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keyboard_manager.cc
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1 // Copyright 2013 The Flutter Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include <memory>
6 #include <string>
7
8 #include "flutter/fml/logging.h"
9 #include "flutter/shell/platform/windows/keyboard_manager.h"
10 #include "flutter/shell/platform/windows/keyboard_utils.h"
11
12 namespace flutter {
13
14 namespace {
15
16 // The maximum number of pending events to keep before
17 // emitting a warning on the console about unhandled events.
18 static constexpr int kMaxPendingEvents = 1000;
19
20 // Returns true if this key is an AltRight key down event.
21 //
22 // This is used to resolve an issue where an AltGr press causes CtrlLeft to hang
23 // when pressed, as reported in https://github.com/flutter/flutter/issues/78005.
24 //
25 // When AltGr is pressed (in a supporting layout such as Spanish), Win32 first
26 // fires a fake CtrlLeft down event, then an AltRight down event.
27 // This is significant because this fake CtrlLeft down event will not be paired
28 // with a up event, which is fine until Flutter redispatches the CtrlDown
29 // event, which Win32 then interprets as a real event, leaving both Win32 and
30 // the Flutter framework thinking that CtrlLeft is still pressed.
31 //
32 // To resolve this, Flutter recognizes this fake CtrlLeft down event using the
33 // following AltRight down event. Flutter then forges a CtrlLeft key up event
34 // immediately after the corresponding AltRight key up event.
35 //
36 // One catch is that it is impossible to distinguish the fake CtrlLeft down
37 // from a normal CtrlLeft down (followed by a AltRight down), since they
38 // contain the exactly same information, including the GetKeyState result.
39 // Fortunately, this will require the two events to occur *really* close, which
40 // would be rare, and a misrecognition would only cause a minor consequence
41 // where the CtrlLeft is released early; the later, real, CtrlLeft up event will
42 // be ignored.
43 static bool IsKeyDownAltRight(int action, int virtual_key, bool extended) {
44 return virtual_key == VK_RMENU && extended &&
45 (action == WM_KEYDOWN || action == WM_SYSKEYDOWN);
46 }
47
48 // Returns true if this key is a key up event of AltRight.
49 //
50 // This is used to assist a corner case described in |IsKeyDownAltRight|.
51 static bool IsKeyUpAltRight(int action, int virtual_key, bool extended) {
52 return virtual_key == VK_RMENU && extended &&
53 (action == WM_KEYUP || action == WM_SYSKEYUP);
54 }
55
56 // Returns true if this key is a key down event of CtrlLeft.
57 //
58 // This is used to assist a corner case described in |IsKeyDownAltRight|.
59 static bool IsKeyDownCtrlLeft(int action, int virtual_key) {
60 return virtual_key == VK_LCONTROL &&
61 (action == WM_KEYDOWN || action == WM_SYSKEYDOWN);
62 }
63
64 // Returns if a character sent by Win32 is a dead key.
65 static bool IsDeadKey(uint32_t ch) {
66 return (ch & kDeadKeyCharMask) != 0;
67 }
68
69 static char32_t CodePointFromSurrogatePair(wchar_t high, wchar_t low) {
70 return 0x10000 + ((static_cast<char32_t>(high) & 0x000003FF) << 10) +
71 (low & 0x3FF);
72 }
73
74 static uint16_t ResolveKeyCode(uint16_t original,
75 bool extended,
76 uint8_t scancode) {
77 switch (original) {
78 case VK_SHIFT:
79 case VK_LSHIFT:
80 return MapVirtualKey(scancode, MAPVK_VSC_TO_VK_EX);
81 case VK_MENU:
82 case VK_LMENU:
83 return extended ? VK_RMENU : VK_LMENU;
84 case VK_CONTROL:
85 case VK_LCONTROL:
86 return extended ? VK_RCONTROL : VK_LCONTROL;
87 default:
88 return original;
89 }
90 }
91
92 static bool IsPrintable(uint32_t c) {
93 constexpr char32_t kMinPrintable = ' ';
94 constexpr char32_t kDelete = 0x7F;
95 return c >= kMinPrintable && c != kDelete;
96 }
97
98 static bool IsSysAction(UINT action) {
99 return action == WM_SYSKEYDOWN || action == WM_SYSKEYUP ||
100 action == WM_SYSCHAR || action == WM_SYSDEADCHAR;
101 }
102
103 } // namespace
104
105 KeyboardManager::KeyboardManager(WindowDelegate* delegate)
106 : window_delegate_(delegate),
107 last_key_is_ctrl_left_down(false),
108 should_synthesize_ctrl_left_up(false),
109 processing_event_(false) {}
110
111 void KeyboardManager::RedispatchEvent(std::unique_ptr<PendingEvent> event) {
112 for (const Win32Message& message : event->session) {
113 // Never redispatch sys keys, because their original messages have been
114 // passed to the system default processor.
115 if (IsSysAction(message.action)) {
116 continue;
117 }
118 pending_redispatches_.push_back(message);
119 UINT result = window_delegate_->Win32DispatchMessage(
120 message.action, message.wparam, message.lparam);
121 if (result != 0) {
122 FML_LOG(ERROR) << "Unable to synthesize event for keyboard event.";
123 }
124 }
125 if (pending_redispatches_.size() > kMaxPendingEvents) {
126 FML_LOG(ERROR)
127 << "There are " << pending_redispatches_.size()
128 << " keyboard events that have not yet received a response from the "
129 << "framework. Are responses being sent?";
130 }
131 }
132
133 bool KeyboardManager::RemoveRedispatchedMessage(UINT const action,
134 WPARAM const wparam,
135 LPARAM const lparam) {
136 for (auto iter = pending_redispatches_.begin();
137 iter != pending_redispatches_.end(); ++iter) {
138 if (action == iter->action && wparam == iter->wparam) {
139 pending_redispatches_.erase(iter);
140 return true;
141 }
142 }
143 return false;
144 }
145
146 bool KeyboardManager::HandleMessage(UINT const action,
147 WPARAM const wparam,
148 LPARAM const lparam) {
149 if (RemoveRedispatchedMessage(action, wparam, lparam)) {
150 return false;
151 }
152 switch (action) {
153 case WM_DEADCHAR:
154 case WM_SYSDEADCHAR:
155 case WM_CHAR:
156 case WM_SYSCHAR: {
157 const Win32Message message =
158 Win32Message{.action = action, .wparam = wparam, .lparam = lparam};
159 current_session_.push_back(message);
160
161 char32_t code_point;
162 if (message.IsHighSurrogate()) {
163 // A high surrogate is always followed by a low surrogate. Process the
164 // session later and consider this message as handled.
165 return true;
166 } else if (message.IsLowSurrogate()) {
167 const Win32Message* last_message =
168 current_session_.size() <= 1
169 ? nullptr
170 : &current_session_[current_session_.size() - 2];
171 if (last_message == nullptr || !last_message->IsHighSurrogate()) {
172 return false;
173 }
174 // A low surrogate always follows a high surrogate, marking the end of
175 // a char session. Process the session after the if clause.
176 code_point =
177 CodePointFromSurrogatePair(last_message->wparam, message.wparam);
178 } else {
179 // A non-surrogate character always appears alone. Process the session
180 // after the if clause.
181 code_point = static_cast<wchar_t>(message.wparam);
182 }
183
184 // If this char message is preceded by a key down message, then dispatch
185 // the key down message as a key down event first, and only dispatch the
186 // OnText if the key down event is not handled.
187 if (current_session_.front().IsGeneralKeyDown()) {
188 const Win32Message first_message = current_session_.front();
189 const uint8_t scancode = (lparam >> 16) & 0xff;
190 const uint16_t key_code = first_message.wparam;
191 const bool extended = ((lparam >> 24) & 0x01) == 0x01;
192 const bool was_down = lparam & 0x40000000;
193 // Certain key combinations yield control characters as WM_CHAR's
194 // lParam. For example, 0x01 for Ctrl-A. Filter these characters. See
195 // https://docs.microsoft.com/en-us/windows/win32/learnwin32/accelerator-tables
196 char32_t character;
197 if (action == WM_DEADCHAR || action == WM_SYSDEADCHAR) {
198 // Mask the resulting char with kDeadKeyCharMask anyway, because in
199 // rare cases the bit is *not* set (US INTL Shift-6 circumflex, see
200 // https://github.com/flutter/flutter/issues/92654 .)
201 character =
202 window_delegate_->Win32MapVkToChar(key_code) | kDeadKeyCharMask;
203 } else {
204 character = IsPrintable(code_point) ? code_point : 0;
205 }
206 auto event = std::make_unique<PendingEvent>(PendingEvent{
207 .key = key_code,
208 .scancode = scancode,
209 .action = static_cast<UINT>(action == WM_SYSCHAR ? WM_SYSKEYDOWN
210 : WM_KEYDOWN),
211 .character = character,
212 .extended = extended,
213 .was_down = was_down,
214 .session = std::move(current_session_),
215 });
216
217 pending_events_.push_back(std::move(event));
218 ProcessNextEvent();
219
220 // SYS messages must not be consumed by `HandleMessage` so that they are
221 // forwarded to the system.
222 return !IsSysAction(action);
223 }
224
225 // If the charcter session is not preceded by a key down message,
226 // mark PendingEvent::action as WM_CHAR, informing |PerformProcessEvent|
227 // to dispatch the text content immediately.
228 //
229 // Only WM_CHAR should be treated as characters. WM_SYS*CHAR are not part
230 // of text input, and WM_DEADCHAR will be incorporated into a later
231 // WM_CHAR with the full character.
232 if (action == WM_CHAR) {
233 auto event = std::make_unique<PendingEvent>(PendingEvent{
234 .action = WM_CHAR,
235 .character = code_point,
236 .session = std::move(current_session_),
237 });
238 pending_events_.push_back(std::move(event));
239 ProcessNextEvent();
240 }
241 return true;
242 }
243
244 case WM_KEYDOWN:
245 case WM_SYSKEYDOWN:
246 case WM_KEYUP:
247 case WM_SYSKEYUP: {
248 if (wparam == VK_PACKET) {
249 return false;
250 }
251
252 const uint8_t scancode = (lparam >> 16) & 0xff;
253 const bool extended = ((lparam >> 24) & 0x01) == 0x01;
254 // If the key is a modifier, get its side.
255 const uint16_t key_code = ResolveKeyCode(wparam, extended, scancode);
256 const bool was_down = lparam & 0x40000000;
257
258 // Detect a pattern of key events in order to forge a CtrlLeft up event.
259 // See |IsKeyDownAltRight| for explanation.
260 if (IsKeyDownAltRight(action, key_code, extended)) {
261 if (last_key_is_ctrl_left_down) {
262 should_synthesize_ctrl_left_up = true;
263 }
264 }
265 if (IsKeyDownCtrlLeft(action, key_code)) {
266 last_key_is_ctrl_left_down = true;
267 ctrl_left_scancode = scancode;
268 should_synthesize_ctrl_left_up = false;
269 } else {
270 last_key_is_ctrl_left_down = false;
271 }
272 if (IsKeyUpAltRight(action, key_code, extended)) {
273 if (should_synthesize_ctrl_left_up) {
274 should_synthesize_ctrl_left_up = false;
275 const LPARAM lParam =
276 (1 /* repeat_count */ << 0) | (ctrl_left_scancode << 16) |
277 (0 /* extended */ << 24) | (1 /* prev_state */ << 30) |
278 (1 /* transition */ << 31);
279 window_delegate_->Win32DispatchMessage(WM_KEYUP, VK_CONTROL, lParam);
280 }
281 }
282
283 current_session_.clear();
284 current_session_.push_back(
285 Win32Message{.action = action, .wparam = wparam, .lparam = lparam});
286 const bool is_keydown_message =
287 (action == WM_KEYDOWN || action == WM_SYSKEYDOWN);
288 // Check if this key produces a character by peeking if this key down
289 // message has a following char message. Certain key messages are not
290 // followed by char messages even though `MapVirtualKey` returns a valid
291 // character (such as Ctrl + Digit, see
292 // https://github.com/flutter/flutter/issues/85587 ).
293 unsigned int character = window_delegate_->Win32MapVkToChar(wparam);
294 UINT next_key_action = PeekNextMessageType(WM_KEYFIRST, WM_KEYLAST);
295 bool has_char_action =
296 (next_key_action == WM_DEADCHAR ||
297 next_key_action == WM_SYSDEADCHAR || next_key_action == WM_CHAR ||
298 next_key_action == WM_SYSCHAR);
299 if (character > 0 && is_keydown_message && has_char_action) {
300 // This key down message has a following char message. Process this
301 // session in the char message, because the character for the key call
302 // should be decided by the char events. Consider this message as
303 // handled.
304 return true;
305 }
306
307 // This key down message is not followed by a char message. Conclude this
308 // session.
309 auto event = std::make_unique<PendingEvent>(PendingEvent{
310 .key = key_code,
311 .scancode = scancode,
312 .action = action,
313 .character = 0,
314 .extended = extended,
315 .was_down = was_down,
316 .session = std::move(current_session_),
317 });
318 pending_events_.push_back(std::move(event));
319 ProcessNextEvent();
320 // SYS messages must not be consumed by `HandleMessage` so that they are
321 // forwarded to the system.
322 return !IsSysAction(action);
323 }
324 default:
325 FML_LOG(FATAL) << "No event handler for keyboard event with action "
326 << action;
327 }
328 return false;
329 }
330
331 void KeyboardManager::ProcessNextEvent() {
332 if (processing_event_ || pending_events_.empty()) {
333 return;
334 }
335 processing_event_ = true;
336 auto pending_event = std::move(pending_events_.front());
337 pending_events_.pop_front();
338 PerformProcessEvent(std::move(pending_event), [this] {
339 FML_DCHECK(processing_event_);
340 processing_event_ = false;
341 ProcessNextEvent();
342 });
343 }
344
345 void KeyboardManager::PerformProcessEvent(std::unique_ptr<PendingEvent> event,
346 std::function<void()> callback) {
347 // PendingEvent::action being WM_CHAR means this is a char message without
348 // a preceding key message, and should be dispatched immediately.
349 if (event->action == WM_CHAR) {
350 DispatchText(*event);
351 callback();
352 return;
353 }
354
355 // A unique_ptr can't be sent into a lambda without C++23's
356 // move_only_function. Until then, `event` is sent as a raw pointer, hoping
357 // WindowDelegate::OnKey to correctly call it once and only once.
358 PendingEvent* event_p = event.release();
359 window_delegate_->OnKey(
360 event_p->key, event_p->scancode, event_p->action, event_p->character,
361 event_p->extended, event_p->was_down,
362 [this, event_p, callback = std::move(callback)](bool handled) {
363 HandleOnKeyResult(std::unique_ptr<PendingEvent>(event_p), handled);
364 callback();
365 });
366 }
367
368 void KeyboardManager::HandleOnKeyResult(std::unique_ptr<PendingEvent> event,
369 bool framework_handled) {
370 const UINT last_action = event->session.back().action;
371 // SYS messages must not be redispached, and their text content is not
372 // dispatched either.
373 bool handled = framework_handled || IsSysAction(last_action);
374
375 if (handled) {
376 return;
377 }
378
379 // Only WM_CHAR should be treated as characters. WM_SYS*CHAR are not part of
380 // text input, and WM_DEADCHAR will be incorporated into a later WM_CHAR with
381 // the full character.
382 if (last_action == WM_CHAR) {
383 DispatchText(*event);
384 }
385
386 RedispatchEvent(std::move(event));
387 }
388
389 void KeyboardManager::DispatchText(const PendingEvent& event) {
390 // Check if the character is printable based on the last wparam, which works
391 // even if the last wparam is a low surrogate, because the only unprintable
392 // keys defined by `IsPrintable` are certain characters at lower ASCII range.
393 // These ASCII control characters are sent as WM_CHAR events for all control
394 // key shortcuts.
395 FML_DCHECK(!event.session.empty());
396 bool is_printable = IsPrintable(event.session.back().wparam);
397 bool valid = event.character != 0 && is_printable;
398 if (valid) {
399 auto text = EncodeUtf16(event.character);
400 window_delegate_->OnText(text);
401 }
402 }
403
404 UINT KeyboardManager::PeekNextMessageType(UINT wMsgFilterMin,
405 UINT wMsgFilterMax) {
406 MSG next_message;
407 BOOL has_msg = window_delegate_->Win32PeekMessage(
408 &next_message, wMsgFilterMin, wMsgFilterMax, PM_NOREMOVE);
409 if (!has_msg) {
410 return 0;
411 }
412 return next_message.message;
413 }
414
415 } // namespace flutter
flutter::KeyboardManager::KeyboardManager
KeyboardManager(WindowDelegate *delegate)
Definition: keyboard_manager.cc:105
scancode
int scancode
Definition: keyboard_key_handler_unittests.cc:115
was_down
bool was_down
Definition: keyboard_key_handler_unittests.cc:119
extended
bool extended
Definition: keyboard_key_handler_unittests.cc:118
flutter::KeyboardManager::WindowDelegate::Win32MapVkToChar
virtual uint32_t Win32MapVkToChar(uint32_t virtual_key)=0
flutter::KeyboardManager::WindowDelegate::OnText
virtual void OnText(const std::u16string &text)=0
character
char32_t character
Definition: keyboard_key_handler_unittests.cc:117
flutter::KeyboardManager::RedispatchEvent
virtual void RedispatchEvent(std::unique_ptr< PendingEvent > event)
Definition: keyboard_manager.cc:111
flutter::EncodeUtf16
std::u16string EncodeUtf16(char32_t character)
Definition: keyboard_utils.cc:11
flutter::KeyboardManager::WindowDelegate
Definition: keyboard_manager.h:52
flutter::KeyboardManager::HandleMessage
bool HandleMessage(UINT const message, WPARAM const wparam, LPARAM const lparam)
Definition: keyboard_manager.cc:146
flutter::KeyboardManager::Win32Message::lparam
LPARAM lparam
Definition: keyboard_manager.h:117
text
std::u16string text
Definition: keyboard_unittests.cc:332
keyboard_utils.h
flutter::KeyboardManager::WindowDelegate::OnKey
virtual void OnKey(int key, int scancode, int action, char32_t character, bool extended, bool was_down, KeyEventCallback callback)=0
flutter::KeyboardManager::PendingEvent::key
WPARAM key
Definition: keyboard_manager.h:129
flutter
Definition: accessibility_bridge_windows.cc:11
flutter::KeyboardManager::Win32Message::IsHighSurrogate
bool IsHighSurrogate() const
Definition: keyboard_manager.h:119
flutter::KeyboardManager::WindowDelegate::Win32PeekMessage
virtual BOOL Win32PeekMessage(LPMSG lpMsg, UINT wMsgFilterMin, UINT wMsgFilterMax, UINT wRemoveMsg)=0
flutter::KeyboardManager::PendingEvent
Definition: keyboard_manager.h:128
flutter::KeyboardManager::Win32Message::wparam
WPARAM wparam
Definition: keyboard_manager.h:116
flutter::KeyboardManager::Win32Message
Definition: keyboard_manager.h:114
message
Win32Message message
Definition: keyboard_unittests.cc:137
flutter::kDeadKeyCharMask
constexpr int kDeadKeyCharMask
Definition: keyboard_utils.h:30
action
int action
Definition: keyboard_key_handler_unittests.cc:116
keyboard_manager.h
flutter::KeyboardManager::PendingEvent::action
UINT action
Definition: keyboard_manager.h:131
flutter::KeyboardManager::Win32Message::action
UINT action
Definition: keyboard_manager.h:115
flutter::KeyboardManager::Win32Message::IsLowSurrogate
bool IsLowSurrogate() const
Definition: keyboard_manager.h:121
callback
FlutterDesktopBinaryReply callback
Definition: flutter_windows_view_unittests.cc:46
flutter::KeyboardManager::WindowDelegate::Win32DispatchMessage
virtual UINT Win32DispatchMessage(UINT Msg, WPARAM wParam, LPARAM lParam)=0