Two fullscreen tkinter windows on separate monitors on Raspbery Pi 4

I have a simple TK app that runs fullscreen just fine on one monitor, but now I want to run two fullscreen windows, one on each display on a Raspberry Pi 4. The two displays have different resolutions and work fine on their own, but I can’t get two fullscreen windows to work, both windows fullscreen just on the first display.

I’m trying to do it with tkinter.Tk().geometry(), is this the way to go or is there something more straightforward?

import tkinter

root = tkinter.Tk()

# specify resolutions of both windows
w0, h0 = 3840, 2160
w1, h1 = 1920, 1080

# set up window for display on HDMI 0 
win0 = tkinter.Toplevel()
win0.geometry(f"{w0}x{h0}")
win0.attributes("-fullscreen", True)
win0.config(cursor="none") # remove cursor 
win0.wm_attributes("-topmost", 1) # make sure this window is on top 

# set up window for display on HDMI 1 
win1 = tkinter.Toplevel()
win1.geometry(f"{w1}x{h1}")
win1.attributes("-fullscreen", True)
win1.config(cursor="none")
win1.wm_attributes("-topmost", 1)

Answer

You have to offset the second window to the right by the width of the first display (The X system puts the display on the HDMI0 port down first, then puts the display from HDMI1 to the right).geometry lets you make sure they don’t overlap and then fullscreen works as expected.

The format of the geometry string is: <width>x<height>+xoffset+yoffset.

root = tkinter.Tk()

# specify resolutions of both windows
w0, h0 = 3840, 2160
w1, h1 = 1920, 1080

# set up window for display on HDMI 0 
win0 = tkinter.Toplevel()
win0.geometry(f"{w0}x{h0}+0+0")
win0.attributes("-fullscreen", True)

# set up window for display on HDMI 1 
win1 = tkinter.Toplevel()
win1.geometry(f"{w1}x{h1}+{w0}+0") # <- the key is shifting right by w0 here 
win1.attributes("-fullscreen", True)

root.withdraw()  # hide the empty root window