Move constants into a shoes.rb to start off shoes.rb as separate

.yardopts

@@ -3,6 +3,8 @@
 --protected
 --no-private
 --template-path docs/yard/template
+--tag incompatibility:"Incompatibilities with Shoes"
+--exclude lib/scarpe/libui
 -
 lib/**/*.rb
 docs/yard/*.md

lib/scarpe.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "shoes"
+
 require_relative "scarpe/logger"
 
 # This will never be triggered -- we use the (...) feature below, which means this
@@ -15,7 +17,6 @@
 # Is there a Shoes::Error class? Should this be two different error classes?
 class Scarpe::Error < StandardError; end
 
-require_relative "scarpe/constants"
 require_relative "scarpe/version"
 require_relative "scarpe/promises"
 require_relative "scarpe/display_service"
@@ -26,16 +27,3 @@ class Scarpe::Error < StandardError; end
 d_s = ENV["SCARPE_DISPLAY_SERVICE"] || "wv_local"
 # This is require, not require_relative, to allow gems to supply a new display service
 require "scarpe/#{d_s}"
-
-include Constants
-
-module Shoes
-  class << self
-    def app(...)
-      app = Shoes::App.new(...)
-      app.init
-      app.run
-      app.destroy
-    end
-  end
-end

lib/shoes.rb

@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+# We're separating Shoes from Scarpe, a little at a time. This should eventually be requirable
+# without using Scarpe at all.
+#
+# This Shoes gem will, if all goes well, be a lot like the old Shoes-core from Shoes4: a way
+# to handle the DSL and command-line parts of Shoes without knowing anything about how the
+# display side works at all.
+
+# This will never be triggered -- we use the (...) feature below, which means this
+# file won't even parse in old Rubies.
+if RUBY_VERSION[0..2] < "3.2"
+  Scarpe::Logger.logger("Scarpe").error("Scarpe requires Ruby 3.2 or higher!")
+  exit(-1)
+end
+
+require_relative "shoes/constants"
+module Kernel
+  include Shoes::Constants
+end
+
+class Shoes::Error < StandardError; end
+
+# The module containing Shoes in all its glory.
+# Shoes is a platform-independent GUI library, designed to create
+# small visual applications in Ruby.
+#
+module Shoes
+  class << self
+    # Creates a Shoes app with a new window. The block parameter is used to create
+    # widgets and set up handlers. Arguments are passed to Shoes::App.new internally.
+    #
+    # @incompatibility In Shoes3, this method will return normally.
+    #   In Scarpe, after the block is executed, the method will not return and Scarpe
+    #   will retain control of execution until the window is closed and the app quits.
+    #
+    # @incompatibility In Shoes3 the parameters were a hash of options, not keyword arguments.
+    #
+    # @example Simple one-button app
+    #   Scarpe.app(title: "Button!", width: 200, height: 200) do
+    #     @p = para "Press it NOW!"
+    #     button("clicky") { @p.replace("You pressed it! CELEBRATION!") }
+    #   end
+    #
+    # @param title [String] The new app window title
+    # @param width [Integer] The new app window width
+    # @param height [Integer] The new app window height
+    # @param resizable [Boolean] Whether the app window should be resizeable
+    # @return [void]
+    # @see Shoes::App#new
+    def app(
+      title: "Scarpe!",
+      width: 480,
+      height: 420,
+      resizable: true,
+      &app_code_body
+    )
+      app = Shoes::App.new(title:, width:, height:, resizable:, &app_code_body)
+      app.init
+      app.run
+      app.destroy
+      nil
+    end
+  end
+end

lib/shoes/constants.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+require "tmpdir"
+
+module Shoes
+  module Constants
+    def self.find_lib_dir
+      homes = [
+        [ENV["LOCALAPPDATA"], "Shoes"],
+        [ENV["APPDATA"], "Shoes"],
+        [ENV["HOME"], ".shoes"],
+        [Dir.tmpdir, "shoes"],
+      ]
+      top, file = homes.detect { |home_top, _| home_top && File.exist?(home_top) }
+      File.join(top, file)
+    end
+
+    LIB_DIR = find_lib_dir
+
+    # Math constants from Shoes3
+    RAD2PI = 0.01745329251994329577
+    TWO_PI = 6.28318530717958647693
+    HALF_PI = 1.57079632679489661923
+    PI = 3.14159265358979323846
+  end
+end