Struct RenderViewport 

pub struct RenderViewport { /* private fields */ }

A render object that is bigger on the inside.

RenderViewport is the visual workhorse of the scrolling machinery. It displays a subset of its children according to its own dimensions and the given offset. As the offset varies, different children are visible through the viewport.

RenderViewport hosts a bidirectional list of slivers in a single shared Axis, anchored on a center sliver, which is placed at the zero scroll offset. The center widget is displayed in the viewport according to the anchor property.

Slivers that are earlier in the child list than center are displayed in reverse order in the reverse RenderViewportBase::axis_direction starting from the center.

RenderViewport cannot contain RenderBox children directly. Instead, use a crate::RenderSliverList, crate::RenderSliverFixedExtentList, or a crate::RenderSliverToBoxAdapter, for example.

Implementations

impl RenderViewport

pub fn new( app: &mut App, cross_axis_direction: AxisDirection, offset: AnyViewportOffset, children: Option<Vec<AnyRenderSliver>>, center: Option<AnyRenderSliver>, ) -> RenderHandle<RenderViewport>

Creates a viewport for AnyRenderSliver objects.

If the center is not specified, then the first child in the children list, if any, is used.

For testing purposes, consider passing a crate::FixedViewportOffset as the offset.

pub fn anchor(self: RenderHandle<Self>, app: &App) -> f64

The relative position of the zero scroll offset.

For example, if the RenderViewportBase::axis_direction is AxisDirection::Down or AxisDirection::Up and the anchor is 0.5, then the zero scroll offset is vertically centered within the viewport. If the anchor is 1.0, and the axis direction is AxisDirection::Right, then the zero scroll offset is on the left edge of the viewport.

pub fn set_anchor(self: RenderHandle<Self>, app: &mut App, value: f64)

Sets anchor.

pub fn center(self: RenderHandle<Self>, app: &App) -> Option<AnyRenderSliver>

The first child in the GrowthDirection::Forward growth direction.

This child will be at the position defined by anchor when the crate::ViewportOffset::pixels of RenderViewportBase::offset is 0.

Children after the center will be placed in the RenderViewportBase::axis_direction relative to the center. Children before it will be placed in the opposite direction, and will have a growth direction of GrowthDirection::Reverse.

The center must be a direct child of the viewport.

pub fn set_center( self: RenderHandle<Self>, app: &mut App, value: Option<AnyRenderSliver>, )

Sets center.

Trait Implementations

impl ContainerRenderObjectMixin for RenderViewport

type ChildType = AnyRenderSliver

Flutter’s ChildType: the protocol of this render object’s children.

type ParentDataType = SliverPhysicalContainerParentData

Flutter’s ParentDataType: the parent data this render object installs on its children.

fn container_data( self: RenderHandle<Self>, app: &App, ) -> &ContainerRenderObjectData<AnyRenderSliver>

Mixin field access.

fn container_data_mut( self: RenderHandle<Self>, app: &mut App, ) -> &mut ContainerRenderObjectData<AnyRenderSliver>

See container_data.

fn child_count(self: RenderHandle<Self>, app: &App) -> usize

The number of children.

fn insert( self: RenderHandle<Self>, app: &mut App, child: Self::ChildType, after: Option<Self::ChildType>, )

Insert child into this render object’s child list after the given child.

fn add(self: RenderHandle<Self>, app: &mut App, child: Self::ChildType)

Append child to the end of this render object’s child list.

fn add_all( self: RenderHandle<Self>, app: &mut App, children: Option<Vec<Self::ChildType>>, )

Add all the children to the end of this render object’s child list.

fn remove(self: RenderHandle<Self>, app: &mut App, child: Self::ChildType)

Remove this child from the child list.

fn remove_all(self: RenderHandle<Self>, app: &mut App)

Remove all their children from this render object’s child list.

fn move_child( self: RenderHandle<Self>, app: &mut App, child: Self::ChildType, after: Option<Self::ChildType>, )

Move the given child in the child list to be after another child.

fn did_attach( self: RenderHandle<Self>, app: &mut App, owner: Handle<PipelineOwner>, )

The body of Flutter’s attach override: attaches every child in the list.

fn did_detach(self: RenderHandle<Self>, app: &mut App)

The body of Flutter’s detach override: detaches every child in the list.

fn redepth_children(self: RenderHandle<Self>, app: &mut App)

Flutter’s redepthChildren: walks the child list.

fn visit_children( self: RenderHandle<Self>, app: &App, visitor: &mut dyn FnMut(AnyRenderObject), )

Flutter’s visitChildren: walks the child list.

fn first_child(self: RenderHandle<Self>, app: &App) -> Option<Self::ChildType>

The first child in the child list.

fn last_child(self: RenderHandle<Self>, app: &App) -> Option<Self::ChildType>

The last child in the child list.

fn child_before( self: RenderHandle<Self>, app: &App, child: Self::ChildType, ) -> Option<Self::ChildType>

The previous child before the given child in the child list.

fn child_after( self: RenderHandle<Self>, app: &App, child: Self::ChildType, ) -> Option<Self::ChildType>

The next child after the given child in the child list.

fn children_as_list(self: RenderHandle<Self>, app: &App) -> Vec<Self::ChildType>

Returns a list containing the children of this render object.

impl RenderAbstractViewport for RenderViewport

fn get_offset_to_reveal( self: RenderHandle<Self>, app: &App, target: AnyRenderObject, alignment: f64, rect: Option<Rect>, axis: Option<Axis>, ) -> RevealedOffset

Returns the offset that would be needed to reveal the target render object.

fn as_abstract_viewport(self: RenderHandle<Self>) -> AnyRenderAbstractViewport

The type-erased RenderAbstractViewport handle. Free: the vtable is a const, and the id is copied.

impl RenderBox for RenderViewport

fn render_box_data(self: RenderHandle<Self>, app: &App) -> &RenderBoxData

Mixin field access.

fn render_box_data_mut( self: RenderHandle<Self>, app: &mut App, ) -> &mut RenderBoxData

See render_box_data.

fn setup_parent_data( self: RenderHandle<Self>, app: &mut App, child: AnyRenderObject, )

Installs BoxParentData unless the child already has it.

fn apply_paint_transform( self: RenderHandle<Self>, app: &App, child: AnyRenderObject, transform: &mut Matrix4, )

Multiply the transform from the parent’s coordinate system to this box’s coordinate system into the given transform.

fn hit_test_children( self: RenderHandle<Self>, app: &mut App, result: &mut BoxHitTestResult<'_>, position: Offset, ) -> bool

Override this method to check whether any children are located at the given position.

fn compute_min_intrinsic_width( self: RenderHandle<Self>, app: &mut App, height: f64, ) -> f64

Computes the value returned by get_min_intrinsic_width. Do not call this function directly, instead, call get_min_intrinsic_width.

fn compute_max_intrinsic_width( self: RenderHandle<Self>, app: &mut App, height: f64, ) -> f64

Computes the value returned by get_max_intrinsic_width. Do not call this function directly, instead, call get_max_intrinsic_width.

fn compute_min_intrinsic_height( self: RenderHandle<Self>, app: &mut App, width: f64, ) -> f64

Computes the value returned by get_min_intrinsic_height. Do not call this function directly, instead, call get_min_intrinsic_height.

fn compute_max_intrinsic_height( self: RenderHandle<Self>, app: &mut App, width: f64, ) -> f64

Computes the value returned by get_max_intrinsic_height. Do not call this function directly, instead, call get_max_intrinsic_height.

fn compute_dry_layout( self: RenderHandle<Self>, app: &mut App, constraints: BoxConstraints, ) -> Size

Computes the value returned by get_dry_layout. Do not call this function directly, instead, call get_dry_layout.

fn constraints(self: RenderHandle<Self>, app: &App) -> BoxConstraints

The box constraints most recently supplied by the parent.

fn get_min_intrinsic_width( self: RenderHandle<Self>, app: &mut App, height: f64, ) -> f64

See AnyRenderBox::get_min_intrinsic_width.

fn get_max_intrinsic_width( self: RenderHandle<Self>, app: &mut App, height: f64, ) -> f64

See AnyRenderBox::get_max_intrinsic_width.

fn get_min_intrinsic_height( self: RenderHandle<Self>, app: &mut App, width: f64, ) -> f64

See AnyRenderBox::get_min_intrinsic_height.

fn get_max_intrinsic_height( self: RenderHandle<Self>, app: &mut App, width: f64, ) -> f64

See AnyRenderBox::get_max_intrinsic_height.

fn get_dry_layout( self: RenderHandle<Self>, app: &mut App, constraints: BoxConstraints, ) -> Size

See AnyRenderBox::get_dry_layout.

fn get_dry_baseline( self: RenderHandle<Self>, app: &mut App, constraints: BoxConstraints, baseline: TextBaseline, ) -> Option<f64>

See AnyRenderBox::get_dry_baseline.

fn compute_dry_baseline( self: RenderHandle<Self>, app: &mut App, constraints: BoxConstraints, baseline: TextBaseline, ) -> Option<f64>

Computes the value returned by get_dry_baseline.

fn debug_cannot_compute_dry_layout( self: RenderHandle<Self>, failure: DryLayoutFailure<'_>, )

Called from compute_dry_layout or compute_dry_baseline if this box does not support calculating a dry layout.

fn get_distance_to_baseline( self: RenderHandle<Self>, app: &mut App, baseline: TextBaseline, only_real: bool, ) -> Option<f64>

See AnyRenderBox::get_distance_to_baseline.

fn get_distance_to_actual_baseline( self: RenderHandle<Self>, app: &mut App, baseline: TextBaseline, ) -> Option<f64>

See AnyRenderBox::get_distance_to_actual_baseline.

fn compute_distance_to_actual_baseline( self: RenderHandle<Self>, app: &mut App, baseline: TextBaseline, ) -> Option<f64>

Returns the distance from the y-coordinate of the position of the box to the y-coordinate of the first given baseline in the box’s contents, if any, or None otherwise.

fn mark_needs_layout(self: RenderHandle<Self>, app: &mut App)

Mark this render object’s layout information as dirty.

fn perform_resize(self: RenderHandle<Self>, app: &mut App)

Updates the box’s size using only the constraints.

fn size(self: RenderHandle<Self>, app: &App) -> Size

The size of this box.

fn paint_bounds(self: RenderHandle<Self>, app: &App) -> Rect

An estimate of the bounds within which this render object will paint: the box’s own size.

fn has_size(self: RenderHandle<Self>, app: &App) -> bool

Whether this render object has undergone layout and has a size.

fn handle_event( self: RenderHandle<Self>, app: &mut App, event: &PointerEvent, entry: &BoxHitTestEntry, )

Override this method to handle pointer events that hit this render object.

fn hit_test( self: RenderHandle<Self>, app: &mut App, result: &mut BoxHitTestResult<'_>, position: Offset, ) -> bool

Determines the set of render objects located at the given position.

fn hit_test_self( self: RenderHandle<Self>, _app: &App, _position: Offset, ) -> bool

Override this method if this render object can be hit even if its children were not hit.

fn set_size(self: RenderHandle<Self>, app: &mut App, size: Size)

Sets the size of this box. Call from RenderObject::perform_layout or RenderObject::perform_resize.

fn layout( self: RenderHandle<Self>, app: &mut App, constraints: BoxConstraints, parent_uses_size: bool, )

See AnyRenderBox::layout.

fn as_box(self: RenderHandle<Self>) -> AnyRenderBox

The type-erased RenderBox handle. Free: the vtable is a const, and the id is copied.

fn as_object(self: RenderHandle<Self>) -> AnyRenderObject

The type-erased RenderObject handle, through as_box.

fn adopt_child(self: RenderHandle<Self>, app: &mut App, child: AnyRenderObject)

See AnyRenderObject::adopt_child.

fn drop_child(self: RenderHandle<Self>, app: &mut App, child: AnyRenderObject)

See AnyRenderObject::drop_child.

fn mark_needs_paint(self: RenderHandle<Self>, app: &mut App)

See AnyRenderObject::mark_needs_paint.

fn mark_needs_composited_layer_update(self: RenderHandle<Self>, app: &mut App)

See AnyRenderObject::mark_needs_composited_layer_update.

fn mark_needs_compositing_bits_update(self: RenderHandle<Self>, app: &mut App)

See AnyRenderObject::mark_needs_compositing_bits_update.

fn schedule_initial_layout(self: RenderHandle<Self>, app: &mut App)

See AnyRenderObject::schedule_initial_layout.

fn parent(self: RenderHandle<Self>, app: &App) -> Option<AnyRenderObject>

See AnyRenderObject::parent.

fn owner(self: RenderHandle<Self>, app: &App) -> Option<Handle<PipelineOwner>>

See AnyRenderObject::owner.

fn attached(self: RenderHandle<Self>, app: &App) -> bool

See AnyRenderObject::attached.

fn debug_needs_layout(self: RenderHandle<Self>, app: &App) -> bool

See AnyRenderObject::debug_needs_layout.

impl RenderObject for RenderViewport

fn render_object_data(self: RenderHandle<Self>, app: &App) -> &RenderObjectData

Mixin field access.

fn render_object_data_mut( self: RenderHandle<Self>, app: &mut App, ) -> &mut RenderObjectData

See render_object_data.

fn visit_children( self: RenderHandle<Self>, app: &App, visitor: &mut dyn FnMut(AnyRenderObject), )

Calls visitor for each immediate child.

fn did_attach( self: RenderHandle<Self>, app: &mut App, owner: Handle<PipelineOwner>, )

The body of Flutter’s attach override after super.attach(owner); the base body has already run. The default attaches the children reported by visit_children.

fn did_detach(self: RenderHandle<Self>, app: &mut App)

The body of Flutter’s detach override after super.detach(). The default detaches the children reported by visit_children.

fn redepth_children(self: RenderHandle<Self>, app: &mut App)

Adjusts the depth of each child reported by visit_children.

fn is_repaint_boundary(self: RenderHandle<Self>, _app: &App) -> bool

Whether this render object repaints separately from its parent.

fn interface(self: RenderHandle<Self>, id: TypeId) -> Option<Box<dyn Any>>

Dart’s object is RenderAbstractViewport for any interface: the erased handle of the interface id names, if this type implements it.

fn sized_by_parent(self: RenderHandle<Self>, _app: &App) -> bool

Whether the constraints are the only input to the sizing algorithm.

fn perform_layout(self: RenderHandle<Self>, app: &mut App)

Do the work of computing the layout for this render object.

fn paint( self: RenderHandle<Self>, app: &mut App, context: &mut PaintingContext, offset: Offset, )

Paint this render object into the given context at the given offset.

fn dispose(self: RenderHandle<Self>, app: &mut App)

Release any resources held by this render object.

fn show_on_screen( self: RenderHandle<Self>, app: &mut App, descendant: Option<AnyRenderObject>, rect: Option<Rect>, duration: Duration, curve: Rc<dyn Curve>, )

Attempt to make (a portion of) this or a descendant RenderObject visible on screen.

fn as_render_object(self: RenderHandle<Self>, app: &App) -> AnyRenderObject

Dart’s implicit upcast of a concrete render object to RenderObject: this object’s type-erased handle, through the vtable the protocol recorded when it created it.

fn perform_resize(self: RenderHandle<Self>, _app: &mut App)

Updates the render object’s size using only the constraints.

fn setup_parent_data( self: RenderHandle<Self>, app: &mut App, child: AnyRenderObject, )

Sets up parent data for child if it has none.

fn apply_paint_transform( self: RenderHandle<Self>, app: &App, child: AnyRenderObject, transform: &mut Matrix4, )

Applies the transform that would be applied when painting the given child to the given matrix.

fn always_needs_compositing(self: RenderHandle<Self>, _app: &App) -> bool

Whether this render object always needs compositing.

fn mouse_tracker_annotation( self: RenderHandle<Self>, _app: &App, ) -> Option<MouseTrackerAnnotation>

Dart’s this is MouseTrackerAnnotation: the annotation this render object implements, read live each time the mouse tracker consults it. None for a render object that is not an annotation, which is the default.

fn update_composited_layer( self: RenderHandle<Self>, app: &mut App, old_layer: Option<AnyOffsetLayer>, ) -> AnyOffsetLayer

Update the composited layer owned by this render object.

impl RenderViewportBase for RenderViewport

fn viewport_data(self: RenderHandle<Self>, app: &App) -> &RenderViewportBaseData

Mixin field access.

fn viewport_data_mut( self: RenderHandle<Self>, app: &mut App, ) -> &mut RenderViewportBaseData

See viewport_data.

fn has_visual_overflow(self: RenderHandle<Self>, app: &App) -> bool

Whether the contents of this viewport would paint outside the bounds of the viewport if paint did not clip.

fn update_out_of_band_data( self: RenderHandle<Self>, app: &mut App, growth_direction: GrowthDirection, child_layout_geometry: SliverGeometry, )

Called during layout_child_sequence for each child.

fn update_child_layout_offset( self: RenderHandle<Self>, app: &mut App, child: AnyRenderSliver, layout_offset: f64, growth_direction: GrowthDirection, )

Called during layout_child_sequence to store the layout offset for the given child.

fn paint_offset_of( self: RenderHandle<Self>, app: &App, child: AnyRenderSliver, ) -> Offset

The offset at which the given child should be painted.

fn scroll_offset_of( self: RenderHandle<Self>, app: &App, child: AnyRenderSliver, scroll_offset_within_child: f64, ) -> f64

Returns the scroll offset within the viewport for the given scroll_offset_within_child within the given child.

fn max_scroll_obstruction_extent_before( self: RenderHandle<Self>, app: &App, child: AnyRenderSliver, ) -> f64

Returns the total scroll obstruction extent of all slivers in the viewport before child.

fn compute_child_main_axis_position( self: RenderHandle<Self>, app: &App, child: AnyRenderSliver, parent_main_axis_position: f64, ) -> f64

Converts the parent_main_axis_position into the child’s coordinate system.

fn index_of_first_child(self: RenderHandle<Self>, app: &App) -> i32

The index of the first child of the viewport relative to the center child.

fn label_for_child(self: RenderHandle<Self>, index: i32) -> String

A short string to identify the child with the given index.

fn axis_direction(self: RenderHandle<Self>, app: &App) -> AxisDirection

The direction in which the SliverConstraints::scroll_offset increases.

fn set_axis_direction( self: RenderHandle<Self>, app: &mut App, value: AxisDirection, )

Sets axis_direction.

fn cross_axis_direction(self: RenderHandle<Self>, app: &App) -> AxisDirection

The direction in which child should be laid out in the cross axis.

fn set_cross_axis_direction( self: RenderHandle<Self>, app: &mut App, value: AxisDirection, )

Sets cross_axis_direction.

fn axis(self: RenderHandle<Self>, app: &App) -> Axis

The axis along which the viewport scrolls.

fn offset(self: RenderHandle<Self>, app: &App) -> AnyViewportOffset

Which part of the content inside the viewport should be visible.

fn set_offset(self: RenderHandle<Self>, app: &mut App, value: AnyViewportOffset)

Sets offset.

fn mark_needs_layout_listener(self: RenderHandle<Self>) -> Listener

Dart’s _offset.addListener(markNeedsLayout) tear-off.

fn scroll_cache_extent(self: RenderHandle<Self>, app: &App) -> ScrollCacheExtent

The viewport has an area before and after the visible area to cache items that are about to become visible when the user scrolls.

fn set_scroll_cache_extent( self: RenderHandle<Self>, app: &mut App, value: Option<ScrollCacheExtent>, )

Sets scroll_cache_extent.

fn cache_extent(self: RenderHandle<Self>, app: &App) -> f64

👎Deprecated:

Use scroll_cache_extent instead.

Deprecated. Use scroll_cache_extent instead.

fn set_cache_extent(self: RenderHandle<Self>, app: &mut App, value: Option<f64>)

👎Deprecated:

Use set_scroll_cache_extent instead.

Deprecated. Use set_scroll_cache_extent instead.

fn cache_extent_style(self: RenderHandle<Self>, app: &App) -> CacheExtentStyle

👎Deprecated:

Use scroll_cache_extent instead.

Deprecated. Use scroll_cache_extent instead.

fn set_cache_extent_style( self: RenderHandle<Self>, app: &mut App, value: CacheExtentStyle, )

👎Deprecated:

Use set_scroll_cache_extent instead.

Deprecated. Use set_scroll_cache_extent instead.

fn paint_order(self: RenderHandle<Self>, app: &App) -> SliverPaintOrder

The order in which to paint the slivers; equivalently, the order in which to arrange them in the z-direction.

fn set_paint_order( self: RenderHandle<Self>, app: &mut App, value: SliverPaintOrder, )

Sets paint_order.

fn clip_behavior(self: RenderHandle<Self>, app: &App) -> Clip

The content will be clipped (or not) according to this option.

fn set_clip_behavior(self: RenderHandle<Self>, app: &mut App, value: Clip)

Sets clip_behavior.

fn did_attach( self: RenderHandle<Self>, app: &mut App, owner: Handle<PipelineOwner>, )

The body of Flutter’s attach override: listens to the offset.

fn did_detach(self: RenderHandle<Self>, app: &mut App)

The body of Flutter’s detach override: stops listening to the offset.

fn debug_throw_if_not_checking_intrinsics(self: RenderHandle<Self>) -> bool

Panics saying that the object does not support returning intrinsic dimensions if, in debug mode, we are not in the debug_checking_intrinsics mode.

fn compute_min_intrinsic_width( self: RenderHandle<Self>, app: &mut App, height: f64, ) -> f64

Zero; a viewport has no intrinsic dimensions.

fn compute_max_intrinsic_width( self: RenderHandle<Self>, app: &mut App, height: f64, ) -> f64

Zero; a viewport has no intrinsic dimensions.

fn compute_min_intrinsic_height( self: RenderHandle<Self>, app: &mut App, width: f64, ) -> f64

Zero; a viewport has no intrinsic dimensions.

fn compute_max_intrinsic_height( self: RenderHandle<Self>, app: &mut App, width: f64, ) -> f64

Zero; a viewport has no intrinsic dimensions.

fn layout_child_sequence( self: RenderHandle<Self>, app: &mut App, child: Option<AnyRenderSliver>, scroll_offset: f64, overlap: f64, layout_offset: f64, remaining_paint_extent: f64, main_axis_extent: f64, cross_axis_extent: f64, growth_direction: GrowthDirection, advance: &SliverAdvance<Self>, remaining_cache_extent: f64, cache_origin: f64, ) -> f64

Determines the size and position of some of the children of the viewport.

fn paint( self: RenderHandle<Self>, app: &mut App, context: &mut PaintingContext, offset: Offset, )

The body of Flutter’s paint override.

fn dispose(self: RenderHandle<Self>, app: &mut App)

Flutter’s dispose: drop the clip layer handle, then super.dispose().

fn paint_contents( self: RenderHandle<Self>, app: &mut App, context: &mut PaintingContext, offset: Offset, )

Flutter’s _paintContents.

fn hit_test_children( self: RenderHandle<Self>, app: &mut App, result: &mut BoxHitTestResult<'_>, position: Offset, ) -> bool

The body of Flutter’s hitTestChildren override.

fn get_offset_to_reveal( self: RenderHandle<Self>, app: &App, target: AnyRenderObject, alignment: f64, rect: Option<Rect>, _axis: Option<Axis>, ) -> RevealedOffset

The body of Flutter’s getOffsetToReveal override.

fn compute_absolute_paint_offset( self: RenderHandle<Self>, app: &App, child: AnyRenderSliver, layout_offset: f64, growth_direction: GrowthDirection, ) -> Offset

The offset at which the given child should be painted.

fn children_in_paint_order( self: RenderHandle<Self>, app: &App, ) -> Vec<AnyRenderSliver>

Walks the children of the viewport, in the order that they should be painted.

fn children_in_hit_test_order( self: RenderHandle<Self>, app: &App, ) -> Vec<AnyRenderSliver>

Walks the children of the viewport, in the order that hit-testing should use.

fn children_last_to_first( self: RenderHandle<Self>, app: &App, ) -> Vec<AnyRenderSliver>

Flutter’s _childrenLastToFirst.

fn show_on_screen( self: RenderHandle<Self>, app: &mut App, descendant: Option<AnyRenderObject>, rect: Option<Rect>, duration: Duration, curve: Rc<dyn Curve>, )

The body of Flutter’s showOnScreen override.