From 7b09facd05ebcc8b915c7cc920dfd0133c2664b3 Mon Sep 17 00:00:00 2001
From: Victor Engmark <victor@engmark.name>
Date: Mon, 14 Oct 2024 17:21:04 +1300
Subject: [PATCH] scarab: Apply scaling factor in Wayland

Sets `AVALONIA_GLOBAL_SCALE_FACTOR` to the GNOME desktop scaling factor
based on
<https://github.com/AvaloniaUI/Avalonia/issues/9390#issuecomment-2382126451>,
falling back to the X FreeType DPI setting if the former is not
available.

Does not include `gsettings` and `xrdb` in build inputs, since these
should be available on the relevant platforms.

Bash does not support decimal/floating point arithmetic, so this *does*
include `bc` in the runtime dependencies.
---
 pkgs/tools/games/scarab/default.nix           |  7 ++++++
 pkgs/tools/games/scarab/scaling-settings.bash | 24 +++++++++++++++++++
 2 files changed, 31 insertions(+)
 create mode 100644 pkgs/tools/games/scarab/scaling-settings.bash

diff --git a/pkgs/tools/games/scarab/default.nix b/pkgs/tools/games/scarab/default.nix
index 26de0b1f9a2937..844d38ed006342 100644
--- a/pkgs/tools/games/scarab/default.nix
+++ b/pkgs/tools/games/scarab/default.nix
@@ -1,5 +1,6 @@
 {
   lib,
+  bc,
   buildDotnetModule,
   fetchFromGitHub,
   copyDesktopItems,
@@ -29,6 +30,10 @@ buildDotnetModule rec {
       -n nuget.org --configfile NuGet.Config
   '';
 
+  runtimeDeps = [
+    bc
+  ];
+
   nativeBuildInputs = [
     copyDesktopItems
     icoutils
@@ -45,6 +50,8 @@ buildDotnetModule rec {
       size=''${sizes[$i]}x''${sizes[$i]}
       install -D omegamaggotprime_''$((i+1))_''${size}x32.png $out/share/icons/hicolor/$size/apps/scarab.png
     done
+
+    wrapProgram "$out/bin/Scarab" --run '. ${./scaling-settings.bash}'
   '';
 
   desktopItems = [
diff --git a/pkgs/tools/games/scarab/scaling-settings.bash b/pkgs/tools/games/scarab/scaling-settings.bash
new file mode 100644
index 00000000000000..8bec5c898ef6ec
--- /dev/null
+++ b/pkgs/tools/games/scarab/scaling-settings.bash
@@ -0,0 +1,24 @@
+# Keep existing value if it is already non-empty
+if [[ -z "${AVALONIA_GLOBAL_SCALE_FACTOR-}" ]] && type gsettings >/dev/null; then
+    echo 'Attempting to get GNOME desktop interface scaling factor' >&2
+    AVALONIA_GLOBAL_SCALE_FACTOR="$(gsettings get org.gnome.desktop.interface scaling-factor)"
+    AVALONIA_GLOBAL_SCALE_FACTOR="${AVALONIA_GLOBAL_SCALE_FACTOR##* }"
+fi
+
+if [[ -z "${AVALONIA_GLOBAL_SCALE_FACTOR-}" ]] && type xrdb >/dev/null; then
+    echo 'Attempting to get scaling factor from X FreeType DPI setting' >&2
+    dpi="$(xrdb -get Xft.dpi)"
+    if [[ -n "${dpi}" ]]; then
+        AVALONIA_GLOBAL_SCALE_FACTOR=$(echo "scale=2; ${dpi}/96" | bc)
+    fi
+fi
+
+if [[ "${AVALONIA_GLOBAL_SCALE_FACTOR-}" == "0" ]]; then
+    echo 'Unset invalid scaling value' >&2
+    unset AVALONIA_GLOBAL_SCALE_FACTOR
+fi
+
+if [[ -n "${AVALONIA_GLOBAL_SCALE_FACTOR-}" ]]; then
+    echo "Applying scale factor: ${AVALONIA_GLOBAL_SCALE_FACTOR}" >&2
+    export AVALONIA_GLOBAL_SCALE_FACTOR
+fi