;+
; @file_comments click on a map and find in which cell the click was
;
; @categories finding where is a point on a grid
;
; @examples 
;
;     res = clickincell()
;     Click with the left button to select a cell. Clicking one more
;     time in the same cell remove the cell from the selection.
;     Click on the right button to quit.  
;
; @keyword     CELLTYPE = 'T', 'W', 'U', 'V' or 'F' This this the type of point
;     that is located in the center of the cell which the click is
;     located. default is T type of cell (with corner defined by F
;     points).
;
; @keyword     /DRAWCELL to draw the cell in which we clicked
;
; @keyword     COLOR  the color used to draw the cells (Clicking one more
;     time in the same cell will draw the cell with the white color)
;
; @keyword     /ORIGINAL to get the position of the cell regarding the original
;     grid (with no key_shift, ixminmesh, iyminmesh...)
;
; @keyword     /IJ see outpus
;
; @keyword     _EXTRA to pass extra keywords to inquad and plot (when /drawcell)
;
; @returns
;     the index of the selected cells regarding to the grid which
;     is in memory in the variable of the common. If /ij keyword is
;     activated give 2D array (2, n) which are the i,j position of the
;     n selected cells. 
;
; @uses common.pro
;
; @examples 
;
;   IDL> plt, findgen(jpi,jpj),/nodata,map=[90,0,0],/ortho
;   IDL> print, clickincell(/draw,color=150,/xy)
;
; @history
;      Sebastien Masson (smasson\@lodyc.jussieu.fr)
;      August 2003
;
;-
FUNCTION clickincell, CELLTYPE = celltype, DRAWCELL = drawcell, COLOR = color, ORIGINAL = original, IJ = ij, _EXTRA = extra
@common
;
; initialization
  cellnum = -1L
  selected = 0
;
; Cell list
; get the grid parameter according to celltype
  oldgrid = vargrid
  IF NOT keyword_set(celltype) THEN celltype = 'T'
  CASE strupcase(celltype) OF
    'T':vargrid = 'F'
    'W':vargrid = 'F'
    'U':vargrid = 'V'
    'V':vargrid = 'U'
    'F':vargrid = 'T'
  ENDCASE
  grille, -1, glam, gphi, -1, nx, ny, nz, firstx, firsty, firstz, lastx, lasty, lastz
  vargrid = oldgrid
; define the corner of the cells in the clockwise direction
  IF keyword_set(key_periodic) AND nx EQ jpi THEN BEGIN
    x1 = glam[*, 0:ny-2]
    y1 = gphi[*, 0:ny-2]
    x2 = glam[*, 1:ny-1]
    y2 = gphi[*, 1:ny-1]
    x3 = shift(glam[*, 1:ny-1], -1, 0)
    y3 = shift(gphi[*, 1:ny-1], -1, 0)
    x4 = shift(glam[*, 0:ny-2], -1, 0)
    y4 = shift(gphi[*, 0:ny-2], -1, 0)
  ENDIF ELSE BEGIN
    x1 = glam[0:nx-2, 0:ny-2]
    y1 = gphi[0:nx-2, 0:ny-2]
    x2 = glam[0:nx-2, 1:ny-1]
    y2 = gphi[0:nx-2, 1:ny-1]
    x3 = glam[1:nx-1, 1:ny-1]
    y3 = gphi[1:nx-1, 1:ny-1]
    x4 = glam[1:nx-1, 0:ny-2]
    y4 = gphi[1:nx-1, 0:ny-2]
  ENDELSE
  glam = -1 ; free memory
  gphi = -1 ; free memory
;
; get mousse position on the reference map
  cursor, x, y, /data, /up
;
  while (!mouse.button ne 4) do BEGIN
    IF finite(x)*finite(x) EQ 0 THEN GOTO, outwhile
;
    case !mouse.button of
      1:BEGIN
; What is the longitude?
        WHILE x GT !x.range[1] DO x = x-360
        WHILE x LT !x.range[0] DO x = x+360
        IF x GT !x.range[1] THEN GOTO, outwhile
        IF y GT !y.range[1] THEN GOTO, outwhile
        IF y LT !y.range[0] THEN GOTO, outwhile
;
        cell = inquad(x, y, x1, y1, x2, y2, x3, y3, x4, y4 $
                      , /onsphere, _extra = extra)
;
        IF cell[0] EQ -1 OR n_elements(cell) GT 1 THEN GOTO, outwhile
        cell = cell[0]
        already = (where(cellnum EQ cell))[0]
        IF already EQ -1 THEN BEGIN
          cellnum = [cellnum, cell]
          selected = [selected, 1]
          already = n_elements(selected)-1 
        ENDIF ELSE selected[already] = 1-selected[already]
        IF keyword_set(drawcell) THEN BEGIN
          oplot, [x1[cell], x2[cell], x3[cell], x4[cell], x1[cell]] $
            , [y1[cell], y2[cell], y3[cell], y4[cell], y1[cell]] $
            , color = color*selected[already] $
            + (!d.n_colors < 255)*(1-selected[already]) $
            , _extra = extra
        ENDIF
      END
      2:                        ; middle button
      ELSE:
    ENDCASE    
; get mousse position on the reference map
outwhile:
    cursor, x, y, /data, /up
  ENDWHILE
;
  good = where(selected NE 0)
  IF good[0] EQ -1 THEN RETURN, -1 
;
  cellnum = cellnum[good]
;
  yy = cellnum/(nx-1+key_periodic*(nx EQ jpi))
  xx = cellnum MOD (nx-1+key_periodic*(nx EQ jpi))
;
  CASE strupcase(celltype) OF
    'T':BEGIN
      xx = xx+firstx+1
      yy = yy+firsty+1
    END
    'W':BEGIN
      xx = xx+firstx+1
      yy = yy+firsty+1
    END
    'U':BEGIN
      xx = xx+firstx
      yy = yy+firsty+1
    END
    'V':BEGIN
      xx = xx+firstx+1
      yy = yy+firsty
    END
    'F':BEGIN
      xx = xx+firstx
      yy = yy+firsty
    END
  ENDCASE
;
  bad = where(xx GE jpi)
  IF bad[0] NE -1 THEN BEGIN
    xx[bad] = xx[bad]-jpi
    yy[bad] = yy[bad]+1
  ENDIF
  bad = where(yy GE jpj)
  IF bad[0] NE -1 THEN stop
;
  IF keyword_set(original) THEN BEGIN
    xx = xx-key_shift
    bad = where(xx LT 0)
    IF bad[0] NE -1 THEN xx[bad] = xx[bad]+jpi
    xx = xx MOD jpi
    xx = xx +ixminmesh
    yy = yy+iyminmesh
  ENDIF
;
  ncell = n_elements(xx) 
  IF keyword_set(ij) THEN $
    RETURN, [reform(xx, 1, ncell, /over) $
             , reform(yy, 1, ncell, /over)] 
;
  IF keyword_set(original) THEN RETURN, xx+jpiglo*yy $
  ELSE RETURN, xx+jpi*yy 
END