Re: [MACTCL] Background colour on macOS Tahoe

[Marc C. <mar...@gm...>]

The background color used by Tk for a Tk window and for a Ttk Frame is an
Apple "semantic color" aptly named WindowBackgroundColor.  The rgb values
for semantic colors depend on the Appearance (Aqua or Dark) and are
determined by the system.  You can view the rgb values by calling the
winfo_rgb method:
`root.winfo_rgb("systemWindowBackgroundColor")
That method calls the Tk command
 `winfo rgb , systemWindowBackgroundColor`.

There is something pretty complicated going on here.  This is what I see on
my Tahoe system with various versions of python and wish:

## Python 3.13 from python.org
>>> import tkinter
>>> root = tkinter.Tk()
>>> root.eval("info patchlevel")
'8.6.16'
>>> root.winfo_rgb("systemWindowBackgroundColor")
(60652, 60652, 60652)

## Python 3.13 built with Tk 9.0.1
>>> import tkinter
>>> root = tkinter.Tk()
>>> root.eval("info patchlevel")
'9.0.1'
>>> root.winfo_rgb("systemWindowBackgroundColor")
(60652, 60652, 60652)

## Wish 9.0
% info patchlevel
9.0.2
% winfo rgb . systemWindowBackgroundColor
60652 60652 60652

## Wish 9.1
% info patchlevel
9.1a0
% winfo rgb . systemWindowBackgroundColor
65535 65535 65535

As you can see, Wish 9.1 changes the background color to white instead of
light gray.  However, I don't think this has anything to do with the
version of Tk being used.  I think it may have to do with the SDK version
used when compiling Tk.  On my system, wish9.0 was built with the 15.5.0
SDK (before I installed Tahoe) and wish9.1 was built with the 26.0.0 SDK.
Note that the target OS (i.e. the one specified with -mmacosx-version-min)
was 11.0 in both cases.

I imagine that the core issue is whether the build sdk supports "Liquid
Glass" or not.

In any case, I don't think this is something that can be addressed by Tk,
assuming that I am correct that the behavior depends on the SDK version
used to build Tk.  Perhaps it can be addressed by developers by specifying
which SDK to use when building an app.

- Marc





On Tue, Oct 7, 2025 at 11:35 AM Andrew Murray <rad...@gm...> wrote:

> Hi. Using Tcl 8.6.17 from Python on macOS Sequoia and Tahoe, I find that
> Sequoia has a gray background, but Tahoe has a white background. This may
> well be intentional, and an accepted part of Apple's updated designs, but I
> just wanted to check if that is the case? Or is it something of a bug that
> a future Tcl will address? Thanks
>
> import tkinter as tk
> from tkinter import ttk
>
> root = tk.Tk()
> root.geometry("200x100")
>
> main_frame = ttk.Frame(root, padding=20, borderwidth=2)
> main_frame.pack(fill="both", expand=True)
>
> label = ttk.Label(main_frame, text="Label")
> label.pack()
>
> root.mainloop()
>
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