Tkinter special math chars

[phil]

So far, on RedHat Linux:
I have used your method successfully in a Label
and in Canvas Text.  very slow.??
In A Text box I just get \N{INFINITY}.

But thanks, I will investigate Text Box more.

Jeff Epler wrote:

> I wrote the following code:
>     import Tkinter
>     t = Tkinter.Label()
>     t.configure(
>         text=u"As the function approaches \N{INFINITY}, \N{HORIZONTAL ELLIPSIS}")
>     t.pack()
>     t.mainloop()
> It worked for me on Windows NT 4.0 with Python 2.4, and on RedHat 9 with
> a self-compiled Python 2.3, showing an infinity symbol and an ellipsis.
> 
> u'\N{...}' stands for the Unicode character named '...'.  Unicode.org
> (and other sites) have lists of Unicode character names. 
> 
> Tk tries very hard to find the requested character in some font
> available on the system, but when it fails it just displays a unicode
> escape sequence like "\u220e" (instead of the END OF PROOF symbol, in
> this case), and there's really no way for Python to find out and fall
> back in some graceful way.
> 
> Relying on this behavior, here's a somewhat-falliable way to detect the
> presence of a symbol in the font used in a given widget:
>     def symbol_exists(s, w, f = None):
>         if f is None:
>             f = w.cget("font")
>         width_symbol = w.tk.call("font", "measure", f, s)
>         width_bench = w.tk.call("font", "measure", f, "000")
>         return width_symbol < width_bench
> This finds the width in pixels of the given symbol (s) and the string "000", in
> the font f.  If the width of the symbol is smaller, then it's probably available.
> If it's wider, then it's probably rendered as an escape sequence like "\u220e".
> This is falliable because there's no guarantee that the symbol would not be as
> wide as 000, but also it's possible for some escape code (say \u1111) to be
> narrower than 000.  Neither of these seem very likely in practice.
> 
> Jeff
>