; example script
; here we make frames for a movie doing a density projection
; while first finding a particular particle ID on which we center

pro follow_particle_movie
@TOOLS/common_blocks.inc
  center_particle_id = 1182L       ; use the particle with this id as center for the movie (-1 for static useing current center

  widget_control, base2, sensitive = 0 ; sets the GUI insensitive while script is working
  ntimes = N_ELEMENTS(times)

  old_log = image_log           ; remember previous settings
  old_log_num = image_log_number
  old_log_string = image_log_string
  oldpindex = parti.index

  image_log = 1                 ; make sure an image gets written every time
  image_log_number = 0L         ; 
  image_log_string = "spframe"  ; use this as file base name
  
                                ; delete all existing frames with same name
  spawn, 'rm '+image_log_directory+image_log_string+'*'
  starttime = 0L
  if time_index lt ntimes-1 then starttime = time_index ;start movie at current timestep
                  ; unless it is the last timestep for which it will strt witht the first loded one

  mh = 0
  for time_index=starttime,ntimes-1,astep DO BEGIN ; loop over all loaded timesteps
     widget_control, TIME_LIST_WIDGET, set_combobox_select=time_index
     select_current_grids 
     check_cancel, stopit=stopit
     if stopit then begin
        stopit = 0
        break
     endif
     parti.read[*] = 0 ; new time step so old particle data not reelvant
     vel.read = 0

; read in the current particle data
     particleindex = (where((*parti.names) eq 'particle_index'))[0]

     fields= [0,1,2, parti.index, particleindex]
     read_particle_data, fields=fields
     
;     parti.index = where((*parti.names) eq 'particle mass')     
;     read_particle_data

     pi = where( (*parti.d[particleindex]) eq center_particle_id) ; find particle

     sidelength = slice_size[2] - slice_size[0]
     sh = sidelength/2.
     ot = where(slice_ori lt 1.e-15)
     os = where(slice_ori gt 1.e-15)
     if pi ge 0 then begin
        center[ot] = [(*parti.d[ot[0]])[pi], (*parti.d[ot[1]])[pi]] ; center on it 
        print, 'center on:', (*parti.d[0])[pi], (*parti.d[1])[pi], (*parti.d[2])[pi]
     endif else printf, 'PARTICLE NOT FOUND WITH ID:', center_particle_id
     slice_size[*] = [center[ot]-sh, center[ot]+sh]
     slice_value[*] = 0.D
     slice_value[os] = center[os]

     image_log = 0
;     J_event, 'NO_VEL'
;     J_EVENT, 'DRAW_BUTTON'
;     J_event, 'VEL_BUTTON'
     J_event, 'DRAW_BUTTON'
     image_log = 1

     a = total(*parti.d[parti.index])
     print, 'total mass value:', a
     mh = [mh[*], a]
     ; mark the center particle
     plots, xy_sl_size/2,xy_sl_size/2, [0.5], psym=4, /device, THICK=2

     save_image_log             ; save frame
     if verbose then print, 'memory use in Mb', memory()/1024./1e3
  endfor
  mh = mh[1:*]

  time_index = N_elements(times)-1
  image_log = old_log
  image_log_number = old_log_num 
  image_log_string = old_log_string
  parti.index = oldpindex
  widget_control, base2, sensitive = 1

return
end

follow_particle_movie
end