function ax = ObserveAxesNextPlot(ax, hsave)

%

% Helper fcn for preparing axes for nextplot, optionally

% preserving specific existing descendants

% GUARANTEED to return an axes in the same figure as the passed-in

% axes, even if that axes gets deleted by an overzealous create or

% delete fcn anywhere in the figure.

% for performance only call ancestor when needed

fig = ax.Parent; 

if ~isempty(fig) && ~strcmp(fig.Type,'figure') 

    fig = ancestor(fig,'figure');

end 

switch ax.NextPlot 

    case 'replaceall' 

        cla(ax, 'reset', hsave);

    case 'replace' 

        % If there are multiple data spaces, ax.prepareForPlot() will do a

        % reset of the properties for the active data space (while

        % preserving other data spaces) and return false to indicate that a

        % full reset is not necessary. Otherwise, ax.prepareForPlot() will

        % return true.

        if (ax.prepareForPlot()) 

            cla(ax, 'reset', hsave); 

        else

            cla(ax, hsave);

        end 

    case 'replacechildren' 

        cla(ax, hsave);

    case 'add' 

        % nothing

end 

if ~any(ishghandle(ax)) && isempty(hsave) 

    if ~any(ishghandle(fig))

        ax = axes;

    else

        ax = axes('Parent',fig);

    end

end