pro qSkyImage_ChangeCoordinates, state, event
;+
; NAME:
;	qSkyImage_ChangeCoordinates
; PURPOSE:
;	Controls the units of the location and viewing directions.
;	Units are either ecliptic or heliographic
; CATEGORY:
;	Widgets: qSkyImage
; CALLING SEQUENCE:
;	qSkyImage_ChangeCoordinates, state, event
; INPUTS:
;	state			array[1]; type: structure
;						qSkyImage state structure
;	event			array[1]; type: structure
;						event structure with event.id=state.wid_ecliptic or
;						state.wid_heliographic
; OUTPUTS:
;	(updates values of state.wid_loc and state.wid_dir)
; CALLS:
;	CarringtonT, TimeSet, CvSky
; SIDE EFFECTS:
; RESTRICTIONS:
; PROCEDURE:
;	The user value of state.wid_clabel stores the information about which coordinate system
;	is currently in use: it stores the widget ID of state.wid_ecliptic of state.wid_heliographic
;	If the event ID does not match this value and event.select=1 then the values
;	of both time widgets are converted to the new units, and the user value of
;	state.wid_clabel is updated accordingly.
; STATE INFO USED:
;	widget_control, state.wid_clabel  , get_uvalue=wid_unit
;	widget_control, state.wid_loc[0] , get_value=loc_lng
;	widget_control, state.wid_loc[1] , get_value=loc_lat
;	widget_control, state.wid_dir[0] , get_value=dir_lng
;	widget_control, state.wid_dir[1] , get_value=dir_lat
;	widget_control, state.wid_earth[0] , get_value=earth_lng
;	widget_control, state.wid_earth[1] , get_value=earth_lat
;	widget_control, state.wid_tdisplay, get_value=tdisplay
;	widget_control, state.wid_tlabel  , get_uvalue=wid_tunit
; STATE INFO MODIFIED:
;	widget_control, state.wid_loc[0] , set_value=loc[0,0]
;	widget_control, state.wid_loc[1] , set_value=loc[1,0]
;	widget_control, state.wid_dir[0] , set_value=loc[0,1]
;	widget_control, state.wid_dir[1] , set_value=loc[1,1]
;	widget_control, state.wid_clabel, set_uvalue=event.id
;	widget_control, state.wid_earth[0] , set_value=loc[0,2]
;	widget_control, state.wid_earth[1] , set_value=loc[0,2]
; MODIFICATION HISTORY:
;	MAY-2000, Paul Hick (UCSD/CASS; pphick@ucsd.edu)
;-
on_error, 2							; On error, return to caller

COMPILE_OPT hidden

widget_control, event.id, set_button=event.select, set_uvalue=event.select

if event.select then begin
	widget_control, state.wid_clabel  , get_uvalue=wid_unit

	if wid_unit ne event.id then begin
		widget_control, state.wid_loc[0] , get_value=loc_lng
		widget_control, state.wid_loc[1] , get_value=loc_lat

		widget_control, state.wid_dir[0] , get_value=dir_lng
		widget_control, state.wid_dir[1] , get_value=dir_lat

		widget_control, state.wid_earth[0] , get_value=earth_lng
		widget_control, state.wid_earth[1] , get_value=earth_lat

		loc = [ [loc_lng, loc_lat], [dir_lng, dir_lat], [earth_lng, earth_lat] ]

		widget_control, state.wid_tdisplay, get_value=tdisplay
		widget_control, state.wid_tlabel  , get_uvalue=wid_tunit

		case wid_tunit of
		state.wid_uttime  : TT = TimeSet(tdisplay)
		state.wid_rotation: TT = Carrington(double(tdisplay))
		endcase

		case event.id of
		state.wid_ecliptic    : loc = CvSky(TT, from_heliographic=loc, /to_ecliptic, /degrees)
		state.wid_heliographic:	loc = CvSky(TT, from_ecliptic=loc, /to_heliographic, /degrees)
		endcase

		widget_control, state.wid_loc[0] , set_value=loc[0,0]
		widget_control, state.wid_loc[1] , set_value=loc[1,0]

		widget_control, state.wid_dir[0] , set_value=loc[0,1]
		widget_control, state.wid_dir[1] , set_value=loc[1,1]

		widget_control, state.wid_earth[0] , set_value=loc[0,2]
		widget_control, state.wid_earth[1] , set_value=loc[1,2]

		widget_control, state.wid_clabel, set_uvalue=event.id
	endif
endif

return  &  end