picom: switch to a configuration file

It's easier to edit rules this way. Also, add some rules.

dotfiles/picom.conf

@@ -0,0 +1,18 @@
+backend = "glx";
+xrender-sync-fence = true;
+vsync = true;
+
+# Opacity
+inactive-opacity = 0.85;
+inactive-opacity-override = true;
+mark-ovredir-focused = true;
+focus-exclude = [
+  "fullscreen"
+];
+fading = true;
+wintypes:
+{
+  popup_menu = { opacity = 1; }
+  dropdown_menu = { opacity = 1; }
+  menu = { opacity = 1; }
+}

dotfiles/systemd/picom.service

@@ -3,10 +3,5 @@ Description=Compositor for X11
 PartOf=graphical-session.target
 
 [Service]
-ExecStart=/usr/bin/picom --backend glx \
+ExecStart=/usr/bin/picom
-                         --xrender-sync-fence \
-                         --vsync \
-                         --inactive-opacity 0.85 \
-                         --opacity-rule 100:fullscreen \
-                         --opacity-rule 100:override_redirect
 Restart=on-failure

dotfiles/xsession

@@ -31,6 +31,7 @@ gtk3.css     .config/gtk-3.0/gtk.css
 qt5ct.conf   .config/qt5ct/qt5ct.conf
 systemd      .config/systemd/user
 dunstrc      .config/dunst/dunstrc
+picom.conf   .config/picom.conf
 polybar.conf .config/polybar/config
 firefox.js   .mozilla/firefox/*/user.js
 EOF