load a runtime file where the prefix is determined at comptime

build.zig

@@ -1,4 +1,5 @@
 const std = @import("std");
+const builtin = @import("builtin");
 
 const Scanner = @import("wayland").Scanner;
 
@@ -6,6 +7,13 @@ pub fn build(b: *std.Build) void {
   const target = b.standardTargetOptions(.{});
   const optimize = b.standardOptimizeOption(.{});
 
+  // TODO: this will probably change based on the install paths, make this a var
+  // that can be passed at comptime?
+  const runtime_path_prefix = switch (builtin.mode) {
+    .Debug => "runtime/",
+    else => "/usr/share",
+  };
+
   // If instead your goal is to create an executable, consider if users might
   // be interested in also being able to embed the core functionality of your
   // program in their own executable in order to avoid the overhead involved in
@@ -60,6 +68,10 @@ pub fn build(b: *std.Build) void {
   mez.linkSystemLibrary("xkbcommon");
   mez.linkSystemLibrary("pixman-1");
 
+  const options = b.addOptions();
+  options.addOption([]const u8, "runtime_path_prefix", runtime_path_prefix);
+  mez.root_module.addOptions("config", options);
+
   b.installArtifact(mez);
 
   const run_step = b.step("run", "Run the app");

runtime/share/mezzaluna/init.lua

@@ -0,0 +1 @@
+print("hello from our runtime file")

src/lua.zig

@@ -0,0 +1,43 @@
+const Lua = @This();
+
+const std = @import("std");
+const config = @import("config");
+const zlua = @import("zlua");
+
+const gpa = std.heap.c_allocator;
+
+state: *zlua.Lua,
+
+fn loadRuntimeDir(self: *Lua) !void {
+  const tmppath = try std.fs.path.join(gpa, &[_][]const u8{
+    config.runtime_path_prefix,
+    "share",
+    "mezzaluna",
+    "init.lua",
+  });
+  var path_buffer = try gpa.alloc(u8, tmppath.len + 1);
+  std.mem.copyForwards(u8, path_buffer[0..tmppath.len], tmppath);
+  path_buffer[tmppath.len] = 0;
+  const path: [:0]u8 = path_buffer[0..tmppath.len :0];
+
+  try self.state.doFile(path);
+}
+
+pub fn init(self: *Lua) !void {
+  self.state = try zlua.Lua.init(gpa);
+  errdefer self.state.deinit();
+  self.state.openLibs();
+
+  {
+    self.state.newTable();
+    defer _ = self.state.pushString("mez");
+  }
+
+  try loadRuntimeDir(self);
+
+  std.log.debug("Loaded lua", .{});
+}
+
+pub fn deinit(self: *Lua) void {
+  self.state.deinit();
+}

src/main.zig

@@ -1,25 +1,20 @@
 const std = @import("std");
 const wlr = @import("wlroots");
 
-const zlua = @import("zlua");
-const Lua = zlua.Lua;
-
 const Server = @import("server.zig");
+const Lua = @import("lua.zig");
 
 const gpa = std.heap.c_allocator;
 
 pub var server: Server = undefined;
+pub var lua: Lua = undefined;
 
 pub fn main() !void {
   wlr.log.init(.err, null);
 
-  var lua = try Lua.init(gpa);
-  defer lua.deinit();
-  lua.openLibs();
-  lua.doString("print('Hello from Lua embedded in Zig!')") catch {};
-
   std.log.info("Starting mezzaluna", .{});
 
+  try lua.init();
   try server.init();
   defer server.deinit();