Pmw.HistoryText reference manual
Description: Pmw - a toolkit for building high-level compound widgets in Python

# Pmw.HistoryText

### Name

  Pmw.HistoryText() - text widget with a course-grained form of history

### Inherits

  Pmw.ScrolledText

### Description

  A history text is a scrolled text widget with added functionality to maintain a history of each screen and allow editing of prior screens. Here, screen refers to the entire contents of the text widget. This widget does not support a fine-grained history of every change made to the text.

  Together with a few buttons and a scrolled text to display the results, a history text can be used as the query-entry part of a simple interactive text-based database query system. When the user enters and executes a query, the query (the entire contents of the text widget) is added to the history list. The user may view previous queries and either execute them again or modify them and execute the new query. If a previously executed query is modified, the user may undo or redo all changes made to the query before the query is executed.

### Options

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

  borderframe
    Initialisation option. If true, the borderframe component will be created. The default is 0.
  columnheader
    Initialisation option. If true, the columnheader component will be created. The default is 0.
  compressany
    See `addhistory()`. The default is 1.
  compresstail
    See `addhistory()`. The default is 1.
  historycommand
    This is a callback to indicate whether the currently displayed entry in the history list has a previous or next entry. The callback is given two arguments, prevstate and nextstate. If the currently displayed entry is first in the history list, then prevstate is 'disabled', otherwise it is 'normal'. If the currently displayed entry is last in the history list, then nextstate is 'disabled', otherwise it is 'normal'. These values can be used, for example, to modify the state of Next and Previous buttons that call the `next()` and `prev()` methods. The default is None.
  hscrollmode
    The horizontal scroll mode. If 'none', the horizontal scrollbar will never be displayed. If 'static', the scrollbar will always be displayed. If 'dynamic', the scrollbar will be displayed only if necessary. The default is 'dynamic'.
  labelmargin
    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.
  labelpos
    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.

  rowcolumnheader
    Initialisation option. If true, the rowcolumnheader component will be created. The default is 0.
  rowheader
    Initialisation option. If true, the rowheader component will be created. The default is 0.
  scrollmargin
    Initialisation option. The distance between the scrollbars and the text widget. The default is 2.
  usehullsize
    Initialisation option. If true, the size of the megawidget is determined solely by the width and height options of the hull component.

    Otherwise, the size of the megawidget is determined by the width and height of the text component, along with the size and/or existence of the other components, such as the label, the scrollbars and the scrollmargin option. All these affect the overall size of the megawidget. The default is 0.

  vscrollmode
    The vertical scroll mode. If 'none', the vertical scrollbar will never be displayed. If 'static', the scrollbar will always be displayed. If 'dynamic', the scrollbar will be displayed only if necessary. The default is 'dynamic'.

### Components

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

  borderframe
    A frame widget which snuggly fits around the text widget, to give the appearance of a text border. It is created with a border so that the text widget, which is created without a border, looks like it has a border. By default, this component is a tkinter.Frame.
  columnheader
    A text widget with a default height of 1 displayed above the main text widget and which scrolls horizontally in sync with the horizontal scrolling of the main text widget. By default, this component is a tkinter.Text. Its component group is Header.
  horizscrollbar
    The horizontal scrollbar. By default, this component is a tkinter.Scrollbar. Its component group is Scrollbar.
  hull
    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.
  label
    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.
  rowcolumnheader
    A text widget displayed to the top left of the main text widget, above the row header and to the left of the column header if they exist. The widget is not scrolled automatically. By default, this component is a tkinter.Text. Its component group is Header.
  rowheader
    A text widget displayed to the left of the main text widget and which scrolls vertically in sync with the vertical scrolling of the main text widget. By default, this component is a tkinter.Text. Its component group is Header.
  text
    The text widget which is scrolled by the scrollbars. If the borderframe option is true, this is created with a borderwidth of 0 to overcome a known problem with text widgets: if a widget inside a text widget extends across one of the edges of the text widget, then the widget obscures the border of the text widget. Therefore, if the text widget has no border, then this overlapping does not occur. By default, this component is a tkinter.Text.
  vertscrollbar
    The vertical scrollbar. By default, this component is a tkinter.Scrollbar. Its component group is Scrollbar.

### Methods

  Only methods specific to this megawidget are described below. For a description of its inherited methods, see the manual for its base class Pmw.ScrolledText.

  addhistory()
    Append the currently displayed text to the history list.

    If compressany is true, a new entry will be added to the history list only if the currently displayed entry has changed.

    If compresstail is true, a new entry will be added to the history list only if the currently displayed entry has changed or if it is not the last entry in the history list.

  gethistory()
    Return the history list. Each entry in the list is a 3-tuple. The first item in a history entry is the original text as added by `addhistory()`. The second item is the edited text (if the user has modified the entry but `addhistory()` has not yet been called on the text). The third item specifies whether the entry should currently display the original or modified text.
  next()
    Display the next screen in the history list.
  prev()
    Display the previous screen in the history list.
  redo()
    Reverse the effect of `undo()`.
  undo()
    Undo all changes made since this entry was added to the history list.

### Example

  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 PanedWidget to hold the query and result
              # windows.
              # !! panedwidget should automatically size to requested size
              panedWidget = Pmw.PanedWidget(parent,
                      orient = 'vertical',
                      hull_height = 400,
                      hull_width = 550)
              panedWidget.add('query', min = 0.05, size = 0.2)
              panedWidget.add('buttons', min = 0.1, max = 0.1)
              panedWidget.add('results', min = 0.05)
              panedWidget.pack(fill = 'both', expand = 1)

              # Create and pack the HistoryText.
              self.historyText = Pmw.HistoryText(panedWidget.pane('query'),
                      text_wrap = 'none',
                      text_width = 60,
                      text_height = 10,
                      historycommand = self.statechange,
              )
              self.historyText.pack(fill = 'both', expand = 1)
              self.historyText.component('text').focus()

              buttonList = (
                  [20, None],
                  ['Clear', self.clear],
                  ['Undo', self.historyText.undo],
                  ['Redo', self.historyText.redo],
                  [20, None],
                  ['Prev', self.historyText.prev],
                  ['Next', self.historyText.next],
                  [30, None],
                  ['Execute', Pmw.busycallback(self.executeQuery)],
              )
              self.buttonDict = {}

              buttonFrame = panedWidget.pane('buttons')
              for text, cmd in buttonList:
                  if type(text) == type(69):
                      frame = tkinter.Frame(buttonFrame, width = text)
                      frame.pack(side = 'left')
                  else:
                      button = tkinter.Button(buttonFrame, text = text, command = cmd)
                      button.pack(side = 'left')
                      self.buttonDict[text] = button

              for text in ('Prev', 'Next'):
                  self.buttonDict[text].configure(state = 'disabled')

              self.results = Pmw.ScrolledText(panedWidget.pane('results'), text_wrap = 'none')
              self.results.pack(fill = 'both', expand = 1)

          def statechange(self, prevstate, nextstate):
              self.buttonDict['Prev'].configure(state = prevstate)
              self.buttonDict['Next'].configure(state = nextstate)

          def clear(self):
              self.historyText.delete('1.0', 'end')

          def addnewlines(self, text):
              if len(text) == 1:
                  text = text + '\n'
              if text[-1] != '\n':
                  text = text + '\n'
              if text[-2] != '\n':
                  text = text + '\n'
              return text

          def executeQuery(self):
              sql = self.historyText.get()
              self.results.insert('end', 'Query:\n' + self.addnewlines(sql))
              self.results.see('end')
              self.results.update_idletasks()
              self.historyText.addhistory()
              results = 'Results:\nfoo'
              if len(results) > 0:
                  self.results.insert('end', self.addnewlines(results))
              self.results.see('end')

Pmw 2.1 - 31 Dec 2020 - Home
Manual page last reviewed: 20 May 2002