Python kivy Problems with rewriting python in kivy

Question

I have some problems with rewriting python code in kivy format

Here is the class "Settings" which has method to change screen.

class SettingsMenu(Screen):
def on_touch_down(self, touch):
    if touch.button == 'right':
        self.parent.transition.direction = "right"
        self.parent.transition.duration = 0.6
        self.parent.current = "MainMenu"

And I want to rewrite it in kivy this way (or something like that):

<SettingsMenu>
name: "SettingsMenu"
on_touch_down:
    if button == "right":
        root.parent.transition.direction = "right"
        root.parent.transition.duration = 0.6
        root.parent.current = "MainMenu"

How should I do it correctly?

(Edit) Here is the full code. I just create two screens and when we are on SettingsMenu screen, I want to switch back to MainMenu screen with right mouse button

(Commented on_touch_down in SettingsMenu python class works correctly, but when I try to make it in kivy way, I switch the screen with any mouse button, but desired was right mouse button)

Python:

from kivy.app import App
from kivy.lang import Builder

from kivy.uix.screenmanager import ScreenManager, Screen

from kivy.config import Config

Config.set('input', 'mouse', 'mouse,multitouch_on_demand')


class MainMenu(Screen):
    pass

class SettingsMenu(Screen):
    pass
    # def on_touch_down(self, touch):
    #     if touch.button == 'right':
    #         self.parent.transition.direction = "right"
    #         self.parent.transition.duration = 0.6
    #         self.parent.current = "MainMenu"


class MenuManager(ScreenManager):
    pass


main_kv = Builder.load_file("test.kv")


class THEApp(App):
    def build(self):
        return main_kv


THEApp().run()

This is the Kivy file (indentation may be broken during copy-paste, but I had no problems with syntax):

MenuManager:
   MainMenu:
   SettingsMenu:

<MainMenu>
    name: "MainMenu"
    FloatLayout:
        size: root.width, root.height
    Button:
        text: "Button 1 on Main Menu Screen"
        on_release:
            root.manager.transition.direction = 'left'
            root.manager.transition.duration = 0.6
            root.manager.current = "SettingsMenu"
<SettingsMenu>
    name: "SettingsMenu"
    button: "right"
    on_touch_down:
        if root.button == "right": \
        root.parent.transition.direction = "right"; \
        root.parent.transition.duration = 0.6; \
        root.parent.current = "MainMenu"
    FloatLayout:
        size: root.width, root.height
        Label:
            text: "Label 1 on SettingsMenu"

Answer 1

You can do python code/logic for an on_touch_down: attribute in a kv file, but it is a bit goofy. I think your kv file will work like this:

<SettingsMenu>
    name: "SettingsMenu"
    on_touch_down:
        if args[1].button == "right": \
        root.parent.transition.direction = "right"; \
        root.parent.transition.duration = 0.6; \
        root.parent.current = "MainMenu"

In the kivy language, you can access the args of an on_<action> method (see documentation). So the code above checks the button attribute of the touch arg.

Note that the if statement in the kv file must be on a single line. That is the reason for the \ characters (to escape endlines) and the ; (to delimit the lines of code).