generate a built-in kernel font

Rsconscript

@@ -4,6 +4,7 @@ configure do
   check_program "grub-mkstandalone"
   check_program "mformat", on_fail: "Install the mtools package"
   check_program "xorriso"
+  check_cfg package: "freetype2", on_fail: "Install libfreetype-dev", use: "freetype"
 end
 
 build do
@@ -13,6 +14,8 @@ build do
   EFI_PART_SIZE = 8
   # HOS partition size (MiB)
   HOS_PART_SIZE = 4
+  # Kernel default font size
+  KFONT_SIZE = 12
 
   class BiosImage < Builder
     def run(options)
@@ -94,14 +97,36 @@ EOF
     end
   end
 
+  class FontGen < Builder
+    def run(options)
+      if @command
+        finalize_command
+      else
+        @sources += ["build/fontgen"]
+        command = %W[build/fontgen #{@sources.first} #{KFONT_SIZE} #{@target}]
+        standard_command("FontGen <target>#{@target}<reset>", command, {})
+      end
+    end
+  end
+
+  # FontGen Environment
+  Environment.new(use: "freetype") do |env|
+    env["CC"] = "gcc"
+    env.Program("build/fontgen", glob("fontgen/**/*.c"))
+  end
+
+  # Kernel Environment
   Environment.new do |env|
     env.add_builder(EfiImage)
     env.add_builder(BiosImage)
+    env.add_builder(FontGen)
     env["CCFLAGS"] += %w[-ffreestanding -Wall]
     env["LDFLAGS"] += %w[-ffreestanding -nostdlib -T src/link.ld]
     env["LIBS"] += %w[gcc]
     env["OBJDUMP"] = "i686-elf-objdump"
-    env.Program("^/hos.elf", glob("src/**/*.{S,c}"))
+    env.FontGen("^/fontgen/fontgen.c", "font/Hack-Regular.ttf")
+    env["CPPPATH"] += ["#{env.build_root}/fontgen"]
+    env.Program("^/hos.elf", glob("src/**/*.{S,c}") + ["^/fontgen/fontgen.c"])
     env.depends("#{env.build_root}/hos.elf", "src/link.ld")
     env.Disassemble("^/hos.elf.txt", "^/hos.elf")
     env.EfiImage("build/hos-efi.img", %w[^/hos.elf])