Comment 8 for bug 2065501

I fear this is a classic throughput versus latency trade-off: Parallel search will occupy all thread-pool threads with text extraction and hence rendering jobs will be enqueued behind that. If you want better latency, parallel search is probably not helpful. (Theoretically, Qt's thread pools have a priority and we already set it to 2 for foreground rendering, 1 for prefetch rendering an QtConcurrent tasks like the search should use the normal value of 0, but this does not seem to be able to preempt an already running QtConcurrent job like the search.)