RE: Dark mode on Windows

[Vince Salvino]

Answering your questions, Po:

> Is this feature available on free operating systems?

This is not a feature of emacs, rather it is a specific feature of Windows 
which is being supported (e.g. the window manager "chrome" around GUI emacs). 
Other operating systems have their own window managers, which actually are 
user-controllable, and would not require such a kludge in emacs :)

> This will not work on Windows NT prior to NT 6.0, or any version of Windows 
> 9x.

I have outlined ideas for this in the README.md in my fork. It would probably 
be possible to create a separate build profile, similar to NT vs Cygwin, etc. 
That is a bit beyond my skills, and I have no way of testing those systems.

> What is the purpose of this define?  Is `DWMWA_USE_IMMERSIVE_DARK_MODE' an 
> undocumented feature?

The value set by that define, and its use in DwmSetWindowAttribute, is 
undocumented (but heavily used and known among developers). See the inspiration 
links in my README.md.

> This needs to be controllable by the user, and will similarly not work on 
> slightly old versions of Windows.

I have recently addressed the version compatibility issue. There is also a TODO 
for the controllable aspect.


Vince Salvino

-----Original Message-----
From: Po Lu <luangruo@yahoo.com> 
Sent: Sunday, October 24, 2021 9:23 PM
To: Vince Salvino <salvino@coderedcorp.com>
Cc: emacs-devel@gnu.org
Subject: Re: Dark mode on Windows

Po Lu <luangruo@yahoo.com> writes:

> Is this feature available on free operating systems?
>
> The X11+GTK port, which runs on free operating systems, needs this 
> feature.
>
> P.S. this is also a problem with the NS port.  The ability to use a 
> dark stylesheet for window decorations is only available on macOS, and 
> not GNUstep.

Some other comments:

+    # darkmode
+    W32_LIBS="$W32_LIBS -ldwmapi"
+    # darkmode

This will not work on Windows NT prior to NT 6.0, or any version of Windows 9x.

+ /* darkmode */
+ #include <dwmapi.h>
+ #ifndef DWMWA_USE_IMMERSIVE_DARK_MODE
+ #define DWMWA_USE_IMMERSIVE_DARK_MODE 20 #endif
+ /* darkmode */

What is the purpose of this define?  Is `DWMWA_USE_IMMERSIVE_DARK_MODE'
an undocumented feature?

+      /* Enable darkmode */
+      BOOL isDarkMode = TRUE;
+      DwmSetWindowAttribute(hwnd,
+                           DWMWA_USE_IMMERSIVE_DARK_MODE,
+                           &isDarkMode,
+                           sizeof(isDarkMode));

This needs to be controllable by the user, and will similarly not work on 
slightly old versions of Windows.