mousewheel does not work on slider

[0x0fe]

So everything is in the title, on slider it is commonly expected that a mouse wheel action when overing allows to modify the value/position of the slider, for some reason it doesn't work and the few method i used did not help. I can see the hovering is correctly detected since the button of the slider changes color, but mousewheel action is ignored.

[dipeshSam]

@0x0fe
You can implement it. If you need any kind of help, let me know.

Regards.

[LorenzoMattia]

Hi @0x0fe, sorry for late answer. Below you can find a possible version of a Custom Slider that is binded with the mouse wheel.

import tkinter
import customtkinter
import numpy as np

class CustomCTkSlider(customtkinter.CTkSlider):
    def __init__(self, master, **kwargs):
        super().__init__(master=master, **kwargs)

        self._update_timer = 0
        self._update_period = 1
        self._rate = 100

    def _handle_disable_timer(self):
        """
        To avoid too many updates for multi MouseWheel events generated by a single scrolling
        """
        if self._update_timer > self._update_period:
            self._update_timer = 0
        else:
            self._update_timer += self._rate
            self.after(self._rate, self._handle_disable_timer)

    def scrolled(self, event):
        if self._state != "normal":
            return

        if self._update_timer >= self._update_period:
            return

        direction = np.sign(event.delta)

        step = 1 / self._number_of_steps
        self._value += direction * step

        self._value = max(0, min(1, self._value))

        self._output_value = self._round_to_step_size(
            self._from_ + self._value * (self._to - self._from_)
        )

        self._value = (self._output_value - self._from_) / (self._to - self._from_)

        self._draw(no_color_updates=False)

        if self._variable is not None:
            self._variable_callback_blocked = True
            self._variable.set(
                round(self._output_value)
                if isinstance(self._variable, tkinter.IntVar)
                else self._output_value
            )
            self._variable_callback_blocked = False

        self._handle_disable_timer()

Note, if you are working on a Linux platform you should bind the slider with Button-4 / Button-5 events and not MouseWheel.

Below is also an extremely simple App that you can use to test the widget:

class App(customtkinter.CTk):
    def __init__(self):
        super().__init__()

        self.geometry("200x200")
        
        # create a container frame
        self.main_frame = customtkinter.CTkFrame(self)

        # Very important to pass number_of_steps 
        self.slider = CustomCTkSlider(self.main_frame, number_of_steps = 10, from_ = 2, to = 10)
        self.slider.bind("<MouseWheel>", self.handle_slider_scrolling)
        self.slider.pack()

        self.main_frame.pack(fill = customtkinter.BOTH)
        self.label = customtkinter.CTkLabel(self, text = str(round(self.slider.get(), ndigits=2)))
        self.label.pack(anchor = customtkinter.NW, side = customtkinter.TOP)

    def handle_slider_scrolling(self, event):
        self.slider.scrolled(event)
        self.label.configure(text = str(round(self.slider.get(), ndigits=2)))


        
app = App()
app.mainloop()

Let me know if you need any help or clarification!