feat(mc): open files with their configured app via xdg-open

Ship `mc.ext.ini` as the `local.mc.extIni` option (like `local.mc.menu`):
Enter browses archives in-place as before and delegates every other type to
`xdg-open`. Add public `mime.nix` with `xdg.mimeApps` defaults (pdf ->
zathura, images -> imv, audio/video -> mpv, office -> libreoffice) -- public
because those handlers are; personal browser/mail defaults stay private.

Also document, at the Hyprland swallow config, how swallowing differs from an
app opening fullscreen/maximized (LibreOffice restores its own maximized state
and looks swallowed but isn't).

modules/assets/mc/mc.ext.ini

@@ -0,0 +1,81 @@
+# Midnight Commander file associations (public baseline).
+#
+# mc reads a SINGLE mc.ext.ini; this user copy fully replaces the system one
+# (they are not merged), so it must also carry the archive entries we keep.
+#
+# Policy: Enter (Open) on an archive mounts it as a virtual filesystem (mc
+# built-in, no external helper). Every other file falls through to [Default],
+# which runs `xdg-open` -- so the app is whatever the XDG mimeapps default
+# resolves to (set those in the private inventory's xdg.mimeApps). One source of
+# truth, shared with every other launcher; nothing app-specific baked in here.
+#
+# Note: office documents (.docx/.odt/.xlsx/...) are ZIP containers, so they are
+# deliberately absent from the [zip] entry below -- otherwise Enter would mount
+# them as archives instead of handing them to LibreOffice via xdg-open.
+#
+# Override contract (this is a types.lines option shipped as mkBefore): append a
+# same-named section to override one key -- mc merges same-named sections and
+# the last key wins -- e.g. add a [Default] with a different Open to change the
+# fallback, or add [pdf] Type=^PDF / Open=mupdf %f & to force one type to a
+# specific app. lib.mkForce "..." replaces this baseline wholesale.
+
+[mc.ext.ini]
+Version=4.0
+
+### Archives: Enter mounts them as a virtual filesystem (F3/F4 unaffected) ###
+
+[tar]
+Regex=\\.(tar(\\.(gz|bz2|xz|zst|lz|lz4|lzo|Z))?|t(gz|az|bz2?|xz|zst|lz))$
+Open=%cd %p/utar://
+
+[zip]
+Regex=\\.(zip|jar|xpi|whl|egg|apk|war|ear)$
+Open=%cd %p/uzip://
+
+[7z]
+Shell=.7z
+Open=%cd %p/u7z://
+
+[rar]
+Regex=\\.r(ar|[0-9][0-9])$
+Open=%cd %p/urar://
+
+[arj]
+Regex=\\.a(rj|[0-9][0-9])$
+Open=%cd %p/uarj://
+
+[cab]
+Shell=.cab
+Open=%cd %p/ucab://
+
+[cpio]
+Regex=\\.cpio(\\.(gz|xz|bz2|zst|lz|lz4|lzo|Z))?$
+Open=%cd %p/ucpio://
+
+[deb]
+Regex=\\.u?deb$
+Open=%cd %p/deb://
+
+[rpm]
+Regex=\\.(rpm|src\\.rpm|spm)$
+Open=%cd %p/rpm://
+
+[iso]
+Shell=.iso
+Open=%cd %p/iso9660://
+
+[patch]
+Regex=\\.(diff|patch)(\\.(gz|bz2|xz|zst|Z))?$
+Open=%cd %p/patchfs://
+
+### Everything else: hand off to the desktop's configured default app ###
+
+# `&` backgrounds xdg-open so mc's shell returns and the launched GUI is orphaned
+# to init. Hyprland only swallows the terminal when the new window's parent-PID
+# chain still has a foot ancestor (getSwallower in Hyprland's Window.cpp), so an
+# orphaned app opens as its own tile instead of swallowing mc (zathura, imv, ...).
+# %f MUST stay unquoted: mc already backslash-escapes the path, so quoting turns
+# those backslashes literal and breaks filenames with spaces.
+
+[Default]
+Open=xdg-open %f &

modules/home.nix

@@ -81,7 +81,7 @@ let
   '';
 in
 {
-  imports = [ ./gpg.nix ./media.nix ./texlive.nix ./librewolf.nix ./mc.nix ];
+  imports = [ ./gpg.nix ./media.nix ./texlive.nix ./librewolf.nix ./mc.nix ./mime.nix ];
 
   # Put ~/.local/bin (the XDG user-bin dir) on PATH so hand-dropped scripts run
   # by name without wiring each through nix.
@@ -521,7 +521,25 @@ in
         # Matches on the *parent* terminal's class. Needs standalone foot: in
         # server/client mode all windows share one process, so PID ancestry can't
         # tell them apart and swallowing breaks — that's why $mod+Return runs
-        # `foot`, not `footclient`.
+        # `foot`, not `footclient`. Swallow is decided by getSwallower() walking
+        # the new window's parent-PID chain (up to 25 hops) for a window whose
+        # class matches swallow_regex; swallow_exception_regex, if set, matches the
+        # *terminal's title*, not the new window's class (a common misreading).
+        #
+        # Do NOT confuse swallowing with an app opening fullscreen/maximized — they
+        # look identical (the launching terminal vanishes) but are different things:
+        #   - real swallow removes the terminal from the layout and restores it only
+        #     when the swallower closes; you cannot un-swallow a live window.
+        #   - a fullscreen/maximized app merely covers the workspace; the launcher
+        #     is still a tile underneath and $mod+f / $mod SHIFT f toggles it back.
+        # `hyprctl clients` is decisive: a real swallow shows the terminal
+        # hidden=true and the new window swallowing!=0x0. LibreOffice trips this —
+        # it restores its own maximized state on open (from mc or a shell), so a
+        # document appears to "swallow" mc when it is only fullscreen. And being
+        # single-instance (one soffice.bin owns every window via IPC handoff), when
+        # it genuinely does swallow, that is fixed by whatever launched its daemon,
+        # not per-open — so it can't do the tile-from-mc / swallow-from-shell split
+        # that single-process handlers like zathura/imv get for free.
         enable_swallow = true;
         swallow_regex = "^(foot)$";
       };

modules/mc.nix

@@ -1,7 +1,9 @@
-# Midnight Commander: TUI file manager. Its config (ini, panels, F2 user menu)
+# Midnight Commander: TUI file manager. Its config (ini, panels, F2 user menu,
-# is opinionated but generic, so it lives in the public baseline alongside the
+# mc.ext.ini file associations) is opinionated but generic, so it lives in the
-# other desktop tooling. The only personal value is the right-panel start dir,
+# public baseline alongside the other desktop tooling. The only personal value
-# exposed as an option defaulting to the consumer's own home.
+# is the right-panel start dir, exposed as an option defaulting to the
+# consumer's own home. mc.ext.ini keeps archive browsing but routes every other
+# type to xdg-open, so the app choices live in xdg.mimeApps (baseline: mime.nix).
 #
 # ouch backs the F2 pack/unpack entries (one tool, archive format inferred from
 # the extension), so it ships with mc to keep the menu self-contained.
@@ -37,16 +39,30 @@
         lib.mkForce to replace it entirely.
       '';
     };
+
+    extIni = lib.mkOption {
+      type = lib.types.lines;
+      description = ''
+        Contents of mc's mc.ext.ini (file-type associations driving Enter/F3/F4).
+        The shipped baseline keeps mc's archive browsing and delegates every
+        other type to xdg-open, so the actual app is the XDG mimeapps default.
+        Like `menu`, it is a mkBefore definition: append a same-named section to
+        override one key (mc merges same-named sections, last key wins), or use
+        lib.mkForce to replace it entirely.
+      '';
+    };
   };
 
   config = {
     home.packages = [ pkgs.mc pkgs.ouch ];
 
     local.mc.menu = lib.mkBefore (builtins.readFile ./assets/mc/menu);
+    local.mc.extIni = lib.mkBefore (builtins.readFile ./assets/mc/mc.ext.ini);
 
     xdg.configFile = {
       "mc/ini".source = ./assets/mc/ini;
       "mc/menu".text = config.local.mc.menu;
+      "mc/mc.ext.ini".text = config.local.mc.extIni;
 
       # Generated (not a static asset) so other_dir tracks the option instead of
       # baking in a personal path.

modules/mime.nix

@@ -0,0 +1,75 @@
+# Default applications per file type -- the single source of truth for "open
+# with" across the desktop: xdg-open, file pickers, and Enter in mc (whose
+# mc.ext.ini delegates every non-archive type to xdg-open; see mc.nix).
+#
+# These belong in the public baseline because the handlers do too: zathura, imv
+# and mpv come from media.nix, libreoffice from home.nix. So "PDF opens in
+# zathura", "images in imv", etc. are the natural defaults of this baseline, not
+# personal choices -- every entry is mkDefault, so a consumer overrides one type
+# by setting the same key (their definition wins), or flips enable off entirely.
+#
+# Personal handlers -- web browser, mail -- are NOT here; they map to a specific
+# browser profile / mail client and live in the private inventory, merging into
+# the same defaultApplications attrset.
+
+{ lib, ... }:
+
+let
+  # Map every mime in the list to one .desktop id, at mkDefault priority.
+  forAll = desktop: mimes: lib.genAttrs mimes (_: lib.mkDefault desktop);
+
+  zathura = "org.pwmt.zathura.desktop";
+  imv     = "imv.desktop";
+  mpv     = "mpv.desktop";
+  writer  = "writer.desktop";
+  calc    = "calc.desktop";
+  impress = "impress.desktop";
+in {
+  xdg.mimeApps.enable = lib.mkDefault true;
+
+  xdg.mimeApps.defaultApplications =
+    (forAll zathura [
+      "application/pdf"
+      "application/epub+zip"
+      "application/oxps"
+      "application/postscript"
+    ])
+    // (forAll imv [
+      "image/png"
+      "image/jpeg"
+      "image/gif"
+      "image/webp"
+      "image/bmp"
+      "image/tiff"
+    ])
+    // (forAll mpv [
+      "video/mp4"
+      "video/x-matroska"
+      "video/webm"
+      "video/x-msvideo"
+      "video/quicktime"
+      "video/mpeg"
+      "audio/mpeg"
+      "audio/flac"
+      "audio/ogg"
+      "audio/x-wav"
+      "audio/mp4"
+      "audio/x-opus+ogg"
+    ])
+    // (forAll writer [
+      "application/vnd.openxmlformats-officedocument.wordprocessingml.document"
+      "application/msword"
+      "application/vnd.oasis.opendocument.text"
+      "application/rtf"
+    ])
+    // (forAll calc [
+      "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
+      "application/vnd.ms-excel"
+      "application/vnd.oasis.opendocument.spreadsheet"
+    ])
+    // (forAll impress [
+      "application/vnd.openxmlformats-officedocument.presentationml.presentation"
+      "application/vnd.ms-powerpoint"
+      "application/vnd.oasis.opendocument.presentation"
+    ]);
+}