rendering library Null safety

The Flutter rendering tree.

To use, import package:flutter/rendering.dart.

The RenderObject hierarchy is used by the Flutter Widgets library to implement its layout and painting back-end. Generally, while you may use custom RenderBox classes for specific effects in your applications, most of the time your only interaction with the RenderObject hierarchy will be in debugging layout issues.

If you are developing your own library or application directly on top of the rendering library, then you will want to have a binding (see BindingBase). You can use RenderingFlutterBinding, or you can create your own binding. If you create your own binding, it needs to import at least ServicesBinding, GestureBinding, SchedulerBinding, PaintingBinding, and RendererBinding. The rendering library does not automatically create a binding, but relies on one being initialized with those features.

Classes

AccessibilityFeatures: Additional accessibility features that may be enabled by the platform.
Accumulator: Mutable wrapper of an integer that can be passed by reference to track a value across a recursive stack.
Alignment: A point within a rectangle.
AlignmentDirectional: An offset that's expressed as a fraction of a Size, but whose horizontal component is dependent on the writing direction.
AlignmentGeometry: Base class for Alignment that allows for text-direction aware resolution.
AlignmentGeometryTween: An interpolation between two AlignmentGeometry.
AlignmentTween: An interpolation between two alignments.
AnnotatedRegionLayer<T extends Object>: A composited layer which annotates its children with a value. Pushing this layer to the tree is the common way of adding an annotation.
AnnotationEntry<T>: Information collected for an annotation that is found in the layer tree.
AnnotationResult<T>: Information collected about a list of annotations that are found in the layer tree.
AnnounceSemanticsEvent: An event for a semantic announcement.
AssetBundleImageKey: Key for the image obtained by an AssetImage or ExactAssetImage.
AssetBundleImageProvider: A subclass of ImageProvider that knows about AssetBundles.
AssetImage: Fetches an image from an AssetBundle, having determined the exact image to use based on the context.
AttributedString: A string that carries a list of StringAttributes.
AttributedStringProperty: A DiagnosticsProperty for AttributedStrings, which shows a string when there are no attributes, and more details otherwise.
AutomaticNotchedShape: A NotchedShape created from ShapeBorders.
BackdropFilterLayer: A composited layer that applies a filter to the existing contents of the scene.
BeveledRectangleBorder: A rectangular border with flattened or "beveled" corners.
Border: A border of a box, comprised of four sides: top, right, bottom, left.
BorderDirectional: A border of a box, comprised of four sides, the lateral sides of which flip over based on the reading direction.
BorderRadius: An immutable set of radii for each corner of a rectangle.
BorderRadiusDirectional: An immutable set of radii for each corner of a rectangle, but with the corners specified in a manner dependent on the writing direction.
BorderRadiusGeometry: Base class for BorderRadius that allows for text-direction aware resolution.
BorderSide: A side of a border of a box.
BoxBorder: Base class for box borders that can paint as rectangles, circles, or rounded rectangles.
BoxConstraints: Immutable layout constraints for RenderBox layout.
BoxDecoration: An immutable description of how to paint a box.
BoxHitTestEntry: A hit test entry used by RenderBox.
BoxHitTestResult: The result of performing a hit test on RenderBoxes.
BoxPainter: A stateful class that can paint a particular Decoration.
BoxParentData: Parent data used by RenderBox and its subclasses.
BoxShadow: A shadow cast by a box.
Canvas: An interface for recording graphical operations.
ChildLayoutHelper: A collection of static functions to layout a RenderBox child with the given set of BoxConstraints.
CircleBorder: A border that fits a circle within the available space.
CircularNotchedRectangle: A rectangle with a smooth circular notch.
ClearSelectionEvent: Clears the selection from the Selectable and removes any existing highlight as if there is no selection at all.
ClipContext: Clip utilities used by PaintingContext.
ClipPathLayer: A composite layer that clips its children using a path.
ClipRectLayer: A composite layer that clips its children using a rectangle.
ClipRRectLayer: A composite layer that clips its children using a rounded rectangle.
Color: An immutable 32 bit color value in ARGB format.
ColorFilter: A description of a color filter to apply when drawing a shape or compositing a layer with a particular Paint. A color filter is a function that takes two colors, and outputs one color. When applied during compositing, it is independently applied to each pixel of the layer being drawn before the entire layer is merged with the destination.
ColorFilterLayer: A composite layer that applies a ColorFilter to its children.
ColorProperty: DiagnosticsProperty that has an Color as value.
ColorSwatch<T>: A color that has a small table of related colors called a "swatch".
Constraints: An abstract set of layout constraints.
ContainerBoxParentData<ChildType extends RenderObject>: Abstract ParentData subclass for RenderBox subclasses that want the ContainerRenderObjectMixin.
ContainerLayer: A composited layer that has a list of children.
ContinuousRectangleBorder: A rectangular border with smooth continuous transitions between the straight sides and the rounded corners.
CustomClipper<T>: An interface for providing custom clips.
CustomPainter: The interface used by CustomPaint (in the widgets library) and RenderCustomPaint (in the rendering library).
CustomPainterSemantics: Contains properties describing information drawn in a rectangle contained by the Canvas used by a CustomPaint.
CustomSemanticsAction: An identifier of a custom semantics action.
Decoration: A description of a box decoration (a decoration applied to a Rect).
DecorationImage: An image for a box decoration.
DecorationImagePainter: The painter for a DecorationImage.
DiagnosticPropertiesBuilder: Builder to accumulate properties and configuration used to assemble a DiagnosticsNode from a Diagnosticable object.
DiagnosticsDebugCreator: A class that creates DiagnosticsNode by wrapping RenderObject.debugCreator.
DiagnosticsNode: Defines diagnostics data for a value.
DiagnosticsProperty<T>: Property with a value of type T.
DoubleProperty: Property describing a double value with an optional unit of measurement.
EdgeInsets: An immutable set of offsets in each of the four cardinal directions.
EdgeInsetsDirectional: An immutable set of offsets in each of the four cardinal directions, but whose horizontal components are dependent on the writing direction.
EdgeInsetsGeometry: Base class for EdgeInsets that allows for text-direction aware resolution.
EnumProperty<T>: An property than displays enum values tersely.
ErrorDescription: An explanation of the problem and its cause, any information that may help track down the problem, background information, etc.
ErrorHint: An ErrorHint provides specific, non-obvious advice that may be applicable.
ErrorSummary: A short (one line) description of the problem that was detected.
ExactAssetImage: Fetches an image from an AssetBundle, associating it with the given scale.
FileImage: Decodes the given File object as an image, associating it with the given scale.
FittedSizes: The pair of sizes returned by applyBoxFit.
FixedColumnWidth: Sizes the column to a specific number of pixels.
FlagProperty: Property where the description is either ifTrue or ifFalse depending on whether value is true or false.
FlexColumnWidth: Sizes the column by taking a part of the remaining space once all the other columns have been laid out.
FlexParentData: Parent data for use with RenderFlex.
FloatingHeaderSnapConfiguration: Specifies how a floating header is to be "snapped" (animated) into or out of view.
FlowDelegate: A delegate that controls the appearance of a flow layout.
FlowPaintingContext: A context in which a FlowDelegate paints.
FlowParentData: Parent data for use with RenderFlow.
FlutterLogoDecoration: An immutable description of how to paint Flutter's logo.
FollowerLayer: A composited layer that applies a transformation matrix to its children such that they are positioned to match a LeaderLayer.
FontWeight: The thickness of the glyphs used to draw the text
FractionalOffset: An offset that's expressed as a fraction of a Size.
FractionalOffsetTween: An interpolation between two fractional offsets.
FractionColumnWidth: Sizes the column to a fraction of the table's constraints' maxWidth.
Gradient: A 2D gradient.
GradientRotation: A GradientTransform that rotates the gradient around the center-point of its bounding box.
GradientTransform: Base class for transforming gradient shaders without applying the same transform to the entire canvas.
HitTestEntry<T extends HitTestTarget>: Data collected during a hit test about a specific HitTestTarget.
HitTestResult: The result of performing a hit test.
HSLColor: A color represented using alpha, hue, saturation, and lightness.
HSVColor: A color represented using alpha, hue, saturation, and value.
ImageCache: Class for caching images.
ImageCacheStatus: Information about how the ImageCache is tracking an image.
ImageChunkEvent: An immutable notification of image bytes that have been incrementally loaded.
ImageConfiguration: Configuration information passed to the ImageProvider.resolve method to select a specific image.
ImageFilterLayer: A composite layer that applies an ImageFilter to its children.
ImageInfo: A dart:ui.Image object with its corresponding scale.
ImageProvider<T extends Object>: Identifies an image without committing to the precise final asset. This allows a set of images to be identified and for the precise image to later be resolved based on the environment, e.g. the device pixel ratio.
ImageShader: A shader (as used by Paint.shader) that tiles an image.
ImageSizeInfo: Tracks the bytes used by a dart:ui.Image compared to the bytes needed to paint that image without scaling it.
ImageStream: A handle to an image resource.
ImageStreamCompleter: Base class for those that manage the loading of dart:ui.Image objects for ImageStreams.
ImageStreamCompleterHandle: An opaque handle that keeps an ImageStreamCompleter alive even if it has lost its last listener.
ImageStreamListener: Interface for receiving notifications about the loading of an image.
InlineSpan: An immutable span of inline content which forms part of a paragraph.
InlineSpanSemanticsInformation: The textual and semantic label information for an InlineSpan.
IntProperty: An int valued property with an optional unit the value is measured in.
IntrinsicColumnWidth: Sizes the column according to the intrinsic dimensions of all the cells in that column.
Key: A Key is an identifier for Widgets, Elements and SemanticsNodes.
Layer: A composited layer.
LayerHandle<T extends Layer>: A handle to prevent a Layer's platform graphics resources from being disposed.
LayerLink: An object that a LeaderLayer can register with.
LeaderLayer: A composited layer that can be followed by a FollowerLayer.
LinearGradient: A 2D linear gradient.
ListBodyParentData: Parent data for use with RenderListBody.
ListWheelChildManager: A delegate used by RenderListWheelViewport to manage its children.
ListWheelParentData: ParentData for use with RenderListWheelViewport.
Locale: An identifier used to select a user's language and formatting preferences.
LocaleStringAttribute: A string attribute that causes the assistive technologies, e.g. VoiceOver, to treat string as a certain language.
LongPressSemanticsEvent: An event which triggers long press semantic feedback.
MaskFilter: A mask filter to apply to shapes as they are painted. A mask filter is a function that takes a bitmap of color pixels, and returns another bitmap of color pixels.
Matrix4: 4D Matrix. Values are stored in column major order.
MatrixUtils: Utility functions for working with matrices.
MaxColumnWidth: Sizes the column such that it is the size that is the maximum of two column width specifications.
MemoryImage: Decodes the given Uint8List buffer as an image, associating it with the given scale.
MinColumnWidth: Sizes the column such that it is the size that is the minimum of two column width specifications.
MouseCursor: An interface for mouse cursor definitions.
MouseTracker: Tracks the relationship between mouse devices and annotations, and triggers mouse events and cursor changes accordingly.
MultiChildLayoutDelegate: A delegate that controls the layout of multiple children.
MultiChildLayoutParentData: ParentData used by RenderCustomMultiChildLayoutBox.
MultiFrameImageStreamCompleter: Manages the decoding and scheduling of image frames.
NetworkImage: Fetches the given URL from the network, associating it with the given scale.
NotchedShape: A shape with a notch in its outline.
Offset: An immutable 2D floating-point offset.
OffsetLayer: A layer that is displayed at an offset from its parent layer.
OneFrameImageStreamCompleter: Manages the loading of dart:ui.Image objects for static ImageStreams (those with only one frame).
OpacityLayer: A composited layer that makes its children partially transparent.
OrdinalSortKey: A SemanticsSortKey that sorts simply based on the double value it is given.
OutlinedBorder: A ShapeBorder that draws an outline with the width and color specified by side.
OvalBorder: A border that fits an elliptical shape.
OverScrollHeaderStretchConfiguration: Specifies how a stretched header is to trigger an AsyncCallback.
Paint: A description of the style to use when drawing on a Canvas.
PaintingContext: A place to paint.
ParentData: Base class for data associated with a RenderObject by its parent.
Path: A complex, one-dimensional subset of a plane.
PerformanceOverlayLayer: A layer that indicates to the compositor that it should display certain performance statistics within it.
PersistentHeaderShowOnScreenConfiguration: Specifies how a pinned header or a floating header should react to RenderObject.showOnScreen calls.
PhysicalModelLayer: A composited layer that uses a physical model to producing lighting effects.
PictureLayer: A composited layer containing a Picture.
PipelineOwner: The pipeline owner manages the rendering pipeline.
PlaceholderDimensions: Holds the Size and baseline required to represent the dimensions of a placeholder in text.
PlaceholderSpan: An immutable placeholder that is embedded inline within text.
PlaceholderSpanIndexSemanticsTag: Used by the RenderParagraph to map its rendering children to their corresponding semantics nodes.
PlatformViewLayer: A layer that shows an embedded UIView on iOS.
PlatformViewRenderBox: A render object for embedding a platform view.
PointerCancelEvent: The input from the pointer is no longer directed towards this receiver.
PointerDownEvent: The pointer has made contact with the device.
PointerEvent: Base class for touch, stylus, or mouse events.
PointerMoveEvent: The pointer has moved with respect to the device while the pointer is in contact with the device.
PointerUpEvent: The pointer has stopped making contact with the device.
RadialGradient: A 2D radial gradient.
Radius: A radius for either circular or elliptical shapes.
Rect: An immutable, 2D, axis-aligned, floating-point rectangle whose coordinates are relative to a given origin.
RelativeRect: An immutable 2D, axis-aligned, floating-point rectangle whose coordinates are given relative to another rectangle's edges, known as the container. Since the dimensions of the rectangle are relative to those of the container, this class has no width and height members. To determine the width or height of the rectangle, convert it to a Rect using toRect() (passing the container's own Rect), and then examine that object.
RenderAbsorbPointer: A render object that absorbs pointers during hit testing.
RenderAbstractViewport: An interface for render objects that are bigger on the inside.
RenderAligningShiftedBox: Abstract class for one-child-layout render boxes that use a AlignmentGeometry to align their children.
RenderAndroidView: A render object for an Android view.
RenderAnimatedOpacity: Makes its child partially transparent, driven from an Animation.
RenderAnimatedSize: A render object that animates its size to its child's size over a given duration and with a given curve. If the child's size itself animates (i.e. if it changes size two frames in a row, as opposed to abruptly changing size in one frame then remaining that size in subsequent frames), this render object sizes itself to fit the child instead of animating itself.
RenderAnnotatedRegion<T extends Object>: Render object which inserts an AnnotatedRegionLayer into the layer tree.
RenderAspectRatio: Attempts to size the child to a specific aspect ratio.
RenderBackdropFilter: Applies a filter to the existing painted content and then paints child.
RenderBaseline: Shifts the child down such that the child's baseline (or the bottom of the child, if the child has no baseline) is baseline logical pixels below the top of this box, then sizes this box to contain the child.
RenderBlockSemantics: Causes the semantics of all earlier render objects below the same semantic boundary to be dropped.
RenderBox: A render object in a 2D Cartesian coordinate system.
RenderClipOval: Clips its child using an oval.
RenderClipPath: Clips its child using a path.
RenderClipRect: Clips its child using a rectangle.
RenderClipRRect: Clips its child using a rounded rectangle.
RenderConstrainedBox: Imposes additional constraints on its child.
RenderConstrainedOverflowBox: A render object that imposes different constraints on its child than it gets from its parent, possibly allowing the child to overflow the parent.
RenderConstraintsTransformBox: A RenderBox that applies an arbitrary transform to its constraints before sizing its child using the new constraints, treating any overflow as error.
RenderCustomMultiChildLayoutBox: Defers the layout of multiple children to a delegate.
RenderCustomPaint: Provides a canvas on which to draw during the paint phase.
RenderCustomSingleChildLayoutBox: Defers the layout of its single child to a delegate.
RenderDecoratedBox: Paints a Decoration either before or after its child paints.
RenderEditable: Displays some text in a scrollable container with a potentially blinking cursor and with gesture recognizers.
RenderEditablePainter: An interface that paints within a RenderEditable's bounds, above or beneath its text content.
RenderErrorBox: A render object used as a placeholder when an error occurs.
RenderExcludeSemantics: Excludes this subtree from the semantic tree.
RenderFittedBox: Scales and positions its child within itself according to fit.
RenderFlex: Displays its children in a one-dimensional array.
RenderFlow: Implements the flow layout algorithm.
RenderFollowerLayer: Transform the child so that its origin is offset from the origin of the RenderLeaderLayer with the same LayerLink.
RenderFractionallySizedOverflowBox: Sizes its child to a fraction of the total available space.
RenderFractionalTranslation: Applies a translation transformation before painting its child.
RenderIgnorePointer: A render object that is invisible during hit testing.
RenderImage: An image in the render tree.
RenderIndexedSemantics: A render objects that annotates semantics with an index.
RenderIndexedStack: Implements the same layout algorithm as RenderStack but only paints the child specified by index.
RenderingFlutterBinding: A concrete binding for applications that use the Rendering framework directly. This is the glue that binds the framework to the Flutter engine.
RenderIntrinsicHeight: Sizes its child to the child's intrinsic height.
RenderIntrinsicWidth: Sizes its child to the child's maximum intrinsic width.
RenderLeaderLayer: Provides an anchor for a RenderFollowerLayer.
RenderLimitedBox: Constrains the child's BoxConstraints.maxWidth and BoxConstraints.maxHeight if they're otherwise unconstrained.
RenderListBody: Displays its children sequentially along a given axis, forcing them to the dimensions of the parent in the other axis.
RenderListWheelViewport: Render, onto a wheel, a bigger sequential set of objects inside this viewport.
RenderMergeSemantics: Causes the semantics of all descendants to be merged into this node such that the entire subtree becomes a single leaf in the semantics tree.
RenderMetaData: Holds opaque meta data in the render tree.
RenderMouseRegion: Calls callbacks in response to pointer events that are exclusive to mice.
RenderObject: An object in the render tree.
RenderOffstage: Lays the child out as if it was in the tree, but without painting anything, without making the child available for hit testing, and without taking any room in the parent.
RenderOpacity: Makes its child partially transparent.
RenderPadding: Insets its child by the given padding.
RenderParagraph: A render object that displays a paragraph of text.
RenderPerformanceOverlay: Displays performance statistics.
RenderPhysicalModel: Creates a physical model layer that clips its child to a rounded rectangle.
RenderPhysicalShape: Creates a physical shape layer that clips its child to a Path.
RenderPointerListener: Calls callbacks in response to common pointer events.
RenderPositionedBox: Positions its child using an AlignmentGeometry.
RenderProxyBox: A base class for render boxes that resemble their children.
RenderProxyBoxWithHitTestBehavior: A RenderProxyBox subclass that allows you to customize the hit-testing behavior.
RenderProxySliver: A base class for sliver render objects that resemble their children.
RenderRepaintBoundary: Creates a separate display list for its child.
RenderRotatedBox: Rotates its child by a integral number of quarter turns.
RenderSemanticsAnnotations: Add annotations to the SemanticsNode for this subtree.
RenderSemanticsGestureHandler: Listens for the specified gestures from the semantics server (e.g. an accessibility tool).
RenderShaderMask: Applies a mask generated by a Shader to its child.
RenderShiftedBox: Abstract class for one-child-layout render boxes that provide control over the child's position.
RenderShrinkWrappingViewport: A render object that is bigger on the inside and shrink wraps its children in the main axis.
RenderSizedOverflowBox: A render object that is a specific size but passes its original constraints through to its child, which it allows to overflow.
RenderSliver: Base class for the render objects that implement scroll effects in viewports.
RenderSliverAnimatedOpacity: Makes its sliver child partially transparent, driven from an Animation.
RenderSliverBoxChildManager: A delegate used by RenderSliverMultiBoxAdaptor to manage its children.
RenderSliverEdgeInsetsPadding: Insets a RenderSliver by applying resolvedPadding on each side.
RenderSliverFillRemaining: A sliver that contains a single box child that is non-scrollable and fills the remaining space in the viewport.
RenderSliverFillRemainingAndOverscroll: A sliver that contains a single box child that is non-scrollable and fills the remaining space in the viewport including any overscrolled area.
RenderSliverFillRemainingWithScrollable: A sliver that contains a single box child that contains a scrollable and fills the viewport.
RenderSliverFillViewport: A sliver that contains multiple box children that each fill the viewport.
RenderSliverFixedExtentBoxAdaptor: A sliver that contains multiple box children that have the same extent in the main axis.
RenderSliverFixedExtentList: A sliver that places multiple box children with the same main axis extent in a linear array.
RenderSliverFloatingPersistentHeader: A sliver with a RenderBox child which shrinks and scrolls like a RenderSliverScrollingPersistentHeader, but immediately comes back when the user scrolls in the reverse direction.
RenderSliverFloatingPinnedPersistentHeader: A sliver with a RenderBox child which shrinks and then remains pinned to the start of the viewport like a RenderSliverPinnedPersistentHeader, but immediately grows when the user scrolls in the reverse direction.
RenderSliverGrid: A sliver that places multiple box children in a two dimensional arrangement.
RenderSliverIgnorePointer: A render object that is invisible during hit testing.
RenderSliverList: A sliver that places multiple box children in a linear array along the main axis.
RenderSliverMultiBoxAdaptor: A sliver with multiple box children.
RenderSliverOffstage: Lays the sliver child out as if it was in the tree, but without painting anything, without making the sliver child available for hit testing, and without taking any room in the parent.
RenderSliverOpacity: Makes its sliver child partially transparent.
RenderSliverPadding: Insets a RenderSliver, applying padding on each side.
RenderSliverPersistentHeader: A base class for slivers that have a RenderBox child which scrolls normally, except that when it hits the leading edge (typically the top) of the viewport, it shrinks to a minimum size (minExtent).
RenderSliverPinnedPersistentHeader: A sliver with a RenderBox child which never scrolls off the viewport in the positive scroll direction, and which first scrolls on at a full size but then shrinks as the viewport continues to scroll.
RenderSliverScrollingPersistentHeader: A sliver with a RenderBox child which scrolls normally, except that when it hits the leading edge (typically the top) of the viewport, it shrinks to a minimum size before continuing to scroll.
RenderSliverSingleBoxAdapter: An abstract class for RenderSlivers that contains a single RenderBox.
RenderSliverToBoxAdapter: A RenderSliver that contains a single RenderBox.
RenderStack: Implements the stack layout algorithm.
RenderTable: A table where the columns and rows are sized to fit the contents of the cells.
RenderTransform: Applies a transformation before painting its child.
RenderUiKitView: A render object for an iOS UIKit UIView.
RenderUnconstrainedBox: Renders a box, imposing no constraints on its child, allowing the child to render at its "natural" size.
RenderView: The root of the render tree.
RenderViewport: A render object that is bigger on the inside.
RenderViewportBase<ParentDataClass extends ContainerParentDataMixin<RenderSliver>>: A base class for render objects that are bigger on the inside.
RenderWrap: Displays its children in multiple horizontal or vertical runs.
ResizeImage: Instructs Flutter to decode the image at the specified dimensions instead of at its native size.
ResizeImageKey: Key used internally by ResizeImage.
RevealedOffset: Return value for RenderAbstractViewport.getOffsetToReveal.
RoundedRectangleBorder: A rectangular border with rounded corners.
RRect: An immutable rounded rectangle with the custom radii for all four corners.
RSTransform: A transform consisting of a translation, a rotation, and a uniform scale.
SelectAllSelectionEvent: Selects all selectable contents.
SelectedContent: The selected content in a Selectable or SelectionHandler.
SelectionEdgeUpdateEvent: Updates a selection edge.
SelectionEvent: An abstract base class for selection events.
SelectionGeometry: The geometry of the current selection.
SelectionHandler: The abstract interface to handle SelectionEvents.
SelectionPoint: The geometry information of a selection point.
SelectionRegistrar: A registrar that keeps track of Selectables in the subtree.
SelectionUtils: A utility class that provides useful methods for handling selection events.
SelectWordSelectionEvent: Selects the whole word at the location.
SemanticsAction: The possible actions that can be conveyed from the operating system accessibility APIs to a semantics node.
SemanticsConfiguration: Describes the semantic information associated with the owning RenderObject.
SemanticsData: Summary information about a SemanticsNode object.
SemanticsEvent: An event sent by the application to notify interested listeners that something happened to the user interface (e.g. a view scrolled).
SemanticsFlag: A Boolean value that can be associated with a semantics node.
SemanticsHandle: A reference to the semantics tree.
SemanticsHintOverrides: Provides hint values which override the default hints on supported platforms.
SemanticsNode: A node that represents some semantic data.
SemanticsOwner: Owns SemanticsNode objects and notifies listeners of changes to the render tree semantics.
SemanticsProperties: Contains properties used by assistive technologies to make the application more accessible.
SemanticsService: Allows access to the platform's accessibility services.
SemanticsSortKey: Base class for all sort keys for SemanticsProperties.sortKey accessibility traversal order sorting.
SemanticsTag: A tag for a SemanticsNode.
SemanticsUpdateBuilder: An object that creates SemanticsUpdate objects.
Shader: Base class for objects such as Gradient and ImageShader which correspond to shaders as used by Paint.shader.
ShaderMaskLayer: A composited layer that applies a shader to its children.
ShaderWarmUp: Interface for drawing an image to warm up Skia shader compilations.
Shadow: A single shadow.
ShapeBorder: Base class for shape outlines.
ShapeBorderClipper: A CustomClipper that clips to the outer path of a ShapeBorder.
ShapeDecoration: An immutable description of how to paint an arbitrary shape.
SingleChildLayoutDelegate: A delegate for computing the layout of a render object with a single child.
Size: Holds a 2D floating-point size.
SliverConstraints: Immutable layout constraints for RenderSliver layout.
SliverGeometry: Describes the amount of space occupied by a RenderSliver.
SliverGridDelegate: Controls the layout of tiles in a grid.
SliverGridDelegateWithFixedCrossAxisCount: Creates grid layouts with a fixed number of tiles in the cross axis.
SliverGridDelegateWithMaxCrossAxisExtent: Creates grid layouts with tiles that each have a maximum cross-axis extent.
SliverGridGeometry: Describes the placement of a child in a RenderSliverGrid.
SliverGridLayout: The size and position of all the tiles in a RenderSliverGrid.
SliverGridParentData: Parent data structure used by RenderSliverGrid.
SliverGridRegularTileLayout: A SliverGridLayout that uses equally sized and spaced tiles.
SliverHitTestEntry: A hit test entry used by RenderSliver.
SliverHitTestResult: The result of performing a hit test on RenderSlivers.
SliverLogicalContainerParentData: Parent data for slivers that have multiple children and that position their children using layout offsets.
SliverLogicalParentData: Parent data structure used by parents of slivers that position their children using layout offsets.
SliverMultiBoxAdaptorParentData: Parent data structure used by RenderSliverMultiBoxAdaptor.
SliverPhysicalContainerParentData: Parent data for slivers that have multiple children and that position their children using absolute coordinates.
SliverPhysicalParentData: Parent data structure used by parents of slivers that position their children using absolute coordinates.
SpellOutStringAttribute: A string attribute that causes the assistive technologies, e.g. VoiceOver, to spell out the string character by character.
StackParentData: Parent data for use with RenderStack.
StadiumBorder: A border that fits a stadium-shaped border (a box with semicircles on the ends) within the rectangle of the widget it is applied to.
StarBorder: A border that fits a star or polygon-shaped border within the rectangle of the widget it is applied to.
StringAttribute: An abstract interface for string attributes that affects how assistive technologies, e.g. VoiceOver or TalkBack, treat the text.
StringProperty: Property which encloses its string value in quotes.
StrutStyle: Defines the strut, which sets the minimum height a line can be relative to the baseline.
SweepGradient: A 2D sweep gradient.
SystemMouseCursors: A collection of system MouseCursors.
TableBorder: Border specification for Table widgets.
TableCellParentData: Parent data used by RenderTable for its children.
TableColumnWidth: Base class to describe how wide a column in a RenderTable should be.
TapSemanticEvent: An event which triggers tap semantic feedback.
TextAlignVertical: The vertical alignment of text within an input box.
TextBox: A rectangle enclosing a run of text.
TextDecoration: A linear decoration to draw near the text.
TextHeightBehavior: Defines how to apply TextStyle.height over and under text.
TextPainter: An object that paints a TextSpan tree into a Canvas.
TextParentData: Parent data for use with RenderParagraph and RenderEditable.
TextPosition: A position in a string of text.
TextRange: A range of characters in a string of text.
TextSelection: A range of text that represents a selection.
TextSelectionPoint: Represents the coordinates of the point in a selection, and the text direction at that point, relative to top left of the RenderEditable that holds the selection.
TextSpan: An immutable span of text.
TextStyle: An immutable style describing how to format and paint text.
TextTreeConfiguration: Configuration specifying how a particular DiagnosticsTreeStyle should be rendered as text art.
TextureBox: A rectangle upon which a backend texture is mapped.
TextureLayer: A composited layer that maps a backend texture to a rectangle.
TooltipSemanticsEvent: An event for a semantic announcement of a tooltip.
TransformLayer: A composited layer that applies a given transformation matrix to its children.
TransformProperty: Property which handles Matrix4 that represent transforms.
VerticalCaretMovementRun: The consecutive sequence of TextPositions that the caret should move to when the user navigates the paragraph using the upward arrow key or the downward arrow key.
ViewConfiguration: The layout constraints for the root render object.
ViewportOffset: Which part of the content inside the viewport should be visible.
WrapParentData: Parent data for use with RenderWrap.

Mixins

ContainerParentDataMixin<ChildType extends RenderObject>: Parent data to support a doubly-linked list of children.
ContainerRenderObjectMixin<ChildType extends RenderObject, ParentDataType extends ContainerParentDataMixin<ChildType>>: Generic mixin for render objects with a list of children.
DebugOverflowIndicatorMixin: An mixin indicator that is drawn when a RenderObject overflows its container.
KeepAliveParentDataMixin: Parent data structure used by RenderSliverWithKeepAliveMixin.
PaintingBinding: Binding for the painting library.
RelayoutWhenSystemFontsChangeMixin: Mixin for RenderObject that will call systemFontsDidChange whenever the system fonts change.
RenderAnimatedOpacityMixin<T extends RenderObject>: Implementation of RenderAnimatedOpacity and RenderSliverAnimatedOpacity.
RenderBoxContainerDefaultsMixin<ChildType extends RenderBox, ParentDataType extends ContainerBoxParentData<ChildType>>: A mixin that provides useful default behaviors for boxes with children managed by the ContainerRenderObjectMixin mixin.
RendererBinding: The glue between the render tree and the Flutter engine.
RenderObjectWithChildMixin<ChildType extends RenderObject>: Generic mixin for render objects with one child.
RenderProxyBoxMixin<T extends RenderBox>: Implementation of RenderProxyBox.
RenderSliverHelpers: Mixin for RenderSliver subclasses that provides some utility functions.
RenderSliverWithKeepAliveMixin: This class exists to dissociate KeepAlive from RenderSliverMultiBoxAdaptor.
Selectable: A mixin that can be selected by users when under a SelectionArea widget.
SelectionRegistrant: A mixin to auto-register the mixer to the registrar.
SemanticsBinding: The glue between the semantics layer and the Flutter engine.

Properties

debugCaptureShaderWarmUpImage ↔ ShaderWarmUpImageCallback: Called by ShaderWarmUp.execute immediately after it creates an Image.
read / write
debugCaptureShaderWarmUpPicture ↔ ShaderWarmUpPictureCallback: Called by ShaderWarmUp.execute immediately after it creates a Picture.
read / write
debugCheckIntrinsicSizes ↔ bool: Check the intrinsic sizes of each RenderBox during layout.
read / write
debugCurrentRepaintColor ↔ HSVColor: The current color to overlay when repainting a layer.
read / write
debugDisableClipLayers ↔ bool: Setting to true will cause all clipping effects from the layer tree to be ignored.
read / write
debugDisableOpacityLayers ↔ bool: Setting to true will cause all opacity effects from the layer tree to be ignored.
read / write
debugDisablePhysicalShapeLayers ↔ bool: Setting to true will cause all physical modeling effects from the layer tree, such as shadows from elevations, to be ignored.
read / write
debugDisableShadows ↔ bool: Whether to replace all shadows with solid color blocks.
read / write
debugEnhanceLayoutTimelineArguments ↔ bool: Adds debugging information to Timeline events related to RenderObject layouts.
read / write
debugEnhancePaintTimelineArguments ↔ bool: Adds debugging information to Timeline events related to RenderObject paints.
read / write
debugImageOverheadAllowance ↔ int: The number of bytes an image must use before it triggers inversion when debugInvertOversizedImages is true.
read / write
debugInvertOversizedImages ↔ bool: If true, the framework will color invert and horizontally flip images that have been decoded to a size taking at least debugImageOverheadAllowance bytes more than necessary.
read / write
debugNetworkImageHttpClientProvider ↔ HttpClientProvider?: Provider from which NetworkImage will get its HttpClient in debug builds.
read / write
debugOnPaintImage ↔ PaintImageCallback?: If not null, called when the framework is about to paint an Image to a Canvas with an ImageSizeInfo that contains the decoded size of the image as well as its output size.
read / write
debugOnProfilePaint ↔ ProfilePaintCallback?: Callback invoked for every RenderObject painted each frame.
read / write
debugPaintBaselinesEnabled ↔ bool: Causes each RenderBox to paint a line at each of its baselines.
read / write
debugPaintLayerBordersEnabled ↔ bool: Causes each Layer to paint a box around its bounds.
read / write
debugPaintPointersEnabled ↔ bool: Causes objects like RenderPointerListener to flash while they are being tapped. This can be useful to see how large the hit box is, e.g. when debugging buttons that are harder to hit than expected.
read / write
debugPaintSizeEnabled ↔ bool: Causes each RenderBox to paint a box around its bounds, and some extra boxes, such as RenderPadding, to draw construction lines.
read / write
debugPrint ↔ DebugPrintCallback: Prints a message to the console, which you can access using the "flutter" tool's "logs" command ("flutter logs").
read / write
debugPrintLayouts ↔ bool: Log the dirty render objects that are laid out each frame.
read / write
debugPrintMarkNeedsLayoutStacks ↔ bool: Log the call stacks that mark render objects as needing layout.
read / write
debugPrintMarkNeedsPaintStacks ↔ bool: Log the call stacks that mark render objects as needing paint.
read / write
debugProfileLayoutsEnabled ↔ bool: Adds dart:developer.Timeline events for every RenderObject layout.
read / write
debugProfilePaintsEnabled ↔ bool: Adds dart:developer.Timeline events for every RenderObject painted.
read / write
debugRepaintRainbowEnabled ↔ bool: Overlay a rotating set of colors when repainting layers in debug mode.
read / write
debugRepaintTextRainbowEnabled ↔ bool: Overlay a rotating set of colors when repainting text in debug mode.
read / write
debugSemanticsDisableAnimations ↔ bool?: Overrides the setting of SemanticsBinding.disableAnimations for debugging and testing.
read / write
imageCache → ImageCache: The singleton that implements the Flutter framework's image cache.
read-only

Functions

applyBoxFit(BoxFit fit, Size inputSize, Size outputSize) → FittedSizes: Apply a BoxFit value.
applyGrowthDirectionToAxisDirection(AxisDirection axisDirection, GrowthDirection growthDirection) → AxisDirection: Flips the AxisDirection if the GrowthDirection is GrowthDirection.reverse.
applyGrowthDirectionToScrollDirection(ScrollDirection scrollDirection, GrowthDirection growthDirection) → ScrollDirection: Flips the ScrollDirection if the GrowthDirection is GrowthDirection.reverse.
axisDirectionIsReversed(AxisDirection axisDirection) → bool: Returns whether traveling along the given axis direction visits coordinates along that axis in numerically decreasing order.
axisDirectionToAxis(AxisDirection axisDirection) → Axis: Returns the Axis that contains the given AxisDirection.
combineSemanticsInfo(List<InlineSpanSemanticsInformation> infoList) → List<InlineSpanSemanticsInformation>: Combines _semanticsInfo entries where permissible.
debugAssertAllPaintingVarsUnset(String reason, {bool debugDisableShadowsOverride = false}) → bool: Returns true if none of the painting library debug variables have been changed.
debugAssertAllRenderVarsUnset(String reason, {bool debugCheckIntrinsicSizesOverride = false}) → bool: Returns true if none of the rendering library debug variables have been changed.
debugDescribeTransform(Matrix4? transform) → List<String>: Returns a list of strings representing the given transform in a format useful for TransformProperty.
debugDumpLayerTree() → void: Prints a textual representation of the entire layer tree.
debugDumpRenderTree() → void: Prints a textual representation of the entire render tree.
debugDumpSemanticsTree([DebugSemanticsDumpOrder childOrder = DebugSemanticsDumpOrder.traversalOrder]) → void: Prints a textual representation of the entire semantics tree. This will only work if there is a semantics client attached. Otherwise, a notice that no semantics are available will be printed.
debugFlushLastFrameImageSizeInfo() → void: Flushes inter-frame tracking of image size information from paintImage.
visibleForTesting">@visibleForTesting
debugPaintPadding(Canvas canvas, Rect outerRect, Rect? innerRect, {double outlineWidth = 2.0}) → void: Paint a diagram showing the given area as padding.
debugResetSemanticsIdCounter() → void: In tests use this function to reset the counter used to generate SemanticsNode.id.
decodeImageFromList(Uint8List bytes) → Future<Image>: Creates an image from a list of bytes.
flipAxis(Axis direction) → Axis: Returns the opposite of the given Axis.
flipAxisDirection(AxisDirection axisDirection) → AxisDirection: Returns the opposite of the given AxisDirection.
flipScrollDirection(ScrollDirection direction) → ScrollDirection: Returns the opposite of the given ScrollDirection.
hashList(Iterable<Object?>? arguments) → int: Combine the Object.hashCode values of an arbitrary number of objects from an Iterable into one value. This function will return the same value if given null as if given an empty list.
Deprecated('Use Object.hashAll() or Object.hashAllUnordered() instead. ' 'This feature was deprecated in v3.1.0-0.0.pre.897')">@Deprecated('Use Object.hashAll() or Object.hashAllUnordered() instead. ' 'This feature was deprecated in v3.1.0-0.0.pre.897')
hashValues(Object? arg01, Object? arg02, [Object? arg03 = _hashEnd, Object? arg04 = _hashEnd, Object? arg05 = _hashEnd, Object? arg06 = _hashEnd, Object? arg07 = _hashEnd, Object? arg08 = _hashEnd, Object? arg09 = _hashEnd, Object? arg10 = _hashEnd, Object? arg11 = _hashEnd, Object? arg12 = _hashEnd, Object? arg13 = _hashEnd, Object? arg14 = _hashEnd, Object? arg15 = _hashEnd, Object? arg16 = _hashEnd, Object? arg17 = _hashEnd, Object? arg18 = _hashEnd, Object? arg19 = _hashEnd, Object? arg20 = _hashEnd]) → int: Combine up to twenty objects' hash codes into one value.
Deprecated('Use Object.hash() instead. ' 'This feature was deprecated in v3.1.0-0.0.pre.897')">@Deprecated('Use Object.hash() instead. ' 'This feature was deprecated in v3.1.0-0.0.pre.897')
paintBorder(Canvas canvas, Rect rect, {BorderSide top = BorderSide.none, BorderSide right = BorderSide.none, BorderSide bottom = BorderSide.none, BorderSide left = BorderSide.none}) → void: Paints a border around the given rectangle on the canvas.
paintImage({required Canvas canvas, required Rect rect, required Image image, String? debugImageLabel, double scale = 1.0, double opacity = 1.0, ColorFilter? colorFilter, BoxFit? fit, Alignment alignment = Alignment.center, Rect? centerSlice, ImageRepeat repeat = ImageRepeat.noRepeat, bool flipHorizontally = false, bool invertColors = false, FilterQuality filterQuality = FilterQuality.low, bool isAntiAlias = false}) → void: Paints an image into the given rectangle on the canvas.
paintZigZag(Canvas canvas, Paint paint, Offset start, Offset end, int zigs, double width) → void: Draw a line between two points, which cuts diagonally back and forth across the line that connects the two points.
positionDependentBox({required Size size, required Size childSize, required Offset target, required bool preferBelow, double verticalOffset = 0.0, double margin = 10.0}) → Offset: Position a child box within a container box, either above or below a target point.
textDirectionToAxisDirection(TextDirection textDirection) → AxisDirection: Returns the AxisDirection in which reading occurs in the given TextDirection.

Enums

Assertiveness: Determines the assertiveness level of the accessibility announcement.
Axis: The two cardinal directions in two dimensions.
AxisDirection: A direction along either the horizontal or vertical Axis.
BlendMode: Algorithms to use when painting on the canvas.
BlurStyle: Styles to use for blurs in MaskFilter objects.
BorderStyle: The style of line to draw for a BorderSide in a Border.
BoxFit: How a box should be inscribed into another box.
BoxShape: The shape to use when rendering a Border or BoxDecoration.
CacheExtentStyle: The unit of measurement for a Viewport.cacheExtent.
Clip: Different ways to clip a widget's content.
CrossAxisAlignment: How the children should be placed along the cross axis in a flex layout.
DebugSemanticsDumpOrder: Used by debugDumpSemanticsTree to specify the order in which child nodes are printed.
DecorationPosition: Where to paint a box decoration.
DiagnosticLevel: The various priority levels used to filter which diagnostics are shown and omitted.
DiagnosticsTreeStyle: Styles for displaying a node in a DiagnosticsNode tree.
FilterQuality: Quality levels for image sampling in ImageFilter and Shader objects that sample images and for Canvas operations that render images.
FlexFit: How the child is inscribed into the available space.
FlutterLogoStyle: Possible ways to draw Flutter's logo.
FontStyle: Whether to slant the glyphs in the font
GrowthDirection: The direction in which a sliver's contents are ordered, relative to the scroll offset axis.
HitTestBehavior: How to behave during hit tests.
ImageRepeat: How to paint any portions of a box not covered by an image.
MainAxisAlignment: How the children should be placed along the main axis in a flex layout.
MainAxisSize: How much space should be occupied in the main axis.
PaintingStyle: Strategies for painting shapes and paths on a canvas.
PathFillType: Determines the winding rule that decides how the interior of a Path is calculated.
PathOperation: Strategies for combining paths.
PerformanceOverlayOption: The options that control whether the performance overlay displays certain aspects of the compositor.
PlaceholderAlignment: Where to vertically align the placeholder relative to the surrounding text.
PlatformViewHitTestBehavior: How an embedded platform view behave during hit tests.
RenderAnimatedSizeState: A RenderAnimatedSize can be in exactly one of these states.
RenderComparison: The description of the difference between two objects, in the context of how it will affect the rendering.
ScrollDirection: The direction of a scroll, relative to the positive scroll offset axis given by an AxisDirection and a GrowthDirection.
SelectionEventType: The type of a SelectionEvent.
SelectionResult: The result after handling a SelectionEvent.
SelectionStatus: The status that indicates whether there is a selection and whether the selection is collapsed.
StackFit: How to size the non-positioned children of a Stack.
StrokeAlign: The relative position of the stroke on a BorderSide in a Border or OutlinedBorder. When set to inside, the stroke is drawn completely inside the widget. For center and outside, a property such as Container.clipBehavior can be used in an outside widget to clip it. If Container.decoration has a border, the container may incorporate BorderSide.width as additional padding:
StrokeCap: Styles to use for line endings.
StrokeJoin: Styles to use for line segment joins.
TableCellVerticalAlignment: Vertical alignment options for cells in RenderTable objects.
TextAffinity: A way to disambiguate a TextPosition when its offset could match two different locations in the rendered string.
TextAlign: Whether and how to align text horizontally.
TextBaseline: A horizontal line used for aligning text.
TextDecorationStyle: The style in which to draw a text decoration
TextDirection: A direction in which text flows.
TextLeadingDistribution: How the "leading" is distributed over and under the text.
TextOverflow: How overflowing text should be handled.
TextSelectionHandleType: The type of selection handle to be displayed.
TextWidthBasis: The different ways of measuring the width of one or more lines of text.
TileMode: Defines what happens at the edge of a gradient or the sampling of a source image in an ImageFilter.
VertexMode: Defines how a list of points is interpreted when drawing a set of triangles.
VerticalDirection: A direction in which boxes flow vertically.
WrapAlignment: How Wrap should align objects.
WrapCrossAlignment: Who Wrap should align children within a run in the cross axis.

Typedefs

BoxConstraintsTransform = BoxConstraints Function(BoxConstraints): Signature for a function that transforms a BoxConstraints to another BoxConstraints.
BoxHitTest = bool Function(BoxHitTestResult result, Offset position): Method signature for hit testing a RenderBox.
BoxHitTestWithOutOfBandPosition = bool Function(BoxHitTestResult result): Method signature for hit testing a RenderBox with a manually managed position (one that is passed out-of-band).
CaretChangedHandler = void Function(Rect caretRect): Signature for the callback that reports when the caret location changes.
ChildLayouter = Size Function(RenderBox child, BoxConstraints constraints): Signature for a function that takes a RenderBox and returns the Size that the RenderBox would have if it were laid out with the given BoxConstraints.
CompositionCallback = void Function(Layer): The signature of the callback added in Layer.addCompositionCallback.
DecoderBufferCallback = Future<Codec> Function(ImmutableBuffer buffer, {bool allowUpscaling, int? cacheHeight, int? cacheWidth}): Performs the decode process for use in ImageProvider.loadBuffer.
DecoderCallback = Future<Codec> Function(Uint8List buffer, {bool allowUpscaling, int? cacheHeight, int? cacheWidth}): Performs the decode process for use in ImageProvider.load.
Deprecated('Use DecoderBufferCallback with ImageProvider.loadBuffer instead. ' 'This feature was deprecated after v2.13.0-1.0.pre.')">@Deprecated('Use DecoderBufferCallback with ImageProvider.loadBuffer instead. ' 'This feature was deprecated after v2.13.0-1.0.pre.')
HttpClientProvider = HttpClient Function(): Signature for a method that returns an HttpClient.
ImageChunkListener = void Function(ImageChunkEvent event): Signature for listening to ImageChunkEvent events.
ImageErrorListener = void Function(Object exception, StackTrace? stackTrace): Signature for reporting errors when resolving images.
ImageListener = void Function(ImageInfo image, bool synchronousCall): Signature for callbacks reporting that an image is available.
InformationCollector = Iterable<DiagnosticsNode> Function(): Signature for FlutterErrorDetails.informationCollector callback and other callbacks that collect information describing an error.
InlineSpanVisitor = bool Function(InlineSpan span): Called on each span as InlineSpan.visitChildren walks the InlineSpan tree.
LayoutCallback<T extends Constraints> = void Function(T constraints): Signature for a function that is called during layout.
MouseDetectorAnnotationFinder = HitTestResult Function(Offset offset): Signature for searching for MouseTrackerAnnotations at the given offset.
MoveCursorHandler = void Function(bool extendSelection): Signature for SemanticsActions that move the cursor.
PaintImageCallback = void Function(ImageSizeInfo): Called when the framework is about to paint an Image to a Canvas with an ImageSizeInfo that contains the decoded size of the image as well as its output size.
PaintingContextCallback = void Function(PaintingContext context, Offset offset): Signature for painting into a PaintingContext.
PointerCancelEventListener = void Function(PointerCancelEvent event): Signature for listening to PointerCancelEvent events.
PointerDownEventListener = void Function(PointerDownEvent event): Signature for listening to PointerDownEvent events.
PointerMoveEventListener = void Function(PointerMoveEvent event): Signature for listening to PointerMoveEvent events.
PointerPanZoomEndEventListener = void Function(PointerPanZoomEndEvent event): Signature for listening to PointerPanZoomEndEvent events.
PointerPanZoomStartEventListener = void Function(PointerPanZoomStartEvent event): Signature for listening to PointerPanZoomStartEvent events.
PointerPanZoomUpdateEventListener = void Function(PointerPanZoomUpdateEvent event): Signature for listening to PointerPanZoomUpdateEvent events.
PointerSignalEventListener = void Function(PointerSignalEvent event): Signature for listening to PointerSignalEvent events.
PointerUpEventListener = void Function(PointerUpEvent event): Signature for listening to PointerUpEvent events.
ProfilePaintCallback = void Function(RenderObject renderObject): Signature for debugOnProfilePaint implementations.
RenderObjectVisitor = void Function(RenderObject child): Signature for a function that is called for each RenderObject.
SemanticsActionHandler = void Function(Object? args): Signature for a handler of a SemanticsAction.
SemanticsBuilderCallback = List<CustomPainterSemantics> Function(Size size): Signature of the function returned by CustomPainter.semanticsBuilder.
SemanticsNodeVisitor = bool Function(SemanticsNode node): Signature for a function that is called for each SemanticsNode.
SetSelectionHandler = void Function(TextSelection selection): Signature for the SemanticsAction.setSelection handlers to change the text selection (or re-position the cursor) to selection.
SetTextHandler = void Function(String text): Signature for the SemanticsAction.setText handlers to replace the current text with the input text.
ShaderCallback = Shader Function(Rect bounds): Signature for a function that creates a Shader for a given Rect.
ShaderWarmUpImageCallback = bool Function(Image): The signature of debugCaptureShaderWarmUpImage.
ShaderWarmUpPictureCallback = bool Function(Picture): The signature of debugCaptureShaderWarmUpPicture.
SliverHitTest = bool Function(SliverHitTestResult result, {required double crossAxisPosition, required double mainAxisPosition}): Method signature for hit testing a RenderSliver.
ValueChanged<T> = void Function(T value): Signature for callbacks that report that an underlying value has changed.
ValueGetter<T> = T Function(): Signature for callbacks that are to report a value on demand.
ValueSetter<T> = void Function(T value): Signature for callbacks that report that a value has been set.
VoidCallback = void Function(): Signature of callbacks that have no arguments and return no data.

Exceptions / Errors

FlutterError: Error class used to report Flutter-specific assertion failures and contract violations.
NetworkImageLoadException: The exception thrown when the HTTP request to load a network image fails.