flutter::KeyboardManager Class Reference

#include <keyboard_manager.h>

Classes
struct	PendingEvent
struct	Win32Message
class	WindowDelegate

Public Types
using	KeyEventCallback = WindowDelegate::KeyEventCallback

Public Member Functions
	KeyboardManager (WindowDelegate *delegate)
bool	HandleMessage (UINT const message, WPARAM const wparam, LPARAM const lparam)

Protected Member Functions
virtual void	RedispatchEvent (std::unique_ptr< PendingEvent > event)

Detailed Description

Definition at line 46 of file keyboard_manager.h.

Member Typedef Documentation

KeyEventCallback

using flutter::KeyboardManager::KeyEventCallback = WindowDelegate::KeyEventCallback

Definition at line 93 of file keyboard_manager.h.

Constructor & Destructor Documentation

KeyboardManager()

flutter::KeyboardManager::KeyboardManager ( WindowDelegate *  delegate )

explicit

Definition at line 103 of file keyboard_manager.cc.

    : window_delegate_(delegate),
      last_key_is_ctrl_left_down(false),
      should_synthesize_ctrl_left_up(false),
      processing_event_(false) {}

Member Function Documentation

HandleMessage()

bool flutter::KeyboardManager::HandleMessage	(	UINT const	message,
		WPARAM const	wparam,
		LPARAM const	lparam
	)

Definition at line 144 of file keyboard_manager.cc.

                                                         {
  if (RemoveRedispatchedMessage(action, wparam, lparam)) {
    return false;
  }
  switch (action) {
    case WM_DEADCHAR:
    case WM_SYSDEADCHAR:
    case WM_CHAR:
    case WM_SYSCHAR: {
      const Win32Message message =
          Win32Message{.action = action, .wparam = wparam, .lparam = lparam};
      current_session_.push_back(message);
 
      char32_t code_point;
      if (message.IsHighSurrogate()) {
        // A high surrogate is always followed by a low surrogate.  Process the
        // session later and consider this message as handled.
        return true;
      } else if (message.IsLowSurrogate()) {
        const Win32Message* last_message =
            current_session_.size() <= 1
                ? nullptr
                : &current_session_[current_session_.size() - 2];
        if (last_message == nullptr || !last_message->IsHighSurrogate()) {
          return false;
        }
        // A low surrogate always follows a high surrogate, marking the end of
        // a char session. Process the session after the if clause.
        code_point =
            CodePointFromSurrogatePair(last_message->wparam, message.wparam);
      } else {
        // A non-surrogate character always appears alone. Process the session
        // after the if clause.
        code_point = static_cast<wchar_t>(message.wparam);
      }
 
      // If this char message is preceded by a key down message, then dispatch
      // the key down message as a key down event first, and only dispatch the
      // OnText if the key down event is not handled.
      if (current_session_.front().IsGeneralKeyDown()) {
        const Win32Message first_message = current_session_.front();
        const uint8_t scancode = (lparam >> 16) & 0xff;
        const uint16_t key_code = first_message.wparam;
        const bool extended = ((lparam >> 24) & 0x01) == 0x01;
        const bool was_down = lparam & 0x40000000;
        // Certain key combinations yield control characters as WM_CHAR's
        // lParam. For example, 0x01 for Ctrl-A. Filter these characters. See
        // https://docs.microsoft.com/en-us/windows/win32/learnwin32/accelerator-tables
        char32_t character;
        if (action == WM_DEADCHAR || action == WM_SYSDEADCHAR) {
          // Mask the resulting char with kDeadKeyCharMask anyway, because in
          // rare cases the bit is *not* set (US INTL Shift-6 circumflex, see
          // https://github.com/flutter/flutter/issues/92654 .)
          character =
              window_delegate_->Win32MapVkToChar(key_code) | kDeadKeyCharMask;
        } else {
          character = IsPrintable(code_point) ? code_point : 0;
        }
        auto event = std::make_unique<PendingEvent>(PendingEvent{
            .key = key_code,
            .scancode = scancode,
            .action = static_cast<UINT>(action == WM_SYSCHAR ? WM_SYSKEYDOWN
                                                             : WM_KEYDOWN),
            .character = character,
            .extended = extended,
            .was_down = was_down,
            .session = std::move(current_session_),
        });
 
        pending_events_.push_back(std::move(event));
        ProcessNextEvent();
 
        // SYS messages must not be consumed by `HandleMessage` so that they are
        // forwarded to the system.
        return !IsSysAction(action);
      }
 
      // If the charcter session is not preceded by a key down message,
      // mark PendingEvent::action as WM_CHAR, informing |PerformProcessEvent|
      // to dispatch the text content immediately.
      //
      // Only WM_CHAR should be treated as characters. WM_SYS*CHAR are not part
      // of text input, and WM_DEADCHAR will be incorporated into a later
      // WM_CHAR with the full character.
      if (action == WM_CHAR) {
        auto event = std::make_unique<PendingEvent>(PendingEvent{
            .action = WM_CHAR,
            .character = code_point,
            .session = std::move(current_session_),
        });
        pending_events_.push_back(std::move(event));
        ProcessNextEvent();
      }
      return true;
    }
 
    case WM_KEYDOWN:
    case WM_SYSKEYDOWN:
    case WM_KEYUP:
    case WM_SYSKEYUP: {
      if (wparam == VK_PACKET) {
        return false;
      }
 
      const uint8_t scancode = (lparam >> 16) & 0xff;
      const bool extended = ((lparam >> 24) & 0x01) == 0x01;
      // If the key is a modifier, get its side.
      const uint16_t key_code = ResolveKeyCode(wparam, extended, scancode);
      const bool was_down = lparam & 0x40000000;
 
      // Detect a pattern of key events in order to forge a CtrlLeft up event.
      // See |IsKeyDownAltRight| for explanation.
      if (IsKeyDownAltRight(action, key_code, extended)) {
        if (last_key_is_ctrl_left_down) {
          should_synthesize_ctrl_left_up = true;
        }
      }
      if (IsKeyDownCtrlLeft(action, key_code)) {
        last_key_is_ctrl_left_down = true;
        ctrl_left_scancode = scancode;
        should_synthesize_ctrl_left_up = false;
      } else {
        last_key_is_ctrl_left_down = false;
      }
      if (IsKeyUpAltRight(action, key_code, extended)) {
        if (should_synthesize_ctrl_left_up) {
          should_synthesize_ctrl_left_up = false;
          const LPARAM lParam =
              (1 /* repeat_count */ << 0) | (ctrl_left_scancode << 16) |
              (0 /* extended */ << 24) | (1 /* prev_state */ << 30) |
              (1 /* transition */ << 31);
          window_delegate_->Win32DispatchMessage(WM_KEYUP, VK_CONTROL, lParam);
        }
      }
 
      current_session_.clear();
      current_session_.push_back(
          Win32Message{.action = action, .wparam = wparam, .lparam = lparam});
      const bool is_keydown_message =
          (action == WM_KEYDOWN || action == WM_SYSKEYDOWN);
      // Check if this key produces a character by peeking if this key down
      // message has a following char message. Certain key messages are not
      // followed by char messages even though `MapVirtualKey` returns a valid
      // character (such as Ctrl + Digit, see
      // https://github.com/flutter/flutter/issues/85587 ).
      unsigned int character = window_delegate_->Win32MapVkToChar(wparam);
      UINT next_key_action = PeekNextMessageType(WM_KEYFIRST, WM_KEYLAST);
      bool has_char_action =
          (next_key_action == WM_DEADCHAR ||
           next_key_action == WM_SYSDEADCHAR || next_key_action == WM_CHAR ||
           next_key_action == WM_SYSCHAR);
      if (character > 0 && is_keydown_message && has_char_action) {
        // This key down message has a following char message. Process this
        // session in the char message, because the character for the key call
        // should be decided by the char events. Consider this message as
        // handled.
        return true;
      }
 
      // This key down message is not followed by a char message. Conclude this
      // session.
      auto event = std::make_unique<PendingEvent>(PendingEvent{
          .key = key_code,
          .scancode = scancode,
          .action = action,
          .character = 0,
          .extended = extended,
          .was_down = was_down,
          .session = std::move(current_session_),
      });
      pending_events_.push_back(std::move(event));
      ProcessNextEvent();
      // SYS messages must not be consumed by `HandleMessage` so that they are
      // forwarded to the system.
      return !IsSysAction(action);
    }
    default:
      FML_LOG(FATAL) << "No event handler for keyboard event with action "
                     << action;
  }
  return false;
}

References flutter::KeyboardManager::Win32Message::action, action, flutter::KeyboardManager::PendingEvent::action, character, extended, flutter::KeyboardManager::Win32Message::IsHighSurrogate(), flutter::KeyboardManager::Win32Message::IsLowSurrogate(), flutter::kDeadKeyCharMask, flutter::KeyboardManager::PendingEvent::key, message, scancode, was_down, flutter::KeyboardManager::WindowDelegate::Win32DispatchMessage(), flutter::KeyboardManager::WindowDelegate::Win32MapVkToChar(), and flutter::KeyboardManager::Win32Message::wparam.

RedispatchEvent()

void flutter::KeyboardManager::RedispatchEvent ( std::unique_ptr< PendingEvent >  event )

protectedvirtual

Definition at line 109 of file keyboard_manager.cc.

                                                                       {
  for (const Win32Message& message : event->session) {
    // Never redispatch sys keys, because their original messages have been
    // passed to the system default processor.
    if (IsSysAction(message.action)) {
      continue;
    }
    pending_redispatches_.push_back(message);
    UINT result = window_delegate_->Win32DispatchMessage(
        message.action, message.wparam, message.lparam);
    if (result != 0) {
      FML_LOG(ERROR) << "Unable to synthesize event for keyboard event.";
    }
  }
  if (pending_redispatches_.size() > kMaxPendingEvents) {
    FML_LOG(ERROR)
        << "There are " << pending_redispatches_.size()
        << " keyboard events that have not yet received a response from the "
        << "framework. Are responses being sent?";
  }
}

References flutter::KeyboardManager::Win32Message::action, flutter::KeyboardManager::Win32Message::lparam, message, flutter::KeyboardManager::WindowDelegate::Win32DispatchMessage(), and flutter::KeyboardManager::Win32Message::wparam.

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The documentation for this class was generated from the following files:

• shell/platform/windows/keyboard_manager.h
• shell/platform/windows/keyboard_manager.cc