Friday, September 23, 2016

Re: Refresh of CellTable via data transmitted via WebSocket delayed

On Friday, September 23, 2016 at 2:04:19 AM UTC+2, Kay Pac wrote:
I have a somewhat complex problem related to a CellTable that updates based on messages received over a WebSocket connection. The problem is as follows: The table does not update in real-time, even though "setRowData" and redraw* are called in real-time. There is a delay in the row appearing in the CellTable, or rather in the DOM as a table row. I realize that redraw does not actually redraw but sets a flag via HasDataPresenter.redraw, which checked elsewhere. It is often the case that mouse movement causes the row to appear - and I have been able to reproduce this behavior. When I put in a timer firing every 300 milliseconds, its execution also causes the row to appear.

That hints at the callback that calls the setRowData and redraw not being wrapped in $entry().
CellTable defers its DOM update using Scheduler.scheduleFinally(), and "finally commands" (and "entry commands") are processed by $entry().
So, your callback schedules a finally task, but because it's not in $entry() it's not called "at the end of the event loop" as it's expected to; it's actually called at the end of the next event loop that uses $entry(), which is the case for almost anything that GWT does: event handlers, timers, etc.
So: make sure your WebSocket's callback is wrapped in $entry() (this also takes care of the GWT.UncaughtExceptionHandler btw)

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