Allow CALIBRE_USE_DARK_PALETTE override registry setting on windows

manual/customize.rst

@@ -8,7 +8,7 @@ Customizing calibre
 calibre has a highly modular design. Various parts of it can be customized. You can learn how to create
 *recipes* to add new sources of online content to calibre in the Section :ref:`news`. Here, you will learn,
 first, how to use environment variables and *tweaks* to customize calibre's behavior,  and then how to
-specify your own static resources like icons and templates to override the defaults and finally how to 
+specify your own static resources like icons and templates to override the defaults and finally how to
 use *plugins* to add functionality to calibre.
 
 .. contents::
@@ -30,7 +30,7 @@ Environment variables
     * ``CALIBRE_DEVELOP_FROM`` - Used to run from a calibre development environment. See :ref:`develop`.
     * ``CALIBRE_OVERRIDE_LANG`` - Used to force the language used by the interface (ISO 639 language code)
     * ``CALIBRE_TEST_TRANSLATION`` - Used to test a translation .po file (should be the path to the .po file)
-    * ``CALIBRE_NO_NATIVE_FILEDIALOGS`` - Causes calibre to not use native file dialogs for selecting files/directories. 
+    * ``CALIBRE_NO_NATIVE_FILEDIALOGS`` - Causes calibre to not use native file dialogs for selecting files/directories.
     * ``CALIBRE_NO_NATIVE_MENUBAR`` - Causes calibre to not create a native (global) menu on Ubuntu Unity and similar linux desktop environments. The menu is instead placed inside the window, as is traditional.
     * ``CALIBRE_USE_SYSTEM_THEME`` - By default, on Linux, calibre uses its own
       builtin Qt style. This is to avoid crashes and hangs caused by incompatibilities
@@ -40,6 +40,8 @@ Environment variables
       the system theme -- beware of crashes and hangs.
     * ``CALIBRE_SHOW_DEPRECATION_WARNINGS`` - Causes calibre to print deprecation warnings to stdout. Useful for calibre developers.
     * ``CALIBRE_NO_DEFAULT_PROGRAMS`` - Prevent calibre from automatically registering the filetypes it is capable of handling with Windows.
+    * ``CALIBRE_USE_DARK_PALETTE`` - Set it to ``1`` to have calibre use dark colors and ``0`` for normal colors (ignored on macOS).
+      On Windows 10 in the absence of this variable, the windows system preference for dark colors is used.
     * ``SYSFS_PATH`` - Use if sysfs is mounted somewhere other than /sys
     * ``http_proxy``, ``https_proxy`` - Used on linux to specify an HTTP(S) proxy
 
@@ -58,7 +60,7 @@ The default values for the tweaks are reproduced below
 Overriding icons, templates, et cetera
 ----------------------------------------
 
-.. note:: 
+.. note::
     calibre has direct support for icon themes, there are several icon themes
     available for calibre, that you can use by going to :guilabel:`Preferences->Interface->Look & Feel->Change Icon theme`.
     The icon themes use the same mechanism as described below for overriding static resources.
@@ -66,15 +68,15 @@ Overriding icons, templates, et cetera
 calibre allows you to override the static resources, like icons, javascript and
 templates for the metadata jacket, catalogs, etc. with customized versions that
 you like.  All static resources are stored in the resources sub-folder of the
-calibre install location. On Windows, this is usually :file:`C:\\Program Files\\Calibre2\\resources`. 
+calibre install location. On Windows, this is usually :file:`C:\\Program Files\\Calibre2\\resources`.
 On macOS, :file:`/Applications/calibre.app/Contents/Resources/resources/`. On linux, if
 you are using the binary installer from the calibre website it will be
 :file:`/opt/calibre/resources`. These paths can change depending on where you
-choose to install calibre. 
+choose to install calibre.
 
 You should not change the files in this resources folder, as your changes will
 get overwritten the next time you update calibre. Instead, go to
-:guilabel:`Preferences->Advanced->Miscellaneous` and click 
+:guilabel:`Preferences->Advanced->Miscellaneous` and click
 :guilabel:`Open calibre configuration directory`. In this configuration directory, create a
 sub-folder called resources and place the files you want to override in it.
 Place the files in the appropriate sub folders, for example place images in
@@ -110,4 +112,3 @@ Customizing calibre with plugins
 calibre has a very modular design. Almost all functionality in calibre comes in the form of plugins. Plugins are used for conversion, for downloading news (though these are called recipes), for various components of the user interface, to connect to different devices, to process files when adding them to calibre and so on. You can get a complete list of all the built-in plugins in calibre by going to :guilabel:`Preferences->Advanced->Plugins`.
 
 You can write your own plugins to customize and extend the behavior of calibre. The plugin architecture in calibre is very simple, see the tutorial :ref:`pluginstutorial`.
-

src/calibre/gui2/__init__.py

@@ -1021,10 +1021,12 @@ class Application(QApplication):
             using_calibre_style = True
         if using_calibre_style:
             use_dark_palette = False
-            if iswindows:
+            if 'CALIBRE_USE_DARK_PALETTE' in os.environ:
-                use_dark_palette = windows_is_system_dark_mode_enabled()
+                if not isosx:
-            elif not isosx:
+                    use_dark_palette = os.environ['CALIBRE_USE_DARK_PALETTE'] != '0'
-                use_dark_palette = os.environ.get('CALIBRE_USE_DARK_PALETTE') == '1'
+            else:
+                if iswindows:
+                    use_dark_palette = windows_is_system_dark_mode_enabled()
             if use_dark_palette:
                 self.set_dark_mode_palette()