import tkinter as tk
from tkhtmlview import HTMLLabel,HTMLScrolledText,HTMLText

root = tk.Tk()
html_label = HTMLScrolledText(root,background="white")
# ,state="normal", html='<h1 style="color: red; text-align: center"> Hello World </H1>')

html_label.set_html(html='<h1 style="color: red; text-align: center"> Hello World </H1>')
html_label.config(selectbackground="red",relief="flat")
# ,inactiveselectbackground=html_label.cget("selectbackground")
html_label.pack(fill="both", expand=True)
html_label.tag_configure("sel",background="red")
html_label.fit_height()

## not working --
html_label.tag_add("sel",1.0,"end")
html_label.configure(selectbackground="red", inactiveselectbackground="green")

def OnButton():
    print (f"selected text: '{html_label.selection_get()}'") 

button = tk.Button(root, text="Get Selection", command=OnButton)
button.pack()


# lb = tk.Label(root,text="new label")
# lb.pack()

# w = tk.Text(root, height=1, borderwidth=0,selectbackground="red",inactiveselectbackground="green")
# w.insert(1.0, "Hello, world!")
# w.pack()

# w.configure(state="disabled")
# w.tag_configure("sel",background="red")
# if tkinter is 8.5 or above you'll want the selection background
# to appear like it does when the widget is activated
# comment this out for older versions of Tkinter
# w.configure(inactiveselectbackground=w.cget("selectbackground"))


# p::selection {   background: lightblue; }
root.mainloop()