AbstractConstructor
Constructor options
Protected_estimatedDefault widget size estimation
we always use estimateWidgetSize
Protected_stateAbstractestimateProvide a best guess for the widget size at position index
This function should be very light to compute especially when
returning the default size.
The default value should be constant (i.e. two calls with null should
return the same value). But it can change for a given index.
Widget position
Estimated widget size
Top padding of the the outer window node.
ReadonlyscrollThe overlap threshold used to decide whether to scroll down to an item below the viewport (smart mode). If the item overlap with the viewport is greater or equal this threshold the item is considered sufficiently visible and will not be scrolled to. The value is the number of pixels in overlap if greater than one, or otherwise a fraction of item height. By default the item is scrolled to if not full visible in the viewport.
ReadonlyscrollThe underlap threshold used to decide whether to scroll up to an item above the viewport (smart mode). If the item part outside the viewport (underlap) is greater than this threshold then the item is considered not sufficiently visible and will be scrolled to. The value is the number of pixels in underlap if greater than one, or otherwise a fraction of the item height. By default the item is scrolled to if not full visible in the viewport.
AbstractwidgetWidget factory for the list items.
Caching the resulting widgets should be done by the callee.
List widget height
List widget height
Test whether the model is disposed.
Items list to be rendered
Items list to be rendered
Number of widgets to render in addition to those visible in the viewport.
Number of widgets to render in addition to those visible in the viewport.
Viewport scroll offset.
Viewport scroll offset.
A signal emitted when any model state changes.
Total number of widgets in the list
Total number of widgets in the list
Whether windowing is active or not.
This is true by default.
Whether windowing is active or not.
Get the scroll offset to display an item in the viewport.
By default, the list will scroll as little as possible to ensure the item is fully visible (auto).
You can control the alignment of the item though by specifying a second alignment parameter.
Acceptable values are:
auto - Automatically align with the top or bottom minimising the amount scrolled,
If alignPreference is given, follow such preferred alignment.
If item is smaller than the viewport and fully visible, do not scroll at all.
smart - If the item is significantly visible, don't scroll at all (regardless of whether it fits in the viewport).
If the item is less than one viewport away, scroll so that it becomes fully visible (following the auto heuristics).
If the item is more than one viewport away, scroll so that it is centered within the viewport (center if smaller than viewport, top-center otherwise).
center - Align the middle of the item with the middle of the viewport (it only works well for items smaller than the viewport).
top-center - Align the top of the item with the middle of the viewport (works well for items larger than the viewport).
end - Align the bottom of the item to the bottom of the list.
start - Align the top of item to the top of the list.
An item is considered significantly visible if:
scrollDownThreshold when below the viewportscrollUpThreshold when above the viewport.Item index
Where to align the item in the viewport
The proportion of viewport to add when aligning with the top/bottom of the list.
Optionalprecomputed: { currentOffset: number; itemMetadata: ItemMetadata; totalSize: number }Precomputed values to use when windowing is disabled.
OptionalalignPreference: BaseScrollToAlignmentAllows to override the alignment of item when the auto heuristic decides that the item needs to be scrolled into view.
The needed scroll offset
Compute the items range to display.
It returns null if the range does not need to be updated.
The current items range to display
Return the viewport top position and height for range spanning from
startIndex to stopIndex.
First item in viewport index
Last item in viewport index
The viewport top position and its height
ProtectedonCallback on list changes
List items
List change
WindowedListModel caches offsets and measurements for each index for performance purposes. This method clears that cached data for all items after (and including) the specified index.
The list will automatically re-render after the index is reset.
Windowed list abstract model.