Initial Linux GN build (#149)

Adds an experimental GN-based build as an alternative to the Make-based
build on Linux.

The example application does not use GN for its own build since it is
intended to serve as an example of using the embedding library, so it
continues to use the more common Make as clients are unlikely to be
using GN.

See issue #114

Author: stuartmorgan

.gitignore

@@ -1 +1,2 @@
+out/
 .DS_Store

.gn

@@ -0,0 +1 @@
+buildconfig = "//build/BUILDCONFIG.gn"

BUILD.gn

@@ -0,0 +1,22 @@
+# Copyright 2018 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+group("gn_all") {
+  deps = [
+    "//library:flutter_embedder",
+    "//plugins/color_panel:color_panel",
+    "//plugins/file_chooser:file_chooser",
+    "//plugins/menubar:menubar",
+  ]
+}

build/BUILD.gn

@@ -0,0 +1,32 @@
+# Copyright 2018 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+config("defaults") {
+  cflags = [
+    "-std=c++14",
+    "-Wall",
+    "-Werror",
+    "-pthread",
+  ]
+  include_dirs = [
+    "//"
+  ]
+}
+
+config("shared_library_defaults") {
+  cflags = [
+    "-shared",
+    "-fPIC",
+  ]
+}

build/BUILDCONFIG.gn

@@ -0,0 +1,42 @@
+# Copyright 2018 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set_default_toolchain("//third_party/chromium/build/toolchain:gcc")
+
+set_defaults("executable") {
+  configs = [ "//build:defaults" ]
+}
+set_defaults("static_library") {
+  configs = [ "//build:defaults" ]
+}
+set_defaults("shared_library") {
+  configs = [ "//build:defaults", "//build:shared_library_defaults" ]
+}
+set_defaults("published_shared_library") {
+  configs = [ "//build:defaults", "//build:shared_library_defaults" ]
+}
+
+if (host_os == "linux") {
+  is_linux = true
+  is_mac = false
+  is_win = false
+} else if (host_os == "mac") {
+  is_linux = false
+  is_mac = true
+  is_win = false
+} else if (host_os == "win") {
+  is_linux = false
+  is_mac = false
+  is_win = true
+}

build/flutter.gni

@@ -0,0 +1,21 @@
+# Copyright 2018 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+declare_args() {
+  # The path to the Flutter tree to use for any Flutter operations or assets.
+  # If empty, assumes a directory called 'flutter' that is a sibling of this
+  # repository (like tools/flutter_location; this duplication avoids shelling
+  # out).
+  flutter_tree_path = rebase_path("../../flutter")
+}

build/linux/config/BUILD.gn

@@ -0,0 +1,31 @@
+# Copyright 2018 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import("//third_party/chromium/build/config/linux/pkg_config.gni")
+
+pkg_config("gtk3") {
+  packages = [ "gtk+-3.0" ]
+}
+
+pkg_config("epoxy") {
+  packages = [ "epoxy" ]
+}
+
+pkg_config("x11") {
+  packages = [ "x11" ]
+}
+
+pkg_config("jsoncpp") {
+  packages = [ "jsoncpp" ]
+}

build/packaging.gni

@@ -0,0 +1,60 @@
+# Copyright 2018 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Puts the public headers of the invoker in public_header_subdir
+# under the top-level include/ directory in the build output.
+#
+# This is intended to make consuming public headers of all the libraries built
+# by GN easy for outside build systems on Linux, by requiring only a single
+# include directory.
+if (is_linux) {
+  template("copy_includes") {
+    copy(target_name) {
+      assert(defined(invoker.sources),
+            "|sources| must be provided for copy_includes.")
+      forward_variables_from(invoker, [ "deps", "sources", "subdir" ])
+      output_dir = "$root_out_dir/include"
+      if (defined(subdir)) {
+        output_dir = "$output_dir/$subdir"
+      }
+      outputs = [ "$output_dir/{{source_file_part}}"]
+    }
+  }
+}
+
+# An abstraction for a shared library with associated headers that is intended
+# to be consumed from the build output.
+#
+# On Linux, this performs a copy_includes in addition to building the library.
+template("published_shared_library") {
+  template_target_name = target_name
+
+  if (is_linux) {
+    copy_includes("_publish_${template_target_name}_headers") {
+      sources = invoker.public
+      subdir = invoker.public_header_subdir
+    }
+
+    shared_library(template_target_name) {
+      forward_variables_from(invoker, "*")
+      assert(defined(public),
+            "|public| must be provided for published_shared_library.")
+
+      if (!defined(deps)) {
+        deps = []
+      }
+      deps += [ ":_publish_${template_target_name}_headers" ]
+    }
+  }
+}

example/linux/Makefile

@@ -58,6 +58,29 @@ BIN_OUT=$(OUT_DIR)/flutter_embedder_example
 ICU_DATA_OUT=$(OUT_DATA_DIR)/$(ICU_DATA_NAME)
 ALL_LIBS_OUT=$(foreach lib,$(ALL_LIBS),$(OUT_LIB_DIR)/$(notdir $(lib)))
 
+# Overrides for the optional GN build.
+ifdef USE_GN
+GN_OUT_DIR=$(PROJECT_ROOT)/out
+# Use GN's out dir even though this isn't a GN build, to group build output.
+OUT_DIR=$(GN_OUT_DIR)/example
+
+# The GN build places all libraries at the top level of the output directory.
+FLUTTER_EMBEDDER_LIB=$(GN_OUT_DIR)/lib$(FLUTTER_EMBEDDER_LIB_NAME).so
+FLUTTER_ENGINE_LIB=$(GN_OUT_DIR)/lib$(FLUTTER_ENGINE_LIB_NAME).so
+PLUGIN_LIBS=$(foreach plugin,$(PLUGIN_NAMES)\
+	,$(GN_OUT_DIR)/lib$(PLUGIN_LIB_NAME_PREFIX)$(plugin).so)
+
+# The GN build places all published headers in a top-level include/.
+INCLUDE_DIRS=$(GN_OUT_DIR)/include
+
+# Override LIBRARY_DIRS since it's used for controlling the external build.
+LIBRARY_DIRS=$(GN_OUT_DIR)
+
+# Additional tools
+GN_WRAPPER=$(TOOLS_DIR)/gn_dart
+NINJA_BIN=ninja
+endif
+
 # Build settings
 CXX=g++ -std=c++14
 CXXFLAGS=-Wall -Werror $(shell pkg-config --cflags jsoncpp)
@@ -85,6 +108,12 @@ $(BIN_OUT): $(SOURCES) $(ALL_LIBS_OUT)
 	$(CXX) $(CXXFLAGS) $(CPPFLAGS) $(SOURCES) $(LDFLAGS) -o $@
 
 # Depedency directories are used as phony targets to invoke their builds.
+ifdef USE_GN
+.PHONY: $(LIBRARY_DIRS)
+$(LIBRARY_DIRS):
+	$(GN_WRAPPER) gen $(GN_OUT_DIR)
+	$(NINJA_BIN) -C $(GN_OUT_DIR) $(FLUTTER_EMBEDDER_LIB_NAME) $(PLUGIN_NAMES)
+else
 .PHONY: $(LIBRARY_DIRS)
 $(LIBRARY_DIRS):
 	$(MAKE) -C $@ $(MAKECMDGOALS)
@@ -93,6 +122,7 @@ $(LIBRARY_DIRS):
 # in parallel in the event that someone supplies the -j flag to `make`.
 # TODO: Fix this in the plugin builds so that it's not necessary at this layer.
 $(PLUGIN_DIRS): $(FLUTTER_EMBEDDER_LIB_DIR)
+endif
 
 # Require that all the library builds run for anything depending on the
 # libraries, but use order-only so that the phony build targets don't trigger

library/BUILD.gn

@@ -0,0 +1,94 @@
+# Copyright 2018 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import("//build/flutter.gni")
+import("//build/packaging.gni")
+import("//library/engine.gni")
+
+published_shared_library("flutter_embedder") {
+  if (is_linux) {
+    sources = [
+      "linux/src/internal/engine_method_result.cc",
+      "linux/src/internal/engine_method_result.h",
+      "linux/src/internal/json_message_codec.cc",
+      "linux/src/internal/json_message_codec.h",
+      "linux/src/internal/keyboard_hook_handler.h",
+      "linux/src/internal/plugin_handler.cc",
+      "linux/src/internal/plugin_handler.h",
+      "linux/src/internal/text_input_model.cc",
+      "linux/src/internal/text_input_model.h",
+      "linux/src/internal/text_input_plugin.cc",
+      "linux/src/internal/text_input_plugin.h",
+      "linux/src/embedder.cc",
+      "linux/src/json_method_call.cc",
+      "linux/src/json_method_codec.cc",
+      "linux/src/json_plugin.cc",
+      "linux/src/method_call.cc",
+      "linux/src/method_channel.cc",
+      "linux/src/method_codec.cc",
+      "linux/src/method_result.cc",
+      "linux/src/plugin.cc",
+    ]
+    public = [
+      "linux/include/flutter_desktop_embedding/binary_messenger.h",
+      "linux/include/flutter_desktop_embedding/embedder.h",
+      "linux/include/flutter_desktop_embedding/json_method_call.h",
+      "linux/include/flutter_desktop_embedding/json_method_codec.h",
+      "linux/include/flutter_desktop_embedding/json_plugin.h",
+      "linux/include/flutter_desktop_embedding/method_call.h",
+      "linux/include/flutter_desktop_embedding/method_channel.h",
+      "linux/include/flutter_desktop_embedding/method_codec.h",
+      "linux/include/flutter_desktop_embedding/method_result.h",
+      "linux/include/flutter_desktop_embedding/plugin.h",
+    ]
+  }
+
+  deps = [
+    ":fetch_flutter_engine",
+  ]
+
+  if (is_linux) {
+    public_header_subdir = "flutter_desktop_embedding"
+
+    deps += [
+      "//library/linux:publish_flutter_engine",
+    ]
+
+    libs = [
+      "glfw",
+      "GL",
+    ]
+
+    configs += [
+      "//build/linux/config:epoxy",
+      "//build/linux/config:gtk3",
+      "//build/linux/config:jsoncpp",
+      "//build/linux/config:x11",
+    ]
+
+    public_configs = [
+      "//library/linux:relative_public_headers",
+    ]
+  }
+}
+
+action("fetch_flutter_engine") {
+  script = "//tools/dart_tools/bin/update_flutter_engine.dart"
+  inputs = [ "$flutter_tree_path/bin/internal/engine.version" ]
+  outputs = engine_files
+  args = [
+    "--flutter_root=$flutter_tree_path",
+    rebase_path(engine_download_dir, root_build_dir),
+  ]
+}