Reposition bars below a closed bar

When a bar is closed it is moved to pos 0, which means all the other
bars below it must now be given a new position number to have their
output still go to the same screen line.

tests/tests_tqdm.py

@@ -1281,20 +1281,78 @@ def test_position():
         t3.update(1)
         t4.update(1)
         res = [m[0] for m in RE_pos.findall(our_file.getvalue())]
-        exres = ['\r1.pos0 bar:   0%',
-                 '\n\r2.pos1 bar:   0%',
-                 '\n\n\r3.pos2 bar:   0%',
+        exres = [*exres,
                  '\r2.pos1 bar:   0%',
+                 '\n\n\r3.pos2 bar:   0%',
                  '\n\n\r4.pos2 bar:   0%',
                  '\r1.pos0 bar:  10%',
-                 '\n\n\r3.pos2 bar:  10%',
-                 '\n\r4.pos2 bar:  10%']
+                 '\n\r3.pos2 bar:  10%',
+                 '\n\n\r4.pos2 bar:  10%']
         pos_line_diff(res, exres)
         t4.close()
         t3.close()
         t1.close()
 
 
+@mark.skipif(nt_and_no_colorama, reason="Windows without colorama")
+@mark.parametrize('leave', [
+    True,   # all bars remain
+    False,  # no bars remain
+    None    # only first bar remains
+])
+def test_position_leave(leave: bool):
+    """Test leaving of nested positioned progress bars"""
+    our_file = StringIO()
+    kwargs = {
+        'file': our_file,
+        'miniters': 1,
+        'mininterval': 0,
+        'maxinterval': 0,
+        'leave': leave,
+    }
+    for _ in trange(2, desc='pos0 bar', position=0, **kwargs):
+        t2 = tqdm(total=2, desc='pos1 bar', position=1, **kwargs)
+        t2.update()
+        t3 = tqdm(total=2, desc='pos2 bar', position=2, **kwargs)
+        t3.update()
+        # complete t2 before t3
+        t2.update()
+        t2.close()
+        t3.update()
+        t3.close()
+
+    out = our_file.getvalue()
+    res = [m[0] for m in RE_pos.findall(out)]
+    # Bar 2 being left from the screen means bar 3 needs extra newline when
+    # positioning. If it is not left, then bar 3 needs to be cleared in its old
+    # position and redrawn in gap left by bar 2.
+    if leave:
+        bar2left, bar3move = '\n', []
+    else:
+        bar2left, bar3move = '', ['\n\n\r            ', '\r\x1b[A\x1b[A']
+    innerex = ['\n\rpos1 bar:   0%',
+               '\n\rpos1 bar:  50%',
+               '\n\n\rpos2 bar:   0%',
+               '\n\n\rpos2 bar:  50%',
+               '\n\rpos1 bar: 100%',
+               '\rpos1 bar: 100%' if leave else '\n\r             ',
+               *bar3move,
+               bar2left + '\n\rpos2 bar:  50%',
+               '\n\rpos2 bar: 100%',
+               '\rpos2 bar: 100%' if leave else '\n\r             ']
+    # Bar 1 being left on screen adds an extra newline to the output
+    # that then shows up as part of the next res line.
+    bar1left = '\n' if leave else ''
+    exres = ['\rpos0 bar:   0%',
+             *innerex,
+             bar1left + '\rpos0 bar:  50%',
+             *innerex,
+             bar1left + '\rpos0 bar: 100%',
+             '\rpos0 bar: 100%' if leave is not False else '\r              ',
+             '\n' if leave is not False else '\r']
+    pos_line_diff(res, exres)
+
+
 def test_set_description():
     """Test set description"""
     with closing(StringIO()) as our_file:
@@ -1895,7 +1953,6 @@ def test_screen_shape():
         assert "one" in res
         assert "two" in res
         assert "three" in res
-        assert "\n\n" not in res
         assert "more hidden" in res
         # double-check ncols
         assert all(len(i) == 50 for i in get_bar(res)

tqdm/std.py

@@ -715,6 +715,27 @@ def _decr_instances(cls, instance):
                     inst = min(instances, key=lambda i: i.pos)
                     inst.clear(nolock=True)
                     inst.pos = abs(instance.pos)
+                else:
+                    # renumber remaining bars with positions below this bar so
+                    # they maintain their positions
+                    apos = abs(instance.pos)
+                    readjust = [
+                        (inst.pos, inst)
+                        for inst in cls._instances
+                        if not inst.disable and abs(getattr(inst, "pos", apos)) > apos
+                    ]
+                    for pos, inst in sorted(readjust, key=lambda pi: -abs(pi[0])):
+                        newpos = inst.pos + (1 if pos < 0 else -1)
+                        if newpos == 0 and inst.leave is None:
+                            # any bars now moving to pos=0 should not be left on
+                            # screen if `leave` was set to `None`.
+                            inst.leave = False
+                        if not inst.leave:
+                            # Clear the old position before moving the bar so we
+                            # don't leave any artefacts on screen.
+                            inst.clear(nolock=True)
+                        inst.pos = newpos
+                        inst.display()
 
     @classmethod
     def write(cls, s, file=None, end="\n", nolock=False):
@@ -1271,41 +1292,43 @@ def close(self):
         # Prevent multiple closures
         self.disable = True
 
-        # decrement instance pos and remove from internal set
-        pos = abs(self.pos)
-        self._decr_instances(self)
+        try:
+            if self.last_print_t < self.start_t + self.delay:
+                # haven't ever displayed; nothing to clear
+                return
 
-        if self.last_print_t < self.start_t + self.delay:
-            # haven't ever displayed; nothing to clear
-            return
+            # GUI mode
+            if getattr(self, 'sp', None) is None:
+                return
 
-        # GUI mode
-        if getattr(self, 'sp', None) is None:
-            return
+            # annoyingly, _supports_unicode isn't good enough
+            def fp_write(s):
+                self.fp.write(str(s))
 
-        # annoyingly, _supports_unicode isn't good enough
-        def fp_write(s):
-            self.fp.write(str(s))
+            try:
+                fp_write('')
+            except ValueError as e:
+                if 'closed' in str(e):
+                    return
+                raise  # pragma: no cover
 
-        try:
-            fp_write('')
-        except ValueError as e:
-            if 'closed' in str(e):
-                return
-            raise  # pragma: no cover
+            pos = abs(self.pos)
+            leave = pos == 0 if self.leave is None else self.leave
 
-        leave = pos == 0 if self.leave is None else self.leave
+            with self._lock:
+                if leave:
+                    # stats for overall rate (no weighted average)
+                    self._ema_dt = lambda: None
+                    self.display(pos=0)
+                    fp_write('\n')
+                else:
+                    # clear previous display
+                    if self.display(msg='', pos=pos) and not pos:
+                        fp_write('\r')
 
-        with self._lock:
-            if leave:
-                # stats for overall rate (no weighted average)
-                self._ema_dt = lambda: None
-                self.display(pos=0)
-                fp_write('\n')
-            else:
-                # clear previous display
-                if self.display(msg='', pos=pos) and not pos:
-                    fp_write('\r')
+        finally:
+            # decrement instance pos and remove from internal set
+            self._decr_instances(self)
 
     def clear(self, nolock=False):
         """Clear current bar display."""