collision overall - support for swap

[adumesny]

Description

big overall of the collision detection code - you can now:

• swap items of same size vertically/horizontally when grid is full (maxRow)
  this has been 5.5years in the making and the most asked question
  It is now also the default in float:false as it feels more natural than pushing new row
  (could add Alt-key to get either behavior of push vs swap ?)
• moving items down or up behave the same way (used to have to push WAY past to insert after)
• optimized the collision code to not do extra work multiple times and only check
  if change and not tried before
• heuristics now checks for >50% past the grid mid point (taking margin into account)a

TODO part II: handle mid point of dragged over items rather 50% of row/column
and check for the most covered when multiple items collide.

• fix Cannot move widget horizontally (Allow horizontal swapping without creating new rows) #149 Its not possible to move item A at bottom of item B #1605 and partial drag heuristics can make it hard to place items (ex: web demo) #1094 (need better support for larger items mid point)

Checklist

• Created tests which fail without the change (if possible)
• All tests passing (yarn test)
• Extended the README / documentation, if necessary

[adumesny]

default float:false (top gravity)

20210215_102443.mp4

float:true case

20210215_103145.mp4

maxRow:3 for full grid, even if float=true

20210215_103416.mp4

[harrington101]

Is there a workaround for the float true case? I do not have a max rows and would like to drag row 3 to 4 and have them swap. Instead, 4 is pushed down and an empty space is left where 3 was.

[adumesny]

@harrington101 that is not the design, so no 'workaround'. if you don't want empty spaces, that is what float:true is for (no empty vertical spaces). If you want some hybrid, you can write your own collision with 5.x letting you specify you own engine...

[harrington101]

I'm not looking for a hybrid. Instead, I'm looking to have box 1 swap with box 2 rather than running away from it. I do want empty spaces which is why I set float to true. The issue is that box 2 moves unexpectedly.