Visibility Detector

https://pub.dev/documentation/visibility_detector/latest/
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Visibility Detector is a Flutter widget that detects when a widget becomes visible or invisible on...
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### GET instance

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetectorController/instance.html

Retrieves the singleton instance of the VisibilityDetectorController.

```APIDOC
## GET instance

### Description
Retrieves the static singleton instance of the VisibilityDetectorController.

### Method
GET

### Endpoint
VisibilityDetectorController.instance

### Response
- **instance** (VisibilityDetectorController) - The singleton instance of the controller.
```

--------------------------------

### Basic Visibility Detection Example

Source: https://pub.dev/packages/visibility_detector

Wrap a widget with VisibilityDetector to receive callbacks when its visibility changes. The callback provides the visibility fraction and the widget's key.

```dart
Widget build(BuildContext context) {
  return VisibilityDetector(
    key: Key('my-widget-key'),
    onVisibilityChanged: (visibilityInfo) {
      var visiblePercentage = visibilityInfo.visibleFraction * 100;
      debugPrint(
          'Widget ${visibilityInfo.key} is ${visiblePercentage}% visible');
    },
    child: someOtherWidget,
  );
}

```

--------------------------------

### Get VisibilityDetectorController Instance

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetectorController/instance.html

Access the singleton instance of VisibilityDetectorController. This is the primary way to interact with the controller.

```dart
static VisibilityDetectorController get instance => _instance;
```

--------------------------------

### GET debugUpdateCount

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetectorController/debugUpdateCount.html

Retrieves the current update count for the visibility detector, available only in debug mode.

```APIDOC
## GET debugUpdateCount

### Description
Returns the current update count from the RenderVisibilityDetectorBase. This property is only available when kDebugMode is true; otherwise, it returns null.

### Method
GET

### Response
#### Success Response (200)
- **debugUpdateCount** (int?) - The current update count or null if not in debug mode.
```

--------------------------------

### Get Debug Update Count

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetectorController/debugUpdateCount.html

Returns the debug update count only when in debug mode. Otherwise, returns null.

```dart
int? get debugUpdateCount {
  if (!kDebugMode) {
    return null;
  }
  return RenderVisibilityDetectorBase.debugUpdateCount;
}
```

--------------------------------

### VisibilityDetector Forget Method

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetectorController/forget.html

Forgets any pending visibility callbacks for the VisibilityDetector with the given key. If the widget gets attached/detached, the callback will be rescheduled. This method can be used to cancel timers after the VisibilityDetector has been detached to avoid pending timers in tests.

```APIDOC
## forget(Key key)

### Description
Forgets any pending visibility callbacks for the VisibilityDetector with the given `key`. If the widget gets attached/detached, the callback will be rescheduled. This method can be used to cancel timers after the VisibilityDetector has been detached to avoid pending timers in tests.

### Method
void

### Endpoint
N/A (This is a method call, not an API endpoint)

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
N/A

### Response
#### Success Response (void)
N/A

#### Response Example
N/A
```

--------------------------------

### VisibilityInfo Constructor Implementation

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/VisibilityInfo.html

The VisibilityInfo constructor initializes key, size, and visibleBounds. The key must not be null. If size or visibleBounds are omitted, they default to Size.zero and Rect.zero respectively, indicating the widget is completely hidden.

```dart
const VisibilityInfo({
  required this.key,
  this.size = Size.zero,
  this.visibleBounds = Rect.zero,
}) : assert(key != null);
```

--------------------------------

### VisibilityInfo Constructor API

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/VisibilityInfo.html

Details of the VisibilityInfo constructor, its parameters, and initialization logic.

```APIDOC
## VisibilityInfo Constructor

### Description
Initializes a VisibilityInfo object with key, size, and visibleBounds.

### Method
Constructor

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
- **key** (Key) - Required - The Key used to construct the corresponding VisibilityDetector widget. Must not be null.
- **size** (Size) - Optional - Defaults to Size.zero. If omitted, indicates the widget is completely hidden.
- **visibleBounds** (Rect) - Optional - Defaults to Rect.zero. If omitted, indicates the widget is completely hidden.

### Request Example
```json
{
  "key": "some_key",
  "size": "100x50",
  "visibleBounds": "{x: 10, y: 20, width: 80, height: 30}"
}
```

### Response
#### Success Response (200)
This constructor does not return a value in the traditional sense; it initializes an object.

#### Response Example
N/A
```

--------------------------------

### SliverVisibilityDetector Implementation

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/SliverVisibilityDetector/SliverVisibilityDetector.html

Shows the internal implementation details of the SliverVisibilityDetector constructor.

```APIDOC
## SliverVisibilityDetector Implementation

### Description
This section details the internal implementation of the SliverVisibilityDetector constructor, including assertions.

### Method
Constructor Implementation

### Endpoint
N/A

### Parameters
#### Path Parameters
- **key** (Key) - Required - Must be non-null.
- **sliver** (Widget) - Required - Must be non-null.
- **onVisibilityChanged** (VisibilityChangedCallback?) - Optional - The callback for visibility changes.

### Request Example
```dart
const SliverVisibilityDetector({
  required Key key,
  required Widget sliver,
  required this.onVisibilityChanged,
})  : assert(key != null),
      assert(sliver != null),
      super(key: key, child: sliver);
```

### Response
#### Success Response (200)
N/A - This is an implementation detail, not an API endpoint.

#### Response Example
N/A
```

--------------------------------

### Constructor: SliverVisibilityDetector

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/SliverVisibilityDetector-class.html

Initializes a new instance of the SliverVisibilityDetector widget.

```APIDOC
## Constructor: SliverVisibilityDetector

### Description
Creates a widget that detects visibility changes for a sliver.

### Parameters
- **key** (Key) - Required - Controls how the widget replaces another in the tree.
- **sliver** (Widget) - Required - The sliver widget to monitor.
- **onVisibilityChanged** (VisibilityChangedCallback?) - Required - The callback invoked when the visibility of the sliver changes.

### Request Example
SliverVisibilityDetector(
  key: Key('my-sliver'),
  sliver: SliverToBoxAdapter(child: Text('Content')),
  onVisibilityChanged: (info) => print('Visibility: ${info.visibleFraction}')
)
```

--------------------------------

### Properties and Methods

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/SliverVisibilityDetector-class.html

Key properties and methods available for the SliverVisibilityDetector class.

```APIDOC
## Properties
- **onVisibilityChanged** (VisibilityChangedCallback?) - The callback to invoke when this widget's visibility changes.

## Methods
- **createRenderObject(BuildContext context)** - Creates the RenderSliverVisibilityDetector object.
- **updateRenderObject(BuildContext context, covariant RenderSliverVisibilityDetector renderObject)** - Updates the render object when the widget configuration changes.
```

--------------------------------

### VisibilityDetectorController Constructor

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetectorController/VisibilityDetectorController.html

Initializes a new instance of the VisibilityDetectorController class.

```APIDOC
## VisibilityDetectorController()

### Description
Creates a new instance of the VisibilityDetectorController class.

### Method
Constructor

### Endpoint
VisibilityDetectorController.new
```

--------------------------------

### VisibilityInfo.fromRects Constructor

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/VisibilityInfo.fromRects.html

Constructs a VisibilityInfo from widget bounds and a corresponding clipping rectangle. `widgetBounds` and `clipRect` are expected to be in the same coordinate system.

```APIDOC
## VisibilityInfo.fromRects Constructor

### Description
Constructs a VisibilityInfo from widget bounds and a corresponding clipping rectangle. `widgetBounds` and `clipRect` are expected to be in the same coordinate system.

### Method
Factory Constructor

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
- **key** (Key) - Required - The key for the widget.
- **widgetBounds** (Rect) - Required - The bounding box of the widget.
- **clipRect** (Rect) - Required - The clipping rectangle.

### Request Example
```dart
VisibilityInfo.fromRects(
  key: UniqueKey(),
  widgetBounds: Rect.fromLTWH(0, 0, 100, 100),
  clipRect: Rect.fromLTWH(0, 0, 50, 50),
)
```

### Response
#### Success Response (200)
- **size** (Size) - The size of the widget.
- **visibleBounds** (Rect) - The visible portion of the widget within the clipping rectangle.

#### Response Example
```json
{
  "size": {"width": 100, "height": 100},
  "visibleBounds": {"left": 0, "top": 0, "width": 50, "height": 50}
}
```
```

--------------------------------

### SliverVisibilityDetector Constructor

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/SliverVisibilityDetector/SliverVisibilityDetector.html

Creates a SliverVisibilityDetector widget. It requires a key, a sliver to wrap, and an optional callback for visibility changes.

```APIDOC
## SliverVisibilityDetector Constructor

### Description
Creates a SliverVisibilityDetector widget that wraps a sliver and detects its visibility.

### Method
Constructor

### Parameters
#### Path Parameters
- **key** (Key) - Required - Used to uniquely identify this widget.
- **sliver** (Widget) - Required - The sliver widget to be detected for visibility.
- **onVisibilityChanged** (VisibilityChangedCallback?) - Optional - A callback function that is invoked when the visibility of the sliver changes. Can be null to disable.

### Request Example
```dart
const SliverVisibilityDetector({
  required Key key,
  required Widget sliver,
  required VisibilityChangedCallback? onVisibilityChanged,
})
```

### Response
#### Success Response (200)
N/A - This is a constructor, not an API endpoint.

#### Response Example
N/A
```

--------------------------------

### Size Property

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/size.html

Details about the size property and its implementation.

```APIDOC
## Size Property

### Description
The size property defines the dimensions of the widget.

### Implementation
```dart
final Size size;
```
```

--------------------------------

### VisibilityDetector Constructor Implementation

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetector/VisibilityDetector.html

The constructor requires a unique key and a child widget, asserting that neither is null.

```dart
const VisibilityDetector({
  required Key key,
  required Widget child,
  required this.onVisibilityChanged,
})  : assert(key != null),
      assert(child != null),
      super(key: key, child: child);
```

--------------------------------

### notifyNow method

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetectorController/notifyNow.html

Forces the immediate firing of all pending visibility callbacks. This is useful before widget tree teardown.

```APIDOC
## void notifyNow()

### Description
Forces firing all pending visibility callbacks immediately. This might be desirable just prior to tearing down the widget tree (such as when switching views or when exiting the application).

### Method
Void

### Endpoint
N/A (Method call)

### Parameters
None

### Request Example
None

### Response
None

### Implementation
```dart
void notifyNow() => RenderVisibilityDetectorBase.notifyNow();
```
```

--------------------------------

### VisibilityInfo Class

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo-class.html

Represents data passed to the VisibilityDetector.onVisibilityChanged callback.

```APIDOC
## Class: VisibilityInfo

### Description
Data passed to the VisibilityDetector.onVisibilityChanged callback.

### Annotations
* @immutable

### Constructors

#### VisibilityInfo({required Key key, Size size = Size.zero, Rect visibleBounds = Rect.zero})
Constructor for VisibilityInfo.

#### VisibilityInfo.fromRects({required Key key, required Rect widgetBounds, required Rect clipRect})
Constructs a VisibilityInfo from widget bounds and a corresponding clipping rectangle.

### Properties

- **hashCode** (int) - The hash code for this object.
- **key** (Key) - The key for the corresponding VisibilityDetector widget.
- **runtimeType** (Type) - A representation of the runtime type of the object.
- **size** (Size) - The size of the widget.
- **visibleBounds** (Rect) - The visible portion of the widget, in the widget's local coordinates.
- **visibleFraction** (double) - A fraction in the range [0, 1] that represents what proportion of the widget is visible (assuming rectangular bounding boxes).

### Methods

- **matchesVisibility(VisibilityInfo info)** (bool) - Returns true if the specified VisibilityInfo object has equivalent visibility to this one.
- **noSuchMethod(Invocation invocation)** (dynamic) - Invoked when a nonexistent method or property is accessed.
- **toString()** (String) - A string representation of this object.

### Operators

- **operator ==(Object other)** (bool) - The equality operator.
```

--------------------------------

### createRenderObject Method

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/SliverVisibilityDetector/createRenderObject.html

This section describes the `createRenderObject` method used by the SliverVisibilityDetector widget to create its corresponding render object.

```APIDOC
## createRenderObject Method

### Description
Creates the render object for the SliverVisibilityDetector widget.

### Method
`createRenderObject`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
None

### Response
#### Success Response (200)
- **RenderSliverVisibilityDetector** (RenderObject) - The created render object.

#### Response Example
```dart
@override
RenderSliverVisibilityDetector createRenderObject(BuildContext context) {
  return RenderSliverVisibilityDetector(
    key: key!,
    onVisibilityChanged: onVisibilityChanged,
  );
}
```
```

--------------------------------

### VisibilityDetector Constructor

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetector-class.html

Initializes a new VisibilityDetector widget to track the visibility of a child widget.

```APIDOC
## Constructor VisibilityDetector

### Description
Creates a widget that fires a specified callback when the widget changes visibility.

### Parameters
- **key** (Key) - Required - Controls how one widget replaces another widget in the tree.
- **child** (Widget) - Required - The widget below this widget in the tree.
- **onVisibilityChanged** (VisibilityChangedCallback?) - Required - The callback to invoke when this widget's visibility changes.

### Request Example
VisibilityDetector(
  key: Key('my-key'),
  child: MyWidget(),
  onVisibilityChanged: (visibilityInfo) {
    print('${visibilityInfo.visibleFraction}');
  },
)
```

--------------------------------

### SliverVisibilityDetector Constructor

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/SliverVisibilityDetector/SliverVisibilityDetector.html

Use this constructor to create a SliverVisibilityDetector. The `key` is essential for widget identification and must be unique. `onVisibilityChanged` can be set to null to disable visibility detection.

```dart
const SliverVisibilityDetector({
  required Key key,
  required Widget sliver,
  required VisibilityChangedCallback? onVisibilityChanged,
})
```

```dart
const SliverVisibilityDetector({
  required Key key,
  required Widget sliver,
  required this.onVisibilityChanged,
})  : assert(key != null),
      assert(sliver != null),
      super(key: key, child: sliver);
```

--------------------------------

### VisibilityDetector Key Property

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/key.html

Documentation for the key property used in the VisibilityDetector widget.

```APIDOC
## key property

### Description
The key for the corresponding VisibilityDetector widget.

### Implementation
```dart
final Key key;
```
```

--------------------------------

### VisibilityInfo.fromRects Implementation

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/VisibilityInfo.fromRects.html

This factory constructor computes the visible portion of a widget based on its bounds and a clipping rectangle. Both input rectangles must be in the same coordinate system.

```dart
factory VisibilityInfo.fromRects({
  required Key key,
  required Rect widgetBounds,
  required Rect clipRect,
}) {
  assert(widgetBounds != null);
  assert(clipRect != null);

  final bool overlaps = widgetBounds.overlaps(clipRect);
  // Compute the intersection in the widget's local coordinates.
  final visibleBounds = overlaps
      ? widgetBounds.intersect(clipRect).shift(-widgetBounds.topLeft)
      : Rect.zero;

  return VisibilityInfo(
    key: key,
    size: widgetBounds.size,
    visibleBounds: visibleBounds,
  );
}
```

--------------------------------

### VisibilityDetectorController API

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetectorController-class.html

This section details the methods and properties of the VisibilityDetectorController.

```APIDOC
## VisibilityDetectorController

A VisibilityDetectorController is a singleton object that can perform actions and change configuration for all VisibilityDetector widgets.

### Properties

- **debugUpdateCount** (int?) - No setter
- **hashCode** (int) - The hash code for this object. No setter. Inherited.
- **runtimeType** (Type) - A representation of the runtime type of the object. No setter. Inherited.
- **updateInterval** (Duration) - The minimum amount of time to wait between firing batches of visibility callbacks. Getter/setter pair.

### Methods

- **forget**(Key key) → void
  Forgets any pending visibility callbacks for the VisibilityDetector with the given `key`.

- **noSuchMethod**(Invocation invocation) → dynamic
  Invoked when a nonexistent method or property is accessed. Inherited.

- **notifyNow**() → void
  Forces firing all pending visibility callbacks immediately.

- **toString**() → String
  A string representation of this object. Inherited.

### Operators

- **operator ==**(Object other) → bool
  The equality operator. Inherited.

### Static Properties

- **instance** (VisibilityDetectorController) - No setter
```

--------------------------------

### matchesVisibility method

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/matchesVisibility.html

Compares the current VisibilityInfo object with another to check for equivalent visibility.

```APIDOC
## matchesVisibility

### Description
Returns true if the specified VisibilityInfo object has equivalent visibility to this one. This is used to determine if two objects are sufficiently similar that callbacks do not need to be fired for both.

### Parameters
#### Arguments
- **info** (VisibilityInfo) - Required - The VisibilityInfo object to compare against.

### Implementation
```dart
bool matchesVisibility(VisibilityInfo info) {
  assert(info != null);
  return size == info.size && visibleBounds == info.visibleBounds;
}
```
```

--------------------------------

### toString Method

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/toString.html

The toString method provides a string representation of the VisibilityInfo object, useful for debugging and logging purposes.

```APIDOC
## toString()

### Description
Returns a string representation of the VisibilityInfo object. This is primarily used for debugging and logging to inspect the object's state.

### Implementation
```dart
@override
String toString() {
  return 'VisibilityInfo(key: $key, size: $size visibleBounds: $visibleBounds)';
}
```
```

--------------------------------

### hashCode Property

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/hashCode.html

Explains the hashCode property, its purpose, and how it should be implemented when the equality operator (==) is overridden.

```APIDOC
## hashCode property

### Description
The hash code for this object. A hash code is a single integer which represents the state of the object that affects operator == comparisons. All objects have hash codes. The default hash code implemented by Object represents only the identity of the object, the same way as the default operator == implementation only considers objects equal if they are identical (see identityHashCode).

If operator == is overridden to use the object state instead, the hash code must also be changed to represent that state, otherwise the object cannot be used in hash based data structures like the default Set and Map implementations.

Hash codes must be the same for objects that are equal to each other according to operator ==. The hash code of an object should only change if the object changes in a way that affects equality. There are no further requirements for the hash codes. They need not be consistent between executions of the same program and there are no distribution guarantees.

Objects that are not equal are allowed to have the same hash code. It is even technically allowed that all instances have the same hash code, but if clashes happen too often, it may reduce the efficiency of hash-based data structures like HashSet or HashMap.

If a subclass overrides hashCode, it should override the operator == operator as well to maintain consistency.

### Implementation
```dart
@override
int get hashCode => Object.hash(key, size, visibleBounds);
```
```

--------------------------------

### Force Immediate Visibility Callbacks

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetectorController/notifyNow.html

Call this method to immediately trigger any pending visibility callbacks. It's recommended before disposing of the widget tree.

```dart
void notifyNow() => RenderVisibilityDetectorBase.notifyNow();
```

--------------------------------

### Calculate Widget Visible Fraction

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/visibleFraction.html

This getter calculates the proportion of the widget that is visible, returning a value between 0 (not visible) and 1 (fully visible). It handles division by zero and snaps values to the valid range to account for floating-point inaccuracies.

```dart
double get visibleFraction {
  final visibleArea = _area(visibleBounds.size);
  final maxVisibleArea = _area(size);

  if (_floatNear(maxVisibleArea, 0)) {
    // Avoid division-by-zero.
    return 0;
  }

  var visibleFraction = visibleArea / maxVisibleArea;

  if (_floatNear(visibleFraction, 0)) {
    visibleFraction = 0;
  } else if (_floatNear(visibleFraction, 1)) {
    // The inexact nature of floating-point arithmetic means that sometimes
    // the visible area might never equal the maximum area (or could even
    // be slightly larger than the maximum).  Snap to the maximum.
    visibleFraction = 1;
  }

  assert(visibleFraction >= 0);
  assert(visibleFraction <= 1);
  return visibleFraction;
}
```

--------------------------------

### Implement createRenderObject for VisibilityDetector

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetector/createRenderObject.html

Overrides the base method to return a RenderVisibilityDetector instance with the provided key and visibility callback.

```dart
@override
RenderVisibilityDetector createRenderObject(BuildContext context) {
  return RenderVisibilityDetector(
    key: key!,
    onVisibilityChanged: onVisibilityChanged,
  );
}
```

--------------------------------

### Implement matchesVisibility method

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/matchesVisibility.html

Compares size and visibleBounds properties of two VisibilityInfo objects. This method is used to determine if visibility callbacks are redundant.

```dart
bool matchesVisibility(VisibilityInfo info) {
  // We don't override `operator ==` so that object equality can be separate
  // from whether two [VisibilityInfo] objects are sufficiently similar
  // that we don't need to fire callbacks for both.  This could be pertinent
  // if other properties are added.
  assert(info != null);
  return size == info.size && visibleBounds == info.visibleBounds;
}
```

--------------------------------

### VisibilityDetector Constructor

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetector/VisibilityDetector.html

The constructor for the VisibilityDetector widget, requiring a unique key, a child widget, and a callback for visibility changes.

```APIDOC
## VisibilityDetector Constructor

### Description
Creates a new VisibilityDetector widget to track the visibility of its child.

### Parameters
#### Constructor Parameters
- **key** (Key) - Required - A unique identifier for the widget.
- **child** (Widget) - Required - The widget to be monitored for visibility.
- **onVisibilityChanged** (VisibilityChangedCallback?) - Required - A callback function triggered when the visibility of the child changes. May be null to disable tracking.

### Implementation
```dart
const VisibilityDetector({
  required Key key,
  required Widget child,
  required this.onVisibilityChanged,
})  : assert(key != null),
      assert(child != null),
      super(key: key, child: child);
```
```

--------------------------------

### Implement createRenderObject for RenderSliverVisibilityDetector

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/SliverVisibilityDetector/createRenderObject.html

This method is an override from RenderObjectWidget. It creates and returns a RenderSliverVisibilityDetector instance, initializing it with a key and an onVisibilityChanged callback.

```dart
@override
RenderSliverVisibilityDetector createRenderObject(BuildContext context) {
  return RenderSliverVisibilityDetector(
    key: key!,
    onVisibilityChanged: onVisibilityChanged,
  );
}
```

--------------------------------

### Declare VisibilityDetector Key

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/key.html

The key for the corresponding VisibilityDetector widget. This property is final and must be initialized.

```dart
final Key key;
```

--------------------------------

### Visibility Detector createRenderObject

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetector/createRenderObject.html

This method is responsible for creating the RenderObject for the VisibilityDetector widget.

```APIDOC
## createRenderObject method

### Description
Creates a `RenderVisibilityDetector` object.

### Method
`createRenderObject`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```dart
RenderVisibilityDetector createRenderObject(BuildContext context) {
  return RenderVisibilityDetector(
    key: key!,
    onVisibilityChanged: onVisibilityChanged,
  );
}
```

### Response
#### Success Response (200)
- **RenderVisibilityDetector** (RenderObject) - The created render object.

#### Response Example
```json
{
  "message": "RenderObject created successfully"
}
```
```

--------------------------------

### operator == method

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/operator_equals.html

The equality operator determines if two VisibilityInfo objects are equivalent by comparing their key, size, and visibleBounds properties.

```APIDOC
## operator ==

### Description
The equality operator checks if two VisibilityInfo objects are equal. It returns true if the other object is an instance of VisibilityInfo and shares the same key, size, and visibleBounds.

### Method
Override

### Parameters
#### Path Parameters
- **other** (Object) - Required - The object to compare against the current instance.

### Request Example
```dart
// Example usage:
final bool isEqual = info1 == info2;
```

### Response
#### Success Response
- **result** (bool) - Returns true if the objects are equivalent, false otherwise.
```

--------------------------------

### VisibilityChangedCallback Typedef

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityChangedCallback.html

Defines the signature for a callback function that is invoked when a visibility change occurs. It accepts a single argument of type VisibilityInfo.

```APIDOC
## VisibilityChangedCallback Typedef

### Description
Defines a function type for callbacks that receive visibility change information.

### Method
N/A (Typedef definition)

### Endpoint
N/A

### Parameters
This typedef does not define parameters directly, but the function it represents accepts one parameter:

#### Function Parameter
- **info** (VisibilityInfo) - Required - An object containing information about the visibility change.

### Request Example
N/A

### Response
N/A (This is a type definition, not an endpoint)

### Error Handling
N/A
```

--------------------------------

### Implement toString Method

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/toString.html

Override the toString method to provide a custom string representation for debugging or logging. This is useful for classes that do not have a default meaningful textual representation.

```dart
@override
String toString() {
  return 'VisibilityInfo(key: $key, size: $size visibleBounds: $visibleBounds)';
}
```

--------------------------------

### Implement Equality Operator (==)

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/operator_equals.html

Override the equality operator to define custom equality logic for a class. Ensure the implementation is an equivalence relation (total, reflexive, symmetric, transitive) and consistent over time. Remember to override hashCode as well.

```dart
@override
bool operator ==(Object other) {
  return other is VisibilityInfo &&
      other.key == key &&
      other.size == size &&
      other.visibleBounds == visibleBounds;
}
```

--------------------------------

### Waiting for Visibility Callbacks in Tests

Source: https://pub.dev/packages/visibility_detector

If not setting the update interval to zero, tests can wait for callbacks to fire by pumping the widget with the controller's update interval duration.

```dart
await tester.pump(VisibilityDetectorController.instance.updateInterval);

```

--------------------------------

### Define size property

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/size.html

The size property represents the dimensions of the widget.

```dart
final Size size;
```

--------------------------------

### Implement updateRenderObject for SliverVisibilityDetector

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/SliverVisibilityDetector/updateRenderObject.html

This method is called when the render object needs to be updated. It asserts that the render object's key matches the widget's key and then updates the onVisibilityChanged callback.

```dart
@override
void updateRenderObject(
    BuildContext context, RenderSliverVisibilityDetector renderObject) {
  assert(renderObject.key == key);
  renderObject.onVisibilityChanged = onVisibilityChanged;
}
```

--------------------------------

### Update RenderObject Method

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetector/updateRenderObject.html

This method is called when the RenderObject needs to be updated. It asserts that the renderObject's key matches the widget's key and then updates the onVisibilityChanged callback.

```dart
@override
void updateRenderObject(
    BuildContext context, RenderVisibilityDetector renderObject) {
  assert(renderObject.key == key);
  renderObject.onVisibilityChanged = onVisibilityChanged;
}
```

--------------------------------

### Define onVisibilityChanged Callback

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetector/onVisibilityChanged.html

The callback signature for handling visibility changes in the widget.

```dart
final VisibilityChangedCallback? onVisibilityChanged;
```

--------------------------------

### Override hashCode implementation

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/hashCode.html

Implementation of the hashCode getter using Object.hash to ensure consistency with equality checks.

```dart
@override
int get hashCode => Object.hash(key, size, visibleBounds);
```

--------------------------------

### updateRenderObject method

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetector/updateRenderObject.html

Updates the render object for the VisibilityDetector widget by assigning the onVisibilityChanged callback.

```APIDOC
## updateRenderObject

### Description
Updates the render object of the VisibilityDetector. This method ensures that the render object's onVisibilityChanged property is synchronized with the widget's current configuration.

### Parameters
- **context** (BuildContext) - Required - The build context of the widget.
- **renderObject** (covariant RenderVisibilityDetector) - Required - The render object to be updated.

### Implementation
```dart
@override
void updateRenderObject(
    BuildContext context, RenderVisibilityDetector renderObject) {
  assert(renderObject.key == key);
  renderObject.onVisibilityChanged = onVisibilityChanged;
}
```
```

--------------------------------

### visibleFraction Property

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/visibleFraction.html

This property calculates and returns the fraction of the widget that is visible. It considers the visible area relative to the total area of the widget.

```APIDOC
## visibleFraction Property

### Description
A fraction in the range [0, 1] that represents what proportion of the widget is visible (assuming rectangular bounding boxes). 0 means not visible; 1 means fully visible.

### Method
Getter

### Endpoint
N/A (This is a property, not an API endpoint)

### Parameters
None

### Request Body
None

### Response
#### Success Response (200)
- **visibleFraction** (double) - The calculated fraction of the widget's visibility.

### Response Example
```json
{
  "visibleFraction": 0.75
}
```

## Implementation Details

```dart
double get visibleFraction {
  final visibleArea = _area(visibleBounds.size);
  final maxVisibleArea = _area(size);

  if (_floatNear(maxVisibleArea, 0)) {
    // Avoid division-by-zero.
    return 0;
  }

  var visibleFraction = visibleArea / maxVisibleArea;

  if (_floatNear(visibleFraction, 0)) {
    visibleFraction = 0;
  } else if (_floatNear(visibleFraction, 1)) {
    // The inexact nature of floating-point arithmetic means that sometimes
    // the visible area might never equal the maximum area (or could even
    // be slightly larger than the maximum).  Snap to the maximum.
    visibleFraction = 1;
  }

  assert(visibleFraction >= 0);
  assert(visibleFraction <= 1);
  return visibleFraction;
}
```
```

--------------------------------

### updateRenderObject Method

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/SliverVisibilityDetector/updateRenderObject.html

The updateRenderObject method is called when the widget configuration changes. It is responsible for updating the associated RenderObject with the new configuration, specifically setting the onVisibilityChanged callback.

```APIDOC
## updateRenderObject Method

### Description
This method updates the `RenderSliverVisibilityDetector` with the new `onVisibilityChanged` callback.

### Method
`updateRenderObject`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
None

### Response
#### Success Response (200)
None

#### Response Example
None

## Implementation Details
```dart
@override
void updateRenderObject(
    BuildContext context,
    covariant RenderSliverVisibilityDetector renderObject) {
  assert(renderObject.key == key);
  renderObject.onVisibilityChanged = onVisibilityChanged;
}
```
```

--------------------------------

### Define VisibilityChangedCallback

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityChangedCallback.html

The callback function signature used to handle visibility updates.

```dart
typedef VisibilityChangedCallback = void Function(VisibilityInfo info);
```

--------------------------------

### updateInterval Property

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetectorController/updateInterval.html

The updateInterval property determines the minimum time between visibility callback batches. Setting it to Duration.zero fires callbacks at the end of each frame, useful for tests. Changing this property does not affect pending callbacks; use notifyNow to flush them.

```APIDOC
## updateInterval Property

### Description
The minimum amount of time to wait between firing batches of visibility callbacks. If set to Duration.zero, callbacks instead will fire at the end of every frame. This is useful for automated tests. Changing updateInterval will not affect any pending callbacks. Clients should call notifyNow explicitly to flush them if desired.

### Type
Duration

### Getter/Setter
This is a getter/setter pair.

### Default Value
`Duration(milliseconds: 500)`

### Implementation Example
```dart
Duration updateInterval = const Duration(milliseconds: 500);
```
```

--------------------------------

### Setting Update Interval to Zero for Tests

Source: https://pub.dev/packages/visibility_detector

In widget tests, set the update interval to zero to ensure visibility changes are reported immediately and to avoid timer-related assertions during widget tree disposal.

```dart
VisibilityDetectorController.instance.updateInterval = Duration.zero;

```

--------------------------------

### Declare visibleBounds property

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/visibleBounds.html

Defines the final Rect property used to store the visible bounds of the widget.

```dart
final Rect visibleBounds;
```

--------------------------------

### Avoiding Timer Assertion in Tests

Source: https://pub.dev/packages/visibility_detector

To avoid the 'Timer is still pending...' assertion when the update interval is not zero, explicitly destroy the widget tree before the test completes by replacing it with a Placeholder.

```dart
await tester.pumpWidget(Placeholder());

```

--------------------------------

### visibleBounds Property

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityInfo/visibleBounds.html

The visibleBounds property returns a Rect object representing the visible portion of the widget in its local coordinates. This is useful for determining how much of the widget is currently displayed on the screen without being affected by the widget's global position.

```APIDOC
## visibleBounds Property

### Description

The visible portion of the widget, in the widget's local coordinates. The bounds are reported using the widget's local coordinates to avoid expectations for the VisibilityChangedCallback to fire if the widget's position changes but retains the same visibility.

### Type

Rect

### Implementation Example

```dart
final Rect visibleBounds;
```
```

--------------------------------

### onVisibilityChanged Property

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/SliverVisibilityDetector/onVisibilityChanged.html

The onVisibilityChanged property defines a callback that is triggered whenever the visibility state of the associated widget changes.

```APIDOC
## onVisibilityChanged

### Description
The callback to invoke when this widget's visibility changes.

### Type
VisibilityChangedCallback?

### Implementation
```dart
final VisibilityChangedCallback? onVisibilityChanged;
```
```

--------------------------------

### Define updateInterval duration

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetectorController/updateInterval.html

Sets the default update interval to 500 milliseconds. Changing this value does not affect pending callbacks.

```dart
Duration updateInterval = const Duration(milliseconds: 500);
```

--------------------------------

### onVisibilityChanged Property

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetector/onVisibilityChanged.html

The onVisibilityChanged property is a callback that is invoked when the visibility status of the widget changes. It allows you to react to these changes programmatically.

```APIDOC
## onVisibilityChanged Property

### Description
The callback to invoke when this widget's visibility changes.

### Type
VisibilityChangedCallback?

### Implementation
```dart
final VisibilityChangedCallback? onVisibilityChanged;
```
```

--------------------------------

### Cancel visibility callbacks with forget

Source: https://pub.dev/documentation/visibility_detector/latest/visibility_detector/VisibilityDetectorController/forget.html

Use this method to clear pending callbacks for a specific key, preventing issues with timers after a widget is detached.

```dart
void forget(Key key) => RenderVisibilityDetectorBase.forget(key);
```
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