engine/src/flutter/impeller/tools/metal_library.gni

# Copyright 2013 The Flutter Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# ------------------------------------------------------------------------------
# @brief           Build a Metal Library. The output is a single file. Use
#                  get_target_outputs to get its location on build.
#
# @param[required] name     The name of the Metal library.
#
# @param[required] sources  The GLSL (4.60) sources to compiled into the Metal
#                           library.
#
# @param[required] metal_version  The Metal language version to compile for.
#
template("metal_library") {
  assert(is_ios || is_mac)
  assert(defined(invoker.name), "Metal library name must be specified.")
  assert(defined(invoker.sources), "Metal source files must be specified.")
  assert(defined(invoker.metal_version),
         "Metal language version must be specified.")

  metal_library_name = invoker.name

  action("$target_name") {
    forward_variables_from(invoker,
                           "*",
                           [
                             "inputs",
                             "outputs",
                             "script",
                             "depfile",
                             "args",
                           ])

    inputs = invoker.sources

    metal_library_path = "$root_out_dir/shaders/$metal_library_name.metallib"
    metal_library_symbols_path =
        "$root_out_dir/shaders/$metal_library_name.metallibsym"

    outputs = [
      metal_library_path,
      metal_library_symbols_path,
    ]

    script = "//flutter/impeller/tools/metal_library.py"

    depfile = "$target_gen_dir/mtl/$metal_library_name.depfile"

    args = [
      "--output",
      rebase_path(metal_library_path, root_out_dir),
      "--depfile",
      rebase_path(depfile),
      "--metal-version=$metal_version",
    ]

    if (is_ios) {
      if (use_ios_simulator) {
        args += [ "--platform=ios-simulator" ]
      } else {
        args += [ "--platform=ios" ]
      }
    } else if (is_mac) {
      args += [ "--platform=mac" ]
    } else {
      assert(false, "Unsupported platform for generating Metal shaders.")
    }

    foreach(source, invoker.sources) {
      args += [
        "--source",
        rebase_path(source, root_out_dir),
      ]
    }
  }
}