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+## Copyright (C) 2012 pdiribarne
+##
+## This program is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or
+## (at your option) any later version.
+##
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn  {Function File} {@var{h} =} struct2hdl (@var{s})
+## @deftypefnx {Function File} {@var{h} =} struct2hdl (@var{s}, @var{p})
+## @deftypefnx {Function File} {@var{h} =} struct2hdl (@var{s}, @var{p}, @var{hilev})
+## Constructs an object from the structure @var{s}. The structure must
+## contain the fields "handle", "type", "children", "properties", and
+## "special".  If the handle of an existing figure or axes is specified,
+## @var{p}, the new object will be created as a child to that object.
+## If no object handle is provided, then a new figure and the necessary
+## children will be constructed using the default object values from
+## the root figure.
+##
+## A third boolean argument @var{hilev} can be passed to specify wether
+## the function should try to preserve listeners/calbacks e.g for
+## legends or hggroups. Default is false.
+## @seealso{findobj, get, hdl2struct, set}
+## @end deftypefn
+
+## Author: pdiribarne <pdiribarne@new-host.home>
+## Created: 2012-03-04
+
+function [ h, matchout ] = struct2hdl (hgS, matchin=[], hilev = false)
+
+  fields = { "handle", "type", "children", "properties", "special"};
+  partypes = {"root", "figure", "axes", "hggroup"};
+  othertypes = {"line", "patch", "surface", "image", "text"};
+  alltypes = [partypes othertypes];
+
+  if (nargin > 3 || ! isstruct (hgS))
+    print_usage ();
+  elseif (! all (isfield (hgS, fields)))
+    print_usage ();
+  elseif (isscalar (matchin))
+    if (! ishandle (matchin))
+      error ("struct2hdl: argument #2 is not a handle to graphic object")
+    endif
+    if (any (strcmp (get (matchin).type, partypes)))
+      paridx = find (strcmp (get (matchin).type, alltypes));
+      kididx = find (strcmp (hgS.type, alltypes));
+      if (kididx <= paridx)
+        error ("struct2hdl: incompatible input handles")
+      endif
+    else
+      error ("struct2hdl: %s object can't be parent object", get (matchin).type)
+    endif
+    hpar = matchin;
+    matchin = [NaN; hpar];
+    ## create appropriate parent if needed
+    if (any (strcmp (hgS.type, othertypes)))
+      for ii = (paridx+1) : (numel (partypes)-1)
+        eval (["hpar = " partypes{ii} "(\"parent\", hpar);"]);
+        matchin = [matchin [NaN; hpar]];
+      endfor
+    elseif (any (strcmp (hgS.type, {"hggroup", "axes"})))
+      for ii = (paridx+1) : (kididx-1)
+        eval (["hpar = " partypes{ii} "(\"parent\", hpar);"]);
+        matchin = [matchin [NaN; hpar]];
+      endfor
+    else
+      par = NaN;
+    endif
+  elseif (isempty (matchin))
+    if (any (strcmp (hgS.type, othertypes)))
+      par = axes ();
+    elseif (any (strcmp (hgS.type, {"hggroup", "axes"})))
+      par = figure ();
+    else
+      par = NaN;
+    endif
+    matchin = [NaN; par];
+  endif
+  ## read parent (last column) in matchin and remove it if duplicate
+  par = matchin (2,end);
+  tst = find (matchin (2,:) == par);
+  if (numel (tst) > 1)
+    matchin = matchin (1:2, 1:(tst(end)-1));
+  endif
+
+  ## create object
+  if (strcmpi (hgS.type, "root"))
+    h = 0;
+    hgS.properties = rmfield (hgS.properties, ...
+                              {"callbackobject", "commandwindowsize", ...
+                               "screendepth", "screenpixelsperinch", ...
+                               "screensize"});
+  elseif (strcmpi (hgS.type, "figure"))
+    h = figure ();
+  elseif (strcmpi (hgS.type, "axes"))
+    ## legends and colorbars are "transformed" in normal axes
+    ## if hilev is not requested
+    if (! hilev)
+      if (strcmp (hgS.properties.tag, "legend"))
+        hgS.properties.tag = "";
+        hgS.properties.userdata = [];
+        par = gcf;
+      elseif (strcmp (hgS.properties.tag, "colorbar"))
+        hgS.properties.tag = "";
+        hgS.properties.userdata = [];
+        par = gcf;
+      endif
+    endif
+
+    [h, hgS] = createaxes (hgS, matchin, par);
+  elseif (strcmpi (hgS.type, "line"))
+    h = createline (hgS, par);
+  elseif (strcmpi (hgS.type, "patch"))
+    [h, hgS] = createpatch (hgS, par);
+  elseif (strcmpi (hgS.type, "text"))
+    h = createtext (hgS, par);
+  elseif (strcmpi (hgS.type, "image"))
+    h = createimage (hgS, par);
+  elseif (strcmpi (hgS.type, "surface"))
+    h = createsurface (hgS, par);
+  elseif (strcmpi (hgS.type, "hggroup"))
+    [h, hgS, matchin] = createhg (hgS, matchin, par, hilev);
+  endif
+
+  ## children
+  matchin = [matchin [hgS.handle; h]]; # [original; new]
+  kids = hgS.children;
+  nkids = length (kids);
+  ii = 0;
+  while nkids
+    ii++;
+    if (! any (ii == hgS.special))
+      [h2, matchin] = struct2hdl (hgS.children(ii),
+                                  [matchin [hgS.handle; h]], hilev);
+    endif
+    nkids--;
+  endwhile
+
+  ## paste properties
+  setprops (hgS, h, matchin, hilev);
+
+  matchout = matchin;
+
+endfunction
+
+function [h, hgSout] = createaxes (hgS, matchin, par);
+  ## regular axes
+  if (strcmpi (hgS.properties.tag, ""))
+    propval = {"position", hgS.properties.position};
+    hid = {"autopos_tag", "looseinset"};
+    for ii = 1:numel (hid)
+      prop = hid{ii};
+      if (isfield (hgS.properties, prop))
+        val = hgS.properties.(prop);
+        propval = [propval, prop, val];
+      endif
+    endfor
+    h = axes (propval{:}, "parent", par);
+
+    if isfield (hgS.properties, "__plotyy_axes__")
+      plty = hgS.properties.__plotyy_axes__;
+      addproperty ("__plotyy_axes__", h, "any")
+      tmp = [matchin [hgS.handle; h]];
+      tst = arrayfun (@(x) any (plty == x), tmp (1:2:end));
+      if sum (tst) == numel (plty)
+        for ii = 1:numel (plty)
+          plty(ii) = tmp (find (tmp == plty(ii)) + 1);
+        endfor
+        for ii = 1:numel (plty)
+          set (plty(ii), "__plotyy_axes__", plty);
+        endfor
+      endif
+      hgS.properties = rmfield (hgS.properties, "__plotyy_axes__");
+    endif
+
+    ## delete non-default and already set properties
+    fields = fieldnames (hgS.properties);
+    tst = cellfun (@(x) isprop (h, x), fields);
+    hgS.properties = rmfield (hgS.properties,  fields(find (tst == 0)));
+
+  elseif (strcmpi (hgS.properties.tag, "legend"))
+    ## legends
+    oldax = hgS.properties.userdata.handle;
+    idx = find (matchin == oldax);
+    newax = matchin(idx+1);
+    strings = {};
+    kids = hgS.children;
+    kids(hgS.special) = [];
+    oldh = unique (arrayfun (@(x) x.properties.userdata(end), kids));
+    for ii = 1:length (oldh)
+      idx = find (matchin(1:2:end) == oldh(ii)) * 2;
+      if (! isempty (idx))
+        newh(ii) = matchin (idx);
+        if (! strcmp (get (newh(ii), "type"), "hggroup"))
+          str = get (newh(ii), "displayname");
+          strings = [strings str];
+        else
+          str = get (get (newh(ii), "children")(1), "displayname");
+          strings = [strings str];
+        endif
+      else
+        error ("struct2hdl: didn't find a legend item")
+      endif
+    endfor
+    location = hgS.properties.location;
+    orientation = hgS.properties.orientation;
+    textpos = hgS.properties.textposition;
+    box = hgS.properties.box;
+
+    h = legend (newax, newh, strings, "location", location, ...
+                "orientation", orientation);
+    set (h, "textposition", textpos); # bug makes "textposition"
+                                # redefine the legend
+    h = legend (newax, newh, strings, "location", location, ...
+                "orientation", orientation);
+    ## box
+    if (strcmp (box, "on"))
+      legend boxon
+    endif
+
+    ## visibility
+    tst = arrayfun (@(x) strcmp (x.properties.visible, "on"), kids);
+    if !any (tst)
+      legend ("hide");
+    endif
+
+    ## remove all properties such as "textposition" that redefines
+    ## the entire legend. Also remove chidren
+    hgS.properties = rmfield (hgS.properties, ...
+                                {"userdata", "xlabel",...
+                                 "ylabel", "zlabel", "location", ...
+                                 "title", "string","orientation", ...
+                                 "visible", "textposition"});
+
+    hgS.children = [];
+
+  elseif (strcmpi (hgS.properties.tag, "colorbar"))
+    ## colorbar
+    oldax = hgS.properties.axes;
+    if (! isempty (idx = find (oldax == matchin)))
+      ax = matchin(idx+1);
+      location = hgS.properties.location;
+      h = colorbar ("peer", ax, location);
+      hgS.properties = rmfield (hgS.properties, ...
+                              {"userdata", "xlabel" ...
+                               "ylabel", "zlabel", ...
+                               "title", "axes"});
+      hgS.children= [];
+    else
+      error ("hdl2struct: didn't find an object")
+    endif
+  endif
+  hgSout = hgS;
+endfunction
+
+function [h] = createline (hgS, par);
+  h = line ("parent", par);
+  addmissingprops (h, hgS.properties);
+endfunction
+
+function [h, hgSout] = createpatch (hgS, par);
+  prp.faces = hgS.properties.faces;
+  prp.vertices = hgS.properties.vertices;
+  prp.facevertexcdata = hgS.properties.facevertexcdata;
+  h = patch (prp);
+  set (h, "parent", par);
+  hgS.properties = rmfield (hgS.properties,
+                            {"faces", "vertices", "facevertexcdata"});
+  addmissingprops (h, hgS.properties);
+  hgSout = hgS;
+endfunction
+
+function [h] = createtext (hgS, par);
+  h = text ("parent", par);
+  addmissingprops (h, hgS.properties)
+endfunction
+
+function [h] = createimage (hgS, par);
+  h = image ("parent", par);
+  addmissingprops (h, hgS.properties)
+endfunction
+
+function [h] = createsurface (hgS, par);
+  h = surface ("parent", par);
+  addmissingprops (h, hgS.properties)
+endfunction
+
+function [h, hgSout, matchout] = createhg (hgS, matchin, par, hilev)
+  ## Here we infer from properties the type of hggroup we should build
+  ## an call corresponding high level functions
+  ## We manually set "hold on" to avoid next hggroup be deleted
+  ## the proper value of axes "nextplot" will finally be recovered
+
+  hold on;
+  if (hilev)
+    [h, hgS, matchin] = createhg_hilev (hgS, matchin, par);
+    if (numel (hgS.children) != numel (get (h).children))
+      warning (["struct2hdl: couldn't infer the hggroup type. ", ...
+                "Will build objects but listener/callback functions ", ...
+                "will be lost"]);
+      if isfield (h, "bargroup")
+        delete (get (h).bargroup);
+      else
+        delete (h);
+      endif
+      h = hggroup ("parent", par);
+      addmissingprops (h, hgS.properties);
+      hgS.special = [];
+    else
+      oldkids = hgS.children;
+      newkids = get (h).children;
+      nkids = numel (oldkids);
+      ii = 1;
+      while nkids
+        matchin = [matchin [oldkids(ii++).handle; newkids(nkids--)]];
+      endwhile
+    endif
+  else
+    h = hggroup ("parent", par);
+    addmissingprops (h, hgS.properties);
+    hgS.special = [];
+  endif
+  hgSout = hgS;
+  matchout = matchin;
+endfunction
+
+function [h, hgSout, matchout] = createhg_hilev (hgS, matchin, par)
+  fields = hgS.properties;
+  if (isfield (fields, "contourmatrix"))
+    ## contours
+    xdata = hgS.properties.xdata;
+    ydata = hgS.properties.ydata;
+    zdata = hgS.properties.zdata;
+    levellist = hgS.properties.levellist;
+    textlist = hgS.properties.textlist;
+
+    ## contour creation
+    if (isempty (hgS.children(1).properties.zdata))
+      if (strcmpi (hgS.properties.fill, "on"))
+        [cm2, h] = contourf (xdata, ydata, zdata, levellist);
+      else
+        [cm2, h] = contour (xdata, ydata, zdata, levellist);
+      endif
+
+      ## labels
+      if (strcmpi (hgS.properties.showtext, "on"))
+        clabel (cm2, h, textlist);
+      endif
+    else
+      [cm2, h] = contour3 (xdata, ydata, zdata, levellist);
+    endif
+
+    ## delete already set properties and children
+    hgS.properties = rmfield (hgS.properties, ...
+                              {"xdata", "ydata", "zdata", ...
+                               "contourmatrix", "levellist", ...
+                               "fill", "labelspacing", ...
+                               "levellistmode", "levelstep", ...
+                               "levelstepmode", "textlist"...
+                               "textlistmode" , "textstep", ...
+                               "textstepmode", "zlevel", ...
+                               "zlevelmode"});
+
+  elseif (isfield (fields, "udata") && isfield (fields, "vdata"))
+    ## quiver
+    xdata = hgS.properties.xdata;
+    ydata = hgS.properties.ydata;
+
+    udata = hgS.properties.udata;
+    vdata = hgS.properties.vdata;
+
+    h = quiver (xdata, ydata, udata, vdata);
+
+    ## delete already set properties and children
+    hgS.properties = rmfield (hgS.properties, ...
+                              {"xdata", "ydata", "zdata", ...
+                               "xdatasource", "ydatasource", "zdatasource", ...
+                               "udata", "vdata", "wdata", ...
+                               "udatasource", "vdatasource", "wdatasource"});
+
+  elseif (isfield (fields, "format"))
+    ##errorbar
+    form = hgS.properties.format;
+    xdata = hgS.properties.xdata;
+    ydata = hgS.properties.ydata;
+    xldata = hgS.properties.xldata;
+    ldata = hgS.properties.ldata;
+    xudata = hgS.properties.xudata;
+    udata = hgS.properties.udata;
+
+    switch form
+      case "xerr"
+        h = errorbar (xdata, ydata, xldata, xudata, ">");
+      case "yerr"
+        h = errorbar (xdata, ydata, ldata, udata, "~");
+      case "xyerr"
+        h = errorbar (xdata, ydata, xldata, xudata, ldata, udata, "~>");
+      case "box"
+        h = errorbar (xdata, ydata, xldata, xudata, "#");
+      case "boxy"
+        h = errorbar (xdata, ydata, ldata, udata, "#~");
+      case "boxxy"
+        h = errorbar (xdata, ydata, xldata, xudata, ldata, udata, "#~>");
+      otherwise
+        error ("struct2hdl: couldn't guess the errorbar format")
+    endswitch
+    ## delete already set properties
+    hgS.properties = rmfield (hgS.properties, ...
+                              {"xdata", "ydata", ...
+                               "xldata", "ldata", ...
+                               "xudata", "udata", ...
+                               "xldatasource", "ldatasource", ...
+                               "xudatasource", "udatasource", ...
+                               "format"});
+
+  elseif (isfield (fields, "bargroup"))
+    ## bar plot
+    ## FIXME - here we don't have access to brothers so we first create all
+    ## the barseries of the bargroup (but the last), then retrieve information,
+    ## and rebuild the whole bargroup.
+    ## The duplicate are deleted after calling "setprops"
+
+    bargroup = hgS.properties.bargroup;
+    oldh = hgS.handle;
+
+    temp = arrayfun (@(x) any(x == bargroup), [matchin(1:2:end) oldh]);
+    tst = sum (temp) == length (bargroup);
+
+    if (isscalar (bargroup) || !tst)
+      xdata = hgS.properties.xdata;
+      ydata = hgS.properties.ydata;
+
+      h = bar (xdata, ydata);
+
+      ## delete already set properties,
+      hgS.properties = rmfield (hgS.properties, ...
+                                {"xdata", "ydata", ...
+                                 "xdatasource", "ydatasource", ...
+                                 "bargroup", ...
+                                 "barwidth", "baseline"});
+    else
+      xdata = [];
+      ydata = [];
+
+      ##build x/y matrix
+      nbar = length (bargroup);
+      tmp = struct ("handle", NaN,"type", "", "children", [], "special", []);
+      for ii = 1:(nbar - 1)
+        idx = find (matchin(1:2:end) == bargroup(ii)) * 2;
+        hdl = matchin (idx);
+        xdata = [xdata get(hdl).xdata];
+        ydata = [ydata get(hdl).ydata];
+        tmp.children(ii) = hdl2struct (hdl);
+      endfor
+
+      xdata = [xdata hgS.properties.xdata];
+      ydata = [ydata hgS.properties.ydata];
+      width = hgS.properties.barwidth;
+      h = bar (ydata, width);
+
+      ## replace previous handles in "match", copy props and delete redundant
+      for ii = 1:(nbar - 1)
+        props = tmp.children(ii).properties;
+        bl = props.baseline;
+        tmp.children(ii).properties = rmfield (props, {"baseline", "bargroup"});
+        setprops (tmp.children(ii), h(ii), matchin, 1);
+        delete (tmp.children(ii).handle);
+        delete (bl);
+        idxpar = find (matchin == tmp.children(ii).handle);
+        matchin (idxpar) = h(ii);
+        idxkid = idxpar - 2;
+        matchin (idxkid) = get (h(ii), "children");
+      endfor
+      matchin (2,((end-nbar+2):end)) = h (1:(end-1));
+      h = h (end);
+
+      ## delete already set properties ,
+      hgS.properties = rmfield (hgS.properties, ...
+                                {"xdata", "ydata", "bargroup"...
+                                 "barwidth", "baseline"});
+    endif
+  elseif (isfield (fields, "baseline"))
+    ## stem plot
+    xdata = hgS.properties.xdata;
+    ydata = hgS.properties.ydata;
+
+    h = stem (xdata, ydata);
+
+    ## delete already set properties,
+    hgS.properties = rmfield (hgS.properties, ...
+                              {"xdata", "ydata", ...
+                               "xdatasource", "ydatasource", ...
+                               "baseline"});
+  elseif (isfield (fields, "basevalue"))
+    ## area plot
+    xdata = hgS.properties.xdata;
+    ydata = hgS.properties.ydata;
+    level = hgS.properties.basevalue;
+
+    h = area (xdata, ydata, level);
+
+    ## delete already set properties,
+    hgS.properties = rmfield (hgS.properties, ...
+                              {"xdata", "ydata", ...
+                               "xdatasource", "ydatasource"});
+  else
+    warning ("struct2hdl: couldn't infer the hggroup type. Will build objects but listener/callback functions will be lost");
+    h = hggroup ("parent", par);
+    addmissingprops (h, hgS.properties);
+    hgS.special = [];           # children will be treated as normal children
+  endif
+  hgSout = hgS;
+  matchout = matchin;
+endfunction
+
+function setprops (hgS, h, matchin, hilev)
+  more off
+  if (strcmpi (hgS.properties.tag, ""))
+    specs = hgS.children(hgS.special);
+    hdls = arrayfun (@(x) x.handle, specs);
+    nh = length(hdls);
+    msg = "";
+    if (! nh)
+      set (h, hgS.properties);
+    else
+      ## Specials are objects that where automatically constructed with
+      ## current object. Among them are "x(yz)labels", "title", high
+      ## level hggroup children
+      fields = fieldnames (hgS.properties);
+      vals = struct2cell (hgS.properties);
+      idx = find (cellfun (@(x) valcomp(x, hdls) , vals));
+      hgS.properties = rmfield (hgS.properties, fields(idx));
+
+      ## set all properties but special handles
+      set (h, hgS.properties);
+
+      ## find  props with val == (one of special handles)
+      nf = length (idx);
+      fields = fields(idx);
+      vals = vals(idx);
+      while nf
+        field = fields{nf};
+        idx = find (hdls == vals{nf});
+        spec = specs(idx);
+        if (isprop (h, field))
+           h2 = get (h , field);
+           set (h2, spec.properties);
+        endif
+        nf--;
+      endwhile
+
+      ## If hggroup children  were created by high level functions,
+      ## copy only usefull properties.
+      if (hilev)
+        if (strcmpi (hgS.type, "hggroup"))
+          nold = numel (hgS.children);
+          nnew = numel (get(h).children);
+
+          if (nold == nnew)
+            hnew = get(h).children;
+            ii = 1;
+            while ii <= nnew
+              try
+                set (hnew (ii), "displayname", ...
+                     hgS.children(ii).properties.displayname);
+              catch
+                sprintf ("struct2hdl: couldn't set hggroup children #%d props.", ii)
+              end_try_catch
+              ii ++;
+            endwhile
+
+          else
+            error ("struct2hdl: non-conformant number of children in hgggroup")
+          endif
+        endif
+      endif
+    endif
+
+  elseif (strcmpi (hgS.properties.tag, "legend")
+          || strcmpi (hgS.properties.tag, "colorbar"))
+    set (h, hgS.properties);
+  endif
+
+endfunction
+
+function out = valcomp (x, hdls)
+  if (isfloat(x) && isscalar(x))
+    out = any (x == hdls);
+  else
+    out = 0;
+  endif
+endfunction
+
+function addmissingprops (h, props)
+  hid = {"autopos_tag", "looseinset"};
+  oldfields = fieldnames (props);
+  curfields = fieldnames (get (h));
+  missing = cellfun (@(x) !any (strcmp (x, curfields)), oldfields);
+  idx = find (missing);
+  for ii = 1:length(idx)
+    prop = oldfields{idx(ii)};
+    if (! any (strcmp (prop, hid)))
+      addproperty (prop, h, "any");
+    endif
+  endfor
+endfunction