[Linux] Return keyboard pressed state (#42346)

## Description

This PR updates the Linux engine in order to answer to keyboard pressed state queries from the framework (as implemented in flutter/flutter#122885).

## Related Issue

Linux engine implementation for flutter/flutter#87391

## Tests

Adds 2 tests.

Author: bleroux

shell/platform/linux/fl_key_embedder_responder.cc

@@ -885,3 +885,8 @@ void fl_key_embedder_responder_sync_modifiers_if_needed(
                        synchronize_pressed_states_loop_body,
                        &sync_state_context);
 }
+
+GHashTable* fl_key_embedder_responder_get_pressed_state(
+    FlKeyEmbedderResponder* self) {
+  return self->pressing_records;
+}

shell/platform/linux/fl_key_embedder_responder.h

@@ -64,6 +64,16 @@ void fl_key_embedder_responder_sync_modifiers_if_needed(
     guint state,
     double event_time);
 
+/**
+ * fl_key_embedder_responder_get_pressed_state:
+ * @responder: the #FlKeyEmbedderResponder self.
+ *
+ * Returns the keyboard pressed state. The hash table contains one entry per
+ * pressed keys, mapping from the logical key to the physical key.
+ */
+GHashTable* fl_key_embedder_responder_get_pressed_state(
+    FlKeyEmbedderResponder* responder);
+
 G_END_DECLS
 
 #endif  // FLUTTER_SHELL_PLATFORM_LINUX_FL_KEY_EMBEDDER_RESPONDER_H_

shell/platform/linux/fl_keyboard_manager.cc

@@ -12,11 +12,16 @@
 #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/key_mapping.h"
+#include "flutter/shell/platform/linux/public/flutter_linux/fl_method_channel.h"
+#include "flutter/shell/platform/linux/public/flutter_linux/fl_standard_method_codec.h"
 
 // Turn on this flag to print complete layout data when switching IMEs. The data
 // is used in unit tests.
 #define DEBUG_PRINT_LAYOUT
 
+static constexpr char kChannelName[] = "flutter/keyboard";
+static constexpr char kGetKeyboardStateMethod[] = "getKeyboardState";
+
 /* Declarations of private classes */
 
 G_DECLARE_FINAL_TYPE(FlKeyboardPendingEvent,
@@ -287,6 +292,9 @@ struct _FlKeyboardManager {
   // 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;
+
+  // The channel used by the framework to query the keyboard pressed state.
+  FlMethodChannel* channel;
 };
 
 G_DEFINE_TYPE(FlKeyboardManager, fl_keyboard_manager, G_TYPE_OBJECT);
@@ -532,7 +540,50 @@ static void guarantee_layout(FlKeyboardManager* self, FlKeyEvent* event) {
   }
 }
 
+// Returns the keyboard pressed state.
+FlMethodResponse* get_keyboard_state(FlKeyboardManager* self) {
+  g_autoptr(FlValue) result = fl_value_new_map();
+
+  GHashTable* pressing_records =
+      fl_keyboard_view_delegate_get_keyboard_state(self->view_delegate);
+
+  g_hash_table_foreach(
+      pressing_records,
+      [](gpointer key, gpointer value, gpointer user_data) {
+        int64_t physical_key = reinterpret_cast<int64_t>(key);
+        int64_t logical_key = reinterpret_cast<int64_t>(value);
+        FlValue* fl_value_map = reinterpret_cast<FlValue*>(user_data);
+
+        fl_value_set_take(fl_value_map, fl_value_new_int(physical_key),
+                          fl_value_new_int(logical_key));
+      },
+      result);
+  return FL_METHOD_RESPONSE(fl_method_success_response_new(result));
+}
+
+// Called when a method call on flutter/keyboard is received from Flutter.
+static void method_call_handler(FlMethodChannel* channel,
+                                FlMethodCall* method_call,
+                                gpointer user_data) {
+  FlKeyboardManager* self = FL_KEYBOARD_MANAGER(user_data);
+
+  const gchar* method = fl_method_call_get_name(method_call);
+
+  g_autoptr(FlMethodResponse) response = nullptr;
+  if (strcmp(method, kGetKeyboardStateMethod) == 0) {
+    response = get_keyboard_state(self);
+  } else {
+    response = FL_METHOD_RESPONSE(fl_method_not_implemented_response_new());
+  }
+
+  g_autoptr(GError) error = nullptr;
+  if (!fl_method_call_respond(method_call, response, &error)) {
+    g_warning("Failed to send method call response: %s", error->message);
+  }
+}
+
 FlKeyboardManager* fl_keyboard_manager_new(
+    FlBinaryMessenger* messenger,
     FlKeyboardViewDelegate* view_delegate) {
   g_return_val_if_fail(FL_IS_KEYBOARD_VIEW_DELEGATE(view_delegate), nullptr);
 
@@ -560,6 +611,13 @@ FlKeyboardManager* fl_keyboard_manager_new(
 
   fl_keyboard_view_delegate_subscribe_to_layout_change(
       self->view_delegate, [self]() { self->derived_layout->clear(); });
+
+  // Setup the flutter/keyboard channel.
+  g_autoptr(FlStandardMethodCodec) codec = fl_standard_method_codec_new();
+  self->channel =
+      fl_method_channel_new(messenger, kChannelName, FL_METHOD_CODEC(codec));
+  fl_method_channel_set_method_call_handler(self->channel, method_call_handler,
+                                            self, nullptr);
   return self;
 }
 
@@ -614,10 +672,22 @@ gboolean fl_keyboard_manager_is_state_clear(FlKeyboardManager* self) {
 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);
+}

shell/platform/linux/fl_keyboard_manager.h

@@ -44,6 +44,7 @@ G_DECLARE_FINAL_TYPE(FlKeyboardManager,
  * Returns: a new #FlKeyboardManager.
  */
 FlKeyboardManager* fl_keyboard_manager_new(
+    FlBinaryMessenger* messenger,
     FlKeyboardViewDelegate* view_delegate);
 
 /**
@@ -83,6 +84,15 @@ void fl_keyboard_manager_sync_modifier_if_needed(FlKeyboardManager* manager,
                                                  guint state,
                                                  double event_time);
 
+/**
+ * fl_keyboard_manager_get_pressed_state:
+ * @manager: the #FlKeyboardManager self.
+ *
+ * Returns the keyboard pressed state. The hash table contains one entry per
+ * pressed keys, mapping from the logical key to the physical key.*
+ */
+GHashTable* fl_keyboard_manager_get_pressed_state(FlKeyboardManager* manager);
+
 G_END_DECLS
 
 #endif  // FLUTTER_SHELL_PLATFORM_LINUX_FL_KEYBOARD_MANAGER_H_

shell/platform/linux/fl_keyboard_manager_test.cc

@@ -8,8 +8,18 @@
 #include <vector>
 
 #include "flutter/shell/platform/embedder/test_utils/key_codes.g.h"
+#include "flutter/shell/platform/linux/fl_binary_messenger_private.h"
+#include "flutter/shell/platform/linux/fl_method_codec_private.h"
+#include "flutter/shell/platform/linux/key_mapping.h"
 #include "flutter/shell/platform/linux/public/flutter_linux/fl_json_message_codec.h"
+#include "flutter/shell/platform/linux/public/flutter_linux/fl_method_codec.h"
+#include "flutter/shell/platform/linux/public/flutter_linux/fl_standard_method_codec.h"
+#include "flutter/shell/platform/linux/testing/fl_test.h"
+#include "flutter/shell/platform/linux/testing/mock_binary_messenger.h"
 #include "flutter/shell/platform/linux/testing/mock_text_input_plugin.h"
+#include "flutter/testing/testing.h"
+
+#include "gmock/gmock.h"
 #include "gtest/gtest.h"
 
 // Define compound `expect` in macros. If they were defined in functions, the
@@ -100,6 +110,10 @@ constexpr guint16 kKeyCodeSemicolon = 0x2fu;
 constexpr guint16 kKeyCodeKeyLeftBracket = 0x22u;
 
 static constexpr char kKeyEventChannelName[] = "flutter/keyevent";
+static constexpr char kKeyboardChannelName[] = "flutter/keyboard";
+static constexpr char kGetKeyboardStateMethod[] = "getKeyboardState";
+static constexpr uint64_t kMockPhysicalKey = 42;
+static constexpr uint64_t kMockLogicalKey = 42;
 
 // All key clues for a keyboard layout.
 //
@@ -129,6 +143,19 @@ G_DECLARE_FINAL_TYPE(FlMockKeyBinaryMessenger,
 
 G_END_DECLS
 
+MATCHER_P(MethodSuccessResponse, result, "") {
+  g_autoptr(FlStandardMethodCodec) codec = fl_standard_method_codec_new();
+  g_autoptr(FlMethodResponse) response =
+      fl_method_codec_decode_response(FL_METHOD_CODEC(codec), arg, nullptr);
+  fl_method_response_get_result(response, nullptr);
+  if (fl_value_equal(fl_method_response_get_result(response, nullptr),
+                     result)) {
+    return true;
+  }
+  *result_listener << ::testing::PrintToString(response);
+  return false;
+}
+
 /***** FlMockKeyBinaryMessenger *****/
 /* Mock a binary messenger that only processes messages from the embedding on
  * the key event channel, and does so according to the callback set by
@@ -322,6 +349,15 @@ static guint fl_mock_view_keyboard_lookup_key(FlKeyboardViewDelegate* delegate,
   return (*group_layout)[key->keycode * 2 + shift];
 }
 
+static GHashTable* fl_mock_view_keyboard_get_keyboard_state(
+    FlKeyboardViewDelegate* view_delegate) {
+  GHashTable* result = g_hash_table_new(g_direct_hash, g_direct_equal);
+  g_hash_table_insert(result, reinterpret_cast<gpointer>(kMockPhysicalKey),
+                      reinterpret_cast<gpointer>(kMockLogicalKey));
+
+  return result;
+}
+
 static void fl_mock_view_keyboard_delegate_iface_init(
     FlKeyboardViewDelegateInterface* iface) {
   iface->send_key_event = fl_mock_view_keyboard_send_key_event;
@@ -331,6 +367,7 @@ static void fl_mock_view_keyboard_delegate_iface_init(
   iface->subscribe_to_layout_change =
       fl_mock_view_keyboard_subscribe_to_layout_change;
   iface->lookup_key = fl_mock_view_keyboard_lookup_key;
+  iface->get_keyboard_state = fl_mock_view_keyboard_get_keyboard_state;
 }
 
 static FlMockViewDelegate* fl_mock_view_delegate_new() {
@@ -406,13 +443,16 @@ static FlKeyEvent* fl_key_event_new_by_mock(bool is_press,
 class KeyboardTester {
  public:
   KeyboardTester() {
+    ::testing::NiceMock<flutter::testing::MockBinaryMessenger> messenger;
+
     view_ = fl_mock_view_delegate_new();
     respondToEmbedderCallsWith(false);
     respondToChannelCallsWith(false);
     respondToTextInputWith(false);
     setLayout(kLayoutUs);
 
-    manager_ = fl_keyboard_manager_new(FL_KEYBOARD_VIEW_DELEGATE(view_));
+    manager_ =
+        fl_keyboard_manager_new(messenger, FL_KEYBOARD_VIEW_DELEGATE(view_));
   }
 
   ~KeyboardTester() {
@@ -926,6 +966,47 @@ TEST(FlKeyboardManagerTest, SynthesizeModifiersIfNeeded) {
                               kLogicalShiftLeft);
 }
 
+TEST(FlKeyboardManagerTest, GetPressedState) {
+  KeyboardTester tester;
+  tester.respondToTextInputWith(true);
+
+  // Dispatch a key event.
+  fl_keyboard_manager_handle_event(
+      tester.manager(),
+      fl_key_event_new_by_mock(true, GDK_KEY_a, kKeyCodeKeyA, 0, false));
+
+  GHashTable* pressedState =
+      fl_keyboard_manager_get_pressed_state(tester.manager());
+  EXPECT_EQ(g_hash_table_size(pressedState), 1u);
+
+  gpointer physical_key =
+      g_hash_table_lookup(pressedState, uint64_to_gpointer(kPhysicalKeyA));
+  EXPECT_EQ(gpointer_to_uint64(physical_key), kLogicalKeyA);
+}
+
+TEST(FlKeyboardPluginTest, KeyboardChannelGetPressedState) {
+  ::testing::NiceMock<flutter::testing::MockBinaryMessenger> messenger;
+
+  g_autoptr(FlKeyboardManager) manager = fl_keyboard_manager_new(
+      messenger, FL_KEYBOARD_VIEW_DELEGATE(fl_mock_view_delegate_new()));
+  EXPECT_NE(manager, nullptr);
+
+  g_autoptr(FlStandardMethodCodec) codec = fl_standard_method_codec_new();
+  g_autoptr(GBytes) message = fl_method_codec_encode_method_call(
+      FL_METHOD_CODEC(codec), kGetKeyboardStateMethod, nullptr, nullptr);
+
+  g_autoptr(FlValue) response = fl_value_new_map();
+  fl_value_set_take(response, fl_value_new_int(kMockPhysicalKey),
+                    fl_value_new_int(kMockLogicalKey));
+  EXPECT_CALL(messenger,
+              fl_binary_messenger_send_response(
+                  ::testing::Eq<FlBinaryMessenger*>(messenger), ::testing::_,
+                  MethodSuccessResponse(response), ::testing::_))
+      .WillOnce(::testing::Return(true));
+
+  messenger.ReceiveMessage(kKeyboardChannelName, message);
+}
+
 // The following layout data is generated using DEBUG_PRINT_LAYOUT.
 
 const MockGroupLayoutData kLayoutUs0{{

shell/platform/linux/fl_keyboard_view_delegate.cc

@@ -64,3 +64,10 @@ guint fl_keyboard_view_delegate_lookup_key(FlKeyboardViewDelegate* self,
 
   return FL_KEYBOARD_VIEW_DELEGATE_GET_IFACE(self)->lookup_key(self, key);
 }
+
+GHashTable* fl_keyboard_view_delegate_get_keyboard_state(
+    FlKeyboardViewDelegate* self) {
+  g_return_val_if_fail(FL_IS_KEYBOARD_VIEW_DELEGATE(self), nullptr);
+
+  return FL_KEYBOARD_VIEW_DELEGATE_GET_IFACE(self)->get_keyboard_state(self);
+}

shell/platform/linux/fl_keyboard_view_delegate.h

@@ -54,6 +54,8 @@ struct _FlKeyboardViewDelegateInterface {
 
   guint (*lookup_key)(FlKeyboardViewDelegate* view_delegate,
                       const GdkKeymapKey* key);
+
+  GHashTable* (*get_keyboard_state)(FlKeyboardViewDelegate* delegate);
 };
 
 /**
@@ -116,6 +118,16 @@ void fl_keyboard_view_delegate_subscribe_to_layout_change(
 guint fl_keyboard_view_delegate_lookup_key(FlKeyboardViewDelegate* delegate,
                                            const GdkKeymapKey* key);
 
+/**
+ * fl_keyboard_view_delegate_get_keyboard_state:
+ *
+ * Returns the keyboard pressed state. The hash table contains one entry per
+ * pressed keys, mapping from the logical key to the physical key.*
+ *
+ */
+GHashTable* fl_keyboard_view_delegate_get_keyboard_state(
+    FlKeyboardViewDelegate* delegate);
+
 G_END_DECLS
 
 #endif  // FLUTTER_SHELL_PLATFORM_LINUX_FL_KEYBOARD_VIEW_DELEGATE_H_

shell/platform/linux/fl_view.cc

@@ -116,7 +116,7 @@ static void init_keyboard(FlView* self) {
   self->text_input_plugin = fl_text_input_plugin_new(
       messenger, im_context, FL_TEXT_INPUT_VIEW_DELEGATE(self));
   self->keyboard_manager =
-      fl_keyboard_manager_new(FL_KEYBOARD_VIEW_DELEGATE(self));
+      fl_keyboard_manager_new(messenger, FL_KEYBOARD_VIEW_DELEGATE(self));
 }
 
 static void init_scrolling(FlView* self) {
@@ -304,6 +304,12 @@ static void fl_view_keyboard_delegate_iface_init(
     g_return_val_if_fail(self->keymap != nullptr, 0);
     return gdk_keymap_lookup_key(self->keymap, key);
   };
+
+  iface->get_keyboard_state =
+      [](FlKeyboardViewDelegate* view_delegate) -> GHashTable* {
+    FlView* self = FL_VIEW(view_delegate);
+    return fl_view_get_keyboard_state(self);
+  };
 }
 
 static void fl_view_scrolling_delegate_iface_init(
@@ -754,3 +760,9 @@ void fl_view_set_textures(FlView* self,
 
   fl_gl_area_queue_render(self->gl_area, textures);
 }
+
+GHashTable* fl_view_get_keyboard_state(FlView* self) {
+  g_return_val_if_fail(FL_IS_VIEW(self), nullptr);
+
+  return fl_keyboard_manager_get_pressed_state(self->keyboard_manager);
+}

shell/platform/linux/fl_view_private.h

@@ -22,4 +22,13 @@ void fl_view_set_textures(FlView* view,
                           GdkGLContext* context,
                           GPtrArray* textures);
 
+/**
+ * fl_view_get_keyboard_state:
+ * @view: an #FlView.
+ *
+ * Returns the keyboard pressed state. The hash table contains one entry per
+ * pressed keys, mapping from the logical key to the physical key.*
+ */
+GHashTable* fl_view_get_keyboard_state(FlView* view);
+
 #endif  // FLUTTER_SHELL_PLATFORM_LINUX_FL_VIEW_PRIVATE_H_