Pmw.MegaArchetype() - abstract base class for all Pmw megawidgets


This class is the basis for all Pmw megawidgets. It provides methods to manage options and component widgets.

This class is normally used as a base class for other classes. If the hullClass argument is specified, such as in the Pmw.MegaWidget and Pmw.MegaToplevel classes, a container widget is created to act as the parent of all other component widgets. Classes derived from these sub classes create other component widgets and options to implement megawidgets that can be used in applications.

If no hullClass argument is given to the constructor, no container widget is created and only the option configuration functionality is available.


A megawidget is generally made up of other widgets packed within the megawidget's containing widget. These sub-widgets are called the components of the megawidget and are given logical names for easy reference. The component mechanism allows the user of a megawidget to gain controlled access to some of the internals of the megawidget, for example to call a method of a component or to set a component's configuration options.

Sub components: If a component is itself a megawidget containing sub-components, then these sub-components can be referred to using the notation component_subcomponent. For example, Pmw.ComboBox has a component named entryfield which is an instance of Pmw.EntryField, which itself has a Tkinter.Entry component named entry. In the context of the combobox, this entry widget can be referred to as entryfield_entry.

Component aliases: Because the sub-component notation may make component names inconveniently long, components and sub-components can be aliased to simpler names. For example, the entryfield_entry sub-component of Pmw.ComboBox is aliased to simply entry. If there is no conflict in component names, sub-component names are usually aliased to the name of the "leaf" component.

Component groups: Similar components of a megawidget can be given a group name, which allows all components of a group to be referenced using the one group name. For example, the two arrow components of Pmw.Counter have a group name of Arrow. Also, megawidgets that can create an unlimited number of similar components, such as Pmw.ButtonBox, create each of these components with the same group name. By convention, group names begin with a capital letter.


A megawidget defines options which allow the megawidget user to modify the appearance and behaviour of the megawidget. Using the same technique as Tkinter widgets, the values of megawidget options may be set in calls to the constructor and to configure() and the values may be queried by calls to cget() and configure(). Like Tkinter widgets, megawidget options are initialised with default values. Also, if the useTkOptionDb option to Pmw.initialise() has been set, then the Tk option database will be queried to get the initial values. Strings found in the option database are converted to python objects (integer, float, tuple, dictionary, etc) using a restricted eval() call. Anything that is not accepted by eval() is treated as a string.

Inherited options: As well as the options defined in a class, a derived class inherits all options of its base classes. The default value of an option defined by a base class may be modified by the derived class.

Initialisation options: Some megawidget options can only be set in the call to the constructor. These are called initialisation options. Unlike normal configuration options, they cannot be set by calling the configure() method.

Component options: Options of the components of a megawidget can be referred to using the notation component_option. Like the megawidget options, component options can be used in calls to the constructor and to the cget() and configure() methods. For example, the state option of the Tkinter.Text text component of Pmw.ScrolledText may be set by calling

 widget.configure(text_state = 'disabled')

Sub-components, component aliases and component groups may also be combined with options. For example, the state option of the entryfield_entry component of Pmw.ComboBox may be set by calling

 combobox.configure(entryfield_entry_state = 'normal')

Since it has an alias, it is more convenient to use the equivalent form

 combobox.configure(entry_state = 'normal')

Also, the background color of both arrows of Pmw.Counter can be set using the Arrow component group.

 counter.configure(Arrow_background = 'aliceblue')

The pyclass component option

The pyclass component option is a special notation that can be used to specify a non-default python class for a component. This can only be used when the component is being constructed. For a component created during the construction of its parent megawidget, this option must be given to the constructor in the form component_pyclass. For example, to change the python class of the text sub-component of Pmw.TextDialog to a class FontText.Text

 dialog = Pmw.TextDialog(text_pyclass = FontText.Text)

For components created after the construction of the parent megawidget, the pyclass option must be passed into the method which constructs the component. For example, to set the python class of a button in Pmw.ButtonBox to a class MyButton:

 buttonBox.add('special', pyclass = MyButton)

The new python class of the component must support all methods and options that are used by the megawidget when operating on the component. The exact interface required for each component is not documented. You will have to examine the Pmw source code. However, any class derived from the default class of a component can be used as the new class of the component, as long as all of the original methods and options are still supported. For example, any class derived from Tkinter.Text can be used as the class of the text sub-component of Pmw.TextDialog.

The pyclass component option should not be confused with the class option that some of the Tk widgets support. The class option sets the Tk option database class for the widget and is used by Tk to query the database for the default values of the widget's other options. The name pyclass was chosen so that it did not conflict with any known Tk options.


The constructors of classes derived from this class all accept the same arguments: one positional argument and any number of keyword arguments. The positional argument defaults to None (meaning the root window) and specifies the widget to use as the parent when creating the megawidget's hull component. The keyword arguments define initial values for options. The format for the constructors of derived classes is:

   def __init__(self, parent = None, **kw):


Add additional options for this megawidget. The optionDefs argument is treated in the same way as for the defineoptions() method.

This method is for use by derived classes. It is only used if a megawidget should conditionally define some options, perhaps depending on the value of other options. Usually, megawidgets unconditionally define all their options in the call to defineoptions() and do not need to use addoptions(). This method must be called after the call to defineoptions() and before the call to initialiseoptions().

Return the current value of option (which should be in the format described in the Options section). This method is also available using object subscripting, for example myWidget['font']. Unlike Tkinter's cget(), which always returns a string, this method returns the same value and type as used when the option was set (except where option is a component option and the component is a Tkinter widget, in which case it returns the string returned by Tcl/Tk).

Return the component widget whose name is name. This allows the user of a megawidget to access and configure component widgets directly.

Return the list of aliases for components. Each item in the list is a tuple whose first item is the name of the alias and whose second item is the name of the component or sub-component it refers to.

Return the group of the component whose name is name or None if it does not have a group.

Return a sorted list of names of the components of this megawidget.

configure(option = None, **kw)
Query or configure the megawidget options.

If no arguments are given, return a tuple consisting of all megawidget options and values, each as a 5-element tuple (name, resourceName, resourceClass, default, value). This is in the same format as the value returned by the standard Tkinter configure() method, except that the resource name is always the same as the option name and the resource class is the option name with the first letter capitalised.

If one argument is given, return the 5 element tuple for option.

Otherwise, set the configuration options specified by the keyword arguments. Each key should be in the format described in the Options section.

createcomponent(componentName, componentAliases, componentGroup, widgetClass, *widgetArgs, **kw)
Create a component widget by calling widgetClass with the arguments given by widgetArgs and any keyword arguments. The componentName argument is the name by which the component will be known and must not contain the underscore, '_', character. The componentGroup argument specifies the group of the component. The componentAliases argument is a sequence of 2-element tuples, whose first item is an alias name and whose second item is the name of the component or sub-component it is to refer to.

If this method is called during megawidget construction, any component options supplied to the megawidget constructor which refer to this component (by componentName or componentGroup) are added to the kw dictionary before calling widgetClass. If the dictionary contains a 'pyclass' key, then this item is removed from the dictionary and the value is used instead of widgetClass. For more details see The pyclass component option section.

This method may be called by derived classes during or after megawidget construction. It returns the instance of the class created.

createlabel(parent, childCols = 1, childRows = 1)
Create a Tkinter.Label component named 'label' in the parent widget. This is a convenience method used by several megawidgets that require an optional label. The widget must have options named labelpos and labelmargin. If labelpos is None, no label is created. Otherwise, a label is created and positioned according to the value of labelpos and labelmargin. The label is added to the parent using the grid() method, with childCols and childRows indicating how many rows and columns the label should span. Note that all other child widgets of the parent must be added to the parent using the grid() method. The createlabel() method may be called by derived classes during megawidget construction.

defineoptions(keywords, optionDefs, dynamicGroups = ())
Create options for this megawidget. The optionDefs argument defines the options. It is a sequence of 3-element tuples, (name, default, callback), where name is the name of the option, default is its default value and callback is the function to call when the value of the option is set by a call to configure(). The keywords argument should be the keyword arguments passed in to the constructor of the megawidget. The user may override the default value of an option by supplying a keyword argument to the constructor.

If any option created by a base class is also defined by optionDefs, then the derived class's default value will take precedence over the base class's. If the callback field is not None, then this will also override the callback set by the base class.

If callback is Pmw.INITOPT, then the option is an initialisation option.

The dynamicGroups argument contains a list of the groups of the components created dynamically by this megawidget. If a group is included in this list, then it not an error if a keyword argument for the group is given to the constructor or to configure(), even when no components with this group have been created.

If defineoptions() is called, it must be called once in the megawidget constructor before the call to the constructor of the base class and there must be a matching call to initialiseoptions() at the end of the constructor.

Destroy the hull component widget, if it exists, including all of its children.

Remove the megawidget component called name. This method may be called by derived classes to destroy a megawidget component. It destroys the component widget and then removes all record of the component from the megawidget.

Return true if the Tk widget corresponding to the hull component has been destroyed.

initialiseoptions(dummy = None)
Check keyword arguments and call option callback functions. This method must be called, at the end of a megawidget constructor, if and only if defineoptions() was also called in the constructor. The dummy argument is not required, but is retained for backwards compatibility.

It checks that all keyword arguments given to the constructor have been used. If not, it raises an error indicating which arguments were unused. A keyword is defined to be used if, during the construction of a megawidget, it is defined in a call to defineoptions() or addoptions() (by the megawidget or one of its base classes), or it references, by name, a component of the megawidget, or it references, by group, at least one component. It also calls the configuration callback function for all options that have a callback.

This method is only effective when called by the constructor of the leaf class, that is, the class in the class hierarchy which first called defineoptions(). For all other classes in the class hierarchy (base classes), the method returns immediately.

Return the widget framing the interior space in which any children of this megawidget should be created. By default, this returns the hull component widget, if one was created, or None otherwise. A subclass should use the widget returned by interior() as the parent of any components or sub-widgets it creates. Megawidgets which can be further subclassed, such as Pmw.Dialog, should redefine this method to return the widget in which subclasses should create children. The overall containing widget is always available as the hull component.

If option is an initialisation option, return true. Otherwise, return false (the option is a configuration option). The option argument must be an option of this megawidget, not an option of a component. Otherwise an exception is raised.

Return a sorted list of this megawidget's options. Each item in the list is a 3-element tuple, (option, default, isinit), where option is the name of the option, default is its default value and isinit is true if the option is an initialisation option.

Pmw 1.3 - 6 Aug 2007 - Home
Manual page last reviewed: 22 May 1998