[Laszlo-user] lz.list and lazy replication: onselect not firing when the list scrolls

[Paulo Scardine]

Hi guys,

I use lz.list frequently. When using a large dataset, I always use 
textlistitem with lazy replication. The problem is that if the list has 
an item selected, and you scroll down the list, the selected 
textlistitem will be reused. This causes some unpleasant/inconsistent 
behavior: another random entry in the list will get selected (the one 
which reuse the same textlistitem from the previous selection); 
list.getSelection() will reflect the new value. Automatically selecting 
another random entry just scrolling down is unexpected; also, in this 
case onselect event will not fire.

I think the behavior I get when using the following hack is more 
consistent with similar widgets from other toolkits:

        <class name="xtd_list" extends="list">
                <attribute name="selectedValue" value="null"/>
                <handler name="onselect" args="d">
                        this.selectedValue = d.value;
                </handler>
                <method name="getValue">
                        return this.selectedValue;
                </method>
                <method name="clearSelection" args="keepSelectedValue">
                        super.clearSelection();
                        if(!keepSelectedValue) {
                                this.selectedValue = null;
                        }
                </method>
        </class>
        <class name="xtd_textlistitem" extends="textlistitem">
                <handler name="ondata" args="d">
                        if(this.value == parent.selectedValue) {
                                parent.select(this);
                        } else if(this.selected) {
                                parent.clearSelection(true);
                        }
                </handler>
        </class>

This makes only works with single selection and if "value" is unique for 
each item, which is almost always true for me, but I'm wondering if 
someone would came up with a more generic or elegant solution.

Thanks in advance,
--
Paulo Scardine

<!-- begin testcase -->
        <dataset name="ds">
            <records>
                 <record value="1">Value1</record>
                 <record value="2">Value1</record>
                 <record value="3">Value1</record>
                 <record value="4">Value1</record>
                 <record value="5">Value1</record>
                 <record value="6">Value1</record>
                 <record value="7">Value1</record>
                 <record value="8">Value1</record>
                 <record value="9">Value1</record>
                 <record value="10">Value10</record>
                 <record value="11">Value11</record>
                 <record value="12">Value12</record>
                 <record value="13">Value13</record>
                 <record value="14">Value14</record>
                 <record value="15">Value15</record>
                 <record value="16">Value16</record>
                 <record value="17">Value17</record>
                 <record value="18">Value18</record>
                 <record value="19">Value19</record>
            </records>
        </dataset>
        <xtd_list width="200" height="60">
             <xtd_textlistitem textlistitem text="$path{'text()'}" 
value="$path{'@value'}">
                 <datapath 
xpath="local:parent.parent.dscasos:/records/record" replication="lazy"/>
             </xtd_textlistitem>
        </xtd_list>
<!-- end testcase -->