KeyboardMap - Fix Japanese layout

Previously, the Japanese layout was not returned as the highest-prio
ASCII-capable layout because not all of the writing-system-keys produced
printable characters.  Specifically, the Backquote key is used as the
hankaku/zenkaku key to switch between half-width and full-width chars.

This cl fixes that by handling the Japanese/Backquote key as a special
case, and the keyboard map returns a descriptive string.

Bug: 891501
Change-Id: Ic473700866d711a532d3946be73ff5ec38db580a
Reviewed-on: https://chromium-review.googlesource.com/c/1340970
Commit-Queue: Gary Kacmarcik <garykac@chromium.org>
Reviewed-by: Joe Downing <joedow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609042}

ui/events/keycodes/dom/dom_keyboard_layout.cc

@@ -38,6 +38,8 @@ const DomCode writing_system_key_domcodes[] = {
 const size_t kWritingSystemKeyDomCodeEntries =
     base::size(writing_system_key_domcodes);
 
+const uint32_t kHankakuZenkakuPlaceholder = 0x89d2;
+
 // Mapping from Unicode combining characters to corresponding printable
 // character.
 const static struct {
@@ -81,9 +83,16 @@ base::flat_map<std::string, std::string> DomKeyboardLayout::GetMap() {
       continue;
 
     std::string key_str;
-    size_t len = base::WriteUnicodeCharacter(unicode, &key_str);
-    if (len == 0)
-      continue;
+    // Special handling for the Japanese BACKQUOTE, which is an IME key used
+    // to switch between half-width and full-width mode.
+    if (unicode == kHankakuZenkakuPlaceholder) {
+      // 半角/全角 = hankaku/zenkaku = halfwidth/fullwidth
+      key_str = "\u534a\u89d2/\u5168\u89d2";
+    } else {
+      size_t len = base::WriteUnicodeCharacter(unicode, &key_str);
+      if (len == 0)
+        continue;
+    }
     dom_map.emplace(KeycodeConverter::DomCodeToCodeString(dom_code), key_str);
   }
   return dom_map;
@@ -91,8 +100,7 @@ base::flat_map<std::string, std::string> DomKeyboardLayout::GetMap() {
 
 bool DomKeyboardLayout::IsAsciiCapable() {
   uint16_t uniA = layout_[DomCode::US_A];
-  uint16_t uniBackquote = layout_[DomCode::BACKQUOTE];
-  return uniA >= 'a' && uniA <= 'z' && uniBackquote != 0;
+  return uniA >= 'a' && uniA <= 'z';
 }
 
 }  // namespace ui

ui/events/keycodes/dom/dom_keyboard_layout.h

@@ -62,6 +62,8 @@ extern const DomCode writing_system_key_domcodes[];
 
 extern const size_t kWritingSystemKeyDomCodeEntries;
 
+extern const uint32_t kHankakuZenkakuPlaceholder;
+
 }  // namespace ui
 
 #endif  // UI_EVENTS_KEYCODES_DOM_DOM_KEYBOARD_LAYOUT_H_

ui/events/keycodes/dom/dom_keyboard_layout_map_base.cc

@@ -56,6 +56,9 @@ void DomKeyboardLayoutMapBase::PopulateLayout(uint32_t keyboard_layout_index,
       unicode_value = dom_key.ToCharacter();
     else if (dom_key.IsDeadKey())
       unicode_value = dom_key.ToDeadKeyCombiningCharacter();
+    else if (dom_key == ui::DomKey::ZENKAKU_HANKAKU)
+      // Placeholder for hankaku/zenkaku string.
+      unicode_value = kHankakuZenkakuPlaceholder;
 
     if (unicode_value != 0)
       layout->AddKeyMapping(dom_code, unicode_value);

ui/events/keycodes/dom/dom_keyboard_layout_map_win.cc

@@ -107,6 +107,16 @@ ui::DomKey DomKeyboardLayoutMapWin::GetDomKeyFromDomCodeForLayout(
   if (key_type == -1)
     return ui::DomKey::DeadKeyFromCombiningCharacter(char_buffer[0]);
 
+  // Special case for Backquote on Japanese keyboard layout.
+  // Technically, this layout is not completely ASCII-capable because the
+  // Backquote key is used as a IME function key (hankaku/zenkaku) and is thus
+  // not a printable key. However, other than this key, it is a perfectly
+  // usable ASCII-capable layout and it matches the values printed on the
+  // keyboard, so we have special handling to allow this key.
+  if (dom_code == ui::DomCode::BACKQUOTE &&
+      0x04110411 == reinterpret_cast<unsigned int>(keyboard_layout))
+    return ui::DomKey::ZENKAKU_HANKAKU;
+
   return ui::DomKey::NONE;
 }