Fix " not a Graphics primitive or directive" error in Dynamic Locator Pane

Question

I am aware this might seem like a duplicate, however, I have viewed these posts (1 & 2) and have been unable to solve this.

   DynamicModule[{pt = {.5, .5}, ll = {}, 
  base = {White, Rectangle[{0, 0}, {2, 2}]}}, 
 LocatorPane[Dynamic[pt, (AppendTo[ll, #]; pt = Last@ll) &], 
  Dynamic[Show@
    Graphics[{base, 
      With[{newpts = Partition[ll, 2, 1]}, 
       Table[{i, Line[newpts[[i]]]}, {i, 1, Length[newpts], 1}]]}]
   ]]]

Would someone be able to help me to solve this error? Thank in advance

Answer 1

A few things in your code were unnecessary (e.g. the Show before Graphics) and others were confusing and the cause of your trouble. Note that Line will take a list of points and construct a polygonal line from it automatically; you do not need to produce each segment in a separate Line statement, so the Partition and Table bits can be avoided.

This works with no errors:

DynamicModule[
 {pt = {.5, .5}, ll = {}, base = {White, Rectangle[{0, 0}, {2, 2}]}},
 LocatorPane[
   Dynamic[pt, (AppendTo[ll, #]; pt = Last@ll) &],
   Dynamic@Graphics[{base, Line@Partition[ll, 2, 1]}]
 ]
]