
                }

                return true;
            });

            result = new Directionality(child: result, TextDirection.ltr);
            result = new WindowProvider(
                window: this.widget.window,
                child: result
            );

            result = new MediaQuery(
                data: MediaQueryData.fromWindow(this.widget.window),
                child: result
            );

            return result;
        }

        Widget _InspectorSelectButtonBuilder(BuildContext context, VoidCallback onPressed) {
            return new _InspectorSelectButton(onPressed);
        }
    }

    class _InspectorSelectButton : StatelessWidget {
        public readonly GestureTapCallback onPressed;

        public _InspectorSelectButton(
            VoidCallback onPressed,
            Key key = null
        ) : base(key) {
            this.onPressed = () => onPressed();
        }

        public override Widget build(BuildContext context) {
            return new GestureDetector(
                onTap: this.onPressed,
                child: new Container(
                    color: Color.fromARGB(255, 0, 0, 255),
                    padding: EdgeInsets.all(10),
                    child: new Text("Select", style: new TextStyle(color: Color.fromARGB(255, 255, 255, 255)))
                )
            );
        }
    }
}