Convert embedder.h to a C API (#267)

Remove remaining C++ from embedder.h, and add extern C. Since the
namespace is removed, use a standard prefix for all function names.

Part of #230

Author: stuartmorgan

library/common/glfw/embedder.cc

@@ -89,9 +89,9 @@ static FlutterEmbedderState *GetSavedEmbedderState(GLFWwindow *window) {
 }
 
 // Converts a FlutterPlatformMessage to an equivalent FlutterEmbedderMessage.
-static flutter_desktop_embedding::FlutterEmbedderMessage
-ConvertToEmbedderMessage(const FlutterPlatformMessage &engine_message) {
-  flutter_desktop_embedding::FlutterEmbedderMessage embedder_message = {};
+static FlutterEmbedderMessage ConvertToEmbedderMessage(
+    const FlutterPlatformMessage &engine_message) {
+  FlutterEmbedderMessage embedder_message = {};
   embedder_message.struct_size = sizeof(embedder_message);
   embedder_message.channel = engine_message.channel;
   embedder_message.message = engine_message.message;
@@ -284,17 +284,18 @@ static void GLFWErrorCallback(int error_code, const char *description) {
 // the necessary callbacks for rendering within a GLFWwindow.
 //
 // Returns a caller-owned pointer to the engine.
-static FlutterEngine RunFlutterEngine(
-    GLFWwindow *window, const std::string &assets_path,
-    const std::string &icu_data_path,
-    const std::vector<std::string> &arguments) {
+static FlutterEngine RunFlutterEngine(GLFWwindow *window,
+                                      const char *assets_path,
+                                      const char *icu_data_path,
+                                      const char **arguments,
+                                      size_t arguments_count) {
   // FlutterProjectArgs is expecting a full argv, so when processing it for
   // flags the first item is treated as the executable and ignored. Add a dummy
   // value so that all provided arguments are used.
   std::vector<const char *> argv = {"placeholder"};
-  std::transform(
-      arguments.begin(), arguments.end(), std::back_inserter(argv),
-      [](const std::string &arg) -> const char * { return arg.c_str(); });
+  if (arguments_count > 0) {
+    argv.insert(argv.end(), &arguments[0], &arguments[arguments_count]);
+  }
 
   FlutterRendererConfig config = {};
   config.type = kOpenGL;
@@ -306,8 +307,8 @@ static FlutterEngine RunFlutterEngine(
   config.open_gl.gl_proc_resolver = GLFWProcResolver;
   FlutterProjectArgs args = {};
   args.struct_size = sizeof(FlutterProjectArgs);
-  args.assets_path = assets_path.c_str();
-  args.icu_data_path = icu_data_path.c_str();
+  args.assets_path = assets_path;
+  args.icu_data_path = icu_data_path;
   args.command_line_argc = argv.size();
   args.command_line_argv = &argv[0];
   args.platform_message_callback = GLFWOnFlutterPlatformMessage;
@@ -322,20 +323,17 @@ static FlutterEngine RunFlutterEngine(
   return engine;
 }
 
-namespace flutter_desktop_embedding {
-
-bool FlutterInit() {
+bool FlutterEmbedderInit() {
   // Before making any GLFW calls, set up a logging error handler.
   glfwSetErrorCallback(GLFWErrorCallback);
   return glfwInit();
 }
 
-void FlutterTerminate() { glfwTerminate(); }
+void FlutterEmbedderTerminate() { glfwTerminate(); }
 
-FlutterWindowRef CreateFlutterWindow(
-    size_t initial_width, size_t initial_height, const std::string &assets_path,
-    const std::string &icu_data_path,
-    const std::vector<std::string> &arguments) {
+FlutterWindowRef FlutterEmbedderCreateWindow(
+    size_t initial_width, size_t initial_height, const char *assets_path,
+    const char *icu_data_path, const char **arguments, size_t argument_count) {
 #ifdef __linux__
   gtk_init(0, nullptr);
 #endif
@@ -348,7 +346,8 @@ FlutterWindowRef CreateFlutterWindow(
   GLFWClearCanvas(window);
 
   // Start the engine.
-  auto engine = RunFlutterEngine(window, assets_path, icu_data_path, arguments);
+  auto engine = RunFlutterEngine(window, assets_path, icu_data_path, arguments,
+                                 argument_count);
   if (engine == nullptr) {
     glfwDestroyWindow(window);
     return nullptr;
@@ -360,14 +359,18 @@ FlutterWindowRef CreateFlutterWindow(
   glfwSetWindowUserPointer(window, state);
   state->engine = engine;
   state->message_dispatcher =
-      std::make_unique<IncomingMessageDispatcher>(state);
-  state->plugin_handler = std::make_unique<PluginHandler>(state);
+      std::make_unique<flutter_desktop_embedding::IncomingMessageDispatcher>(
+          state);
+  state->plugin_handler =
+      std::make_unique<flutter_desktop_embedding::PluginHandler>(state);
 
   // Set up the keyboard handlers.
   state->keyboard_hook_handlers.push_back(
-      std::make_unique<KeyEventHandler>(state->plugin_handler.get()));
+      std::make_unique<flutter_desktop_embedding::KeyEventHandler>(
+          state->plugin_handler.get()));
   state->keyboard_hook_handlers.push_back(
-      std::make_unique<TextInputPlugin>(state->plugin_handler.get()));
+      std::make_unique<flutter_desktop_embedding::TextInputPlugin>(
+          state->plugin_handler.get()));
 
   // Trigger an initial size callback to send size information to Flutter.
   state->monitor_screen_coordinates_per_inch = GetScreenCoordinatesPerInch();
@@ -382,7 +385,7 @@ FlutterWindowRef CreateFlutterWindow(
   return state;
 }
 
-void FlutterWindowLoop(FlutterWindowRef flutter_window) {
+void FlutterEmbedderRunWindowLoop(FlutterWindowRef flutter_window) {
   GLFWwindow *window = flutter_window->window;
 #ifdef __linux__
   // Necessary for GTK thread safety.
@@ -438,5 +441,3 @@ void FlutterEmbedderEnableInputBlocking(FlutterWindowRef flutter_window,
                                         const char *channel) {
   flutter_window->message_dispatcher->EnableInputBlockingForChannel(channel);
 }
-
-}  // namespace flutter_desktop_embedding

library/common/glfw/flutter_window_controller.cc

@@ -14,6 +14,7 @@
 
 #include "library/include/flutter_desktop_embedding/glfw/flutter_window_controller.h"
 
+#include <algorithm>
 #include <iostream>
 
 #include "library/common/internal/plugin_handler.h"
@@ -22,20 +23,21 @@ namespace flutter_desktop_embedding {
 
 FlutterWindowController::FlutterWindowController(std::string &icu_data_path)
     : icu_data_path_(icu_data_path) {
-  init_succeeded_ = FlutterInit();
+  init_succeeded_ = FlutterEmbedderInit();
 }
 
 FlutterWindowController::~FlutterWindowController() {
   if (init_succeeded_) {
-    FlutterTerminate();
+    FlutterEmbedderTerminate();
   }
 }
 
 bool FlutterWindowController::CreateWindow(
     size_t width, size_t height, const std::string &assets_path,
     const std::vector<std::string> &arguments) {
   if (!init_succeeded_) {
-    std::cerr << "Could not create window; FlutterInit failed." << std::endl;
+    std::cerr << "Could not create window; FlutterEmbedderInit failed."
+              << std::endl;
     return false;
   }
 
@@ -44,8 +46,14 @@ bool FlutterWindowController::CreateWindow(
     return false;
   }
 
-  window_ = CreateFlutterWindow(width, height, assets_path, icu_data_path_,
-                                arguments);
+  std::vector<const char *> engine_arguments;
+  std::transform(
+      arguments.begin(), arguments.end(), std::back_inserter(engine_arguments),
+      [](const std::string &arg) -> const char * { return arg.c_str(); });
+
+  window_ = FlutterEmbedderCreateWindow(
+      width, height, assets_path.c_str(), icu_data_path_.c_str(),
+      &engine_arguments[0], engine_arguments.size());
   if (!window_) {
     std::cerr << "Failed to create window." << std::endl;
     return false;
@@ -69,7 +77,7 @@ PluginRegistrar *FlutterWindowController::GetRegistrarForPlugin(
 
 void FlutterWindowController::RunEventLoop() {
   if (window_) {
-    FlutterWindowLoop(window_);
+    FlutterEmbedderRunWindowLoop(window_);
   }
 }
 

library/include/flutter_desktop_embedding/glfw/embedder.h

@@ -15,9 +15,8 @@
 #ifndef LIBRARY_INCLUDE_FLUTTER_DESKTOP_EMBEDDING_GLFW_EMBEDDER_H_
 #define LIBRARY_INCLUDE_FLUTTER_DESKTOP_EMBEDDING_GLFW_EMBEDDER_H_
 
-#include <memory>
-#include <string>
-#include <vector>
+#include <stddef.h>
+#include <stdint.h>
 
 // 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
@@ -34,29 +33,31 @@
 #include "../fde_export.h"
 #endif
 
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
 // Opaque reference to a Flutter window.
 typedef struct FlutterEmbedderState *FlutterWindowRef;
 
 // Opaque handle for tracking responses to messages.
 typedef struct _FlutterPlatformMessageResponseHandle
     FlutterEmbedderMessageResponseHandle;
 
-namespace flutter_desktop_embedding {
-
 // Sets up the embedder's graphic context. Must be called before any other
 // methods.
 //
 // Note: Internally, this library uses GLFW, which does not support multiple
 // copies within the same process. Internally this calls glfwInit, which will
 // fail if you have called glfwInit elsewhere in the process.
-FDE_EXPORT bool FlutterInit();
+FDE_EXPORT bool FlutterEmbedderInit();
 
 // Tears down embedder state. Must be called before the process terminates.
-FDE_EXPORT void FlutterTerminate();
+FDE_EXPORT void FlutterEmbedderTerminate();
 
 // Creates a Window running a Flutter Application.
 //
-// FlutterInit() must be called prior to this function.
+// FlutterEmbedderInit() must be called prior to this function.
 //
 // The |assets_path| is the path to the flutter_assets folder for the Flutter
 // application to be run. |icu_data_path| is the path to the icudtl.dat file
@@ -67,19 +68,18 @@ FDE_EXPORT void FlutterTerminate();
 // for details. Not all arguments will apply to embedding mode.
 //
 // Returns a null pointer in the event of an error. Otherwise, the pointer is
-// valid until FlutterWindowLoop has been called and returned. Note that calling
-// CreateFlutterWindow without later calling FlutterWindowLoop on that pointer
-// is a memory leak.
-FDE_EXPORT FlutterWindowRef CreateFlutterWindow(
-    size_t initial_width, size_t initial_height, const std::string &assets_path,
-    const std::string &icu_data_path,
-    const std::vector<std::string> &arguments);
+// valid until FlutterEmbedderRunWindowLoop has been called and returned.
+// Note that calling FlutterEmbedderCreateWindow without later calling
+// FlutterEmbedderRunWindowLoop on the returned reference is a memory leak.
+FDE_EXPORT FlutterWindowRef FlutterEmbedderCreateWindow(
+    size_t initial_width, size_t initial_height, const char *assets_path,
+    const char *icu_data_path, const char **arguments, size_t argument_count);
 
 // Loops on Flutter window events until the window is closed.
 //
 // Once this function returns, FlutterWindowRef is no longer valid, and must
 // not be used again.
-FDE_EXPORT void FlutterWindowLoop(FlutterWindowRef flutter_window);
+FDE_EXPORT void FlutterEmbedderRunWindowLoop(FlutterWindowRef flutter_window);
 
 // A received from Flutter.
 typedef struct {
@@ -141,6 +141,8 @@ FDE_EXPORT void FlutterEmbedderSetMessageCallback(
 FDE_EXPORT void FlutterEmbedderEnableInputBlocking(
     FlutterWindowRef flutter_window, const char *channel);
 
-}  // namespace flutter_desktop_embedding
+#if defined(__cplusplus)
+}  // extern "C"
+#endif
 
 #endif  // LIBRARY_INCLUDE_FLUTTER_DESKTOP_EMBEDDING_GLFW_EMBEDDER_H_

library/include/flutter_desktop_embedding/glfw/flutter_window_controller.h

@@ -79,7 +79,7 @@ class FDE_EXPORT FlutterWindowController {
   // for any window created.
   std::string icu_data_path_;
 
-  // Whether or not FlutterInit succeeded at creation time.
+  // Whether or not FlutterEmbedderInit succeeded at creation time.
   bool init_succeeded_ = false;
 
   // The curent Flutter window, if any.