[linux] Switch to GN, and remove Makefiles

For the library and plugins, switch to GN as the only supported build
system on Linux. GN will be used for the library in the flutter/engine
repository, so the make build will no longer be necessary; remove it now
to avoid the overhead of maintaining an extra build system until the
transition happens.

The example continues to use Make in order to show typical usage of the
library, and the color_panel plugin has an example makefile (updated to
reflect the use of GN to build the library) as an example/starting point
for someone making a plugin outside of the FDE repository.

Addresses google#114 for Linux.

Author: stuartmorgan-g

.travis.yml

@@ -14,19 +14,6 @@
 
 matrix:
   include:
-    - os: linux
-      dist: xenial
-      language: cpp
-      before_install:
-        - sudo apt-get update
-      install:
-        - build/ci/linux/install_dependencies
-        - build/ci/install_flutter $TRAVIS_BUILD_DIR/..
-      before_script:
-        - export PATH=$PATH:$TRAVIS_BUILD_DIR/../flutter/bin:$TRAVIS_BUILD_DIR/bin
-      script:
-        - make -C example/linux_fde
-
     - os: linux
       dist: xenial
       language: cpp
@@ -39,7 +26,7 @@ matrix:
       before_script:
         - export PATH=$PATH:$TRAVIS_BUILD_DIR/bin
       script:
-        - make -C example/linux_fde USE_GN=1
+        - make -C example/linux_fde
 
     - os: osx
       language: objective-c

example/linux_fde/Makefile

@@ -37,28 +37,31 @@ FLUTTER_EMBEDDER_LIB_DIR=$(FDE_ROOT)/library/linux
 PLUGINS_DIR=$(FDE_ROOT)/plugins
 TOOLS_DIR=$(FDE_ROOT)/tools
 FLUTTER_DIR=$(shell $(TOOLS_DIR)/flutter_location)
+GN_OUT_DIR=$(FDE_ROOT)/out
 
 # Libraries
 FLUTTER_EMBEDDER_LIB_NAME=flutter_embedder
-FLUTTER_EMBEDDER_LIB=$(FLUTTER_EMBEDDER_LIB_DIR)/lib$(FLUTTER_EMBEDDER_LIB_NAME).so
+FLUTTER_EMBEDDER_LIB=$(GN_OUT_DIR)/lib$(FLUTTER_EMBEDDER_LIB_NAME).so
 
 FLUTTER_ENGINE_LIB_NAME=flutter_engine
-FLUTTER_ENGINE_LIB=$(FLUTTER_EMBEDDER_LIB_DIR)/lib$(FLUTTER_ENGINE_LIB_NAME).so
+FLUTTER_ENGINE_LIB=$(GN_OUT_DIR)/lib$(FLUTTER_ENGINE_LIB_NAME).so
 
 PLUGIN_LIB_NAME_PREFIX=flutter_embedder_
 PLUGIN_LIBS=$(foreach plugin,$(PLUGIN_NAMES)\
-	,$(PLUGINS_DIR)/$(plugin)/linux/lib$(PLUGIN_LIB_NAME_PREFIX)$(plugin).so)
+	,$(GN_OUT_DIR)/lib$(PLUGIN_LIB_NAME_PREFIX)$(plugin).so)
 
 ALL_LIBS=$(FLUTTER_EMBEDDER_LIB) $(FLUTTER_ENGINE_LIB) $(PLUGIN_LIBS)
 
 # Headers
 PLUGIN_DIRS=$(patsubst %,$(PLUGINS_DIR)/%/linux,$(PLUGIN_NAMES))
-LIBRARY_DIRS=$(FLUTTER_EMBEDDER_LIB_DIR) $(PLUGIN_DIRS)
-INCLUDE_DIRS=$(patsubst %,%/include,$(LIBRARY_DIRS)) $(FDE_ROOT)/library/include
+# The GN build places all published headers in a top-level include/.
+INCLUDE_DIRS=$(GN_OUT_DIR)/include
 
 # Tools
 BUILD_ASSETS_BIN=$(TOOLS_DIR)/build_flutter_assets
 FLUTTER_BIN=$(FLUTTER_DIR)/bin/flutter
+GN_WRAPPER=$(TOOLS_DIR)/gn_dart
+NINJA_BIN=ninja
 
 # Resources
 ICU_DATA_NAME=icudtl.dat
@@ -75,36 +78,12 @@ 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=$(FDE_ROOT)/out
-
-# The GN build places all libraries at the top level of the output directory.
-FLUTTER_EMBEDDER_LIB=$(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.release=-DNDEBUG
 CXXFLAGS=-Wall -Werror $(shell pkg-config --cflags jsoncpp glfw3) \
 				 $(CXXFLAGS.$(BUILD))
 CPPFLAGS=$(patsubst %,-I%,$(INCLUDE_DIRS))
-ifdef USE_GN
-CPPFLAGS+=-DUSE_FLATTENED_INCLUDES
-endif
 LDFLAGS=-L$(OUT_LIB_DIR) \
 	$(shell pkg-config --libs jsoncpp glfw3) \
 	-l$(FLUTTER_EMBEDDER_LIB_NAME) \
@@ -124,27 +103,16 @@ $(BIN_OUT): $(SOURCES) $(ALL_LIBS_OUT)
 	mkdir -p $(@D)
 	$(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)
+.PHONY: gnbuild
+gnbuild: $(GN_OUT_DIR)
 	$(NINJA_BIN) -C $(GN_OUT_DIR) $(FLUTTER_EMBEDDER_LIB_NAME) $(PLUGIN_NAMES)
-else
-.PHONY: $(LIBRARY_DIRS)
-$(LIBRARY_DIRS):
-	$(MAKE) -C $@ $(MAKECMDGOALS)
-
-# Enforce relative ordering. This prevents accidentally building the targets
-# in parallel in the event that someone supplies the -j flag to `make`.
-# TODO: Fix this in the plugin builds so that it's not necessary at this layer.
-$(PLUGIN_DIRS): $(FLUTTER_EMBEDDER_LIB_DIR)
-endif
-
-# Require that all the library builds run for anything depending on the
-# libraries, but use order-only so that the phony build targets don't trigger
-# rebuilds of all dependencies every time.
-$(ALL_LIBS): | $(LIBRARY_DIRS)
+
+$(GN_OUT_DIR):
+	$(GN_WRAPPER) gen $(GN_OUT_DIR)
+
+# Run the GN build for anything depending on the libraries, but use order-only
+# so that it doesn't trigger rebuilds of all dependencies every time.
+$(ALL_LIBS): | gnbuild
 
 # This is slightly inefficient in that it copies all libraries if any of them
 # changes, but is far simpler than setting up individual rules for each library.

example/linux_fde/flutter_embedder_example.cc

@@ -21,13 +21,8 @@
 
 #include <color_panel/color_panel_plugin.h>
 #include <file_chooser/file_chooser_plugin.h>
-#include <menubar/menubar_plugin.h>
-
-#ifdef USE_FLATTENED_INCLUDES
 #include <flutter_desktop_embedding/flutter_window_controller.h>
-#else
-#include <flutter_desktop_embedding/glfw/flutter_window_controller.h>
-#endif
+#include <menubar/menubar_plugin.h>
 
 namespace {
 

library/GN.md

@@ -1,20 +1,18 @@
 # Using GN
 
-If you are building on Linux or Windows, you can use GN instead of Make or
-Visual Studio.
-
-This is currently optional and is under evaluation, but in the future it may
-become the build system used on all platforms.
+If you are building on Windows, you can use GN instead of Visual Studio.
 
 ## Dependencies
 
+### Tools
+
 In addition to the normal dependencies, you will need to install:
 * [ninja](https://github.com/ninja-build/ninja/wiki/Pre-built-Ninja-packages)
 * [gn](https://gn.googlesource.com/gn/)
 
 Ensure that both binaries are in your path.
 
-### Windows
+### Path setup
 
 Windows also requires the 64 bit compiler, linker and setup scripts to be in
 your path. They are found under:
@@ -29,7 +27,9 @@ e.g.:
 > C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build
 ```
 
-Windows requires jsoncpp to be downloaded to
+### jsoncpp
+
+jsoncpp must be manually downloaded to
 `library/windows/third_party/jsoncpp`. Use
 `tools/dart_tools/bin/fetch_jsoncpp.dart` to automatically download `jsoncpp`
 as shown below:
@@ -74,19 +74,12 @@ $ ninja -C out
 
 ### Example
 
-#### Linux
-
-To use the GN build for the depedencies of the example application, when
-running `make` for the example add `USE_GN=1` to the end of the command.
-
-#### Windows
-
 Building the example with GN is not currently supported. Follow the [Visual
 Studio example build instructions](../example/README.md) to build the example
 app.
 
 ## Feedback
 
-If you encounter issues with the GN build, please test with Make or Visual
+If you encounter issues with the GN build, please test with Visual
 Studio before filing a bug so that the report can include whether the issue is
 specific to GN, or a general build issue.

library/README.md

@@ -37,7 +37,7 @@ the ICU data from the Flutter engine.
 
 #### Dependencies
 
-First you will need to install the relevant dependencies:
+First you will need to install the relevant library dependencies:
 *   GLFW3
 *   GTK 3
 *   jsoncpp
@@ -52,16 +52,32 @@ $ sudo apt-get install libglfw3-dev libepoxy-dev libjsoncpp-dev libgtk-3-dev \
       libx11-dev pkg-config
 ```
 
+You will need to install the build tools if you don't already have them:
+* [ninja](https://github.com/ninja-build/ninja/wiki/Pre-built-Ninja-packages)
+* [gn](https://gn.googlesource.com/gn/)
+
+Ensure that both binaries are in your path.
+
 #### Using the Library
 
-Run `make` under `linux/`, then link `libflutter_embedder.so` into your
-binary. See
-[flutter_window_controller.h](include/flutter_desktop_embedding/glfw/flutter_window_controller.h)
-for details on calling into the library.
+To build the library, run the following at the root of this repository:
+
+```
+$ tools/gn_dart gen out
+$ ninja -C out flutter_embedder
+```
+Subsequent builds only require the `ninja` step, as the build will automatically
+re-run GN generation if necessary.
 
-You will also need to link `libflutter_engine.so` into your binary.
+The build results will be in the top-level `out/` directory. You will need to
+link `libflutter_embedder.so` and `libflutter_engine.so` into your binary.
+Public headers will be in `out/include/`; you should point dependent
+builds at that location rather than the `include/` directories in the
+source tree.
 
-_Note: There is also a [GN build](GN.md) available as an alternative to Make._
+See
+[flutter_window_controller.h](include/flutter_desktop_embedding/glfw/flutter_window_controller.h)
+for details on calling into the library.
 
 ### macOS
 
@@ -103,6 +119,8 @@ the `flutter_engine.dll`, and if using a dynamic library
 
 The output files are located in `bin\x64\$(Configuration)\GLFW Library\`.
 
+_Note: There is also a [GN build](GN.md) available as an alternative._
+
 ## Caveats
 
 * There is currently no versioning system for coordinating the version

library/include/flutter_desktop_embedding/glfw/embedder.h

@@ -19,6 +19,15 @@
 #include <string>
 #include <vector>
 
+// On Linux, the header output is always flattened; on Windows the GN build
+// is still optional. Once GN is required on Windows, eliminate this and just
+// use FLUTTER_DESKTOP_EMBEDDING_IMPL to control include paths.
+#ifndef USE_FLATTENED_INCLUDES
+#if !defined(FLUTTER_DESKTOP_EMBEDDING_IMPL) && defined(__linux__)
+#define USE_FLATTENED_INCLUDES 1
+#endif
+#endif
+
 #ifdef USE_FLATTENED_INCLUDES
 #include "fde_export.h"
 #include "plugin_registrar.h"

library/linux/.gitignore

@@ -32,24 +32,27 @@ Build the Xcode project under the macos diretory for each plugin you
 want to use, then link the resulting framework in your project.
 
 When you set up your FLEViewController, before calling `launchEngine...`,
-call `-addPlugin:` with an instance of each plugin you want to use. For
+call `-registerWithRegistrar:` on each plugin you want to use. For
 instance:
 
 ```objc
-  [myFlutterViewController addPlugin:[[FLEColorPanelPlugin alloc] init]];
+  [FLEFileChooserPlugin registerWithRegistrar:
+      [myFlutterViewController registrarForPlugin:"FLEFileChooserPlugin"]];
 ```
 
 ### Linux
 
-Run `make` in the `linux` directory for each plugin you want to use, then
-link the resulting library in your application.
+Run `ninja -C out` at the root of the repository to build all plugins, then
+link the libraries for the plugins you want into your application. As with the
+library build, `out/` and `out/include/` will contain all the files you need.
 
-After creating your Flutter window, call AddPlugin with an instance of each
-plugin you want to use. For instance:
+After creating your Flutter window controller, call your plugin's registrar
+method. For instance:
 
 ```cpp
-  AddPlugin(window,
-            std::make_unique<plugins_color_panel::ColorPanelPlugin>());
+  plugins_color_panel::ColorPanelPlugin::RegisterWithRegistrar(
+      my_flutter_controller.GetRegistrarForPlugin(
+          "plugins_color_panel::ColorPanelPlugin"));
 ```
 
 ### Example Application
@@ -63,7 +66,8 @@ optional plugins on the Dart side.
 ## Writing your own plugins
 
 You can easily create local packages following the model of plugins here to
-use in your own projects.
+use in your own projects. In particular, the color_panel plugin has examples
+of typical platform builds for plugins.
 
 If you think they would be generally useful, feel free to submit a pull request
 and they could potentially be folded into this repository. In the future, as