Consolidate GN rules (#268)

De-dups some common code between the Windows and Linux GN files, and
consolidates some of the Windows-specific code into one location.

Adjusts embedder library rule to be clearer about which portions are
specific to the GLFW-based implementation.

Author: stuartmorgan

build/win/config/BUILD.gn

@@ -16,9 +16,16 @@ import("//build/flutter.gni")
 import("//build/packaging.gni")
 import("//library/engine.gni")
 
+declare_args() {
+  # Whether to use the GLFW embedding implementation. Currently overriding this
+  # would not work since each platform only has one working implementation,
+  # but in the future GLFW may be one of multiple supported implementations.
+  use_glfw = is_linux || is_win
+}
+
 published_shared_library("flutter_embedder") {
   # GLFW embedding implementation.
-  if (is_linux || is_win) {
+  if (use_glfw) {
     public = [
       "include/flutter_desktop_embedding/glfw/embedder.h",
       "include/flutter_desktop_embedding/glfw/flutter_window_controller.h",
@@ -64,7 +71,7 @@ published_shared_library("flutter_embedder") {
   }
 
   deps = [
-    ":fetch_flutter_engine",
+    ":flutter_engine",
   ]
 
   defines = [ "FLUTTER_DESKTOP_EMBEDDING_IMPL" ]
@@ -74,31 +81,30 @@ published_shared_library("flutter_embedder") {
   public_configs = [ ":relative_public_headers" ]
 
   if (is_linux) {
-    libs = [ "GL" ]
-
-    deps += [ "//library/linux:publish_flutter_engine" ]
-
-    configs += [
-      "//build/linux/config:epoxy",
-      "//build/linux/config:glfw3",
-      "//build/linux/config:gtk3",
-      "//build/linux/config:jsoncpp",
-      "//build/linux/config:x11",
-    ]
+    configs += [ "//build/linux/config:jsoncpp" ]
   }
 
   if (is_win) {
-    deps += [
-      "//library/windows:fetch_glfw",
-      "//library/windows:publish_flutter_engine",
-      "//third_party/jsoncpp:jsoncpp",
-    ]
+    deps += [ "//third_party/jsoncpp:jsoncpp" ]
 
     libs = [ engine_files[2] ]
+  }
 
-    public_configs += [
-      "//library/windows:relative_glfw_dependencies",
-    ]
+  if (use_glfw) {
+    if (is_linux) {
+      libs = [ "GL" ]
+
+      configs += [
+        "//build/linux/config:epoxy",
+        "//build/linux/config:glfw3",
+        "//build/linux/config:gtk3",
+        "//build/linux/config:x11",
+      ]
+    }
+
+    if (is_win) {
+      deps += [ "//library/windows:fetch_glfw" ]
+    }
   }
 }
 
@@ -114,6 +120,13 @@ config("relative_engine_headers") {
   include_dirs = [ "$engine_download_dir" ]
 }
 
+group("flutter_engine") {
+  public_deps = [
+    ":fetch_flutter_engine",
+    ":publish_flutter_engine",
+  ]
+}
+
 action("fetch_flutter_engine") {
   script = "//tools/dart_tools/bin/update_flutter_engine.dart"
   inputs = [
@@ -126,3 +139,20 @@ action("fetch_flutter_engine") {
   ]
   public_configs = [ ":relative_engine_headers" ]
 }
+
+# Places the downloaded Flutter engine library at the top level of the
+# output directory where built libraries go, so that it doesn't require
+# special link handling, and publishes its header.
+copy("publish_flutter_engine") {
+  sources = engine_files
+
+  # Remove the header, since "SDK" clients don't need access to that.
+  sources -= [ engine_files[0] ]
+
+  outputs = [
+    "$root_out_dir/{{source_file_part}}",
+  ]
+  deps = [
+    ":fetch_flutter_engine",
+  ]
+}

library/BUILD.gn

@@ -12,46 +12,24 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import("//build/packaging.gni")
-import("//library/engine.gni")
 import("//library/windows/glfw.gni")
 
 action("fetch_glfw") {
   script = "//tools/dart_tools/bin/fetch_glfw.dart"
   outputs = glfw_files
   args = [ rebase_path(glfw_download_dir, root_build_dir) ]
-  public_configs = [ "//build/win/config:glfw3" ]
+  public_configs = [ ":glfw3" ]
 }
 
-config("relative_glfw_dependencies") {
-  include_dirs = [ glfw_include_dir ]
-  lib_dirs = [ glfw_download_dir ]
-}
+config("glfw3") {
+  libs = [
+    "$glfw_lib_name",
+    "opengl32.lib",
 
-copy_includes("_publish_engine_headers") {
-  sources = [
-    engine_files[0],
-  ]
-  deps = [
-    "//library:fetch_flutter_engine",
-  ]
-}
-
-# Places the downloaded Flutter engine library at the top level of the
-# output directory where built libraries go, so that it doesn't require
-# special link handling, and publishes its header.
-copy("publish_flutter_engine") {
-  sources = [
-    engine_files[1],
-    engine_files[2],
-    engine_files[3],
-    engine_files[4],
-  ]
-  outputs = [
-    "$root_out_dir/{{source_file_part}}",
-  ]
-  deps = [
-    ":_publish_engine_headers",
-    "//library:fetch_flutter_engine",
+    "user32.lib",
+    "gdi32.lib",
+    "shell32.lib",
   ]
+  lib_dirs = [ glfw_download_dir ]
+  include_dirs = [ glfw_include_dir ]
 }