Programming Python, 3rd Edition

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It’s been said that Tkinter’s strongest points may be its Text and Canvas widgets. Both provide a remarkable amount of functionality. For instance, the Tkinter Text widget was powerful enough to implement the web pages of Grail, an experimental web browser coded in Python; Text supports complex font-style settings, embedded images, unlimited undo and redo, and much more. The Tkinter Canvas widget, a general-purpose drawing device, allows for efficient free-form graphics and has been the basis of sophisticated image processing and visualization applications.

In Chapter 12, we’ll put these two widgets to use to implement text editors (PyEdit), paint programs (PyDraw), clock GUIs (PyClock), and photo slideshows (PyView). For the purposes of this tour chapter, though, let’s start out using these widgets in simpler ways. Example 10-10 implements a simple scrolled-text display, which knows how to fill its display with a text string or file.

Example 10-10. PP3E\Gui\Tour\scrolledtext.py

# a simple text or file viewer component print 'PP3E scrolledtext' from Tkinter import * class ScrolledText(Frame): def _ _init_ _(self, parent=None, text='', file=None): Frame._ _init_ _(self, parent) self.pack(expand=YES, fill=BOTH) # make me expandable self.makewidgets( ) self.settext(text, file) def makewidgets(self): sbar = Scrollbar(self) text = Text(self, relief=SUNKEN) sbar.config(command=text.yview) # xlink sbar and text text.config(yscrollcommand=sbar.set) # move one moves other sbar.pack(side=RIGHT, ...