Feature/visible background cells

[stfnhdr]

Checklist

• I've tested my changes.
• I've read the Contribution Guidelines.
• I've updated the documentation if necessary.
• I've added additional Tests where/if it makes sense.

Motivation and Context

Needed this feature for a own project an saw the help wanted on this feature in the issue tab

closes #40

tried it with different values from 1 to 10 cards on every possible device size

Description

removed this part to enable top stacking cards.
if cvMinY > cardMinY + cardHeight + minimumLineSpacing + collectionView.contentInset.top {
cvMinY = 0
}

• added bool to set if the stacking should be on top or at the bottom

• added int for the amout of cards shown in the background.

• defining an newRect so cards in the background won't be removed from the collectionView

let y = collectionView.bounds.minY - cellHeight * CGFloat(topStackCount)
let newRect = CGRect(x: 0, y: y < 0 ? 0 : y, width: collectionView.bounds.maxX, height: collectionView.bounds.maxY)
let items = NSArray(array: super.layoutAttributesForElements(in: newRect)!, copyItems: true)

i am very open for improvements because this is kind of a quick shot.

[JoniVR]

Hi @stfnhdr
Thanks for the PR! I'll look into testing this soon!

[stfnhdr]

there's a lint warning - fixing it right now.

[JoniVR]

Ok, so it works pretty well, great work here!

I did find a few things that broke so far:

• First off was the indexesForVisibleCards variable, that was my mistake really because it was not built for more stacked cards. I fixed that in a commit to include all cards (also stacked ones), since that makes more sense anyways.

• I think this issue was already present, just not visible because the stack was at the bottom, I'm not sure, but since we're working on multiple card stacking I think we should slowly fade out the lowest card on the stack. It currently looks pretty weird, the card simply disappears, a slow fade out would be better I think.

• If the firstItemTransform property is set to a higher value (say 0.25) and we have lots of stacked cards the transform will reverse, this should be pretty easy to fix I think.

[stfnhdr]

added your requested changes, have a good night!

[JoniVR]

Don't worry about the build fail for now, I think it's just the UI Tests that are flaky from time to time and there seems to be no way to manually trigger a rebuild for PR's with travis.. I need to migrate to CircleCI or something different soon anyways..

I'll look into reviewing this in the next few days, thanks again for your awesome work on this!

[stfnhdr]

Ok, i tried the tests before pushing, and they all succeeded.

Thanks, this is by far the best Solution for stacking cards i found! Great Work!

I'll put more effort into this in the future - next goal is to implement the background color fade like shazam.

[JoniVR]

Hmm all seems to work well but I still think the fading needs some work, I think we need to either make only the last card (the one that's going to disappear) fade out or gradually change the color of the cells to match the background color of the VerticalCardSwiperView background. Currently it takes away from the stack effect if all cells start fading once they are not focussed anymore.

[stfnhdr]

changed the fade out to the last card in the stack

[stfnhdr]

hey, please don't forget about this pull request ;)

[JoniVR]

Thanks for reminding me, don't worry, I haven't forgotten, it's on my TODO-list but I'm pretty busy with some other stuff right now. I'll try to review & merge it somewhere in the next few days! Thanks for all the work you've done on this!

[JoniVR]

I'm probably going to release this as a 2.0.0 version. I might have jumped the gun on 1.0.0 so I think this is best because there will be some minor api breaking changes.

Anyways, it works very well for me, thanks so much for the PR and I'm sorry it took this long! I pledged to myself that I wouldn't be that guy but life kinda got in the way for a bit.