third_party/vello/BUILD.gn

# Copyright 2023 Google LLC
#
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import("../../gn/skia.gni")
import("../third_party.gni")

# The following shells out to bazelisk to compile static library dependencies that bridge the
# vello_cpp crate Rust code and its C++ FFI symbols. This produces a single static library target
# that is reachable via the ":vello" target.
#
# Pre-compiled shader dependencies:
#
#   The vello_shaders crate bundles compute shaders that are pre-compiled into a target format based
#   on the GPU backend. This is driven by build arguments defined in //gn/skia.gni.

if (skia_enable_vello_shaders) {
  bazel_args = []
  if (is_mac) {
    if (host_cpu == "arm64") {
      bazel_args += [ "--host_platform=//bazel/platform:mac_arm64_hermetic" ]
    }
    if (target_cpu == "arm64") {
      bazel_args += [
        "--platforms=//bazel/platform:mac_arm64_hermetic",
        "--cc_output_directory_tag=mac_arm64",
      ]
    }
  }
  if (!is_debug) {
    bazel_args += [ "--compilation_mode=opt" ]
  }
  if (skia_use_metal) {
    bazel_args += [ "--define=VELLO_MSL_SHADERS=true" ]
  }
  if (skia_use_dawn) {
    bazel_args += [ "--define=VELLO_WGSL_SHADERS=true" ]
  }
  action("compile_vello_ffi") {
    script = "../../gn/bazel_build.py"
    sources = [
      "BUILD.bazel",
      "src/lib.rs",
    ]
    outputs = [
      "$root_out_dir/libvello_ffi.a",
      "$root_out_dir/third_party/vello/src/lib.rs.h",
    ]
    args = [
             "//third_party/vello:vello_ffi",
             rebase_path("//bazel-bin/third_party/vello/libvello_ffi.a",
                         root_build_dir),

             # we want the header to not simply be copied into the output directory,
             # but in the same path as the Bazel build uses.
             rebase_path("//bazel-bin/third_party/vello/src/lib.rs.h",
                         root_build_dir) + "=third_party/vello/src/lib.rs.h",
           ] + bazel_args
  }

  action("compile_vello_rust") {
    script = "../../gn/bazel_build.py"
    sources = [
      "BUILD.bazel",
      "src/encoding.rs",
      "src/lib.rs",
      "src/shaders.rs",
    ]
    outputs = [ "$root_out_dir/libvello_rust.a" ]
    args = [
             "//third_party/vello:vello_rust",
             rebase_path("//bazel-bin/third_party/vello/libvello_rust.a",
                         root_build_dir),
           ] + bazel_args
  }
}

third_party("vello") {
  # this is where third_party/vello/src/lib.rs.h was generated and exists.
  public_include_dirs = [ "$root_out_dir" ]
  libs = [
    "$root_out_dir/libvello_ffi.a",
    "$root_out_dir/libvello_rust.a",
  ]
  deps = [
    ":compile_vello_ffi",
    ":compile_vello_rust",
  ]
}