Rounding error in datepicker _checkOffset()

[janis-ps]

We encountered a problem where the datepicker position would be incorrect for a date input inside a Bootstrap modal. The datepicker would end up offscreen, far below the actual input element.

The culprit was this line of code (as well as the line above it):

https://github.com/jquery/jquery-ui/blob/main/ui/widgets/datepicker.js#L931

This code uses strict equality (===) to compare two floating-point numbers; not pixels, but fractions of pixels. Here's how we fixed it (and how the line above it should be fixed):

                offset.left -= ( this._get( inst, "isRTL" ) ? ( dpWidth - inputWidth ) : 0 );
                offset.left -= ( isFixed && offset.left === inst.input.offset().left ) ? $( document ).scrollLeft() : 0;
-               offset.top -= ( isFixed && offset.top === ( inst.input.offset().top + inputHeight ) ) ? $( document ).scrollTop() : 0;
+               offset.top -= ( isFixed && Math.floor(offset.top) === Math.floor( inst.input.offset().top + inputHeight ) ) ? $( document ).scrollTop() : 0;
 
                // Now check if datepicker is showing outside window viewport - move to a better place if so.
                offset.left -= Math.min( offset.left, ( offset.left + dpWidth > viewWidth && viewWidth > dpWidth ) ?

[fgerodez]

Encountered this as well in 1.13.1

Applied the patch and it solved the issue, thanks

[andrerom]

Can confirm this fixed offset.top bug for me on Firefox (135 & 138), when Datepicker is placed inside Bootstrap modal.
Top ended up being set to twice the size of my screen height, some 2400px, making it invisible.

For some reason not this issue in Chrome.

1.13.2 and 1.14.1 with jQuery 3.7.1.