packages/flutter/lib/src/cupertino/magnifier.dart - mirrors/flutter - Git at Google

 // Copyright 2014 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 import 'dart:math' as math;
 import 'package:flutter/widgets.dart';

 /// A [CupertinoMagnifier] used for magnifying text in cases where a user's
 /// finger may be blocking the point of interest, like a selection handle.
 ///
 /// Delegates styling to [CupertinoMagnifier] with its position depending on
 /// [magnifierInfo].
 ///
 /// Specifically, the [CupertinoTextMagnifier] follows the following rules.
 /// [CupertinoTextMagnifier]:
 /// - is positioned horizontally inside the screen width, with [horizontalScreenEdgePadding] padding.
 /// - is hidden if a gesture is detected [hideBelowThreshold] units below the line
 ///   that the magnifier is on, shown otherwise.
 /// - follows the x coordinate of the gesture directly (with respect to rule 1).
 /// - has some vertical drag resistance; i.e. if a gesture is detected k units below the field,
 ///   then has vertical offset [dragResistance] * k.
 class CupertinoTextMagnifier extends StatefulWidget {
   /// Constructs a [RawMagnifier] in the Cupertino style, positioning with respect to
   /// [magnifierInfo].
   ///
   /// The default constructor parameters and constants were eyeballed on
   /// an iPhone XR iOS v15.5.
   const CupertinoTextMagnifier({
     super.key,
     this.animationCurve = Curves.easeOut,
     required this.controller,
     this.dragResistance = 10.0,
     this.hideBelowThreshold = 48.0,
     this.horizontalScreenEdgePadding = 10.0,
     required this.magnifierInfo,
   });

   /// The curve used for the in / out animations.
   final Curve animationCurve;

   /// This magnifier's controller.
   ///
   /// The [CupertinoTextMagnifier] requires a [MagnifierController]
   /// in order to show / hide itself without removing itself from the
   /// overlay.
   final MagnifierController controller;

   /// A drag resistance on the downward Y position of the lens.
   final double dragResistance;

   /// The difference in Y between the gesture position and the caret center
   /// so that the magnifier hides itself.
   final double hideBelowThreshold;

   /// The padding on either edge of the screen that any part of the magnifier
   /// cannot exist past.
   ///
   /// This includes any part of the magnifier, not just the center; for example,
   /// the left edge of the magnifier cannot be outside the [horizontalScreenEdgePadding].v
   ///
   /// If the screen has width w, then the magnifier is bound to
   /// `_kHorizontalScreenEdgePadding, w - _kHorizontalScreenEdgePadding`.
   final double horizontalScreenEdgePadding;

   /// [CupertinoTextMagnifier] will determine its own positioning
   /// based on the [MagnifierInfo] of this notifier.
   final ValueNotifier<MagnifierInfo>
       magnifierInfo;

   /// The duration that the magnifier drags behind its final position.
   static const Duration _kDragAnimationDuration = Duration(milliseconds: 45);

   @override
   State<CupertinoTextMagnifier> createState() =>
       _CupertinoTextMagnifierState();
 }

 class _CupertinoTextMagnifierState extends State<CupertinoTextMagnifier>
     with SingleTickerProviderStateMixin {
   // Initialize to dummy values for the event that the initial call to
   // _determineMagnifierPositionAndFocalPoint calls hide, and thus does not
   // set these values.
   Offset _currentAdjustedMagnifierPosition = Offset.zero;
   double _verticalFocalPointAdjustment = 0;
   late AnimationController _ioAnimationController;
   late Animation<double> _ioAnimation;

   @override
   void initState() {
     super.initState();
     _ioAnimationController = AnimationController(
       value: 0,
       vsync: this,
       duration: CupertinoMagnifier._kInOutAnimationDuration,
     )..addListener(() => setState(() {}));

     widget.controller.animationController = _ioAnimationController;
     widget.magnifierInfo
         .addListener(_determineMagnifierPositionAndFocalPoint);

     _ioAnimation = Tween<double>(
       begin: 0.0,
       end: 1.0,
     ).animate(CurvedAnimation(
       parent: _ioAnimationController,
       curve: widget.animationCurve,
     ));
   }

   @override
   void dispose() {
     widget.controller.animationController = null;
     _ioAnimationController.dispose();
     widget.magnifierInfo
         .removeListener(_determineMagnifierPositionAndFocalPoint);
     super.dispose();
   }

   @override
   void didUpdateWidget(CupertinoTextMagnifier oldWidget) {
     if (oldWidget.magnifierInfo != widget.magnifierInfo) {
       oldWidget.magnifierInfo.removeListener(_determineMagnifierPositionAndFocalPoint);
       widget.magnifierInfo.addListener(_determineMagnifierPositionAndFocalPoint);
     }
     super.didUpdateWidget(oldWidget);
   }

   @override
   void didChangeDependencies() {
     _determineMagnifierPositionAndFocalPoint();
     super.didChangeDependencies();
   }

   void _determineMagnifierPositionAndFocalPoint() {
     final MagnifierInfo textEditingContext =
         widget.magnifierInfo.value;

     // The exact Y of the center of the current line.
     final double verticalCenterOfCurrentLine =
         textEditingContext.caretRect.center.dy;

     // If the magnifier is currently showing, but we have dragged out of threshold,
     // we should hide it.
     if (verticalCenterOfCurrentLine -
             textEditingContext.globalGesturePosition.dy <
         -widget.hideBelowThreshold) {
       // Only signal a hide if we are currently showing.
       if (widget.controller.shown) {
         widget.controller.hide(removeFromOverlay: false);
       }
       return;
     }

     // If we are gone, but got to this point, we shouldn't be: show.
     if (!widget.controller.shown) {
       _ioAnimationController.forward();
     }

     // Never go above the center of the line, but have some resistance
     // going downward if the drag goes too far.
     final double verticalPositionOfLens = math.max(
         verticalCenterOfCurrentLine,
         verticalCenterOfCurrentLine -
             (verticalCenterOfCurrentLine -
                     textEditingContext.globalGesturePosition.dy) /
                 widget.dragResistance);

     // The raw position, tracking the gesture directly.
     final Offset rawMagnifierPosition = Offset(
       textEditingContext.globalGesturePosition.dx -
           CupertinoMagnifier.kDefaultSize.width / 2,
       verticalPositionOfLens -
           (CupertinoMagnifier.kDefaultSize.height -
               CupertinoMagnifier.kMagnifierAboveFocalPoint),
     );

     final Rect screenRect = Offset.zero & MediaQuery.sizeOf(context);

     // Adjust the magnifier position so that it never exists outside the horizontal
     // padding.
     final Offset adjustedMagnifierPosition = MagnifierController.shiftWithinBounds(
       bounds: Rect.fromLTRB(
           screenRect.left + widget.horizontalScreenEdgePadding,
           // iOS doesn't reposition for Y, so we should expand the threshold
           // so we can send the whole magnifier out of bounds if need be.
           screenRect.top -
               (CupertinoMagnifier.kDefaultSize.height +
                   CupertinoMagnifier.kMagnifierAboveFocalPoint),
           screenRect.right - widget.horizontalScreenEdgePadding,
           screenRect.bottom +
               (CupertinoMagnifier.kDefaultSize.height +
                   CupertinoMagnifier.kMagnifierAboveFocalPoint)),
       rect: rawMagnifierPosition & CupertinoMagnifier.kDefaultSize,
     ).topLeft;

     setState(() {
       _currentAdjustedMagnifierPosition = adjustedMagnifierPosition;
       // The lens should always point to the center of the line.
       _verticalFocalPointAdjustment =
           verticalCenterOfCurrentLine - verticalPositionOfLens;
     });
   }

   @override
   Widget build(BuildContext context) {
     return AnimatedPositioned(
       duration: CupertinoTextMagnifier._kDragAnimationDuration,
       curve: widget.animationCurve,
       left: _currentAdjustedMagnifierPosition.dx,
       top: _currentAdjustedMagnifierPosition.dy,
       child: CupertinoMagnifier(
         inOutAnimation: _ioAnimation,
         additionalFocalPointOffset: Offset(0, _verticalFocalPointAdjustment),
       ),
     );
   }
 }

 /// A [RawMagnifier] used for magnifying text in cases where a user's
 /// finger may be blocking the point of interest, like a selection handle.
 ///
 /// [CupertinoMagnifier] is a wrapper around [RawMagnifier] that handles styling
 /// and transitions.
 ///
 /// {@macro flutter.widgets.magnifier.intro}
 ///
 /// See also:
 ///
 /// * [RawMagnifier], the backing implementation.
 /// * [CupertinoTextMagnifier], a widget that positions [CupertinoMagnifier] based on
 /// [MagnifierInfo].
 /// * [MagnifierController], the controller for this magnifier.
 class CupertinoMagnifier extends StatelessWidget {
   /// Creates a [RawMagnifier] in the Cupertino style.
   ///
   /// The default constructor parameters and constants were eyeballed on
   /// an iPhone XR iOS v15.5.
   const CupertinoMagnifier({
     super.key,
     this.size = kDefaultSize,
     this.borderRadius = const BorderRadius.all(Radius.elliptical(60, 50)),
     this.additionalFocalPointOffset = Offset.zero,
     this.shadows = const <BoxShadow>[
       BoxShadow(
         color: Color.fromARGB(25, 0, 0, 0),
         blurRadius: 11,
         spreadRadius: 0.2,
       ),
     ],
     this.borderSide =
         const BorderSide(color: Color.fromARGB(255, 232, 232, 232)),
     this.inOutAnimation,
   });

   /// The shadows displayed under the magnifier.
   final List<BoxShadow> shadows;

   /// The border, or "rim", of this magnifier.
   final BorderSide borderSide;

   /// The vertical offset that the magnifier is along the Y axis above
   /// the focal point.
   @visibleForTesting
   static const double kMagnifierAboveFocalPoint = -26;

   /// The default size of the magnifier.
   ///
   /// This is public so that positioners can choose to depend on it, although
   /// it is overridable.
   @visibleForTesting
   static const Size kDefaultSize = Size(80, 47.5);

   /// The duration that this magnifier animates in / out for.
   ///
   /// The animation is a translation and a fade. The translation
   /// begins at the focal point, and ends at [kMagnifierAboveFocalPoint].
   /// The opacity begins at 0 and ends at 1.
   static const Duration _kInOutAnimationDuration = Duration(milliseconds: 150);

   /// The size of this magnifier.
   final Size size;

   /// The border radius of this magnifier.
   final BorderRadius borderRadius;

   /// This [RawMagnifier]'s controller.
   ///
   /// Since [CupertinoMagnifier] has no knowledge of shown / hidden state,
   /// this animation should be driven by an external actor.
   final Animation<double>? inOutAnimation;

   /// Any additional focal point offset, applied over the regular focal
   /// point offset defined in [kMagnifierAboveFocalPoint].
   final Offset additionalFocalPointOffset;

   @override
   Widget build(BuildContext context) {
     Offset focalPointOffset =
         Offset(0, (kDefaultSize.height / 2) - kMagnifierAboveFocalPoint);
     focalPointOffset.scale(1, inOutAnimation?.value ?? 1);
     focalPointOffset += additionalFocalPointOffset;

     return Transform.translate(
       offset: Offset.lerp(
         const Offset(0, -kMagnifierAboveFocalPoint),
         Offset.zero,
         inOutAnimation?.value ?? 1,
       )!,
       child: RawMagnifier(
         size: size,
         focalPointOffset: focalPointOffset,
         decoration: MagnifierDecoration(
           opacity: inOutAnimation?.value ?? 1,
           shape: RoundedRectangleBorder(
             borderRadius: borderRadius,
             side: borderSide,
           ),
           shadows: shadows,
         ),
       ),
     );
   }
 }
	// Copyright 2014 The Flutter Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	import 'dart:math' as math;
	import 'package:flutter/widgets.dart';

	/// A [CupertinoMagnifier] used for magnifying text in cases where a user's
	/// finger may be blocking the point of interest, like a selection handle.
	///
	/// Delegates styling to [CupertinoMagnifier] with its position depending on
	/// [magnifierInfo].
	///
	/// Specifically, the [CupertinoTextMagnifier] follows the following rules.
	/// [CupertinoTextMagnifier]:
	/// - is positioned horizontally inside the screen width, with [horizontalScreenEdgePadding] padding.
	/// - is hidden if a gesture is detected [hideBelowThreshold] units below the line
	/// that the magnifier is on, shown otherwise.
	/// - follows the x coordinate of the gesture directly (with respect to rule 1).
	/// - has some vertical drag resistance; i.e. if a gesture is detected k units below the field,
	/// then has vertical offset [dragResistance] * k.
	class CupertinoTextMagnifier extends StatefulWidget {
	/// Constructs a [RawMagnifier] in the Cupertino style, positioning with respect to
	/// [magnifierInfo].
	///
	/// The default constructor parameters and constants were eyeballed on
	/// an iPhone XR iOS v15.5.
	const CupertinoTextMagnifier({
	super.key,
	this.animationCurve = Curves.easeOut,
	required this.controller,
	this.dragResistance = 10.0,
	this.hideBelowThreshold = 48.0,
	this.horizontalScreenEdgePadding = 10.0,
	required this.magnifierInfo,
	});

	/// The curve used for the in / out animations.
	final Curve animationCurve;

	/// This magnifier's controller.
	///
	/// The [CupertinoTextMagnifier] requires a [MagnifierController]
	/// in order to show / hide itself without removing itself from the
	/// overlay.
	final MagnifierController controller;

	/// A drag resistance on the downward Y position of the lens.
	final double dragResistance;

	/// The difference in Y between the gesture position and the caret center
	/// so that the magnifier hides itself.
	final double hideBelowThreshold;

	/// The padding on either edge of the screen that any part of the magnifier
	/// cannot exist past.
	///
	/// This includes any part of the magnifier, not just the center; for example,
	/// the left edge of the magnifier cannot be outside the [horizontalScreenEdgePadding].v
	///
	/// If the screen has width w, then the magnifier is bound to
	/// `_kHorizontalScreenEdgePadding, w - _kHorizontalScreenEdgePadding`.
	final double horizontalScreenEdgePadding;

	/// [CupertinoTextMagnifier] will determine its own positioning
	/// based on the [MagnifierInfo] of this notifier.
	final ValueNotifier<MagnifierInfo>
	magnifierInfo;

	/// The duration that the magnifier drags behind its final position.
	static const Duration _kDragAnimationDuration = Duration(milliseconds: 45);

	@override
	State<CupertinoTextMagnifier> createState() =>
	_CupertinoTextMagnifierState();
	}

	class _CupertinoTextMagnifierState extends State<CupertinoTextMagnifier>
	with SingleTickerProviderStateMixin {
	// Initialize to dummy values for the event that the initial call to
	// _determineMagnifierPositionAndFocalPoint calls hide, and thus does not
	// set these values.
	Offset _currentAdjustedMagnifierPosition = Offset.zero;
	double _verticalFocalPointAdjustment = 0;
	late AnimationController _ioAnimationController;
	late Animation<double> _ioAnimation;

	@override
	void initState() {
	super.initState();
	_ioAnimationController = AnimationController(
	value: 0,
	vsync: this,
	duration: CupertinoMagnifier._kInOutAnimationDuration,
	)..addListener(() => setState(() {}));

	widget.controller.animationController = _ioAnimationController;
	widget.magnifierInfo
	.addListener(_determineMagnifierPositionAndFocalPoint);

	_ioAnimation = Tween<double>(
	begin: 0.0,
	end: 1.0,
	).animate(CurvedAnimation(
	parent: _ioAnimationController,
	curve: widget.animationCurve,
	));
	}

	@override
	void dispose() {
	widget.controller.animationController = null;
	_ioAnimationController.dispose();
	widget.magnifierInfo
	.removeListener(_determineMagnifierPositionAndFocalPoint);
	super.dispose();
	}

	@override
	void didUpdateWidget(CupertinoTextMagnifier oldWidget) {
	if (oldWidget.magnifierInfo != widget.magnifierInfo) {
	oldWidget.magnifierInfo.removeListener(_determineMagnifierPositionAndFocalPoint);
	widget.magnifierInfo.addListener(_determineMagnifierPositionAndFocalPoint);
	}
	super.didUpdateWidget(oldWidget);
	}

	@override
	void didChangeDependencies() {
	_determineMagnifierPositionAndFocalPoint();
	super.didChangeDependencies();
	}

	void _determineMagnifierPositionAndFocalPoint() {
	final MagnifierInfo textEditingContext =
	widget.magnifierInfo.value;

	// The exact Y of the center of the current line.
	final double verticalCenterOfCurrentLine =
	textEditingContext.caretRect.center.dy;

	// If the magnifier is currently showing, but we have dragged out of threshold,
	// we should hide it.
	if (verticalCenterOfCurrentLine -
	textEditingContext.globalGesturePosition.dy <
	-widget.hideBelowThreshold) {
	// Only signal a hide if we are currently showing.
	if (widget.controller.shown) {
	widget.controller.hide(removeFromOverlay: false);
	}
	return;
	}

	// If we are gone, but got to this point, we shouldn't be: show.
	if (!widget.controller.shown) {
	_ioAnimationController.forward();
	}

	// Never go above the center of the line, but have some resistance
	// going downward if the drag goes too far.
	final double verticalPositionOfLens = math.max(
	verticalCenterOfCurrentLine,
	verticalCenterOfCurrentLine -
	(verticalCenterOfCurrentLine -
	textEditingContext.globalGesturePosition.dy) /
	widget.dragResistance);

	// The raw position, tracking the gesture directly.
	final Offset rawMagnifierPosition = Offset(
	textEditingContext.globalGesturePosition.dx -
	CupertinoMagnifier.kDefaultSize.width / 2,
	verticalPositionOfLens -
	(CupertinoMagnifier.kDefaultSize.height -
	CupertinoMagnifier.kMagnifierAboveFocalPoint),
	);

	final Rect screenRect = Offset.zero & MediaQuery.sizeOf(context);

	// Adjust the magnifier position so that it never exists outside the horizontal
	// padding.
	final Offset adjustedMagnifierPosition = MagnifierController.shiftWithinBounds(
	bounds: Rect.fromLTRB(
	screenRect.left + widget.horizontalScreenEdgePadding,
	// iOS doesn't reposition for Y, so we should expand the threshold
	// so we can send the whole magnifier out of bounds if need be.
	screenRect.top -
	(CupertinoMagnifier.kDefaultSize.height +
	CupertinoMagnifier.kMagnifierAboveFocalPoint),
	screenRect.right - widget.horizontalScreenEdgePadding,
	screenRect.bottom +
	(CupertinoMagnifier.kDefaultSize.height +
	CupertinoMagnifier.kMagnifierAboveFocalPoint)),
	rect: rawMagnifierPosition & CupertinoMagnifier.kDefaultSize,
	).topLeft;

	setState(() {
	_currentAdjustedMagnifierPosition = adjustedMagnifierPosition;
	// The lens should always point to the center of the line.
	_verticalFocalPointAdjustment =
	verticalCenterOfCurrentLine - verticalPositionOfLens;
	});
	}

	@override
	Widget build(BuildContext context) {
	return AnimatedPositioned(
	duration: CupertinoTextMagnifier._kDragAnimationDuration,
	curve: widget.animationCurve,
	left: _currentAdjustedMagnifierPosition.dx,
	top: _currentAdjustedMagnifierPosition.dy,
	child: CupertinoMagnifier(
	inOutAnimation: _ioAnimation,
	additionalFocalPointOffset: Offset(0, _verticalFocalPointAdjustment),
	),
	);
	}
	}

	/// A [RawMagnifier] used for magnifying text in cases where a user's
	/// finger may be blocking the point of interest, like a selection handle.
	///
	/// [CupertinoMagnifier] is a wrapper around [RawMagnifier] that handles styling
	/// and transitions.
	///
	/// {@macro flutter.widgets.magnifier.intro}
	///
	/// See also:
	///
	/// * [RawMagnifier], the backing implementation.
	/// * [CupertinoTextMagnifier], a widget that positions [CupertinoMagnifier] based on
	/// [MagnifierInfo].
	/// * [MagnifierController], the controller for this magnifier.
	class CupertinoMagnifier extends StatelessWidget {
	/// Creates a [RawMagnifier] in the Cupertino style.
	///
	/// The default constructor parameters and constants were eyeballed on
	/// an iPhone XR iOS v15.5.
	const CupertinoMagnifier({
	super.key,
	this.size = kDefaultSize,
	this.borderRadius = const BorderRadius.all(Radius.elliptical(60, 50)),
	this.additionalFocalPointOffset = Offset.zero,
	this.shadows = const <BoxShadow>[
	BoxShadow(
	color: Color.fromARGB(25, 0, 0, 0),
	blurRadius: 11,
	spreadRadius: 0.2,
	),
	],
	this.borderSide =
	const BorderSide(color: Color.fromARGB(255, 232, 232, 232)),
	this.inOutAnimation,
	});

	/// The shadows displayed under the magnifier.
	final List<BoxShadow> shadows;

	/// The border, or "rim", of this magnifier.
	final BorderSide borderSide;

	/// The vertical offset that the magnifier is along the Y axis above
	/// the focal point.
	@visibleForTesting
	static const double kMagnifierAboveFocalPoint = -26;

	/// The default size of the magnifier.
	///
	/// This is public so that positioners can choose to depend on it, although
	/// it is overridable.
	@visibleForTesting
	static const Size kDefaultSize = Size(80, 47.5);

	/// The duration that this magnifier animates in / out for.
	///
	/// The animation is a translation and a fade. The translation
	/// begins at the focal point, and ends at [kMagnifierAboveFocalPoint].
	/// The opacity begins at 0 and ends at 1.
	static const Duration _kInOutAnimationDuration = Duration(milliseconds: 150);

	/// The size of this magnifier.
	final Size size;

	/// The border radius of this magnifier.
	final BorderRadius borderRadius;

	/// This [RawMagnifier]'s controller.
	///
	/// Since [CupertinoMagnifier] has no knowledge of shown / hidden state,
	/// this animation should be driven by an external actor.
	final Animation<double>? inOutAnimation;

	/// Any additional focal point offset, applied over the regular focal
	/// point offset defined in [kMagnifierAboveFocalPoint].
	final Offset additionalFocalPointOffset;

	@override
	Widget build(BuildContext context) {
	Offset focalPointOffset =
	Offset(0, (kDefaultSize.height / 2) - kMagnifierAboveFocalPoint);
	focalPointOffset.scale(1, inOutAnimation?.value ?? 1);
	focalPointOffset += additionalFocalPointOffset;

	return Transform.translate(
	offset: Offset.lerp(
	const Offset(0, -kMagnifierAboveFocalPoint),
	Offset.zero,
	inOutAnimation?.value ?? 1,
	)!,
	child: RawMagnifier(
	size: size,
	focalPointOffset: focalPointOffset,
	decoration: MagnifierDecoration(
	opacity: inOutAnimation?.value ?? 1,
	shape: RoundedRectangleBorder(
	borderRadius: borderRadius,
	side: borderSide,
	),
	shadows: shadows,
	),
	),
	);
	}
	}