quicker TUI blanking when search restarts

1. Blanking is not immediate, because it causes flickering. But the TUI screen update delay is too long when the search results come in slowly. This change fixes that.
2. continue TUI file queueing, but more slowly after a large number was queued (64K to half a million files), to indicate that more files are still searchable and are queued (while not overusing the CPU to do so)

man/ugrep.1

@@ -1,4 +1,4 @@
-.TH UGREP "1" "November 03, 2023" "ugrep 4.3.2" "User Commands"
+.TH UGREP "1" "November 06, 2023" "ugrep 4.3.2" "User Commands"
 .SH NAME
 \fBugrep\fR, \fBug\fR -- file pattern searcher
 .SH SYNOPSIS
@@ -791,7 +791,7 @@ file types can be (where \fB\-t\fRlist displays a detailed list):
 `scala', `scheme', `shell', `Shell', `smalltalk', `sql', `svg',
 `swift', `tcl', `tex', `text', `tiff', `Tiff', `tt',
 `typescript', `verilog', `vhdl', `vim', `xml', `Xml', `yacc',
-`yaml', 'zig'.
+`yaml', `zig'.
 .TP
 \fB\-\-tabs\fR[=\fINUM\fR]
 Set the tab size to NUM to expand tabs for option \fB\-k\fR.  The value of

src/output.hpp

@@ -573,10 +573,10 @@ class Output {
     mode_ |= FLUSH;
   }
 
-  // flush if output is line buffered to flush each line
-  void check_flush()
+  // flush if output is line buffered to flush each line, unless we have to wait to acquire the output lock
+  inline void check_flush()
   {
-    if (mode_ == FLUSH)
+    if (mode_ == FLUSH && (sync == NULL || sync->try_acquire(lock_)))
       flush();
   }
 

src/query.cpp

@@ -1522,11 +1522,10 @@ void Query::search()
 
   select_ = -1;
   select_all_ = false;
+  updated_ = false;
+  tick_ = 4;
 
   draw();
-  status(true);
-
-  updated_ = false;
 }
 
 // display the status line

src/ugrep.cpp

@@ -166,7 +166,7 @@ After this, you may want to test ugrep and install it (optional):
 # define MAX_JOBS 16
 #endif
 
-// limit the job queue size to wait to give the worker threads some slack
+// default limit on the job queue size to wait for worker threads to finish more work
 #ifndef DEFAULT_MAX_JOB_QUEUE_SIZE
 # define DEFAULT_MAX_JOB_QUEUE_SIZE 8192
 #endif
@@ -2172,17 +2172,6 @@ struct Grep {
       queue_work.notify_one();
     }
 
-    // try to add a job to the queue if the queue is not too large
-    bool try_enqueue(const char *pathname, uint16_t cost, size_t slot)
-    {
-      if (todo >= flag_max_queue)
-        return false;
-
-      enqueue(pathname, cost, slot);
-
-      return true;
-    }
-
     // pop a job
     void dequeue(Job& job)
     {
@@ -4095,12 +4084,6 @@ struct GrepWorker : public Grep {
     jobs.enqueue(pathname, cost, slot);
   }
 
-  // submit a job to this worker
-  bool try_submit_job(const char *pathname, uint16_t cost, size_t slot)
-  {
-    return jobs.try_enqueue(pathname, cost, slot);
-  }
-
   // receive a job for this worker, wait until one arrives
   void next_job(Job& job)
   {
@@ -4184,12 +4167,25 @@ void GrepMaster::submit(const char *pathname, uint16_t cost)
       iworker = min_worker;
     }
 
-    // try to submit, if not successful then the queue reached max specified size
+#ifdef WITH_LOCK_FREE_JOB_QUEUE
+
     if (iworker->try_submit_job(pathname, cost, sync.next) || out.eof || out.cancelled())
       break;
 
     // give the worker threads some slack to make progress, then try again
     std::this_thread::sleep_for(std::chrono::milliseconds(1));
+
+#else
+
+    // give the worker threads some slack to make progress when their queues reached a soft max size
+    if (min_todo > flag_max_queue && flag_max_queue > 0)
+      std::this_thread::sleep_for(std::chrono::milliseconds(1));
+
+    // submit job to worker, do not loop
+    iworker->submit_job(pathname, cost, sync.next);
+    break;
+
+#endif
   }
 
   ++sync.next;
@@ -4535,7 +4531,7 @@ int main(int argc, const char **argv)
     if (!flag_no_messages && Static::warnings > 0)
       abort("option -Q: warnings are present, specify -s to ignore");
 
-    // queue more files than we queue for more optimized searching by default
+    // increase worker threads queue
     flag_max_queue = 65536;
 
     // -Q: TUI query mode