sxmo: auto-scale the environment to accomodate non-mobile-friendly apps

this is hacky, but it hopefully makes gnome-maps usable, quickly.
an alternative fix would be to theme gnome-maps.
it's likely also that it becomes more mobile-friendly in the gnome 45
release.

hosts/common/programs/default.nix

@@ -67,6 +67,7 @@
     ./stepmania.nix
     ./sublime-music.nix
     ./supertuxkart.nix
+    ./sway-autoscaler
     ./swaynotificationcenter.nix
     ./tangram.nix
     ./tor-browser-bundle-bin.nix

hosts/common/programs/sway-autoscaler/default.nix

@@ -0,0 +1,44 @@
+{ config, lib, pkgs, ... }:
+let
+  cfg = config.sane.programs.sway-autoscaler;
+in
+{
+  sane.programs.sway-autoscaler = {
+    configOption = with lib; mkOption {
+      default = {};
+      type = types.submodule {
+        options.autostart = mkOption {
+          type = types.bool;
+          default = false;
+        };
+
+        options.defaultScale = mkOption {
+          type = types.number;
+          default = 1;
+        };
+        options.interval = mkOption {
+          type = types.number;
+          default = 5;
+        };
+      };
+    };
+
+    package = pkgs.static-nix-shell.mkBash {
+      pname = "sway-autoscaler";
+      pkgs = [ "jq" "sway" ];
+      src = ./.;
+    };
+
+    services.sway-autoscaler = {
+      description = "adjust global desktop scale to match the activate application";
+      wantedBy = lib.mkIf cfg.config.autostart [ "default.target" ];
+      serviceConfig = {
+        ExecStart = "${cfg.package}/bin/sway-autoscaler --loop-sec ${builtins.toString cfg.config.interval}";
+        Type = "simple";
+        Restart = "always";
+        RestartSec = "10s";
+      };
+      environment.SWAY_DEFAULT_SCALE = builtins.toString cfg.config.defaultScale;
+    };
+  };
+}

hosts/common/programs/sway-autoscaler/sway-autoscaler

@@ -0,0 +1,69 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash -p jq -p sway
+
+help() {
+  echo "queries the focused window and apply an appropriate display-wide scale."
+  echo "this should be considered a temporary workaround until more apps support small displays."
+  echo ""
+  echo "args:"
+  echo "  -v | --verbose"
+  echo "  --loop-sec N  re-compute the scale every N seconds. else, run once and exit."
+  echo ""
+  echo "environment variables:"
+  echo "  SWAY_DEFAULT_SCALE=N  scale to apply when no known window is selected."
+  # TODO: could use map-style environment variables to allow external per-app config
+  # - SWAY_SCALE_org.gnome.Maps=1  ; ...
+}
+
+options=$(getopt -l verbose,loop-sec: -o v -- "" "${@}")
+eval "set -- ${options}"
+
+verbose=false
+loop=false
+loop_sec=
+while true; do
+  case "$1" in
+    (-v|--verbose)
+      verbose=true
+      shift
+    ;;
+    (--loop-sec)
+      shift
+      loop=true
+      loop_sec="$1"
+      shift
+    ;;
+    (--)
+      shift
+      if [ $# -eq 1 ]; then
+        break
+      fi
+    ;;
+    (*)
+      echo "invalid arguments: '$1'"
+      exit 1
+    ;;
+  esac
+done
+
+autoscale() {
+  focused=$(swaymsg -t get_tree | jq --raw-output '.. | select(.type?) | select(.focused==true) | .app_id')
+  $verbose && echo "focused: '$focused'"
+
+  scale=${SWAY_DEFAULT_SCALE:-1}
+  case "$focused" in
+    org.gnome.Maps) scale=1
+  esac
+
+  $verbose && echo "scaling to $scale"
+  swaymsg -q -- output '*' scale "$scale"
+}
+
+if $loop; then
+  while true; do
+    autoscale
+    sleep "$loop_sec"
+  done
+else
+  autoscale
+fi

hosts/modules/gui/sxmo/default.nix

@@ -236,6 +236,7 @@ in
             # SXMO_WM = mkSettingsOpt "sway" "sway or dwm. ordinarily initialized by sxmo_{x,w}init.sh";
             SXMO_NO_AUDIO = mkSettingsOpt "1" "don't start pipewire/pulseaudio in sxmo_hook_start.sh";
             SXMO_STATES = mkSettingsOpt "unlock screenoff" "list of states the device should support (unlock, lock, screenoff)";
+            SXMO_SWAY_SCALE = mkSettingsOpt "1" "sway output scale";
           };
       };
       default = {};
@@ -265,6 +266,7 @@ in
           "bemenu"  # specifically to import its theming
           "sfeed"      # want this here so that the user's ~/.sfeed/sfeedrc gets created
           # "superd"     # make superctl (used by sxmo) be on PATH
+          "sway-autoscaler"
         ];
 
         persist.byStore.cryptClearOnBoot = [
@@ -382,6 +384,8 @@ in
 
         sane.programs.sxmoApps.enableFor.user.colin = true;
 
+        sane.programs.sway-autoscaler.config.defaultScale = builtins.fromJSON cfg.settings.SXMO_SWAY_SCALE;
+
         # sxmo internally uses doas instead of sudo
         security.doas.enable = true;
         security.doas.wheelNeedsPassword = false;