ibusの周辺テキストをつかった漢字入力に対応したアプリの例。

imcontext-demo.py

#!/usr/bin/python3
#
# Copyright (c) 2017 Esrille Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at:
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import gi
gi.require_version('Gtk', '3.0')
from gi.repository import Gtk, Gdk, GLib
import cairo

class Example(Gtk.Window):
    def __init__(self):
        super(Example, self).__init__()

        canvas = Gtk.DrawingArea()
        canvas.connect("draw", self.on_draw)
        self.add(canvas)

        self.set_title("IMContext Demo")
        self.resize(640, 48)
        self.set_position(Gtk.WindowPosition.CENTER)
        self.connect("delete-event", Gtk.main_quit)
        self.show_all()

        self.connect("key-press-event", self.on_key_press)
        self.connect("key-release-event", self.on_key_release)
        self.connect("focus-in-event", self.on_focus_in)
        self.connect("focus-out-event", self.on_focus_out)

        self.im_context = Gtk.IMMulticontext();
        self.im_context.set_client_window(canvas.get_window())
        self.im_context.connect("commit", self.on_commit);
        self.im_context.connect("delete-surrounding", self.on_delete_surrounding);
        self.im_context.connect("retrieve-surrounding", self.on_retrieve_surrounding);
        self.im_context.connect("preedit-changed", self.on_preedit_changed);
        self.im_context.connect("preedit-end", self.on_preedit_end);
        self.im_context.connect("preedit-start", self.on_preedit_start);

        self.__text = 'こんにちは、世界！'
        self.__cur = len(self.__text)
        self.__blink = True
        self.__active = False
        self.__preedit = ('', None, 0)

        GLib.timeout_add(600, self.on_blink)

    def on_blink(self):
        self.__blink ^= True
        self.queue_draw()
        return True

    def on_draw(self, wid, cr):

        context = wid.get_style_context()
        width = wid.get_allocated_width()
        height = wid.get_allocated_height()
        cr.set_source_rgb(255, 255, 255)
        cr.rectangle(0, 0, width, height)
        cr.fill()

        cr.set_source_rgb(0, 0, 0)
        cr.select_font_face("Noto Sans Mono CJK JP", cairo.FONT_SLANT_NORMAL, cairo.FONT_WEIGHT_NORMAL)
        cr.set_font_size(16)
        cr.move_to(10, 26)

        current = self.__text[:self.__cur]
        if self.__preedit[0]:
            text = current + self.__preedit[0] + self.__text[self.__cur:]
            current += self.__preedit[0][:self.__preedit[2]]
        else:
            text = self.__text
        cr.show_text(text)
        ext = cr.text_extents(current)

        # Display the caret:
        #
        # Pick x_advance not width.
        # ext would look like (2.0, -14.0, 206.0, 16.0, 256.0, 0.0).
        r = Gdk.Rectangle()
        r.x, r.y, r.width, r.height = 10 + ext[4], 12, 2, 16
        self.im_context.set_cursor_location(r)
        if self.__blink and self.__active:
            cr.rectangle(r.x, r.y, r.width, r.height)
            cr.fill()

    def on_focus_in(self, wid, event):
        self.__active = True
        self.im_context.focus_in()
        return True;

    def on_focus_out(self, wid, event):
        self.__active = False
        self.im_context.focus_out()
        return True;

    def on_key_press(self, wid, event):
        # print("'", Gdk.keyval_name(event.keyval), "', ", event.state, sep='')
        if self.im_context.filter_keypress(event):
            return True;
        if event.keyval == Gdk.KEY_BackSpace:
            if 0 < self.__cur:
                self.__text = self.__text[:self.__cur - 1] + self.__text[self.__cur:]
                self.__cur -= 1
                self.queue_draw()
                return True
        elif event.keyval == Gdk.KEY_Left:
            if 0 < self.__cur:
                self.__cur -= 1
                self.queue_draw()
                return True
        elif event.keyval == Gdk.KEY_Right:
            if self.__cur < len(self.__text):
                self.__cur += 1
                self.queue_draw()
                return True
        elif event.keyval == Gdk.KEY_Home:
            if 0 < self.__cur:
                self.__cur = 0
                self.queue_draw()
                return True
        elif event.keyval == Gdk.KEY_End:
            if self.__cur < len(self.__text):
                self.__cur = len(self.__text)
                self.queue_draw()
                return True
        return False;

    def on_key_release(self, wid, event):
        if self.im_context.filter_keypress(event):
            return True;
        return False;

    def on_commit(self, wid, str):
        self.__text = self.__text[:self.__cur] + str + self.__text[self.__cur:]
        self.__cur += len(str)
        self.queue_draw()

    def on_retrieve_surrounding(self, wid):
        self.im_context.set_surrounding(self.__text, len(self.__text.encode()), len(self.__text[:self.__cur].encode()))
        return True

    def on_delete_surrounding(self, wid, offset, n_chars):
        begin = self.__cur + offset
        if begin < 0:
            return False
        end = self.__cur + offset + n_chars
        if len(self.__text) < end:
            return False
        self.__text = self.__text[:begin] + self.__text[end:]
        if end <= self.__cur:
            self.__cur -= n_chars
        elif begin <= self.__cur:
            self.__cur = begin
        self.queue_draw()
        return True

    def on_preedit_changed(self, wid):
        self.__preedit = self.im_context.get_preedit_string()
        self.queue_draw()
        return False

    def on_preedit_end(self, wid):
        self.__preedit = self.im_context.get_preedit_string()
        self.queue_draw()
        return False

    def on_preedit_start(self, wid):
        self.__preedit = self.im_context.get_preedit_string()
        self.queue_draw()
        return False

def main():
    app = Example()
    Gtk.main()

if __name__ == "__main__":
    main()

フォントはnotoをつかっています。インストール手順は、

$ sudo apt install fonts-noto-cjk

です。