Implement backdrop.

Runtime/material/animated_icons/animated_icons.cs

 using Unity.UIWidgets.ui;
 using Unity.UIWidgets.widgets;
 using UnityEngine;
+using Canvas = Unity.UIWidgets.ui.Canvas;
-          D.assert(progress <= 1.0f);
-          D.assert(progress >= 0.0f);
-          if (values.Count == 1)
-            return values[0];
-          float targetIdx = MathUtils.lerpFloat(0, values.Count -1, progress);
-          int lowIdx = targetIdx.floor();
-          int highIdx = targetIdx.ceil();
-          float t = targetIdx - lowIdx;
-          return interpolator(values[lowIdx], values[highIdx], t);
+            D.assert(progress <= 1.0f);
+            D.assert(progress >= 0.0f);
+            if (values.Count == 1) {
+                return values[0];
+            }
+
+            float targetIdx = MathUtils.lerpFloat(0, values.Count - 1, progress);
+            int lowIdx = targetIdx.floor();
+            int highIdx = targetIdx.ceil();
+            float t = targetIdx - lowIdx;
+            return interpolator(values[lowIdx], values[highIdx], t);
-    
+
-
-      public AnimatedIcon(
-        Key key = null,
-        AnimatedIconData icon = null,
-        Animation<float> progress = null,
-        Color color = null,
-        float? size = null
-      ) : base(key: key) {
+        public AnimatedIcon(
+            Key key = null,
+            AnimatedIconData icon = null,
+            Animation<float> progress = null,
+            Color color = null,
+            float? size = null
+        ) : base(key: key) {
             D.assert(progress != null);
             D.assert(icon != null);
             this.progress = progress;
-      }
+        }
-      public readonly Animation<float> progress;
+        public readonly Animation<float> progress;
-      public readonly Color color;
+        public readonly Color color;
-      public readonly float? size;
+        public readonly float? size;
-      public readonly AnimatedIconData icon;
+        public readonly AnimatedIconData icon;
+
+        public static readonly _UiPathFactory _pathFactory = () => new Path();
-      public static readonly _UiPathFactory _pathFactory = () => new Path();
+        public override Widget build(BuildContext context) {
+            _AnimatedIconData iconData = (_AnimatedIconData) this.icon;
+            IconThemeData iconTheme = IconTheme.of(context);
+            float iconSize = this.size ?? iconTheme.size ?? 0.0f;
+            float? iconOpacity = iconTheme.opacity;
+            Color iconColor = this.color ?? iconTheme.color;
+            if (iconOpacity != 1.0f) {
+                iconColor = iconColor.withOpacity(iconColor.opacity * (iconOpacity ?? 1.0f));
+            }
-      public override Widget build(BuildContext context) {
-        _AnimatedIconData iconData = (_AnimatedIconData) this.icon;
-        IconThemeData iconTheme = IconTheme.of(context);
-        float iconSize = this.size ?? iconTheme.size ?? 0.0f;
-        float? iconOpacity = iconTheme.opacity;
-        Color iconColor = this.color ?? iconTheme.color;
-        if (iconOpacity != 1.0f)
-          iconColor = iconColor.withOpacity(iconColor.opacity * (iconOpacity ?? 1.0f));
-        return new CustomPaint(
-            size: new Size(iconSize, iconSize),
-            painter: new _AnimatedIconPainter(
-              paths: iconData.paths,
-              progress: this.progress,
-              color: iconColor,
-              scale: iconSize / iconData.size.width,
-              uiPathFactory: _pathFactory
-            )
-        );
-      }
+            return new CustomPaint(
+                size: new Size(iconSize, iconSize),
+                painter: new _AnimatedIconPainter(
+                    paths: iconData.paths,
+                    progress: this.progress,
+                    color: iconColor,
+                    scale: iconSize / iconData.size.width,
+                    uiPathFactory: _pathFactory
+                )
+            );
+        }
     }
 
     public delegate Path _UiPathFactory();
             this.uiPathFactory = uiPathFactory;
         }
 
-      public readonly List<_PathFrames> paths;
-      public readonly Animation<float> progress;
-      public readonly Color color;
-      public readonly float? scale;
-      public readonly bool? shouldMirror;
-      public readonly _UiPathFactory uiPathFactory;
+        public readonly List<_PathFrames> paths;
+        public readonly Animation<float> progress;
+        public readonly Color color;
+        public readonly float? scale;
+        public readonly bool? shouldMirror;
+        public readonly _UiPathFactory uiPathFactory;
-      public override void paint(ui.Canvas canvas, Size size) {
-        canvas.scale(this.scale ?? 1.0f, this.scale ?? 1.0f);
-        if (this.shouldMirror == true) {
-          canvas.rotate(Mathf.PI);
-          canvas.translate(-size.width, -size.height);
-        }
+        public override void paint(Canvas canvas, Size size) {
+            canvas.scale(this.scale ?? 1.0f, this.scale ?? 1.0f);
+            if (this.shouldMirror == true) {
+                canvas.rotate(Mathf.PI);
+                canvas.translate(-size.width, -size.height);
+            }
-        float clampedProgress = this.progress.value.clamp(0.0f, 1.0f);
-        foreach (_PathFrames path in this.paths)
-          path.paint(canvas, this.color, this.uiPathFactory, clampedProgress);
-      }
+            float clampedProgress = this.progress.value.clamp(0.0f, 1.0f);
+            foreach (_PathFrames path in this.paths) {
+                path.paint(canvas, this.color, this.uiPathFactory, clampedProgress);
+            }
+        }
-      public override bool shouldRepaint(CustomPainter _oldDelegate) {
-        _AnimatedIconPainter oldDelegate = _oldDelegate as _AnimatedIconPainter;
-        return oldDelegate.progress.value != this.progress.value
-            || oldDelegate.color != this.color
-            || oldDelegate.paths != this.paths
-            || oldDelegate.scale != this.scale
-            || oldDelegate.uiPathFactory != this.uiPathFactory;
-      }
+        public override bool shouldRepaint(CustomPainter _oldDelegate) {
+            _AnimatedIconPainter oldDelegate = _oldDelegate as _AnimatedIconPainter;
+            return oldDelegate.progress.value != this.progress.value
+                   || oldDelegate.color != this.color
+                   || oldDelegate.paths != this.paths
+                   || oldDelegate.scale != this.scale
+                   || oldDelegate.uiPathFactory != this.uiPathFactory;
+        }
-      public override bool? hitTest(Offset position) => null;
+        public override bool? hitTest(Offset position) {
+            return null;
+        }
     }
 
     class _PathFrames {
             this.opacities = opacities;
         }
 
-      public readonly List<_PathCommand> commands;
-      public readonly List<float> opacities;
+        public readonly List<_PathCommand> commands;
+        public readonly List<float> opacities;
+
+        public void paint(Canvas canvas, Color color, _UiPathFactory uiPathFactory, float progress) {
+            float opacity = AnimatedIconUtils._interpolate<float>(this.opacities, progress, MathUtils.lerpFloat);
+            Paint paint = new Paint();
+            paint.style = PaintingStyle.fill;
+            paint.color = color.withOpacity(color.opacity * opacity);
+            Path path = uiPathFactory();
+            foreach (_PathCommand command in this.commands) {
+                command.apply(path, progress);
+            }
-      public void paint(ui.Canvas canvas, Color color, _UiPathFactory uiPathFactory, float progress) {
-        float opacity = AnimatedIconUtils._interpolate<float>(this.opacities, progress, MathUtils.lerpFloat);
-        Paint paint = new Paint();
-        paint.style = PaintingStyle.fill;
-        paint.color = color.withOpacity(color.opacity * opacity);
-        Path path = uiPathFactory();
-        foreach (_PathCommand command in this.commands)
-          command.apply(path, progress);
-        canvas.drawPath(path, paint);
-      }
+            canvas.drawPath(path, paint);
+        }
-      public _PathCommand() {}
+        public _PathCommand() {
+        }
-      public abstract void apply(Path path, float progress);
+        public abstract void apply(Path path, float progress);
     }
 
     class _PathMoveTo : _PathCommand {
 
-      public readonly List<Offset> points;
+        public readonly List<Offset> points;
-      public override void apply(Path path, float progress) {
-        Offset offset = AnimatedIconUtils._interpolate<Offset>(this.points, progress, Offset.lerp);
-        path.moveTo(offset.dx, offset.dy);
-      }
+        public override void apply(Path path, float progress) {
+            Offset offset = AnimatedIconUtils._interpolate<Offset>(this.points, progress, Offset.lerp);
+            path.moveTo(offset.dx, offset.dy);
+        }
-      public _PathCubicTo(List<Offset> controlPoints1, List<Offset> controlPoints2, List<Offset> targetPoints) {
-          this.controlPoints1 = controlPoints1;
-          this.controlPoints2 = controlPoints2;
-          this.targetPoints = targetPoints;
-      }
+        public _PathCubicTo(List<Offset> controlPoints1, List<Offset> controlPoints2, List<Offset> targetPoints) {
+            this.controlPoints1 = controlPoints1;
+            this.controlPoints2 = controlPoints2;
+            this.targetPoints = targetPoints;
+        }
-      public readonly List<Offset> controlPoints2;
-      public readonly List<Offset> controlPoints1;
-      public readonly List<Offset> targetPoints;
+        public readonly List<Offset> controlPoints2;
+        public readonly List<Offset> controlPoints1;
+        public readonly List<Offset> targetPoints;
-      public override void apply(Path path, float progress) {
-        Offset controlPoint1 = AnimatedIconUtils._interpolate<Offset>(this.controlPoints1, progress, Offset.lerp);
-        Offset controlPoint2 = AnimatedIconUtils._interpolate<Offset>(this.controlPoints2, progress, Offset.lerp);
-        Offset targetPoint = AnimatedIconUtils._interpolate<Offset>(this.targetPoints, progress, Offset.lerp);
-        // TODO: replace with cubicTo
-        path.bezierTo(
-          controlPoint1.dx, controlPoint1.dy,
-          controlPoint2.dx, controlPoint2.dy,
-          targetPoint.dx, targetPoint.dy
-        );
-      }
+        public override void apply(Path path, float progress) {
+            Offset controlPoint1 = AnimatedIconUtils._interpolate<Offset>(this.controlPoints1, progress, Offset.lerp);
+            Offset controlPoint2 = AnimatedIconUtils._interpolate<Offset>(this.controlPoints2, progress, Offset.lerp);
+            Offset targetPoint = AnimatedIconUtils._interpolate<Offset>(this.targetPoints, progress, Offset.lerp);
+            // TODO: replace with cubicTo
+            path.bezierTo(
+                controlPoint1.dx, controlPoint1.dy,
+                controlPoint2.dx, controlPoint2.dy,
+                targetPoint.dx, targetPoint.dy
+            );
+        }
     }
 
     class _PathLineTo : _PathCommand {
 
-      List<Offset> points;
+        List<Offset> points;
-      public override void apply(Path path, float progress) {
-        Offset point = AnimatedIconUtils._interpolate<Offset>(this.points, progress, Offset.lerp);
-        path.lineTo(point.dx, point.dy);
-      }
+        public override void apply(Path path, float progress) {
+            Offset point = AnimatedIconUtils._interpolate<Offset>(this.points, progress, Offset.lerp);
+            path.lineTo(point.dx, point.dy);
+        }
-      public _PathClose() {}
+        public _PathClose() {
+        }
-      public override void apply(Path path, float progress) {
-        path.close();
-      }
+        public override void apply(Path path, float progress) {
+            path.close();
+        }
-
 }

Runtime/material/animated_icons/animated_icons_data.cs

 using System.Collections.Generic;
 using Unity.UIWidgets.ui;
-using UnityEngine;
+        public static readonly AnimatedIconData add_event = AnimatedIconsData._add_event;
-      public static readonly AnimatedIconData add_event = AnimatedIconsData._add_event;
+        public static readonly AnimatedIconData arrow_menu = AnimatedIconsData._arrow_menu;
-      public static readonly AnimatedIconData arrow_menu = AnimatedIconsData._arrow_menu;
+        public static readonly AnimatedIconData close_menu = AnimatedIconsData._close_menu;
-      public static readonly AnimatedIconData close_menu = AnimatedIconsData._close_menu;
-
-      // public readonly AnimatedIconData ellipsis_search = AnimatedIconsData._ellipsis_search;
+        // public readonly AnimatedIconData ellipsis_search = AnimatedIconsData._ellipsis_search;
-      // public readonly AnimatedIconData event_add = AnimatedIconsData._event_add;
+        // public readonly AnimatedIconData event_add = AnimatedIconsData._event_add;
-      // public readonly AnimatedIconData home_menu = AnimatedIconsData._home_menu;
+        // public readonly AnimatedIconData home_menu = AnimatedIconsData._home_menu;
-      // public readonly AnimatedIconData list_view = AnimatedIconsData._list_view;
+        // public readonly AnimatedIconData list_view = AnimatedIconsData._list_view;
-      // public readonly AnimatedIconData menu_arrow = AnimatedIconsData._menu_arrow;
+        // public readonly AnimatedIconData menu_arrow = AnimatedIconsData._menu_arrow;
-      // public readonly AnimatedIconData menu_close = AnimatedIconsData._menu_close;
+        // public readonly AnimatedIconData menu_close = AnimatedIconsData._menu_close;
-      // public readonly AnimatedIconData menu_home = AnimatedIconsData._menu_home;
+        // public readonly AnimatedIconData menu_home = AnimatedIconsData._menu_home;
-      // public readonly AnimatedIconData pause_play = AnimatedIconsData._pause_play;
+        // public readonly AnimatedIconData pause_play = AnimatedIconsData._pause_play;
-      // public readonly AnimatedIconData play_pause = AnimatedIconsData._play_pause;
+        // public readonly AnimatedIconData play_pause = AnimatedIconsData._play_pause;
-      // public readonly AnimatedIconData search_ellipsis = AnimatedIconsData._search_ellipsis;
+        // public readonly AnimatedIconData search_ellipsis = AnimatedIconsData._search_ellipsis;
-      // public readonly AnimatedIconData view_list = AnimatedIconsData._view_list;
+        // public readonly AnimatedIconData view_list = AnimatedIconsData._view_list;
-      public AnimatedIconData() {}
+        public AnimatedIconData() {
+        }
-      public abstract bool matchTextDirection { get; }
+        public abstract bool matchTextDirection { get; }
-      public _AnimatedIconData(Size size, List<_PathFrames> paths, bool matchTextDirection = false) {
-          this.size = size;
-          this.paths = paths;
-          this.matchTextDirection = matchTextDirection;
-      }
+        public _AnimatedIconData(Size size, List<_PathFrames> paths, bool matchTextDirection = false) {
+            this.size = size;
+            this.paths = paths;
+            this.matchTextDirection = matchTextDirection;
+        }
-      public readonly Size size;
-      public readonly List<_PathFrames> paths;
+        public readonly Size size;
+        public readonly List<_PathFrames> paths;
-      public override bool matchTextDirection { get; }
+        public override bool matchTextDirection { get; }
-
 }

Samples/UIWidgetsGallery/gallery/backdrop.cs

 using UnityEngine;
 
 namespace UIWidgetsGallery.gallery {
-    public class BackdropConstants {
+    class BackdropConstants {
         public const float _kFrontHeadingHeight = 32.0f;
         public const float _kFrontClosedHeight = 92.0f;
         public const float _kBackAppBarHeight = 56.0f;
         }
     }
 
-    class Backdrop : StatefulWidget {
+    public class Backdrop : StatefulWidget {
         public Backdrop(
             Widget frontAction,
             Widget frontTitle,

Runtime/widgets/visibility.cs

+using Unity.UIWidgets.foundation;
+
+namespace Unity.UIWidgets.widgets {
+    public class Visibility : StatelessWidget {
+        public Visibility(
+            Key key = null,
+            Widget child = null,
+            Widget replacement = null,
+            bool visible = true,
+            bool maintainState = false,
+            bool maintainAnimation = false,
+            bool maintainSize = false,
+            bool maintainInteractivity = false
+        ) : base(key: key) {
+            D.assert(child != null);
+            D.assert(replacement != null);
+            D.assert(maintainState == true || maintainAnimation == false,
+                "Cannot maintain animations if the state is not also maintained.");
+            D.assert(maintainAnimation == true || maintainSize == false,
+                "Cannot maintain size if animations are not maintained.");
+            D.assert(maintainSize == true || maintainInteractivity == false,
+                "Cannot maintain interactivity if size is not maintained.");
+            this.replacement = replacement ?? SizedBox.shrink();
+            this.child = child;
+            this.visible = visible;
+            this.maintainState = maintainState;
+            this.maintainAnimation = maintainAnimation;
+            this.maintainSize = maintainSize;
+            this.maintainInteractivity = maintainInteractivity;
+        }
+
+        public readonly Widget child;
+
+        public readonly Widget replacement;
+
+        public readonly bool visible;
+
+        public readonly bool maintainState;
+
+        public readonly bool maintainAnimation;
+
+        public readonly bool maintainSize;
+
+        public readonly bool maintainInteractivity;
+
+        public override Widget build(BuildContext context) {
+            if (this.maintainSize) {
+                Widget result = this.child;
+                if (!this.maintainInteractivity) {
+                    result = new IgnorePointer(
+                        child: this.child,
+                        ignoring: !this.visible
+                    );
+                }
+
+                return new Opacity(
+                    opacity: this.visible ? 1.0f : 0.0f,
+                    child: result
+                );
+            }
+
+            D.assert(!this.maintainInteractivity);
+            D.assert(!this.maintainSize);
+            if (this.maintainState) {
+                Widget result = this.child;
+                if (!this.maintainAnimation) {
+                    result = new TickerMode(child: this.child, enabled: this.visible);
+                }
+
+                return new Offstage(
+                    child: result,
+                    offstage: !this.visible
+                );
+            }
+
+            D.assert(!this.maintainAnimation);
+            D.assert(!this.maintainState);
+            return this.visible ? this.child : this.replacement;
+        }
+
+        public override void debugFillProperties(DiagnosticPropertiesBuilder properties) {
+            base.debugFillProperties(properties);
+            properties.add(new FlagProperty("visible", value: this.visible, ifFalse: "hidden", ifTrue: "visible"));
+            properties.add(new FlagProperty("maintainState", value: this.maintainState, ifFalse: "maintainState"));
+            properties.add(new FlagProperty("maintainAnimation", value: this.maintainAnimation,
+                ifFalse: "maintainAnimation"));
+            properties.add(new FlagProperty("maintainSize", value: this.maintainSize, ifFalse: "maintainSize"));
+            properties.add(new FlagProperty("maintainInteractivity", value: this.maintainInteractivity,
+                ifFalse: "maintainInteractivity"));
+        }
+    }
+}

Runtime/widgets/visibility.cs.meta

+fileFormatVersion: 2
+guid: f24846c5a2354d9a8b02bf83f3e8398e
+timeCreated: 1552895385