Tuesday, September 22, 2015

Re: CellTable rebuilding rows unnecessarily

Or is it not possible for the celltable to only redraw new rows? Will it always redraw the whole table when adding to it?

On Monday, September 21, 2015 at 10:07:38 AM UTC-4, William Davis wrote:
I have found an interesting issue, and I am wondering if I am misusing or overlooking something. I have a large CellTable that is vertically scrollable. I want to show all the rows at once instead of traditional pagination. So at the bottom of my table I have a row that the user can click to load 50 more rows. I have provided the table with a custom table builder (setTableBuilder(new Builder());). When the user clicks "load more" I query the data, add to the ListDataProvider and call table.setVisibleRange(0, dataProvider.getList().size());. 

I put a log statement in the 

public void buildRowImpl(Object rowValue, int absRowIndex) {

method to see when it was building rows. I notice that it would build 0-dataProvider.getList().size() (all the rows), then it would build oldLength-dataProvider.getList().size() (the new rows). For instance, if I have 100 rows and then load 50 more it would build 0-150, and then rebuild 100-50. What I want is for it to only build the new rows, obviously. 

So I start debugging to see why it is rebuilding the whole table each time. What I found was in com.google.gwt.user.cellview.client.HasDataPresenter<T> it would set the "redrawRequired" flag to true at line 1325:

else if (range1 == null && range0 != null && range0.getStart() == pageStart
        && (replaceDiff >= oldRowDataCount || replaceDiff > oldPageSize)) {
      // Redraw if the new data completely overlaps the old data.
 redrawRequired = true;

So my question is why does it think that the new data completely overlaps the old data?

Am I using something incorrectly, is there a better way? This gets to be quite a slow down when it has to redraw thousands of rows that don't need to be redrawn.


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