import sys, os, string

def vtkLoadPythonTkWidgets(interp):
    """vtkLoadPythonTkWidgets(interp) -- load vtk-tk widget extensions

    This is a mess of mixed python and tcl code that searches for the
    shared object file that contains the python-vtk-tk widgets.  Both
    the python path and the tcl path are searched.
    """
    name = 'vtkRenderingPythonTkWidgets'
    pkgname = string.capitalize(string.lower(name))

    # find out if the file is already loaded
    loaded = interp.call('info', 'loaded')
    if string.find(loaded, pkgname) >= 0:
        return

    # create the platform-dependent file name
    prefix = ''
    if sys.platform == 'cygwin':
        prefix = 'cyg'
    elif os.name == 'posix':
        prefix = 'lib'
    extension = interp.call('info', 'sharedlibextension')
    filename = prefix+name+extension

    # create an extensive list of paths to search
    pathlist = sys.path
    # add tcl paths, ensure that {} is handled properly
    try:
        auto_paths = string.split(interp.getvar('auto_path'))
    except AttributeError:
        auto_paths = interp.getvar('auto_path')
    for path in auto_paths:
        prev = str(pathlist[-1])
        try:            
            # try block needed when one uses Gordon McMillan's Python
            # Installer.
            if len(prev) > 0 and prev[0] == '{' and prev[-1] != '}':
                pathlist[-1] = prev+' '+path
            else:
                pathlist.append(path)
        except AttributeError:
            pass
    # a common place for these sorts of things  
    if os.name == 'posix':
        pathlist.append('/usr/local/lib')

    # attempt to load
    for path in pathlist:
        try:
            # try block needed when one uses Gordon McMillan's Python
            # Installer.
            if len(path) > 0 and path[0] == '{' and path[-1] == '}':
                path = path[1:-1]
            fullpath = os.path.join(path, filename)
        except AttributeError:
            pass
        if ' ' in fullpath:
            fullpath = '{'+fullpath+'}'
        if interp.eval('catch {load '+fullpath+' '+pkgname+'}') == '0':
            return

    # re-generate the error
    interp.call('load', filename)
    
