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Incorrect calculation of nextOffsetY #333

@Hooked74

Description

@Hooked74

When recalculating nextOffsetY when popup goes beyond the viewport boundaries incorrect calculations occur.
I see problems in these lines:

nextOffsetX = targetAlignPointTL.x - popupAlignPointBR.x - popupOffsetX;

nextOffsetX = targetAlignPointBR.x - popupAlignPointTL.x - popupOffsetX;

Let's analyze each line separately.


nextOffsetX = targetAlignPointTL.x - popupAlignPointBR.x - popupOffsetX; 

suppose
the target's bounding box is

{
  width: 200px
  left: 300px
  right: 500px
}

the popup's bounding box is

{
  width: 600px
  left: 0px
  right: 600px
}

first popup calculation without flip recalculation

{
  width: 600px
  left: 300px
  right: 900px
}

x viewport border for example is 600px
Our popup climbs out of the border, so we implement the recalculation of nextOffsetX.
targetAlignPointTL.x = 300px
popupAlignPointBR.x = 600px
popupOffsetX = 0
nextOffsetX = 300px - 600px - 0 = -300px

Total we get that our popup left offset is -300px
and right 600px - 300px = 300px
And we observe approximately the following picture
image

In order to get the correct offset, you need to subtract the right coordinate of popup not from the left coordinate of the target, but from the right.
In other words, change targetAlignPointTL to targetAlignPointBR and get

nextOffsetX = targetAlignPointBR.x - popupAlignPointBR.x - popupOffsetX; 

The situation is similar with Left to Right

nextOffsetX = targetAlignPointBR.x - popupAlignPointTL.x - popupOffsetX;

if we take fake data
target bb

{
  width: 200px
  left: 100px
  right: 300px
}

popup bb

{
  width: 500px
  left: 0px
  right: 500px
}

popup calculated bb

{
  width: 500px
  left: -200px
  right: 300px
}

viewport left border 0px
popupOffsetX = 0px
then substituting into the current formula we get
nextOffsetX = 300px - 0px - 0px = 300px

Popup offset is 300px this is the right border of the target.
Why not just take the left offset of target and make it equal to nextOffsetX?
Well, or as a last resort, add the right border of the target to the existing offset
nextOffsetX = nextOffsetX + targetAlignPointBR.x = -200px + 300px = 100px
We will get the same 100px


In general, the problem is on the face and it brings a lot of inconvenience. Please pay attention to it!

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