tabpanelfcn(fcn, varargin)

function handles = tabpanelfcn(fcn, varargin)
%TABPANELFCN Helper function for tab panels constructed using GUIDE.
%
% handles = tabpanelfcn('make_groups', group_name, panel_names, handles, 1);
% - Puts a field into handles for each entry in the cell array panel_names.
%   These fields contain a list of all component handles with UserData matching
%   the name in panel_names.
% - Puts a field into the handles structure called GROUP_NAME_all for easy 
%   visibility handling.
% 
% handles = tabpanelfcn('tab_group_handler', hObject, handles, group_name);
% - Hides components linked to group_name with user data not matching that of
%   hObject.
% - Shows components linked to group_name with the same user data as hObject
% - Raises the selected tab 2 pixels and returns the last_tab to its previous
%   position.
% - Updates the last_tab field.
%
% Note: UserData for panels must be unique for all tab groups in a figure.

switch fcn
 case 'tab_group_handler'
  handles = tab_group_handler(varargin{:});
 case 'make_groups'
  handles = make_groups(varargin{:});
 otherwise
  error('Unrecognized command option.  See HELP TABPANELFCN');
end


% --- helper function for tab buttons
% --- Makes controls for selected tab visible and hides others
% --- Note: this modifies the handles structure - caller must store
function handles = tab_group_handler(hObject, handles, group_name)

if ~isfield(handles,'last_tab') | handles.last_tab ~= hObject
    % define some constants for to improve cross platform look and feel
    if ispc
        edge_offset   = 1;
        bottom_offset = 1;
        width_offset  = 3;
        height        = 1;
    elseif isunix
        edge_offset   = 3;
        bottom_offset = 0;
        width_offset  = 6;
        height        = 2;
    end
    
    % create the blank text object if it has not been created yet
    if ~isfield(handles, 'blank_patch')
        handles.blank_patch = uicontrol('style','text', ...
            'units','pixels','Position',[0,0,1,height]);%,'backg','r');
    end
    
    % make only my children visible
    my_kids = getfield(handles, get(hObject,'UserData'));
    set(getfield(handles,[group_name, '_all']),'Visible','off');
    set(my_kids,'Visible','on');
    
    % make sure my kids are on top
    uistack(my_kids,'top');
    
    % get locations for patch and this button
    old_patch_position = get_position_using_pixels(handles.blank_patch);
    old_this_position = get_position_using_pixels(hObject);

    % move the patch under this button
    new_patch_position = old_patch_position;
    % make sure bottom is correct
    new_patch_position(2) = old_this_position(2) + bottom_offset;
    % adjust left edge position
    new_patch_position(1) = old_this_position(1) + edge_offset;
    % adjust width
    new_patch_position(3) = old_this_position(3) - width_offset;
    % update position
    set_position_using_pixels(handles.blank_patch, new_patch_position);
    
    % make this button 3 pixels taller and one pixel lower to give it a raised look
    new_this_position = old_this_position;
    new_this_position(2) = new_this_position(2) - 1;
    new_this_position(4) = new_this_position(4) + 2;
    set_position_using_pixels(hObject, new_this_position);
    
    % shrink previous button to original size and location
    if isfield(handles,'last_tab')
        old_last_tab_position = get_position_using_pixels(handles.last_tab);
        old_last_tab_position(4) = old_last_tab_position(4) - 2;
        old_last_tab_position(2) = old_last_tab_position(2) + 1;
        set_position_using_pixels(handles.last_tab, old_last_tab_position);
    end
    
    % update last_tab
    handles.last_tab = hObject;
    
end


% --- helper function for tab buttons
% --- Updates handles structure with fields for tab_group_handler
function handles = make_groups(group_name, panel_names, handles, top_panel_index)

all_panel_children = [];
for i = 1:length(panel_names)
    % find all the components with the given UserData - this will include the
    % tab push button
    this_set = findobj(handles.figure1, 'UserData', panel_names{i});
    % remove the tab push button from the list
    this_set = setdiff(this_set, getfield(handles, group_name));
    % update the handles structure with a new field for these handles - all
    % the components belonging to the panel with this UserData
    handles = setfield(handles, panel_names{i}, this_set);
    % keep a list of all panel children for access later
    all_panel_children = [all_panel_children, this_set];
end

% store all panel children for later showing/hiding
handles = setfield(handles, [group_name, '_all'], all_panel_children);

% bring top panel to front by faking a click on top panel's toggle button
top_panel_name = panel_names{top_panel_index};
toggle_button_handle = findobj(handles.figure1, ...
                               'UserData', top_panel_name, ...
                               'Tag', group_name);
handles = tab_group_handler(toggle_button_handle, handles, group_name);

% --- helper function for setting position
function set_position_using_pixels(hObject, position)
old_units = get(hObject, 'Units');
set(hObject, 'Units', 'pixels');
was_error = 0;
try
    set(hObject, 'Position', position)
catch
    was_error = 1;
end
set(hObject, 'Units', old_units);
if was_error
    error(lasterr);
end

% --- helper function for getting position
function position = get_position_using_pixels(hObject)
old_units = get(hObject, 'Units');
set(hObject, 'Units', 'pixels');
position = get(hObject, 'Position');
set(hObject, 'Units', old_units);