# Copyright 2014 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import("//build/symlink.gni")

# There are three machines involved with building and running tests:
# * the build host, where GN, ninja, and the build tools run
# * the test host, where the swarming task runs
# * the test target, where the test collateral runs
#
# image_diff runs on the test host.
#
# Normally all three machines can be built for using the same toolchain, but
# cross-compilation is an important exception. A few of these are:
# * Linux build host + Windows test host + Windows test target
# * Linux build host + Linux test host + Android test target
#
# Since the concept of a 'test host' toolchain is very rarely needed, GN does
# not provide it. Instead, determine it here.
if (target_os == "win" && host_os != "win") {
  # When targeting Windows from not Windows, use the test target toolchain.
  imagediff_toolchain = default_toolchain
} else if (target_os != host_os) {
  # In common cross-compilation scenarios, the build host matches the test host.
  # TODO: In chrome/android-on-mac cross builds, image_diff would still have to
  # be built for Linux and this line is wrong.
  imagediff_toolchain = host_toolchain
} else {
  # When not cross-compiling, use the test target toolchain.
  imagediff_toolchain = default_toolchain
}

# If the current toolchain is the test host toolchain, build the tool.
if (current_toolchain == imagediff_toolchain) {
  executable("imagediff") {
    output_name = "image_diff"  # Different than dir name for historical
                                # reasons.
    sources = [
      "image_diff.cc",
      "image_diff_png.cc",
      "image_diff_png.h",
    ]

    configs += [ "//build/config/compiler:wexit_time_destructors" ]

    deps = [
      "//base",
      "//build/win:default_exe_manifest",
      "//third_party/libpng",
      "//third_party/zlib",
    ]
  }
  # Otherwise, if the current toolchain is the test target toolchain, make a
  # symlink to the test host toolchain output so the tests can find it.
  #
  # Note that Windows does not follow links when searching for DLLs, so
  # image_diff.exe from component builds won't run via symlink. Fortunately,
  # Windows builds use the default_toolchain and so avoid making the link.
} else if (current_toolchain == default_toolchain &&
           default_toolchain != imagediff_toolchain) {
  binary_symlink("imagediff") {
    binary_label = ":$target_name($imagediff_toolchain)"
    binary_output_name = "image_diff"

    # For Windows builds, the test host and test target are both Windows and so
    # binary_symlink needs to use the Windows binary suffix.
    if (target_os == "win") {
      binary_output_name += ".exe"
    }
  }
}