Build key map DomCodeToKey() for Windows

ui/events/keycodes/platform_key_map_win.cc

+// Copyright (c) 2016 The Chromium 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 "ui/events/keycodes/platform_key_map_win.h"
+
+#include <utility>
+
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/threading/thread_local_storage.h"
+
+#include "ui/events/event_constants.h"
+#include "ui/events/keycodes/dom/dom_code.h"
+
+namespace ui {
+
+namespace {
+
+struct DomCodeEntry {
+  DomCode dom_code;
+  int scan_code;
+};
+#define USB_KEYMAP_DECLARATION const DomCodeEntry supported_dom_code_list[] =
+#define USB_KEYMAP(usb, evdev, xkb, win, mac, code, id) {DomCode::id, win}
+#include "ui/events/keycodes/dom/keycode_converter_data.inc"
+#undef USB_KEYMAP
+#undef USB_KEYMAP_DECLARATION
+
+// List of modifiers mentioned in https://w3c.github.io/uievents/#keys-modifiers
+// Some modifiers are commented out because they usually don't change keys.
+const EventFlags modifier_flags[] = {
+    EF_SHIFT_DOWN,
+    EF_CONTROL_DOWN,
+    EF_ALT_DOWN,
+    // EF_COMMAND_DOWN,
+    EF_ALTGR_DOWN,
+    // EF_NUM_LOCK_ON,
+    EF_CAPS_LOCK_ON,
+    // EF_SCROLL_LOCK_ON
+};
+const int kModifierFlagsCombinations = (1 << arraysize(modifier_flags)) - 1;
+
+int GetModifierFlags(int combination) {
+  int flags = EF_NONE;
+  for (int i = 0; i < arraysize(modifier_flags); ++i) {
+    if (combination & (1 << i))
+      flags |= modifier_flags[i];
+  }
+  return flags;
+}
+
+void SetModifierState(BYTE* keyboard_state, int flags) {
+  // According to MSDN GetKeyState():
+  // 1. If the high-order bit is 1, the key is down; otherwise, it is up.
+  // 2. If the low-order bit is 1, the key is toggled. A key, such as the
+  //    CAPS LOCK key, is toggled if it is turned on. The key is off and
+  //    untoggled if the low-order bit is 0.
+  // See https://msdn.microsoft.com/en-us/library/windows/desktop/ms646301.aspx
+  if (flags & EF_SHIFT_DOWN)
+    keyboard_state[VK_SHIFT] |= 0x80;
+
+  if (flags & EF_CONTROL_DOWN)
+    keyboard_state[VK_CONTROL] |= 0x80;
+
+  if (flags & EF_ALT_DOWN)
+    keyboard_state[VK_MENU] |= 0x80;
+
+  if (flags & EF_ALTGR_DOWN) {
+    // AltGr should be RightAlt+LeftControl within Windows, but actually only
+    // the non-located keys will work here.
+    keyboard_state[VK_MENU] |= 0x80;
+    keyboard_state[VK_CONTROL] |= 0x80;
+  }
+
+  if (flags & EF_COMMAND_DOWN)
+    keyboard_state[VK_LWIN] |= 0x80;
+
+  if (flags & EF_NUM_LOCK_ON)
+    keyboard_state[VK_NUMLOCK] |= 0x01;
+
+  if (flags & EF_CAPS_LOCK_ON)
+    keyboard_state[VK_CAPITAL] |= 0x01;
+
+  if (flags & EF_SCROLL_LOCK_ON)
+    keyboard_state[VK_SCROLL] |= 0x01;
+}
+
+void CleanupKeyMapTls(void* data) {
+  PlatformKeyMap* key_map = reinterpret_cast<PlatformKeyMap*>(data);
+  delete key_map;
+}
+
+struct PlatformKeyMapInstanceTlsTraits
+    : public base::DefaultLazyInstanceTraits<base::ThreadLocalStorage::Slot> {
+  static base::ThreadLocalStorage::Slot* New(void* instance) {
+    // Use placement new to initialize our instance in our preallocated space.
+    // TODO(chongz): Use std::default_delete instead of providing own function.
+    return new (instance) base::ThreadLocalStorage::Slot(CleanupKeyMapTls);
+  }
+};
+
+base::LazyInstance<base::ThreadLocalStorage::Slot,
+                   PlatformKeyMapInstanceTlsTraits>
+    g_platform_key_map_tls_lazy = LAZY_INSTANCE_INITIALIZER;
+
+}  // anonymous namespace
+
+PlatformKeyMap::PlatformKeyMap() {}
+
+PlatformKeyMap::PlatformKeyMap(HKL layout) {
+  UpdateLayout(layout);
+}
+
+DomKey PlatformKeyMap::DomCodeAndFlagsToDomKey(DomCode code, int flags) const {
+  const int flags_to_try[] = {
+      // Trying to match Firefox's behavior and UIEvents DomKey guidelines.
+      // If the combination doesn't produce a printable character, the key value
+      // should be the key with no modifiers except for Shift and AltGr.
+      // See https://w3c.github.io/uievents/#keys-guidelines
+      flags,
+      flags & (EF_SHIFT_DOWN | EF_ALTGR_DOWN | EF_CAPS_LOCK_ON),
+      flags & (EF_SHIFT_DOWN | EF_CAPS_LOCK_ON),
+      EF_NONE,
+  };
+
+  DomKey key = DomKey::NONE;
+  for (auto try_flags : flags_to_try) {
+    const auto& it = code_to_key_.find(std::make_pair(static_cast<int>(code),
+                                                      try_flags));
+    if (it != code_to_key_.end()) {
+      key = it->second;
+      if (key != DomKey::NONE)
+        break;
+    }
+  }
+  return key;
+}
+
+// static
+DomKey PlatformKeyMap::DomCodeAndFlagsToDomKeyStatic(DomCode code, int flags) {
+  // Use TLS because KeyboardLayout is per thread.
+  // However currently PlatformKeyMap will only be used by the host application,
+  // which is just one process and one thread.
+  base::ThreadLocalStorage::Slot* platform_key_map_tls =
+      g_platform_key_map_tls_lazy.Pointer();
+  PlatformKeyMap* platform_key_map =
+      reinterpret_cast<PlatformKeyMap*>(platform_key_map_tls->Get());
+  if (!platform_key_map) {
+    platform_key_map = new PlatformKeyMap();
+    platform_key_map_tls->Set(platform_key_map);
+  }
+
+  HKL current_layout = ::GetKeyboardLayout(0);
+  platform_key_map->UpdateLayout(current_layout);
+  return platform_key_map->DomCodeAndFlagsToDomKey(code, flags);
+}
+
+void PlatformKeyMap::UpdateLayout(HKL layout) {
+  if (layout == keyboard_layout_)
+    return;
+
+  // TODO(chongz): Optimize layout switching (see crbug.com/587147).
+  keyboard_layout_ = layout;
+  code_to_key_.clear();
+  // Map size for some sample keyboard layouts:
+  // US: 428, French: 554, Persian: 434, Vietnamese: 1388
+  code_to_key_.reserve(500);
+
+  BYTE keyboard_state_to_restore[256];
+  ::GetKeyboardState(keyboard_state_to_restore);

[brucedawson, 2016/02/19 19:17:54]

The /analyze builder points out that this function can fail, and if it does then
keyboard_state_to_restore will be uninitialized, and read from.

I don't know whether GetKeyboardState() can *actually* fail - /analyze is
notoriously unreliable/uninformative on this sort of information - but perhaps
an if (!GetKeyboardState()) return; would be a good idea?

[Wez, 2016/02/19 21:26:42]

Agreed that that seems a sensible precaution - at least then we'll see messed-up
keyboard events rather than some other subtle bug.

Might it even be appropriate to CHECK if we're asserting that it can never fail?

+
+  for (int eindex = 0; eindex <= kModifierFlagsCombinations; ++eindex) {
+    BYTE keyboard_state[256];
+    memset(keyboard_state, 0, sizeof(keyboard_state));
+    int flags = GetModifierFlags(eindex);
+    SetModifierState(keyboard_state, flags);
+    for (const auto& dom_code_entry : supported_dom_code_list) {
+      wchar_t translated_chars[5];
+      int key_code = ::MapVirtualKeyEx(dom_code_entry.scan_code,
+                                       MAPVK_VSC_TO_VK, keyboard_layout_);
+      int rv = ::ToUnicodeEx(key_code, 0, keyboard_state, translated_chars,
+                             arraysize(translated_chars), 0, keyboard_layout_);
+
+      if (rv == -1) {
+        // Dead key, injecting VK_SPACE to get character representation.
+        BYTE empty_state[256];
+        memset(empty_state, 0, sizeof(empty_state));
+        rv = ::ToUnicodeEx(VK_SPACE, 0, empty_state, translated_chars,
+                           arraysize(translated_chars), 0, keyboard_layout_);
+        // Expecting a dead key character (not followed by a space).
+        if (rv == 1) {
+          code_to_key_[std::make_pair(static_cast<int>(dom_code_entry.dom_code),
+                                      flags)] =
+              DomKey::DeadKeyFromCombiningCharacter(translated_chars[0]);
+        } else {
+          // TODO(chongz): Check if this will actually happen.
+        }
+      } else if (rv == 1) {
+        if (translated_chars[0] >= 0x20) {
+          code_to_key_[std::make_pair(static_cast<int>(dom_code_entry.dom_code),
+                                      flags)] =
+              DomKey::FromCharacter(translated_chars[0]);
+        } else {
+          // Ignores legacy non-printable control characters.
+        }
+      } else {
+        // TODO(chongz): Handle rv <= -2 and rv >= 2.
+      }
+    }
+  }
+  ::SetKeyboardState(keyboard_state_to_restore);
+}
+
+}  // namespace ui