Interface ItemOffsetMapping

Interface used to determine the size and positioning offset for items in a single dimension.

interface ItemOffsetMapping {
    itemOffset(itemIndex: number): number;
    itemSize(itemIndex: number): number;
    offsetToItem(offset: number): [itemIndex: number, startOffset: number];
}

Methods

itemOffset itemSize offsetToItem

Methods

itemOffset

  • itemOffset(itemIndex: number): number

    Offset from start of container to specified item

    itemOffset(n) should be equal to Sum{i:0->n-1}(itemSize(i))

    To efficiently support large containers, cost should be O(logn) or better.

    Parameters

    • itemIndex: number

    Returns number

itemSize

offsetToItem

  • offsetToItem(offset: number): [itemIndex: number, startOffset: number]

    Given an offset, return the index of the item that intersects that offset, together with the start offset of that item

    Parameters

    • offset: number

    Returns [itemIndex: number, startOffset: number]

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