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Correcting start index of repeater #124

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Correcting start index of repeater #124

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13 changes: 8 additions & 5 deletions src/angular-vs-repeat.js
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Original file line number Diff line number Diff line change
Expand Up @@ -510,11 +510,14 @@
);
}
else {
__startIndex = Math.max(
Math.floor(
($scrollPosition - $scope.offsetBefore - scrollOffset) / $scope.elementSize
) - $scope.excess / 2,
0
__startIndex = Math.min(
Math.max(
Math.floor(
($scrollPosition - $scope.offsetBefore - scrollOffset) / $scope.elementSize
) - $scope.excess / 2,
0
),
originalLength
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Although I appreciate the direction of this change, I'm not sure this is safe.

There are many circumstances - especially where using window as the scroll-parent - where the expression:

($scrollPosition - $scope.offsetBefore - scrollOffset) / $scope.elementSize

can become (positive) Infinity, but this is a deficiency in the calculation, not an indication that we've actually scrolled well past the end of the list.

In my setup, I have used:

vs-repeat
vs-autosize
vs-scroll-parent="window"

and this pretty much guarantees that $scope.elementSize is zero at all times, which throws the maths out completely.

Ultimately, I think more careful consideration of the maths involved is needed, and the motivation for this fix should be part of it.

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@dmitry-dedukhin dmitry-dedukhin Feb 25, 2018 •
edited
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I have 14 expandable/collapsable vs-repeat containers and 600 items in each. My vs-scroll-parent is a window.
When I expand e.g. 4-th container and scroll down all looks well until I scroll close to the end of the window. At this point my expanded container is not visible in viewport and while I scroll down __startIndex becomes 601, which is wrong. But sometimes __startIndex becomes 602 and this cause digestRequired set to true. After that, digest is triggered and height of the $beforeContent is constantly increasing so I can't scroll to the end at all.
I've fixed my issue by adding the following check after __startIndex calculation:

if(__startIndex > originalLength) {
	__startIndex = originalLength;
}

);

__endIndex = Math.min(
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