Simple LD_PRELOAD shim that requests a dark theme by setting
GTK_THEME, GTK2_RC_FILES and the X window property _GTK_THEME_VARIANT.
Uses hardcoded values for theme, edit the source if you want something besides the default Adwaita.
Does not work with anything that itself uses dlopen to find libX11.so. Examples include Wine and SDL.
sudo make install
LD_PRELOAD=libdark.so app
The usual caveats apply, software WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. LD_PRELOAD'ing random code can lead to badness. Don't blame me if libdark crashes your app, eats your data, or elopes with your husband!
Emacs, and potentially other applications, uses the shell's original environment variables and not the ones set in the process when spawning a new one, leading to any apps launched by Emacs inheriting the dark theme. You can work around this by unsetting the theme variables in .emacs:
(setenv "GTK_THEME" "")
(setenv "GTK2_RC_FILES" "")
Adwaita and some others have a bug in the gtk-2.0 theme that fails to override the theme from the environment. The following change needs to be applied:
--- /usr/share/themes/Adwaita-dark/gtk-2.0/main.rc 2018-03-22 18:36:35.000000000 +0100
+++ /usr/share/themes/Adwaita-dark/gtk-2.0/main.rc.mod 2018-08-17 19:14:53.347692164 +0200
@@ -5,7 +5,7 @@
# which is also mostly done in this file. Sadly not all of them can be overcome
# so there will always be a visible difference between the GTK+ 2 and 3 theme.
-style "default" {
+style "standard-default" {
xthickness = 1
ythickness = 1
@@ -2474,7 +2474,7 @@ style "disable_separator" {
# by its own but also less bug-prune and more consistent. However there is some
# widget specific stuff that needs to be taken care of, which is the point of
# every other style below.
-class "GtkWidget" style "default"
+class "GtkWidget" style "standard-default"
######################################
# Override padding, style and colour #