toolhead: Delay calculating homing print_time until ready to move

If the homing move is exceptionally long, it could take a long time
for the host to process the look-ahead queue.  Delay the print_time
calculation until moves are ready to be sent.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/toolhead.py

@@ -244,6 +244,7 @@ class ToolHead:
         self.idle_flush_print_time = 0.
         self.print_stall = 0
         self.drip_completion = None
+        self.drip_need_calc_print_time = False
         # Setup iterative solver
         ffi_main, ffi_lib = chelper.get_ffi()
         self.cmove = ffi_main.gc(ffi_lib.move_alloc(), ffi_lib.free)
@@ -292,6 +293,9 @@ class ToolHead:
             return self.print_time
         if self.special_queuing_state == "Drip":
             # In "Drip" state - wait until ready to send next move
+            if self.drip_need_calc_print_time:
+                self.drip_need_calc_print_time = False
+                self._calc_print_time()
             while 1:
                 if self.drip_completion.test():
                     raise DripModeEndSignal()
@@ -434,6 +438,7 @@ class ToolHead:
         self.reactor.update_timer(self.flush_timer, self.reactor.NEVER)
         self.move_queue.set_flush_time(self.reactor.NEVER)
         self.drip_completion = self.reactor.completion()
+        self.drip_need_calc_print_time = True
         # Split move into many tiny moves and queue them
         num_moves = max(1, int(math.ceil(move.min_move_t / DRIP_SEGMENT_TIME)))
         inv_num_moves = 1. / float(num_moves)
@@ -445,7 +450,6 @@ class ToolHead:
             prev_pos = next_pos
         self.move_queue.add_move(Move(self, prev_pos, move.end_pos, speed))
         # Transmit moves
-        self._calc_print_time()
         try:
             self.move_queue.flush()
         except DripModeEndSignal as e: