Steps to Reproduce

run the attached example zk-5000.zul

case A) click a plus icon without scrolling down (on a row with index below 50)

case B) click a plus icon after scrolling down ... (on a row with index above 50)

Current Result

case A)

1. the new row is added
2. after a delay the row indices in the first column update

profiling result shows a dedicated block updating the link labels (rerendering the whole widget's DOM elements)

case B)

1. the new row is added empty (white row)
2. after a delay the row indices in the first column update
3. after another delay the empty row is filled with the new row contents

profiling result now show 2 addtional blocks updating the link labels (rerendering the whole widget's DOM elements) and rendering the row contents

Expected Result

avoid delayed updates, avoid rebuilding whole widget's DOM structure in case only single properties such as label text changes

Debug Information

https://github.com/zkoss/zk/blob/v9.6.0/zul/src/archive/web/js/zul/LabelImageWidget.js#L31-L34

LabelImageWidget rerenders the whole DOM content even when only the label text changes.

Workaround

override the setLabel in zul.wgt.A:
below a naive approach (which doesn't cover all possible edge cases) to find/set the textNode.nodeValue directly

		setLabel : function(label) {
		    if(this._label === label) {
		        return;
		    }
		    this._label = label;
		    if(this.desktop) {
		        var textNode = Array.prototype.find.call(this.$n().childNodes, node => node.nodeType === Node.TEXT_NODE);
		        textNode.nodeValue = label;
		    }
		}