如何在Tkinter文本小部件中配置默认​​的双鼠标单击行为？

Question

On a tkinter text widget, the default behavior of double click will be to select the text under the mouse.

The event will select all characters between " " (space) char.

So - assume the text widget has: 1111111 222222 double click on over the first word (all 1 ) will select only it (and double clicking on 2 word will select it)

I would like to have a similar behavior, but add additional char as work seperators (eg, . , ( , ) ) currently, if the text has 111111.222222 - double click anywhere over the text will highlight all characters (won't separate the words by . )

Is there a way to do it?

Answer 1

Changing what is a 'word'

The double click is defined to select the 'word' under the cursor. If you are wanting to change the default behavior for all text widgets, tkinter has a way to tell it what is a "word" character. If you change what tkinter thinks is a "word", you change what gets selected with a double-click. This requires that we directly call the built-in tcl interpreter upon which tkinter is based.

Note: this will affect other aspects of the widget as well, such as key bindings for moving the cursor to the beginning or ending of a word.

Here's an example:

import tkinter as tk

def set_word_boundaries(root):
    # this first statement triggers tcl to autoload the library
    # that defines the variables we want to override.  
    root.tk.call('tcl_wordBreakAfter', '', 0) 

    # this defines what tcl considers to be a "word". For more
    # information see http://www.tcl.tk/man/tcl8.5/TclCmd/library.htm#M19
    root.tk.call('set', 'tcl_wordchars', '[a-zA-Z0-9_.,]')
    root.tk.call('set', 'tcl_nonwordchars', '[^a-zA-Z0-9_.,]')

root = tk.Tk()
set_word_boundaries(root)

text = tk.Text(root)
text.pack(fill="both", expand=True)
text.insert("end", "foo 123.45,678 bar")

root.mainloop()

Custom key binding

If you do not want to affect any widget except one, or do not want to affect other aspects of tkinter that depend on the definition of a 'word', you can create your own binding to select whatever you want.

The important thing to remember is that your binding should return the string "break" in order prevent the default behavior for double-click:

def handle_double_click(event):
    <your code for selecting whatever you want>
    return "break"
...
text.bind("<Double-1>", handle_double_click)

To facilitate this, the text widget has a search method that makes it possible to search backwards and forwards through the text for a given string or regular expression.

Answer 2

Is there a way to do it?

Of course, and not even one way. But anyway - we need a custom class for our Text widget, so let's start:

class CustomText(tk.Text):
    def __init__(self, parent, delimiters=[]):
        tk.Text.__init__(self, parent)
        #   test text
        self.insert('1.0', '1111111 222222'
                           '\n'
                           '1111111.222222'
                           '\n'
                           '1111111.222222,333333'
                           '\n'
                           '444444444444444444')
        #   binds
        self.bind('<Double-1>', self.on_dbl_click)
        self.bind('<<Selection>>', self.handle_selection)
        #   our delimiters
        self.delimiters = ''.join(delimiters)
        #   stat dictionary for double-click event
        self.dbl_click_stat = {'clicked': False,
                               'current': '',
                               'start': '',
                               'end': ''
                               }

The optional delimiters leads to two options:

1. If delimiters are presented we can rely on RegEx search for delimiters.

2. If delimiters are ommited we can rely on build-in expressions, especially those two (RegEx-like word boundaries): wordstart and wordend . According to docs :

   wordstart and wordend moves the index to the beginning (end) of the current word. Words are sequences of letters, digits, and underline, or single non-space characters.

The logic is simple - when double click occures - we trace this event and store indexes in a dictionary. After that we handle change of the selection, and act accordingly the choosen option (see above).

Here's a complete snippet:

try:
    import tkinter as tk
except ImportError:
    import Tkinter as tk


class CustomText(tk.Text):
    def __init__(self, parent, delimiters=[]):
        tk.Text.__init__(self, parent)
        #   test text
        self.insert('1.0', '1111111 222222'
                           '\n'
                           '1111111.222222'
                           '\n'
                           '1111111.222222,333333'
                           '\n'
                           '444444444444444444')

        #   binds
        self.bind('<Double-1>', self.on_dbl_click)
        self.bind('<<Selection>>', self.handle_selection)
        #   our delimiters
        self.delimiters = ''.join(delimiters)
        #   stat dictionary for double-click event
        self.dbl_click_stat = {'clicked': False,
                               'current': '',
                               'start': '',
                               'end': ''
                               }

    def on_dbl_click(self, event):
        #   store stats on dbl-click
        self.dbl_click_stat['clicked'] = True
        #   clicked position
        self.dbl_click_stat['current'] = self.index('@%s,%s' % (event.x, event.y))
        #   start boundary
        self.dbl_click_stat['start'] = self.index('@%s,%s wordstart' % (event.x, event.y))
        #   end boundary
        self.dbl_click_stat['end'] = self.index('@%s,%s wordend' % (event.x, event.y))


    def handle_selection(self, event):
        if self.dbl_click_stat['clicked']:
            #   False to prevent a loop
            self.dbl_click_stat['clicked'] = False
            if self.delimiters:
                #   Preserve "default" selection
                start = self.index('sel.first')
                end = self.index('sel.last')
                #   Remove "default" selection
                self.tag_remove('sel', '1.0', 'end')
                #   search for occurrences
                occurrence_forward = self.search(r'[%s]' % self.delimiters, index=self.dbl_click_stat['current'],
                                                 stopindex=end, regexp=True)
                occurrence_backward = self.search(r'[%s]' % self.delimiters, index=self.dbl_click_stat['current'],
                                                  stopindex=start, backwards=True, regexp=True)

                boundary_one = occurrence_backward + '+1c' if occurrence_backward else start
                boundary_two = occurrence_forward if occurrence_forward else end
                #   Add selection by boundaries
                self.tag_add('sel', boundary_one, boundary_two)
            else:
                #   Remove "default" selection
                self.tag_remove('sel', '1.0', 'end')
                #   Add selection by boundaries
                self.tag_add('sel', self.dbl_click_stat['start'], self.dbl_click_stat['end'])


root = tk.Tk()

text = CustomText(root)
text.pack()

root.mainloop()

In conclusion, if you doesn't really care about delimiters, but about words - the second option is OK, otherwise - the first one.

Update:

Many thanks to @Bryan Oakley for pointing that 'break' -string prevents the default behaviour, so code can be shortened to just one callback, there's no need in <<Selection>> anymore:

...
def on_dbl_click(self, event):
    if self.delimiters:
        #   click position
        current_idx = self.index('@%s,%s' % (event.x, event.y))
        #   start boundary
        start_idx = self.search(r'[%s\s]' % self.delimiters, index=current_idx,
                                stopindex='1.0', backwards=True, regexp=True)
        #   quick fix for first word
        start_idx = start_idx + '+1c' if start_idx else '1.0'
        #   end boundary
        end_idx = self.search(r'[%s\s]' % self.delimiters, index=current_idx,
                              stopindex='end', regexp=True)
    else:
        #   start boundary
        start_idx = self.index('@%s,%s wordstart' % (event.x, event.y))
        #   end boundary
        end_idx = self.index('@%s,%s wordend' % (event.x, event.y))

    self.tag_add('sel', start_idx, end_idx)
    return 'break'
...