How to modify a part of a text of a gtk textview

Question

I learn GTK with Python and I've a problem with the widget texview. I'd like to changed / modify specific part of a text in a buffer (textview).

For example, the text buffer:

    long_text = "line 1 word 1 word 2 word 3 \n" \
                "line 2 [WORD TO REPLACE]  \n" \
                "line 3 \n"

I 'd to replace the section [WORD TO REPLACE] by the value of a Gtk.Entry. I know how to add the entry a the end of the buffer, but I'm not able to replace from inside the text itself.

The entire code:

from gi.repository import Gtk
import sys


class MyWindow(Gtk.ApplicationWindow):

    def __init__(self, app):
        Gtk.Window.__init__(self, title="TextView Example", application=app)
        self.set_default_size(300, 450)

        # a scrollbar for the child widget (that is going to be the textview)
        scrolled_window = Gtk.ScrolledWindow()
        scrolled_window.set_border_width(5)
        # we scroll only if needed
        scrolled_window.set_policy(
            Gtk.PolicyType.AUTOMATIC, Gtk.PolicyType.AUTOMATIC)
        scrolled_window.set_min_content_height(400)
        scrolled_window.set_min_content_width(400)

        # a text buffer (stores text)
        self.text_buffer = Gtk.TextBuffer()

        #Test texte
        long_text = "line 1 word 1 word 2 word 3 \n" \
                    "line 2 <WORD TO REPLACE>  \n" \
                    "line 3 \n"

        # a textview (displays the buffer)
        self.textview = Gtk.TextView(buffer=self.text_buffer)
        # wrap the text, if needed, breaking lines in between words
        self.textview.set_wrap_mode(Gtk.WrapMode.WORD)

        self.text_buffer = self.textview.get_buffer()
        self.text_buffer.insert_at_cursor(long_text)

        # textview is scrolled
        scrolled_window.add(self.textview)

        self.entry=Gtk.Entry()
        self.entry.set_text("Entry")

        btnUpdate = Gtk.Button(label="Update")
        btnUpdate.connect("clicked", self.update_textview)


        grid = Gtk.Grid()
        grid.attach(self.entry,0,1,1,1)
        grid.attach(btnUpdate,0,2,1,1)
        grid.attach(scrolled_window,0,3,1,1)
        self.add(grid)

    def update_textview(self, widget):
        self.text_buffer.insert_at_cursor(self.entry.get_text() + '\n')

class MyApplication(Gtk.Application):

    def __init__(self):
        Gtk.Application.__init__(self)

    def do_activate(self):
        win = MyWindow(self)
        win.show_all()

    def do_startup(self):
        Gtk.Application.do_startup(self)

app = MyApplication()
exit_status = app.run(sys.argv)
sys.exit(exit_status)

Any idea is welcome. Thanks.

Answer 1

The way to do this is to find <WORD TO REPLACE>, delete it, and type in the new word at the place where <WORD TO REPLACE> was.

Finding the word

To find a word, you can take advantage of Gtk.TextIter's forward_search() method. It requires two arguments: the string to find, and the how to search (this argument has to be an attribute of Gtk.TextSearchFlags). I just use Gtk.TextSearchFlags.VISIBLE_ONLY for this, because I'm not searching for something that's not visible.

self.text_buffer.get_start_iter().forward_search(
    "<WORD TO REPLACE>",
    Gtk.TextSearchFlags.VISIBLE_ONLY
)

Deleting the word

The forward_search() method returns a two-item tuple: the word's start iter and the word's end iter (unless it doesn't find anything, in which case it returns None; more on that in a bit). These iters come in very handy, because all we have to do is simply pass them along to Gtk.TextBuffer's delete() method.

start, end = i.forward_search("<WORD TO REPLACE>", Gtk.TextSearchFlags.VISIBLE_ONLY)
self.text_buffer.delete(start, end)

Inserting the new word

You can use Gtk.TextBuffer's insert() method for this. It takes three arguments: the iter at which to insert the text, the text, and the length of the text (you can just use -1 to specify any length). Here I use self.entry.get_text() for the text argument.

start, end = i.forward_search("<WORD TO REPLACE>", Gtk.TextSearchFlags.VISIBLE_ONLY)
self.text_buffer.delete(start, end)
self.text_buffer.insert(start, self.entry.get_text(), -1)

Putting it all together

Here is what the entire update_textview() method should look like:

def update_textview(self, widget):

    # Get the start iter of the textview
    i = self.text_buffer.get_start_iter()

    # Get the start and end index of <WORD TO REPLACE>
    search_result = i.forward_search("<WORD TO REPLACE>", Gtk.TextSearchFlags.VISIBLE_ONLY)

    # Make sure that the search actually found something
    if search_result is not None:
        start, end = search_result

        # Delete <WORD TO REPLACE>...
        self.text_buffer.delete(start, end)

        # ...and insert the text from the entry.
        self.text_buffer.insert(start, self.entry.get_text(), -1)

Note that I use if search_result is not None to make sure that the search actually found something. If this if statement wasn't there, you would get a TypeError if you clicked the Update button and <WORD TO REPLACE> wasn't there.