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add flag for changing default reverse for staired grid #357

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add flag for changing default reverse for staired grid #357

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38 changes: 17 additions & 21 deletions lib/src/layouts/staired.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -33,15 +33,15 @@ class StairedGridTile {
}

/// Controls the layout of tiles in a staired grid.
class SliverStairedGridDelegate
extends SliverPatternGridDelegate<StairedGridTile> {
class SliverStairedGridDelegate extends SliverPatternGridDelegate<StairedGridTile> {
/// Creates a [SliverStairedGridDelegate].
const SliverStairedGridDelegate({
required List<StairedGridTile> pattern,
double mainAxisSpacing = 0,
double crossAxisSpacing = 0,
this.tileBottomSpace = 0,
this.startCrossAxisDirectionReversed = false,
this.haveDefaultReverse = true,
}) : assert(tileBottomSpace >= 0),
super.count(
pattern: pattern,
Expand All @@ -59,6 +59,9 @@ class SliverStairedGridDelegate
/// axis direction.
final bool startCrossAxisDirectionReversed;

/// on or off default reverse axis direction
final bool haveDefaultReverse;

@override
SliverPatternGridGeometries getGeometries(
SliverConstraints constraints,
Expand All @@ -71,8 +74,7 @@ class SliverStairedGridDelegate
);
int i = 0;
double mainAxisOffset = 0;
double crossAxisOffset =
startCrossAxisDirectionReversed ? maxCrossAxisExtent : 0;
double crossAxisOffset = startCrossAxisDirectionReversed ? maxCrossAxisExtent : 0;
bool reversed = startCrossAxisDirectionReversed;
while (i < tileCount) {
int startIndex = i;
Expand All @@ -87,9 +89,7 @@ class SliverStairedGridDelegate
}
final tileBottomSpaceSum = tileBottomSpace * (i - startIndex);
final isHorizontal = constraints.axis == Axis.horizontal;
final usableCrossAxisExtent = ((startIndex == 0
? maxCrossAxisExtent
: maxCrossAxisExtent - crossAxisSpacing) -
final usableCrossAxisExtent = ((startIndex == 0 ? maxCrossAxisExtent : maxCrossAxisExtent - crossAxisSpacing) -
(i - startIndex - 1) * crossAxisSpacing -
(i == tileCount ? crossAxisSpacing : 0) -
(isHorizontal ? tileBottomSpaceSum : 0))
Expand All @@ -98,12 +98,9 @@ class SliverStairedGridDelegate
double targetMainAxisOffset = 0;
for (int j = startIndex; j < i; j++) {
final tile = pattern[j];
final crossAxisExtent = usableCrossAxisExtent * tile.crossAxisRatio +
(isHorizontal ? tileBottomSpace : 0);
final mainAxisExtent = crossAxisExtent / tile.aspectRatio +
(isHorizontal ? 0 : tileBottomSpace);
crossAxisOffset =
reversed ? crossAxisOffset - crossAxisExtent : crossAxisOffset;
final crossAxisExtent = usableCrossAxisExtent * tile.crossAxisRatio + (isHorizontal ? tileBottomSpace : 0);
final mainAxisExtent = crossAxisExtent / tile.aspectRatio + (isHorizontal ? 0 : tileBottomSpace);
crossAxisOffset = reversed ? crossAxisOffset - crossAxisExtent : crossAxisOffset;
final tileRect = SliverGridGeometry(
scrollOffset: mainAxisOffset,
crossAxisOffset: crossAxisOffset,
Expand All @@ -112,9 +109,8 @@ class SliverStairedGridDelegate
);
final endMainAxisOffset = mainAxisOffset + mainAxisExtent;

crossAxisOffset = reversed
? crossAxisOffset - crossAxisSpacing
: crossAxisOffset + crossAxisExtent + crossAxisSpacing;
crossAxisOffset =
reversed ? crossAxisOffset - crossAxisSpacing : crossAxisOffset + crossAxisExtent + crossAxisSpacing;
mainAxisOffset += mainAxisSpacing;
geometries[j] = tileRect;
if (endMainAxisOffset > targetMainAxisOffset) {
Expand All @@ -123,9 +119,10 @@ class SliverStairedGridDelegate
}

mainAxisOffset = targetMainAxisOffset + mainAxisSpacing;
reversed = !reversed;
crossAxisOffset =
reversed ? maxCrossAxisExtent - crossAxisSpacing : crossAxisSpacing;

if (haveDefaultReverse) reversed = !reversed;

crossAxisOffset = reversed ? maxCrossAxisExtent - crossAxisSpacing : crossAxisSpacing;
}

return SliverPatternGridGeometries(tiles: geometries, bounds: geometries);
Expand All @@ -135,7 +132,6 @@ class SliverStairedGridDelegate
bool shouldRelayout(SliverStairedGridDelegate oldDelegate) {
return super.shouldRelayout(oldDelegate) ||
oldDelegate.tileBottomSpace != tileBottomSpace ||
oldDelegate.startCrossAxisDirectionReversed !=
startCrossAxisDirectionReversed;
oldDelegate.startCrossAxisDirectionReversed != startCrossAxisDirectionReversed;
}
}