pro snowflake_event,event
;event that triggers the growth of the snowflake
widget_control,event.top,get_uvalue=object
if obj_valid(object) then object->grow
return
end

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pro snowflake::grow
;method to grow snowflake
;uses a variation of the parity rule for cellular automata

fourneighbor = [[0,1,0], $ ;neighborhood for convolution
                [1,1,1], $
                [0,1,0]]

ind = where(*self.image eq 1) ;find the "frozen" ones
*self.image = convol(*self.image,fourneighbor)
*self.image = *self.image mod 2B ;odd freezes even doesn't
(*self.image)[ind] = 1B ;add the original frozen ones in
self.oImage ->setProperty,data=bytscl(*self.image)
widget_control,self.base,timer=self.interval ;set timer

return
end
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pro snowflake::cleanup
;clean everything up
self->IDLgrModel::cleanup
if obj_valid(self.oImage) then obj_destroy,self.oImage
if ptr_valid(self.image) then ptr_free,self.image

return
end

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function snowflake::init, interval=interval

if not keyword_set(interval) then interval=1
self.interval = interval

;initialize the super class. THIS HAS TO BE DONE!
IF (self->IDLgrModel::Init(_EXTRA=extra) NE 1) THEN RETURN, 0

image = bytarr(256,256)
image[128,128] = 1B
self.image = ptr_new(image,/no_copy)
;have to bytscl image since it is only 0 and 1's
self.oImage = obj_new('IDLgrImage',bytscl(*self.image) )
;put it in the center
x = [0,1,1,0]-.5
y = [0,0,1,1] -.5
z = [0,0,0,0]
oPoly = obj_new('IDLgrPolygon',x,y,z,color=[255,255,255],texture_map=self.oImage, $
                texture_coord = [[0,0], [1,0], [1,1], [0,1]], /texture_interp)
self->add, oPoly
;create an invisible base that generates timer events
self.base = widget_base(map=0)
widget_control,self.base,/realize
widget_control,self.base,timer=self.interval
widget_control,self.base,set_uvalue=self
xmanager,'snowflake',self.base,/no_block

return,1
end

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pro snowflake__define
;definition of the snowflake object
void = { snowflake, $
         inherits IDLgrmodel, $
         oImage : obj_new(), $ ;image object
         image : ptr_new(), $ ;original data
         base : 0L, $ ;widget base
         interval : 0 } ;interval for growth

return
end

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; Widget code starts here
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pro snowflakeObjectDemo_event,event

widget_control,event.top,get_uvalue=state

if tag_names(event,/structure_name) eq 'WIDGET_TIMER' then begin
  state.oRotateModel->rotate,[1,1,1],5 ;rotate object
  state.oWindow->Draw, state.oView
  widget_control, event.id, timer=.1 ;set new event
  return
endif

if (event.type EQ 4) then begin ;expose events here
                state.oWindow->Draw, state.oView
endif

return
end

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pro snowflakeObjectExit,event
;called from pull down
widget_control,event.top,/destroy

return
end

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pro snowflakeObjectDemoCleanup, base
;cleans up all the objects
widget_control,base,get_uvalue=state
obj_destroy, state.oContainer
tvlct,state.colorTable ;reload orig color table

return
end

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pro snowflakeObjectDemo,  interval=interval

;  Get the current color table.
;  It will be restored when exiting.
;
tvlct, savedR, savedG, savedB, /GET
colorTable=[[savedR],[savedG],[savedB]]

;  Get the screen size.
;
device, get_screen_size = screenSize
xdim = screenSize[0]*.50 ;about 50 percent of the screen size
ydim=xdim  ;keep isotropic

wTopBase=widget_base(TITLE='Snowflake', $
             XPAD=0, YPAD=0, $
            /COLUMN,/tlb_size_events,MBAR=barBase)

fileId = widget_button(barBase, value='File', /menu)
quitter = widget_button(fileId, /separator, value='Exit', $
           event_pro='snowflakeObjectExit')

drawId=widget_draw(wTopBase, xsize=xdim, $
                    ysize=ydim, $  ;keep isotropic
                    graphics_level=2, retain=0, /expose_events)

widget_control, wTopBase, /realize
widget_control, hourglass=1
widget_control, drawId, get_value=oWindow
;  Create the objects.
mView = [-1,-1,2,2]
maxDim = max([xdim,ydim])
maxDim = 1.
;  Create view object.
oView = obj_new('IDLgrView', projection=1, eye=maxDim + 0.1, $
        color=[0,0,0], $
        view=myView, zclip=[maxDim,-maxDim])
oRotateModel = obj_new('IDLgrModel') ;need a model to rotate
oSnow = obj_new('snowflake' ,interval=interval ) ;snowflake object
oRotateModel->add, oSnow
oView -> add, oRotateModel
owindow->Draw, oView

oContainer = OBJ_NEW('IDL_Container');store objects for cleanup
oContainer->add, oView
oContainer -> add, oRotateModel
oContainer -> add, oSnow

;  Build state structure used in event handlers.
;
state={ drawId:drawId, $             ; Widget draw ID
        oContainer: oContainer, $  ; Container object
        oWindow:oWindow, $         ; Window object
        oView:oView, $             ; View object
        oRotateModel : oRotateModel, $ ;rotating model
        colorTable:colorTable  } ;orig color table

widget_control, wTopBase, set_uvalue=state, /no_copy
widget_control, hourglass=0
widget_control, drawId, timer=.1 ;start timer
xmanager, 'snowflakeObjectDemo', wTopBase, /no_block, $
           cleanup='snowflakeObjectDemoCleanup'

return
end