shell/platform/linux/fl_keyboard_manager.cc - external/github.com/flutter/engine - Git at Google

 // Copyright 2013 The Flutter Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 #include "flutter/shell/platform/linux/fl_keyboard_manager.h"

 #include <array>
 #include <cinttypes>
 #include <memory>
 #include <string>

 #include "flutter/shell/platform/linux/fl_key_channel_responder.h"
 #include "flutter/shell/platform/linux/fl_key_embedder_responder.h"
 #include "flutter/shell/platform/linux/fl_keyboard_layout.h"
 #include "flutter/shell/platform/linux/fl_keyboard_pending_event.h"
 #include "flutter/shell/platform/linux/key_mapping.h"

 // Turn on this flag to print complete layout data when switching IMEs. The data
 // is used in unit tests.
 #define DEBUG_PRINT_LAYOUT

 /* Declarations of private classes */

 G_DECLARE_FINAL_TYPE(FlKeyboardManagerUserData,
                      fl_keyboard_manager_user_data,
                      FL,
                      KEYBOARD_MANAGER_USER_DATA,
                      GObject);

 /* End declarations */

 namespace {

 static bool is_eascii(uint16_t character) {
   return character < 256;
 }

 #ifdef DEBUG_PRINT_LAYOUT
 // Prints layout entries that will be parsed by `MockLayoutData`.
 void debug_format_layout_data(std::string& debug_layout_data,
                               uint16_t keycode,
                               uint16_t clue1,
                               uint16_t clue2) {
   if (keycode % 4 == 0) {
     debug_layout_data.append("    ");
   }

   constexpr int kBufferSize = 30;
   char buffer[kBufferSize];
   buffer[0] = 0;
   buffer[kBufferSize - 1] = 0;

   snprintf(buffer, kBufferSize, "0x%04x, 0x%04x, ", clue1, clue2);
   debug_layout_data.append(buffer);

   if (keycode % 4 == 3) {
     snprintf(buffer, kBufferSize, " // 0x%02x", keycode);
     debug_layout_data.append(buffer);
   }
 }
 #endif

 }  // namespace

 /* Define FlKeyboardManagerUserData */

 /**
  * FlKeyboardManagerUserData:
  * The user_data used when #FlKeyboardManager sends event to
  * responders.
  */

 struct _FlKeyboardManagerUserData {
   GObject parent_instance;

   // The owner manager.
   GWeakRef manager;
   uint64_t sequence_id;
 };

 G_DEFINE_TYPE(FlKeyboardManagerUserData,
               fl_keyboard_manager_user_data,
               G_TYPE_OBJECT)

 static void fl_keyboard_manager_user_data_dispose(GObject* object) {
   g_return_if_fail(FL_IS_KEYBOARD_MANAGER_USER_DATA(object));
   FlKeyboardManagerUserData* self = FL_KEYBOARD_MANAGER_USER_DATA(object);

   g_weak_ref_clear(&self->manager);

   G_OBJECT_CLASS(fl_keyboard_manager_user_data_parent_class)->dispose(object);
 }

 static void fl_keyboard_manager_user_data_class_init(
     FlKeyboardManagerUserDataClass* klass) {
   G_OBJECT_CLASS(klass)->dispose = fl_keyboard_manager_user_data_dispose;
 }

 static void fl_keyboard_manager_user_data_init(
     FlKeyboardManagerUserData* self) {}

 // Creates a new FlKeyboardManagerUserData private class with all information.
 static FlKeyboardManagerUserData* fl_keyboard_manager_user_data_new(
     FlKeyboardManager* manager,
     uint64_t sequence_id) {
   FlKeyboardManagerUserData* self = FL_KEYBOARD_MANAGER_USER_DATA(
       g_object_new(fl_keyboard_manager_user_data_get_type(), nullptr));

   g_weak_ref_init(&self->manager, manager);
   self->sequence_id = sequence_id;
   return self;
 }

 /* Define FlKeyboardManager */

 struct _FlKeyboardManager {
   GObject parent_instance;

   GWeakRef view_delegate;

   // An array of #FlKeyResponder. Elements are added with
   // #fl_keyboard_manager_add_responder immediately after initialization and are
   // automatically released on dispose.
   GPtrArray* responder_list;

   // An array of #FlKeyboardPendingEvent.
   //
   // Its elements are *not* unreferenced when removed. When FlKeyboardManager is
   // disposed, this array will be set with a free_func so that the elements are
   // unreferenced when removed.
   GPtrArray* pending_responds;

   // An array of #FlKeyboardPendingEvent.
   //
   // Its elements are unreferenced when removed.
   GPtrArray* pending_redispatches;

   // The last sequence ID used. Increased by 1 by every use.
   uint64_t last_sequence_id;

   // Record the derived layout.
   //
   // It is cleared when the platform reports a layout switch. Each entry,
   // which corresponds to a group, is only initialized on the arrival of the
   // first event for that group that has a goal keycode.
   FlKeyboardLayout* derived_layout;

   // A static map from keycodes to all layout goals.
   //
   // It is set up when the manager is initialized and is not changed ever after.
   std::unique_ptr<std::map<uint16_t, const LayoutGoal*>> keycode_to_goals;

   // A static map from logical keys to all mandatory layout goals.
   //
   // It is set up when the manager is initialized and is not changed ever after.
   std::unique_ptr<std::map<uint64_t, const LayoutGoal*>>
       logical_to_mandatory_goals;
 };

 G_DEFINE_TYPE(FlKeyboardManager, fl_keyboard_manager, G_TYPE_OBJECT);

 // This is an exact copy of g_ptr_array_find_with_equal_func.  Somehow CI
 // reports that can not find symbol g_ptr_array_find_with_equal_func, despite
 // the fact that it runs well locally.
 static gboolean g_ptr_array_find_with_equal_func1(GPtrArray* haystack,
                                                   gconstpointer needle,
                                                   GEqualFunc equal_func,
                                                   guint* index_) {
   guint i;
   g_return_val_if_fail(haystack != NULL, FALSE);
   if (equal_func == NULL) {
     equal_func = g_direct_equal;
   }
   for (i = 0; i < haystack->len; i++) {
     if (equal_func(g_ptr_array_index(haystack, i), needle)) {
       if (index_ != NULL) {
         *index_ = i;
       }
       return TRUE;
     }
   }

   return FALSE;
 }

 // Compare a #FlKeyboardPendingEvent with the given sequence_id.
 static gboolean compare_pending_by_sequence_id(gconstpointer a,
                                                gconstpointer b) {
   FlKeyboardPendingEvent* pending =
       FL_KEYBOARD_PENDING_EVENT(const_cast<gpointer>(a));
   uint64_t sequence_id = *reinterpret_cast<const uint64_t*>(b);
   return fl_keyboard_pending_event_get_sequence_id(pending) == sequence_id;
 }

 // Compare a #FlKeyboardPendingEvent with the given hash.
 static gboolean compare_pending_by_hash(gconstpointer a, gconstpointer b) {
   FlKeyboardPendingEvent* pending =
       FL_KEYBOARD_PENDING_EVENT(const_cast<gpointer>(a));
   uint64_t hash = *reinterpret_cast<const uint64_t*>(b);
   return fl_keyboard_pending_event_get_hash(pending) == hash;
 }

 // Try to remove a pending event from `pending_redispatches` with the target
 // hash.
 //
 // Returns true if the event is found and removed.
 static bool fl_keyboard_manager_remove_redispatched(FlKeyboardManager* self,
                                                     uint64_t hash) {
   guint result_index;
   gboolean found = g_ptr_array_find_with_equal_func1(
       self->pending_redispatches, static_cast<const uint64_t*>(&hash),
       compare_pending_by_hash, &result_index);
   if (found) {
     // The removed object is freed due to `pending_redispatches`'s free_func.
     g_ptr_array_remove_index_fast(self->pending_redispatches, result_index);
     return TRUE;
   } else {
     return FALSE;
   }
 }

 // The callback used by a responder after the event was dispatched.
 static void responder_handle_event_callback(bool handled,
                                             gpointer user_data_ptr) {
   g_return_if_fail(FL_IS_KEYBOARD_MANAGER_USER_DATA(user_data_ptr));
   FlKeyboardManagerUserData* user_data =
       FL_KEYBOARD_MANAGER_USER_DATA(user_data_ptr);

   g_autoptr(FlKeyboardManager) self =
       FL_KEYBOARD_MANAGER(g_weak_ref_get(&user_data->manager));
   if (self == nullptr) {
     return;
   }

   g_autoptr(FlKeyboardViewDelegate) view_delegate =
       FL_KEYBOARD_VIEW_DELEGATE(g_weak_ref_get(&self->view_delegate));
   if (view_delegate == nullptr) {
     return;
   }

   guint result_index = -1;
   gboolean found = g_ptr_array_find_with_equal_func1(
       self->pending_responds, &user_data->sequence_id,
       compare_pending_by_sequence_id, &result_index);
   g_return_if_fail(found);
   FlKeyboardPendingEvent* pending = FL_KEYBOARD_PENDING_EVENT(
       g_ptr_array_index(self->pending_responds, result_index));
   g_return_if_fail(pending != nullptr);
   fl_keyboard_pending_event_mark_replied(pending, handled);
   // All responders have replied.
   if (fl_keyboard_pending_event_is_complete(pending)) {
     g_object_unref(user_data_ptr);
     gpointer removed =
         g_ptr_array_remove_index_fast(self->pending_responds, result_index);
     g_return_if_fail(removed == pending);
     bool should_redispatch =
         !fl_keyboard_pending_event_get_any_handled(pending) &&
         !fl_keyboard_view_delegate_text_filter_key_press(
             view_delegate, fl_keyboard_pending_event_get_event(pending));
     if (should_redispatch) {
       g_ptr_array_add(self->pending_redispatches, pending);
       fl_keyboard_view_delegate_redispatch_event(
           view_delegate,
           FL_KEY_EVENT(fl_keyboard_pending_event_get_event(pending)));
     } else {
       g_object_unref(pending);
     }
   }
 }

 static uint16_t convert_key_to_char(FlKeyboardViewDelegate* view_delegate,
                                     guint keycode,
                                     gint group,
                                     gint level) {
   GdkKeymapKey key = {keycode, group, level};
   constexpr int kBmpMax = 0xD7FF;
   guint origin = fl_keyboard_view_delegate_lookup_key(view_delegate, &key);
   return origin < kBmpMax ? origin : 0xFFFF;
 }

 // Make sure that Flutter has derived the layout for the group of the event,
 // if the event contains a goal keycode.
 static void guarantee_layout(FlKeyboardManager* self, FlKeyEvent* event) {
   g_autoptr(FlKeyboardViewDelegate) view_delegate =
       FL_KEYBOARD_VIEW_DELEGATE(g_weak_ref_get(&self->view_delegate));
   if (view_delegate == nullptr) {
     return;
   }

   guint8 group = fl_key_event_get_group(event);
   if (fl_keyboard_layout_has_group(self->derived_layout, group)) {
     return;
   }
   if (self->keycode_to_goals->find(fl_key_event_get_keycode(event)) ==
       self->keycode_to_goals->end()) {
     return;
   }

   // Clone all mandatory goals. Each goal is removed from this cloned map when
   // fulfilled, and the remaining ones will be assigned to a default position.
   std::map<uint64_t, const LayoutGoal*> remaining_mandatory_goals =
       *self->logical_to_mandatory_goals;

 #ifdef DEBUG_PRINT_LAYOUT
   std::string debug_layout_data;
   for (uint16_t keycode = 0; keycode < 128; keycode += 1) {
     std::vector<uint16_t> this_key_clues = {
         convert_key_to_char(view_delegate, keycode, group, 0),
         convert_key_to_char(view_delegate, keycode, group, 1),  // Shift
     };
     debug_format_layout_data(debug_layout_data, keycode, this_key_clues[0],
                              this_key_clues[1]);
   }
 #endif

   // It's important to only traverse layout goals instead of all keycodes.
   // Some key codes outside of the standard keyboard also gives alpha-numeric
   // letters, and will therefore take over mandatory goals from standard
   // keyboard keys if they come first. Example: French keyboard digit 1.
   for (const LayoutGoal& keycode_goal : layout_goals) {
     uint16_t keycode = keycode_goal.keycode;
     std::vector<uint16_t> this_key_clues = {
         convert_key_to_char(view_delegate, keycode, group, 0),
         convert_key_to_char(view_delegate, keycode, group, 1),  // Shift
     };

     // The logical key should be the first available clue from below:
     //
     //  - Mandatory goal, if it matches any clue. This ensures that all alnum
     //    keys can be found somewhere.
     //  - US layout, if neither clue of the key is EASCII. This ensures that
     //    there are no non-latin logical keys.
     //  - A value derived on the fly from keycode & keyval.
     for (uint16_t clue : this_key_clues) {
       auto matching_goal = remaining_mandatory_goals.find(clue);
       if (matching_goal != remaining_mandatory_goals.end()) {
         // Found a key that produces a mandatory char. Use it.
         g_return_if_fail(fl_keyboard_layout_get_logical_key(
                              self->derived_layout, group, keycode) == 0);
         fl_keyboard_layout_set_logical_key(self->derived_layout, group, keycode,
                                            clue);
         remaining_mandatory_goals.erase(matching_goal);
         break;
       }
     }
     bool has_any_eascii =
         is_eascii(this_key_clues[0]) || is_eascii(this_key_clues[1]);
     // See if any produced char meets the requirement as a logical key.
     if (fl_keyboard_layout_get_logical_key(self->derived_layout, group,
                                            keycode) == 0 &&
         !has_any_eascii) {
       auto found_us_layout = self->keycode_to_goals->find(keycode);
       if (found_us_layout != self->keycode_to_goals->end()) {
         fl_keyboard_layout_set_logical_key(
             self->derived_layout, group, keycode,
             found_us_layout->second->logical_key);
       }
     }
   }

   // Ensure all mandatory goals are assigned.
   for (const auto mandatory_goal_iter : remaining_mandatory_goals) {
     const LayoutGoal* goal = mandatory_goal_iter.second;
     fl_keyboard_layout_set_logical_key(self->derived_layout, group,
                                        goal->keycode, goal->logical_key);
   }
 }

 static void fl_keyboard_manager_dispose(GObject* object) {
   FlKeyboardManager* self = FL_KEYBOARD_MANAGER(object);

   g_weak_ref_clear(&self->view_delegate);

   self->keycode_to_goals.reset();
   self->logical_to_mandatory_goals.reset();

   g_ptr_array_free(self->responder_list, TRUE);
   g_ptr_array_set_free_func(self->pending_responds, g_object_unref);
   g_ptr_array_free(self->pending_responds, TRUE);
   g_ptr_array_free(self->pending_redispatches, TRUE);
   g_clear_object(&self->derived_layout);

   G_OBJECT_CLASS(fl_keyboard_manager_parent_class)->dispose(object);
 }

 static void fl_keyboard_manager_class_init(FlKeyboardManagerClass* klass) {
   G_OBJECT_CLASS(klass)->dispose = fl_keyboard_manager_dispose;
 }

 static void fl_keyboard_manager_init(FlKeyboardManager* self) {
   self->derived_layout = fl_keyboard_layout_new();

   self->keycode_to_goals =
       std::make_unique<std::map<uint16_t, const LayoutGoal*>>();
   self->logical_to_mandatory_goals =
       std::make_unique<std::map<uint64_t, const LayoutGoal*>>();
   for (const LayoutGoal& goal : layout_goals) {
     (*self->keycode_to_goals)[goal.keycode] = &goal;
     if (goal.mandatory) {
       (*self->logical_to_mandatory_goals)[goal.logical_key] = &goal;
     }
   }

   self->responder_list = g_ptr_array_new_with_free_func(g_object_unref);

   self->pending_responds = g_ptr_array_new();
   self->pending_redispatches = g_ptr_array_new_with_free_func(g_object_unref);

   self->last_sequence_id = 1;
 }

 FlKeyboardManager* fl_keyboard_manager_new(
     FlKeyboardViewDelegate* view_delegate) {
   g_return_val_if_fail(FL_IS_KEYBOARD_VIEW_DELEGATE(view_delegate), nullptr);

   FlKeyboardManager* self = FL_KEYBOARD_MANAGER(
       g_object_new(fl_keyboard_manager_get_type(), nullptr));

   g_weak_ref_init(&self->view_delegate, view_delegate);

   // The embedder responder must be added before the channel responder.
   g_ptr_array_add(
       self->responder_list,
       FL_KEY_RESPONDER(fl_key_embedder_responder_new(
           [](const FlutterKeyEvent* event, FlutterKeyEventCallback callback,
              void* callback_user_data, void* send_key_event_user_data) {
             FlKeyboardManager* self =
                 FL_KEYBOARD_MANAGER(send_key_event_user_data);
             g_autoptr(FlKeyboardViewDelegate) view_delegate =
                 FL_KEYBOARD_VIEW_DELEGATE(g_weak_ref_get(&self->view_delegate));
             if (view_delegate == nullptr) {
               return;
             }
             fl_keyboard_view_delegate_send_key_event(
                 view_delegate, event, callback, callback_user_data);
           },
           self)));
   g_ptr_array_add(self->responder_list,
                   FL_KEY_RESPONDER(fl_key_channel_responder_new(
                       fl_keyboard_view_delegate_get_messenger(view_delegate))));

   return self;
 }

 gboolean fl_keyboard_manager_handle_event(FlKeyboardManager* self,
                                           FlKeyEvent* event) {
   g_return_val_if_fail(FL_IS_KEYBOARD_MANAGER(self), FALSE);
   g_return_val_if_fail(event != nullptr, FALSE);

   guarantee_layout(self, event);

   uint64_t incoming_hash = fl_key_event_hash(event);
   if (fl_keyboard_manager_remove_redispatched(self, incoming_hash)) {
     return FALSE;
   }

   FlKeyboardPendingEvent* pending = fl_keyboard_pending_event_new(
       event, ++self->last_sequence_id, self->responder_list->len);

   g_ptr_array_add(self->pending_responds, pending);
   FlKeyboardManagerUserData* user_data = fl_keyboard_manager_user_data_new(
       self, fl_keyboard_pending_event_get_sequence_id(pending));
   uint64_t specified_logical_key = fl_keyboard_layout_get_logical_key(
       self->derived_layout, fl_key_event_get_group(event),
       fl_key_event_get_keycode(event));
   for (guint i = 0; i < self->responder_list->len; i++) {
     FlKeyResponder* responder =
         FL_KEY_RESPONDER(g_ptr_array_index(self->responder_list, i));
     fl_key_responder_handle_event(responder, event,
                                   responder_handle_event_callback, user_data,
                                   specified_logical_key);
   }

   return TRUE;
 }

 gboolean fl_keyboard_manager_is_state_clear(FlKeyboardManager* self) {
   g_return_val_if_fail(FL_IS_KEYBOARD_MANAGER(self), FALSE);
   return self->pending_responds->len == 0 &&
          self->pending_redispatches->len == 0;
 }

 void fl_keyboard_manager_sync_modifier_if_needed(FlKeyboardManager* self,
                                                  guint state,
                                                  double event_time) {
   g_return_if_fail(FL_IS_KEYBOARD_MANAGER(self));

   // The embedder responder is the first element in
   // FlKeyboardManager.responder_list.
   FlKeyEmbedderResponder* responder =
       FL_KEY_EMBEDDER_RESPONDER(g_ptr_array_index(self->responder_list, 0));
   fl_key_embedder_responder_sync_modifiers_if_needed(responder, state,
                                                      event_time);
 }

 GHashTable* fl_keyboard_manager_get_pressed_state(FlKeyboardManager* self) {
   g_return_val_if_fail(FL_IS_KEYBOARD_MANAGER(self), nullptr);

   // The embedder responder is the first element in
   // FlKeyboardManager.responder_list.
   FlKeyEmbedderResponder* responder =
       FL_KEY_EMBEDDER_RESPONDER(g_ptr_array_index(self->responder_list, 0));
   return fl_key_embedder_responder_get_pressed_state(responder);
 }

 void fl_keyboard_manager_notify_layout_changed(FlKeyboardManager* self) {
   g_return_if_fail(FL_IS_KEYBOARD_MANAGER(self));
   g_clear_object(&self->derived_layout);
   self->derived_layout = fl_keyboard_layout_new();
 }
	// Copyright 2013 The Flutter Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	#include "flutter/shell/platform/linux/fl_keyboard_manager.h"

	#include <array>
	#include <cinttypes>
	#include <memory>
	#include <string>

	#include "flutter/shell/platform/linux/fl_key_channel_responder.h"
	#include "flutter/shell/platform/linux/fl_key_embedder_responder.h"
	#include "flutter/shell/platform/linux/fl_keyboard_layout.h"
	#include "flutter/shell/platform/linux/fl_keyboard_pending_event.h"
	#include "flutter/shell/platform/linux/key_mapping.h"

	// Turn on this flag to print complete layout data when switching IMEs. The data
	// is used in unit tests.
	#define DEBUG_PRINT_LAYOUT

	/* Declarations of private classes */

	G_DECLARE_FINAL_TYPE(FlKeyboardManagerUserData,
	fl_keyboard_manager_user_data,
	FL,
	KEYBOARD_MANAGER_USER_DATA,
	GObject);

	/* End declarations */

	namespace {

	static bool is_eascii(uint16_t character) {
	return character < 256;
	}

	#ifdef DEBUG_PRINT_LAYOUT
	// Prints layout entries that will be parsed by `MockLayoutData`.
	void debug_format_layout_data(std::string& debug_layout_data,
	uint16_t keycode,
	uint16_t clue1,
	uint16_t clue2) {
	if (keycode % 4 == 0) {
	debug_layout_data.append(" ");
	}

	constexpr int kBufferSize = 30;
	char buffer[kBufferSize];
	buffer[0] = 0;
	buffer[kBufferSize - 1] = 0;

	snprintf(buffer, kBufferSize, "0x%04x, 0x%04x, ", clue1, clue2);
	debug_layout_data.append(buffer);

	if (keycode % 4 == 3) {
	snprintf(buffer, kBufferSize, " // 0x%02x", keycode);
	debug_layout_data.append(buffer);
	}
	}
	#endif

	} // namespace

	/* Define FlKeyboardManagerUserData */

	/**
	* FlKeyboardManagerUserData:
	* The user_data used when #FlKeyboardManager sends event to
	* responders.
	*/

	struct _FlKeyboardManagerUserData {
	GObject parent_instance;

	// The owner manager.
	GWeakRef manager;
	uint64_t sequence_id;
	};

	G_DEFINE_TYPE(FlKeyboardManagerUserData,
	fl_keyboard_manager_user_data,
	G_TYPE_OBJECT)

	static void fl_keyboard_manager_user_data_dispose(GObject* object) {
	g_return_if_fail(FL_IS_KEYBOARD_MANAGER_USER_DATA(object));
	FlKeyboardManagerUserData* self = FL_KEYBOARD_MANAGER_USER_DATA(object);

	g_weak_ref_clear(&self->manager);

	G_OBJECT_CLASS(fl_keyboard_manager_user_data_parent_class)->dispose(object);
	}

	static void fl_keyboard_manager_user_data_class_init(
	FlKeyboardManagerUserDataClass* klass) {
	G_OBJECT_CLASS(klass)->dispose = fl_keyboard_manager_user_data_dispose;
	}

	static void fl_keyboard_manager_user_data_init(
	FlKeyboardManagerUserData* self) {}

	// Creates a new FlKeyboardManagerUserData private class with all information.
	static FlKeyboardManagerUserData* fl_keyboard_manager_user_data_new(
	FlKeyboardManager* manager,
	uint64_t sequence_id) {
	FlKeyboardManagerUserData* self = FL_KEYBOARD_MANAGER_USER_DATA(
	g_object_new(fl_keyboard_manager_user_data_get_type(), nullptr));

	g_weak_ref_init(&self->manager, manager);
	self->sequence_id = sequence_id;
	return self;
	}

	/* Define FlKeyboardManager */

	struct _FlKeyboardManager {
	GObject parent_instance;

	GWeakRef view_delegate;

	// An array of #FlKeyResponder. Elements are added with
	// #fl_keyboard_manager_add_responder immediately after initialization and are
	// automatically released on dispose.
	GPtrArray* responder_list;

	// An array of #FlKeyboardPendingEvent.
	//
	// Its elements are not unreferenced when removed. When FlKeyboardManager is
	// disposed, this array will be set with a free_func so that the elements are
	// unreferenced when removed.
	GPtrArray* pending_responds;

	// An array of #FlKeyboardPendingEvent.
	//
	// Its elements are unreferenced when removed.
	GPtrArray* pending_redispatches;

	// The last sequence ID used. Increased by 1 by every use.
	uint64_t last_sequence_id;

	// Record the derived layout.
	//
	// It is cleared when the platform reports a layout switch. Each entry,
	// which corresponds to a group, is only initialized on the arrival of the
	// first event for that group that has a goal keycode.
	FlKeyboardLayout* derived_layout;

	// A static map from keycodes to all layout goals.
	//
	// It is set up when the manager is initialized and is not changed ever after.
	std::unique_ptr<std::map<uint16_t, const LayoutGoal*>> keycode_to_goals;

	// A static map from logical keys to all mandatory layout goals.
	//
	// It is set up when the manager is initialized and is not changed ever after.
	std::unique_ptr<std::map<uint64_t, const LayoutGoal*>>
	logical_to_mandatory_goals;
	};

	G_DEFINE_TYPE(FlKeyboardManager, fl_keyboard_manager, G_TYPE_OBJECT);

	// This is an exact copy of g_ptr_array_find_with_equal_func. Somehow CI
	// reports that can not find symbol g_ptr_array_find_with_equal_func, despite
	// the fact that it runs well locally.
	static gboolean g_ptr_array_find_with_equal_func1(GPtrArray* haystack,
	gconstpointer needle,
	GEqualFunc equal_func,
	guint* index_) {
	guint i;
	g_return_val_if_fail(haystack != NULL, FALSE);
	if (equal_func == NULL) {
	equal_func = g_direct_equal;
	}
	for (i = 0; i < haystack->len; i++) {
	if (equal_func(g_ptr_array_index(haystack, i), needle)) {
	if (index_ != NULL) {
	*index_ = i;
	}
	return TRUE;
	}
	}

	return FALSE;
	}

	// Compare a #FlKeyboardPendingEvent with the given sequence_id.
	static gboolean compare_pending_by_sequence_id(gconstpointer a,
	gconstpointer b) {
	FlKeyboardPendingEvent* pending =
	FL_KEYBOARD_PENDING_EVENT(const_cast<gpointer>(a));
	uint64_t sequence_id = reinterpret_cast<const uint64_t>(b);
	return fl_keyboard_pending_event_get_sequence_id(pending) == sequence_id;
	}

	// Compare a #FlKeyboardPendingEvent with the given hash.
	static gboolean compare_pending_by_hash(gconstpointer a, gconstpointer b) {
	FlKeyboardPendingEvent* pending =
	FL_KEYBOARD_PENDING_EVENT(const_cast<gpointer>(a));
	uint64_t hash = reinterpret_cast<const uint64_t>(b);
	return fl_keyboard_pending_event_get_hash(pending) == hash;
	}

	// Try to remove a pending event from `pending_redispatches` with the target
	// hash.
	//
	// Returns true if the event is found and removed.
	static bool fl_keyboard_manager_remove_redispatched(FlKeyboardManager* self,
	uint64_t hash) {
	guint result_index;
	gboolean found = g_ptr_array_find_with_equal_func1(
	self->pending_redispatches, static_cast<const uint64_t*>(&hash),
	compare_pending_by_hash, &result_index);
	if (found) {
	// The removed object is freed due to `pending_redispatches`'s free_func.
	g_ptr_array_remove_index_fast(self->pending_redispatches, result_index);
	return TRUE;
	} else {
	return FALSE;
	}
	}

	// The callback used by a responder after the event was dispatched.
	static void responder_handle_event_callback(bool handled,
	gpointer user_data_ptr) {
	g_return_if_fail(FL_IS_KEYBOARD_MANAGER_USER_DATA(user_data_ptr));
	FlKeyboardManagerUserData* user_data =
	FL_KEYBOARD_MANAGER_USER_DATA(user_data_ptr);

	g_autoptr(FlKeyboardManager) self =
	FL_KEYBOARD_MANAGER(g_weak_ref_get(&user_data->manager));
	if (self == nullptr) {
	return;
	}

	g_autoptr(FlKeyboardViewDelegate) view_delegate =
	FL_KEYBOARD_VIEW_DELEGATE(g_weak_ref_get(&self->view_delegate));
	if (view_delegate == nullptr) {
	return;
	}

	guint result_index = -1;
	gboolean found = g_ptr_array_find_with_equal_func1(
	self->pending_responds, &user_data->sequence_id,
	compare_pending_by_sequence_id, &result_index);
	g_return_if_fail(found);
	FlKeyboardPendingEvent* pending = FL_KEYBOARD_PENDING_EVENT(
	g_ptr_array_index(self->pending_responds, result_index));
	g_return_if_fail(pending != nullptr);
	fl_keyboard_pending_event_mark_replied(pending, handled);
	// All responders have replied.
	if (fl_keyboard_pending_event_is_complete(pending)) {
	g_object_unref(user_data_ptr);
	gpointer removed =
	g_ptr_array_remove_index_fast(self->pending_responds, result_index);
	g_return_if_fail(removed == pending);
	bool should_redispatch =
	!fl_keyboard_pending_event_get_any_handled(pending) &&
	!fl_keyboard_view_delegate_text_filter_key_press(
	view_delegate, fl_keyboard_pending_event_get_event(pending));
	if (should_redispatch) {
	g_ptr_array_add(self->pending_redispatches, pending);
	fl_keyboard_view_delegate_redispatch_event(
	view_delegate,
	FL_KEY_EVENT(fl_keyboard_pending_event_get_event(pending)));
	} else {
	g_object_unref(pending);
	}
	}
	}

	static uint16_t convert_key_to_char(FlKeyboardViewDelegate* view_delegate,
	guint keycode,
	gint group,
	gint level) {
	GdkKeymapKey key = {keycode, group, level};
	constexpr int kBmpMax = 0xD7FF;
	guint origin = fl_keyboard_view_delegate_lookup_key(view_delegate, &key);
	return origin < kBmpMax ? origin : 0xFFFF;
	}

	// Make sure that Flutter has derived the layout for the group of the event,
	// if the event contains a goal keycode.
	static void guarantee_layout(FlKeyboardManager* self, FlKeyEvent* event) {
	g_autoptr(FlKeyboardViewDelegate) view_delegate =
	FL_KEYBOARD_VIEW_DELEGATE(g_weak_ref_get(&self->view_delegate));
	if (view_delegate == nullptr) {
	return;
	}

	guint8 group = fl_key_event_get_group(event);
	if (fl_keyboard_layout_has_group(self->derived_layout, group)) {
	return;
	}
	if (self->keycode_to_goals->find(fl_key_event_get_keycode(event)) ==
	self->keycode_to_goals->end()) {
	return;
	}

	// Clone all mandatory goals. Each goal is removed from this cloned map when
	// fulfilled, and the remaining ones will be assigned to a default position.
	std::map<uint64_t, const LayoutGoal*> remaining_mandatory_goals =
	*self->logical_to_mandatory_goals;

	#ifdef DEBUG_PRINT_LAYOUT
	std::string debug_layout_data;
	for (uint16_t keycode = 0; keycode < 128; keycode += 1) {
	std::vector<uint16_t> this_key_clues = {
	convert_key_to_char(view_delegate, keycode, group, 0),
	convert_key_to_char(view_delegate, keycode, group, 1), // Shift
	};
	debug_format_layout_data(debug_layout_data, keycode, this_key_clues[0],
	this_key_clues[1]);
	}
	#endif

	// It's important to only traverse layout goals instead of all keycodes.
	// Some key codes outside of the standard keyboard also gives alpha-numeric
	// letters, and will therefore take over mandatory goals from standard
	// keyboard keys if they come first. Example: French keyboard digit 1.
	for (const LayoutGoal& keycode_goal : layout_goals) {
	uint16_t keycode = keycode_goal.keycode;
	std::vector<uint16_t> this_key_clues = {
	convert_key_to_char(view_delegate, keycode, group, 0),
	convert_key_to_char(view_delegate, keycode, group, 1), // Shift
	};

	// The logical key should be the first available clue from below:
	//
	// - Mandatory goal, if it matches any clue. This ensures that all alnum
	// keys can be found somewhere.
	// - US layout, if neither clue of the key is EASCII. This ensures that
	// there are no non-latin logical keys.
	// - A value derived on the fly from keycode & keyval.
	for (uint16_t clue : this_key_clues) {
	auto matching_goal = remaining_mandatory_goals.find(clue);
	if (matching_goal != remaining_mandatory_goals.end()) {
	// Found a key that produces a mandatory char. Use it.
	g_return_if_fail(fl_keyboard_layout_get_logical_key(
	self->derived_layout, group, keycode) == 0);
	fl_keyboard_layout_set_logical_key(self->derived_layout, group, keycode,
	clue);
	remaining_mandatory_goals.erase(matching_goal);
	break;
	}
	}
	bool has_any_eascii =
	is_eascii(this_key_clues[0]) \|\| is_eascii(this_key_clues[1]);
	// See if any produced char meets the requirement as a logical key.
	if (fl_keyboard_layout_get_logical_key(self->derived_layout, group,
	keycode) == 0 &&
	!has_any_eascii) {
	auto found_us_layout = self->keycode_to_goals->find(keycode);
	if (found_us_layout != self->keycode_to_goals->end()) {
	fl_keyboard_layout_set_logical_key(
	self->derived_layout, group, keycode,
	found_us_layout->second->logical_key);
	}
	}
	}

	// Ensure all mandatory goals are assigned.
	for (const auto mandatory_goal_iter : remaining_mandatory_goals) {
	const LayoutGoal* goal = mandatory_goal_iter.second;
	fl_keyboard_layout_set_logical_key(self->derived_layout, group,
	goal->keycode, goal->logical_key);
	}
	}

	static void fl_keyboard_manager_dispose(GObject* object) {
	FlKeyboardManager* self = FL_KEYBOARD_MANAGER(object);

	g_weak_ref_clear(&self->view_delegate);

	self->keycode_to_goals.reset();
	self->logical_to_mandatory_goals.reset();

	g_ptr_array_free(self->responder_list, TRUE);
	g_ptr_array_set_free_func(self->pending_responds, g_object_unref);
	g_ptr_array_free(self->pending_responds, TRUE);
	g_ptr_array_free(self->pending_redispatches, TRUE);
	g_clear_object(&self->derived_layout);

	G_OBJECT_CLASS(fl_keyboard_manager_parent_class)->dispose(object);
	}

	static void fl_keyboard_manager_class_init(FlKeyboardManagerClass* klass) {
	G_OBJECT_CLASS(klass)->dispose = fl_keyboard_manager_dispose;
	}

	static void fl_keyboard_manager_init(FlKeyboardManager* self) {
	self->derived_layout = fl_keyboard_layout_new();

	self->keycode_to_goals =
	std::make_unique<std::map<uint16_t, const LayoutGoal*>>();
	self->logical_to_mandatory_goals =
	std::make_unique<std::map<uint64_t, const LayoutGoal*>>();
	for (const LayoutGoal& goal : layout_goals) {
	(*self->keycode_to_goals)[goal.keycode] = &goal;
	if (goal.mandatory) {
	(*self->logical_to_mandatory_goals)[goal.logical_key] = &goal;
	}
	}

	self->responder_list = g_ptr_array_new_with_free_func(g_object_unref);

	self->pending_responds = g_ptr_array_new();
	self->pending_redispatches = g_ptr_array_new_with_free_func(g_object_unref);

	self->last_sequence_id = 1;
	}

	FlKeyboardManager* fl_keyboard_manager_new(
	FlKeyboardViewDelegate* view_delegate) {
	g_return_val_if_fail(FL_IS_KEYBOARD_VIEW_DELEGATE(view_delegate), nullptr);

	FlKeyboardManager* self = FL_KEYBOARD_MANAGER(
	g_object_new(fl_keyboard_manager_get_type(), nullptr));

	g_weak_ref_init(&self->view_delegate, view_delegate);

	// The embedder responder must be added before the channel responder.
	g_ptr_array_add(
	self->responder_list,
	FL_KEY_RESPONDER(fl_key_embedder_responder_new(
	[](const FlutterKeyEvent* event, FlutterKeyEventCallback callback,
	void* callback_user_data, void* send_key_event_user_data) {
	FlKeyboardManager* self =
	FL_KEYBOARD_MANAGER(send_key_event_user_data);
	g_autoptr(FlKeyboardViewDelegate) view_delegate =
	FL_KEYBOARD_VIEW_DELEGATE(g_weak_ref_get(&self->view_delegate));
	if (view_delegate == nullptr) {
	return;
	}
	fl_keyboard_view_delegate_send_key_event(
	view_delegate, event, callback, callback_user_data);
	},
	self)));
	g_ptr_array_add(self->responder_list,
	FL_KEY_RESPONDER(fl_key_channel_responder_new(
	fl_keyboard_view_delegate_get_messenger(view_delegate))));

	return self;
	}

	gboolean fl_keyboard_manager_handle_event(FlKeyboardManager* self,
	FlKeyEvent* event) {
	g_return_val_if_fail(FL_IS_KEYBOARD_MANAGER(self), FALSE);
	g_return_val_if_fail(event != nullptr, FALSE);

	guarantee_layout(self, event);

	uint64_t incoming_hash = fl_key_event_hash(event);
	if (fl_keyboard_manager_remove_redispatched(self, incoming_hash)) {
	return FALSE;
	}

	FlKeyboardPendingEvent* pending = fl_keyboard_pending_event_new(
	event, ++self->last_sequence_id, self->responder_list->len);

	g_ptr_array_add(self->pending_responds, pending);
	FlKeyboardManagerUserData* user_data = fl_keyboard_manager_user_data_new(
	self, fl_keyboard_pending_event_get_sequence_id(pending));
	uint64_t specified_logical_key = fl_keyboard_layout_get_logical_key(
	self->derived_layout, fl_key_event_get_group(event),
	fl_key_event_get_keycode(event));
	for (guint i = 0; i < self->responder_list->len; i++) {
	FlKeyResponder* responder =
	FL_KEY_RESPONDER(g_ptr_array_index(self->responder_list, i));
	fl_key_responder_handle_event(responder, event,
	responder_handle_event_callback, user_data,
	specified_logical_key);
	}

	return TRUE;
	}

	gboolean fl_keyboard_manager_is_state_clear(FlKeyboardManager* self) {
	g_return_val_if_fail(FL_IS_KEYBOARD_MANAGER(self), FALSE);
	return self->pending_responds->len == 0 &&
	self->pending_redispatches->len == 0;
	}

	void fl_keyboard_manager_sync_modifier_if_needed(FlKeyboardManager* self,
	guint state,
	double event_time) {
	g_return_if_fail(FL_IS_KEYBOARD_MANAGER(self));

	// The embedder responder is the first element in
	// FlKeyboardManager.responder_list.
	FlKeyEmbedderResponder* responder =
	FL_KEY_EMBEDDER_RESPONDER(g_ptr_array_index(self->responder_list, 0));
	fl_key_embedder_responder_sync_modifiers_if_needed(responder, state,
	event_time);
	}

	GHashTable* fl_keyboard_manager_get_pressed_state(FlKeyboardManager* self) {
	g_return_val_if_fail(FL_IS_KEYBOARD_MANAGER(self), nullptr);

	// The embedder responder is the first element in
	// FlKeyboardManager.responder_list.
	FlKeyEmbedderResponder* responder =
	FL_KEY_EMBEDDER_RESPONDER(g_ptr_array_index(self->responder_list, 0));
	return fl_key_embedder_responder_get_pressed_state(responder);
	}

	void fl_keyboard_manager_notify_layout_changed(FlKeyboardManager* self) {
	g_return_if_fail(FL_IS_KEYBOARD_MANAGER(self));
	g_clear_object(&self->derived_layout);
	self->derived_layout = fl_keyboard_layout_new();
	}