In Progress: Displaying Formatted Text (Writing Widgets in Python, Part 5)

June 2003 | Fredrik Lundh

This article is being updated.

The Widget Construction Kit (WCK) is a programming interface that you can use to create new widgets for Tkinter and other toolkits, in pure Python.

This is the fifth article in a series. In this article, we’ll look at how to display nicely formatted text in a WCK widget.

:::

Not much here yet!

Formatting Text Paragraphs

from WCK import Widget, FONT, FOREGROUND

class SimpleTextView(Widget):

    ui_option_text = ""

    ui_option_width = 200
    ui_option_height = 100

    ui_option_font = FONT

    ui_option_foreground = FOREGROUND

    def ui_handle_config(self):
        self.font = self.ui_font(
            self.ui_option_foreground, self.ui_option_font
            )
        return int(self.ui_option_width), int(self.ui_option_height)

    def ui_handle_repair(self, draw, x0, y0, x1, y1):
        space = draw.textsize(" ", self.font)[0]
        words = self.ui_option_text.split()
        x = y = 0
        for word in words:
            # check size of this word
            w, h = draw.textsize(word, self.font)
            # figure out where to draw it
            if x:
                x += space
                if x + w > x1:
                    # new line
                    x = 0
                    y += h
            draw.text((x, y), word, self.font)
            x += w

The drawing code treats the text as a single paragraph, consisting of one long list of words. Note that the code always draws words that start at the left margin, even if they won’t fit on the line. For all other words (where x is not zero), the code checks if there’s room for a space character and the word on the current line. If not (that is, if x+w>x1 where x1 is the right margin), it moves on to the next line.

Here’s an example:

from Tkinter import *

root = Tk()

TEXT = """
I tell you I have been in the editorial business going on fourteen
years, and it is the first time I ever heard of a man's having to know
anything in order to edit a newspaper. You turnip!
"""

text = SimpleTextView(root, text=TEXT)
text.pack(fill=BOTH, expand=1)

mainloop()

Speeding Things Up

A little refactoring:

from WCK import Widget, FONT, FOREGROUND

class SimpleTextView(Widget):

    ui_option_text = ""

    ui_option_width = 200
    ui_option_height = 100

    ui_option_font = FONT

    ui_option_foreground = FOREGROUND

    def __init__(self, master, **options):
        self.width = None
        self.words = None
        self.ui_init(master, options)

    def ui_handle_resize(self, width, height):
        if width != self.width:
            self.width = width
            self.words = None # force reflow

    def ui_handle_config(self):
        self.font = self.ui_font(
            self.ui_option_foreground, self.ui_option_font
            )
        self.words = None
        return int(self.ui_option_width), int(self.ui_option_height)

    def ui_handle_repair(self, draw, x0, y0, x1, y1):
        if self.words is None:
            # reflow the text
            if not self.width:
                return
            self.words = []
            x = y = 0
            f = self.font
            space = draw.textsize(" ", f)[0]
            for word in self.ui_option_text.split():
                w, h = draw.textsize(word, f)
                if x:
                    x += space
                    if x + w > self.width:
                        x = 0
                        y += h
                self.words.append(((x, y), word, f))
                x += w
        # render
        text = draw.text
        for args in self.words:
            text(*args)

Displaying Styled Text

Displaying Scrolling Pages

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