function [g,info] = gabwin(g,a,M,varargin);
%GABWIN  Compute a Gabor window from text or cell array
%   Usage: [g,info] = gabwin(g,a,M,L);
%
%   [g,info]=GABWIN(g,a,M,L) computes a window that fits well with the
%   specified number of channels M, time shift a and transform length
%   L. The window itself is specified by a text description or a cell array
%   containing additional parameters.
%
%   The window can be specified directly as a vector of numerical
%   values. In this case, GABWIN only checks assumptions about transform
%   sizes etc.
%
%   [g,info]=GABWIN(g,a,M) does the same, but the window must be a FIR
%   window, as the transform length is unspecified.
%
%   GABWIN(g,a,M,L,lt) or GABWIN(g,a,M,[],lt) does as above but for a
%   non-separable lattice specified by lt. Please see the help of
%   MATRIX2LATTICETYPE for a precise description of the parameter lt.
%
%   The window can be specified as one of the following text strings:
%  
%     'gauss'      Gaussian window fitted to the lattice,
%                  i.e. tfr=a*M/L.
%
%     'dualgauss'  Canonical dual of Gaussian window.
%
%     'tight'      Tight window generated from a Gaussian.
%
%   In these cases, a long window is generated with a length of L.
%
%   It is also possible to specify one of the window names from FIRWIN. In
%   such a case, GABWIN will generate the specified FIR window with a length
%   of M.
%
%   The window can also be specified as cell array. The possibilities are:
%
%     {'gauss',...}
%         Additional parameters are passed to PGAUSS.
%
%     {'dual',...}
%         Canonical dual window of whatever follows. See the examples below.
%
%     {'tight',...} 
%         Canonical tight window of whatever follows.
%
%   It is also possible to specify one of the window names from FIRWIN as
%   the first field in the cell array. In this case, the remaining
%   entries of the cell array are passed directly to FIRWIN.
%
%   Some examples: To compute a Gaussian window of length L fitted for a
%   system with time-shift a and M channels use:
%
%     g=gabwin('gauss',a,M,L);
%
%   To compute Gaussian window with equal time and frequency support
%   irrespective of a and M*:
%
%     g=gabwin({'gauss',1},a,M,L);
%
%   To compute the canonical dual of a Gaussian window fitted for a
%   system with time-shift a and M channels:
%
%     gd=gabwin('gaussdual',a,M,L);
%
%   To compute the canonical tight window of the Gaussian window fitted
%   for the system:
%
%     gd=gabwin({'tight','gauss'},a,M,L);
%
%   To compute the dual of a Hann window of length 20:  
% 
%     g=gabwin({'dual',{'hann',20}},a,M,L);
%
%   The structure info provides some information about the computed
%   window:
%
%     info.gauss
%        True if the window is a Gaussian.
%
%     info.tfr
%        Time/frequency support ratio of the window. Set whenever it makes sense.
%
%     info.wasrow
%        Input was a row window
%
%     info.isfir
%        Input is an FIR window
%
%     info.isdual
%        Output is the dual window of the auxiliary window.
%
%     info.istight
%        Output is known to be a tight window.
%
%     info.auxinfo
%        Info about auxiliary window.
%   
%     info.gl
%        Length of window.
%
%   See also: pgauss, firwin, wilwin
%
%   Url: http://ltfat.github.io/doc/gabor/gabwin.html

% Copyright (C) 2005-2015 Peter L. Soendergaard <peter@sonderport.dk>.
% This file is part of LTFAT version 2.1.1
%
% 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 this program.  If not, see <http://www.gnu.org/licenses/>.
  
% Assert correct input.
if nargin<3
  error('%s: Too few input parameters.',upper(mfilename));
end;

definput.keyvals.L=[];
definput.keyvals.lt=[0 1];
definput.keyvals.callfun='GABWIN';
definput.flags.phase={'freqinv','timeinv'};
[flags,kv,L,lt]=ltfatarghelper({'L','lt'},definput,varargin);

[g,info] = comp_window(g,a,M,L,lt,kv.callfun);

if (info.isfir)  
  if info.istight
      %g=g/sqrt(2);
  end;  
end;

