DynamicModule with Plots and EventHandler

Question

I am making a little animation in Mathematica, along the lines of some of the Wolfram demo projects. I'd like to animate a simulated trajectory of a random process (say a Poisson process), and while it is running, change the parameters using "MouseDown".

Here's a trajectory animated in the front end:

Framed @ DynamicModule[{t = 0.001},
  trajnormal = RandomFunction[PoissonProcess[1], {0, 100}]["PathFunction"];
  step = .05;
  Column[{
     Dynamic[t = If[trajnormal[t] <= 50, t + step, t] ] , 
     Dynamic[Plot[trajnormal[x], {x, 0.001, t}, PlotRange -> {{0, 60}, {0, 60}}, 
                                                PlotPoints -> 1000, ImageSize -> 500] ]
    }]
  ]

And here's my failed attempt at using EventHandler to change the simulated function with a mouse click:

Framed @ DynamicModule[{t = 0.001, i = 1},
s = 0;
step = .05; 
trajnormal = RandomFunction[PoissonProcess[1], {0, 100}]["PathFunction"]; 
trajdiscount = RandomFunction[PoissonProcess[5], {0, 100}]["PathFunction"];

(* show[1] is trajectory of Poisson[1] process *)
show[1] = Dynamic[Plot[50 - trajnormal[x], {x, 0.001, t},  PlotPoints -> 1000,
                                  PlotRange -> {{0, 70}, {0, 55}}, ImageSize -> 500] ]; 
(* show[2] is trajectory of Poisson[1] with Poisson[5] added at time of click = s *)
show[2] = Dynamic[Plot[50 - trajnormal[x] - trajdiscount[Max[x - s, 0]], {x, 0, t}, 
              PlotRange -> {{0, 70}, {0, 55}}, ImageSize -> 500, PlotPoints -> 1000] ]; 

EventHandler[ 
  EventHandler[ 
    Column[{
      Dynamic[t = If[trajnormal[t] <= 50, t + step, t] ] ,
      Dynamic[s],
      Dynamic[ show[i] ]
      }],
  "MouseDown" :> (i = 2)], 
    "MouseDown" :>  (s = t), 
PassEventsUp -> True ] ] 

The mouse click changes the function from show[1] to show[2], but the plots are not displayed.

I'd appreciate any corrections or help.

Answer 1

Based on the discussion in chat among Kuba halirutan and Michael Hale:

trajnormal = RandomFunction[PoissonProcess[1], {0, 100}]["PathFunction"];
trajdiscount = RandomFunction[PoissonProcess[5], {0, 100}]["PathFunction"];

Clear[show]
show[1, t_, step_] :=
      ListLinePlot[
             {#, 50 - trajnormal[#]}\[Transpose] & @ Range[0, t, step],
             InterpolationOrder -> 0,
             PlotRange -> {{0, 70}, {0, 55}}, ImageSize -> 500]
show[2, s_, t_, step_] :=
      ListLinePlot[
             {#, 50 - trajnormal[#] - trajdiscount[Max[# - s, 0] & /@ #]}\[Transpose] & @
                 Range[0, t, step],
             PlotStyle -> Red, InterpolationOrder -> 0,
             PlotRange -> {{0, 70}, {0, 55}}, ImageSize -> 500]

step = .05;
Framed@DynamicModule[{t = 0, i = 1, s = 0},

        EventHandler[
            Dynamic[
                Column[{
                        t = Clock[{1, 50, step}, 30, 1],
                        s, i,
                        If[i == 1, show[1, t, step], show[2, s, t, step]]
                        }]
                ],
            "MouseDown" :> {i = 2, s = t}]
        ]