shell/platform/linux/fl_key_channel_responder.cc

// 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_key_channel_responder.h"

#include <gtk/gtk.h>
#include <cinttypes>

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

struct _FlKeyChannelResponder {
  GObject parent_instance;

  FlKeyEventChannel* channel;
};

G_DEFINE_TYPE(FlKeyChannelResponder, fl_key_channel_responder, G_TYPE_OBJECT)

// Handles a response from the method channel to a key event sent to the
// framework earlier.
static void handle_response(GObject* object,
                            GAsyncResult* result,
                            gpointer user_data) {
  g_autoptr(GTask) task = G_TASK(user_data);

  gboolean handled = FALSE;
  g_autoptr(GError) error = nullptr;
  if (!fl_key_event_channel_send_finish(object, result, &handled, &error)) {
    g_warning("Unable to retrieve framework response: %s", error->message);
  }

  gboolean* return_value = g_new0(gboolean, 1);
  *return_value = handled;
  g_task_return_pointer(task, return_value, g_free);
}

// Disposes of an FlKeyChannelResponder instance.
static void fl_key_channel_responder_dispose(GObject* object) {
  FlKeyChannelResponder* self = FL_KEY_CHANNEL_RESPONDER(object);

  g_clear_object(&self->channel);

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

// Initializes the FlKeyChannelResponder class methods.
static void fl_key_channel_responder_class_init(
    FlKeyChannelResponderClass* klass) {
  G_OBJECT_CLASS(klass)->dispose = fl_key_channel_responder_dispose;
}

// Initializes an FlKeyChannelResponder instance.
static void fl_key_channel_responder_init(FlKeyChannelResponder* self) {}

// Creates a new FlKeyChannelResponder instance, with a messenger used to send
// messages to the framework, and an FlTextInputHandler that is used to handle
// key events that the framework doesn't handle.
FlKeyChannelResponder* fl_key_channel_responder_new(
    FlBinaryMessenger* messenger) {
  g_return_val_if_fail(FL_IS_BINARY_MESSENGER(messenger), nullptr);

  FlKeyChannelResponder* self = FL_KEY_CHANNEL_RESPONDER(
      g_object_new(fl_key_channel_responder_get_type(), nullptr));

  self->channel = fl_key_event_channel_new(messenger);

  return self;
}

void fl_key_channel_responder_handle_event(FlKeyChannelResponder* self,
                                           FlKeyEvent* event,
                                           uint64_t specified_logical_key,
                                           GCancellable* cancellable,
                                           GAsyncReadyCallback callback,
                                           gpointer user_data) {
  g_return_if_fail(event != nullptr);
  g_return_if_fail(callback != nullptr);

  FlKeyEventType type = fl_key_event_get_is_press(event)
                            ? FL_KEY_EVENT_TYPE_KEYDOWN
                            : FL_KEY_EVENT_TYPE_KEYUP;
  int64_t scan_code = fl_key_event_get_keycode(event);
  int64_t unicode_scalar_values =
      gdk_keyval_to_unicode(fl_key_event_get_keyval(event));

  // For most modifier keys, GTK keeps track of the "pressed" state of the
  // modifier keys. Flutter uses this information to keep modifier keys from
  // being "stuck" when a key-up event is lost because it happens after the app
  // loses focus.
  //
  // For Lock keys (ShiftLock, CapsLock, NumLock), however, GTK keeps track of
  // the state of the locks themselves, not the "pressed" state of the key.
  //
  // Since Flutter expects the "pressed" state of the modifier keys, the lock
  // state for these keys is discarded here, and it is substituted for the
  // pressed state of the key.
  //
  // This code has the flaw that if a key event is missed due to the app losing
  // focus, then this state will still think the key is pressed when it isn't,
  // but that is no worse than for "regular" keys until we implement the
  // sync/cancel events on app focus changes.
  //
  // This is necessary to do here instead of in the framework because Flutter
  // does modifier key syncing in the framework, and will turn on/off these keys
  // as being "pressed" whenever the lock is on, which breaks a lot of
  // interactions (for example, if shift-lock is on, tab traversal is broken).

  // Remove lock states from state mask.
  guint state =
      fl_key_event_get_state(event) & ~(GDK_LOCK_MASK | GDK_MOD2_MASK);

  static bool shift_lock_pressed = FALSE;
  static bool caps_lock_pressed = FALSE;
  static bool num_lock_pressed = FALSE;
  switch (fl_key_event_get_keyval(event)) {
    case GDK_KEY_Num_Lock:
      num_lock_pressed = fl_key_event_get_is_press(event);
      break;
    case GDK_KEY_Caps_Lock:
      caps_lock_pressed = fl_key_event_get_is_press(event);
      break;
    case GDK_KEY_Shift_Lock:
      shift_lock_pressed = fl_key_event_get_is_press(event);
      break;
  }

  // Add back in the state matching the actual pressed state of the lock keys,
  // not the lock states.
  state |= (shift_lock_pressed || caps_lock_pressed) ? GDK_LOCK_MASK : 0x0;
  state |= num_lock_pressed ? GDK_MOD2_MASK : 0x0;

  fl_key_event_channel_send(
      self->channel, type, scan_code, fl_key_event_get_keyval(event), state,
      unicode_scalar_values, specified_logical_key, nullptr, handle_response,
      g_task_new(self, cancellable, callback, user_data));
}

gboolean fl_key_channel_responder_handle_event_finish(
    FlKeyChannelResponder* self,
    GAsyncResult* result,
    gboolean* handled,
    GError** error) {
  g_return_val_if_fail(g_task_is_valid(result, self), FALSE);

  g_autofree gboolean* return_value =
      static_cast<gboolean*>(g_task_propagate_pointer(G_TASK(result), error));
  if (return_value == nullptr) {
    return FALSE;
  }

  *handled = *return_value;
  return TRUE;
}