Scroll loading does not work when browser zoom is not 100%

[doctorj]

In v1 when zoom is <= 80% and >= 125%
In v2 when zoom is <= 90% and >= 110%

new entries are not displayed when scrolled to bottom.

What I tested, and works in both v1 and v2, is minor change compared to code before changes introduced as a fix for #862: replacing == with >=, like this:

if (JsMath.abs(offsetHeight) + JsMath.abs(scrollTop)
	>= Double.valueOf(scrollHeight).intValue()) {
dataTable.fireTableEvent(new BodyScrollEvent(ScrollPosition.BOTTOM));
}

[howudodat]

it's broken at 100% as well. I added this simple log:

GWT.log("scrollTop:" + scrollTop + " offset:"+offsetHeight + " scroll:" + scrollHeight + " client:"+clientHeight
		+ " triggerPos:"+(JsMath.abs(offsetHeight) + JsMath.abs(scrollTop))
		+ " compareTo:"+ new Double(scrollHeight + (offsetHeight - clientHeight)).intValue()
		);

and you can see in the log below that at 100% it's 1 pixel short of scrolling after the 2nd expand.

scrollTop:4 offset:718 scroll:950 client:718 triggerPos:722 compareTo:950
scrollTop:16 offset:718 scroll:950 client:718 triggerPos:734 compareTo:950
scrollTop:37 offset:718 scroll:950 client:718 triggerPos:755 compareTo:950
scrollTop:69 offset:718 scroll:950 client:718 triggerPos:787 compareTo:950
scrollTop:114 offset:718 scroll:950 client:718 triggerPos:832 compareTo:950
scrollTop:165 offset:718 scroll:950 client:718 triggerPos:883 compareTo:950
scrollTop:205 offset:718 scroll:950 client:718 triggerPos:923 compareTo:950
scrollTop:227 offset:718 scroll:950 client:718 triggerPos:945 compareTo:950
scrollTop:232 offset:718 scroll:950 client:718 triggerPos:950 compareTo:950
Firing event
scrollTop:246 offset:718 scroll:1771 client:718 triggerPos:964 compareTo:1771
scrollTop:290 offset:718 scroll:1771 client:718 triggerPos:1008 compareTo:1771
scrollTop:358 offset:718 scroll:1771 client:718 triggerPos:1076 compareTo:1771
scrollTop:444 offset:718 scroll:1771 client:718 triggerPos:1162 compareTo:1771
scrollTop:554 offset:718 scroll:1771 client:718 triggerPos:1272 compareTo:1771
scrollTop:679 offset:718 scroll:1771 client:718 triggerPos:1397 compareTo:1771
scrollTop:808 offset:718 scroll:1771 client:718 triggerPos:1526 compareTo:1771
scrollTop:923 offset:718 scroll:1771 client:718 triggerPos:1641 compareTo:1771
scrollTop:1004 offset:718 scroll:1771 client:718 triggerPos:1722 compareTo:1771
scrollTop:1044 offset:718 scroll:1771 client:718 triggerPos:1762 compareTo:1771
scrollTop:1053 offset:718 scroll:1771 client:718 triggerPos:1771 compareTo:1771
Firing event
scrollTop:1057 offset:718 scroll:2707 client:718 triggerPos:1775 compareTo:2707
scrollTop:1075 offset:718 scroll:2707 client:718 triggerPos:1793 compareTo:2707
scrollTop:1117 offset:718 scroll:2707 client:718 triggerPos:1835 compareTo:2707
scrollTop:1202 offset:718 scroll:2707 client:718 triggerPos:1920 compareTo:2707
scrollTop:1329 offset:718 scroll:2707 client:718 triggerPos:2047 compareTo:2707
scrollTop:1492 offset:718 scroll:2707 client:718 triggerPos:2210 compareTo:2707
scrollTop:1676 offset:718 scroll:2707 client:718 triggerPos:2394 compareTo:2707
scrollTop:1840 offset:718 scroll:2707 client:718 triggerPos:2558 compareTo:2707
scrollTop:1946 offset:718 scroll:2707 client:718 triggerPos:2664 compareTo:2707
scrollTop:1987 offset:718 scroll:2707 client:718 triggerPos:2705 compareTo:2707
scrollTop:1988 offset:718 scroll:2707 client:718 triggerPos:2706 compareTo:2707

I would propose that there be a configurable "pad" that is included in the calculation. So that instead of it requiring to be at the end of the list, it could load at a row or two above. Something like:

int nPad = 25; // get this from config somewhere
GWT.log("PAD:" + JsMath.abs(
		JsMath.abs(offsetHeight) + JsMath.abs(scrollTop)
				- new Double(scrollHeight + (offsetHeight - clientHeight)).intValue()));
if (JsMath.abs(
		JsMath.abs(offsetHeight) + JsMath.abs(scrollTop)
				- new Double(scrollHeight + (offsetHeight - clientHeight)).intValue()) <= nPad) {
	GWT.log("Firing event");
	dataTable.fireTableEvent(new BodyScrollEvent(ScrollPosition.BOTTOM));
}