Pmw.MessageBar() - information line for displaying short messages




A message bar contains a single-line message display area. Messages of several different types may displayed. Messages are cleared after a period defined for each message type. Each message type has a priority so that if the application attempts to display more than one message at a time, the message with the highest priority will be displayed. Messages may be accompanied by a number of audible bells.

This megawidget can be used for both interactive help messages (when the mouse enters certain widgets) and also for other general messages.

To perform the help function it can cooperate with the Pmw.Balloon megawidget so that the programmer (or user) can choose either balloon help, message bar help, both or neither.

This megawidget supports a configurable number of message types. The default types include 'state', 'help', 'usererror' and 'systemerror'. The difference between these are the length of time they are displayed, the number of bells that are rung and the priority of the message. For example, the 'help' message type is lower in priority than the 'usererror', so that error messages will always be displayed in preference to help messages regardless of the order the messages are created. The 'state' message type is lowest in priority but has no timeout, so it should contain messages describing the current state of the application, such as Waiting for database connection or 'Waiting for file to be unlocked'. Generally this should be set to the empty string when the application is running normally. By default the help messages (with message type 'help') time out after 5 seconds, so that if the cursor happens to be left over a widget, the application state will be redisplayed after a short time.


Options for this megawidget and its base classes are described below.

Initialisation option. If the labelpos option is not None, this specifies the distance between the label component and the rest of the megawidget. The default is 0.

Initialisation option. Specifies where to place the label component. If not None, it should be a concatenation of one or two of the letters 'n', 's', 'e' and 'w'. The first letter specifies on which side of the megawidget to place the label. If a second letter is specified, it indicates where on that side to place the label. For example, if labelpos is 'w', the label is placed in the center of the left hand side; if it is 'wn', the label is placed at the top of the left hand side; if it is 'ws', the label is placed at the bottom of the left hand side.

If None, a label component is not created. The default is None.

Initialisation option. This defines what message types are supported by the message bar and the characteristics of those message types. It is a dictionary where the key is a string specifying a message type and the value is a tuple of four integers, (priority, showtime, bells, logmessage), where priority is the rank of the message type, showtime is the number of seconds to display messages of this message type, bells is the number of audible bells to ring and logmessage is a boolean specifying whether this message should be logged for retrieval later. Messages with a higher priority are displayed in preference to those with lower priority. If a high priority message times out (because it has been displayed for showtime seconds), then a lower priority message may be displayed. A showtime of 0 means that the message will never time out and is useful for displaying messages describing the current state of the application as opposed to messages describing events. Logging is not currently implemented. The default is

     'systemerror'  : (5, 10, 2, 1),
     'usererror'    : (4, 5, 1, 0),
     'busy'         : (3, 0, 0, 0),
     'systemevent'  : (2, 5, 0, 0),
     'userevent'    : (2, 5, 0, 0),
     'help'         : (1, 5, 0, 0),
     'state'        : (0, 0, 0, 0),
If true, no audible bells will sound, regardless of the value for bells defined in the messagetypes option. The default is 0.

Initialisation option. The default is 'ew'.


Components created by this megawidget and its base classes are described below.

The widget where the messages are displayed. Long messages may be scrolled horizontally by dragging with the middle mouse button. By default, this component is a Tkinter.Entry.

This acts as the body for the entire megawidget. Other components are created as children of the hull to further specialise this class. By default, this component is a Tkinter.Frame.

If the labelpos option is not None, this component is created as a text label for the megawidget. See the labelpos option for details. Note that to set, for example, the text option of the label, you need to use the label_text component option. By default, this component is a Tkinter.Label.


Only methods specific to this megawidget are described below. For a description of its inherited methods, see the manual for its base class Pmw.MegaWidget. In addition, methods from the Tkinter.Entry class are forwarded by this megawidget to the entry component.

A convenience method to display text in the message bar according to the characteristics defined by the help message type. Equivalent to message('help', text).

message(type, text)
Display text in the message bar according to the characteristics defined by the type message type, as discussed under messagetypes.

Clear the type message and all message types with a lower priority, except permanent messages, such as state. This is useful to clear the busy message and any outstanding event and help messages.


The image at the top of this manual is a snapshot of the window (or part of the window) produced by the following code.

class Demo:
    def __init__(self, parent):
        # Create and pack the MessageBar.
        self._messagebar = Pmw.MessageBar(parent,
                entry_width = 40,
                labelpos = 'w',
                label_text = 'Status:')
        self._messagebar.pack(side = 'bottom', fill = 'x',
                expand = 1, padx = 10, pady = 10)

        # Create and pack the ScrolledListBox to change the MessageBar. = Pmw.ScrolledListBox(parent,
                items=('state', 'help', 'userevent', 'systemevent',
                        'usererror', 'systemerror', 'busy',),
                label_text='Message type',
                selectioncommand=self.selectionCommand) = 'both', expand = 'yes', padx = 10, pady = 10)

        self._index = 0
        self._stateCounter = 0

    def selectionCommand(self):
        sels =
        if len(sels) > 0:
            self._index = self._index + 1
            messagetype = sels[0]
            if messagetype == 'state':
                self._stateCounter = (self._stateCounter + 1) % 3
                text = stateMessages[self._stateCounter]
                if text != '':
                    text = text + ' (' + messagetype + ')'
                self._messagebar.message('state', text)
                text = messages[messagetype]
                text = text + ' (' + messagetype + ')'
                self._messagebar.message(messagetype, text)
                if messagetype == 'busy':
                    text = 'All files successfully removed'
                    text = text + ' (userevent)'
                    self._messagebar.message('userevent', text)

messages = {
    'help': 'Save current file',
    'userevent': 'Saving file "foo"',
    'busy': 'Busy deleting all files from file system ...',
    'systemevent': 'File "foo" saved',
    'usererror': 'Invalid file name "foo/bar"',
    'systemerror': 'Failed to save file: file system full',

stateMessages = {
    0: '',
    1: 'Database is down',
    2: 'Waiting for reply from database',

Pmw 1.3 - 6 Aug 2007 - Home