perf(column): avoid counting when max signs are removed from a range

test/functional/ui/decorations_spec.lua

@@ -4989,6 +4989,21 @@ l5
                           |
     ]]}
   end)
+
+  it('correct width with multiple overlapping signs', function()
+    screen:try_resize(20, 4)
+    insert(example_test3)
+    meths.buf_set_extmark(0, ns, 0, -1, {sign_text='S1', end_row=2})
+    meths.buf_set_extmark(0, ns, 1, -1, {sign_text='S2', end_row=2})
+    feed('gg')
+
+    screen:expect{grid=[[
+      S1{1:  }^l1              |
+      S1S2l2              |
+      S1S2l3              |
+                          |
+    ]]}
+  end)
 end)
 
 describe('decorations: virt_text', function()

test/functional/ui/sign_spec.lua

@@ -367,11 +367,12 @@ describe('Signs', function()
                                                              |
       ]]}
       -- line deletion deletes signs.
+      command('3move1')
       command('2d')
       screen:expect([[
-        {1:>>}{8:XX}{2:  }{6:  1 }a                                          |
-        {8:XX}{1:>>}WW{6:  2 }^c                                          |
-        {2:      }{6:  3 }                                           |
+        {1:>>}{8:XX}{6:  1 }a                                            |
+        {8:XX}{1:>>}{6:  2 }^b                                            |
+        {2:    }{6:  3 }                                             |
         {0:~                                                    }|
         {0:~                                                    }|
         {0:~                                                    }|