megapixels: place photos in ~/Pictures/Photos instead of directly in ~/Pictures

hosts/common/home/xdg-dirs.nix

@@ -3,11 +3,15 @@
 {
   # XDG defines things like ~/Desktop, ~/Downloads, etc.
   # these clutter the home, so i mostly don't use them.
+  # note that several of these are not actually standardized anywhere.
+  # some are even non-conventional, like:
+  # - XDG_PHOTOS_DIR: only works because i patch e.g. megapixels
   sane.user.fs.".config/user-dirs.dirs".symlink.text = ''
     XDG_DESKTOP_DIR="$HOME/.xdg/Desktop"
     XDG_DOCUMENTS_DIR="$HOME/dev"
     XDG_DOWNLOAD_DIR="$HOME/tmp"
     XDG_MUSIC_DIR="$HOME/Music"
+    XDG_PHOTOS_DIR="$HOME/Pictures/Photos"
     XDG_PICTURES_DIR="$HOME/Pictures"
     XDG_PUBLICSHARE_DIR="$HOME/.xdg/Public"
     XDG_SCREENSHOTS_DIR="$HOME/Pictures/Screenshots"

hosts/common/programs/megapixels.nix

@@ -1,6 +1,13 @@
-{ ... }:
+{ pkgs, ... }:
 {
   sane.programs.megapixels = {
+    packageUnwrapped = pkgs.megapixels.overrideAttrs (upstream: {
+      postPatch = (upstream.postPatch or "") + ''
+        # patch it to save photos in a more specific directory
+        substituteInPlace src/process_pipeline.c \
+          --replace-fail 'XDG_PICTURES_DIR' 'XDG_PHOTOS_DIR'
+      '';
+    });
     # megapixels sandboxing is tough:
     # if misconfigured, preview will alternately be OK, black, or only 1/4 of it will be rendered -- with no obvious pattern.
     # adding all of ~ to the sandbox will sometimes (?) fix the flakiness, even when `strace` doesn't show it accessing any files...
@@ -19,7 +26,7 @@
       ".local/share/applications"  #< needed for viewing photos, until i can sort out the portal stuff
       ".cache/mesa_shader_cache"  # loads way faster
       "tmp"
-      "Pictures"  #< TODO: make this Pictures/Photos and save photos there
+      "Pictures/Photos"
       # also it addresses a lot via relative path.
     ];
     sandbox.extraPaths = [