[Remoting Host] Handle text event characters that are not presented on the keyboard

remoting/host/linux/x11_key_mapper.cc

Index: remoting/host/linux/x11_key_mapper.cc
diff --git a/remoting/host/linux/x11_key_mapper.cc b/remoting/host/linux/x11_key_mapper.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b7af88dd6558d08ca51421612e465767790e73d0
--- /dev/null
+++ b/remoting/host/linux/x11_key_mapper.cc
@@ -0,0 +1,109 @@
+// Copyright 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 "remoting/host/linux/x11_key_mapper.h"
+
+#include <algorithm>
+
+#include "base/memory/ptr_util.h"
+#include "base/time/default_tick_clock.h"
+#include "base/time/time.h"
+#include "remoting/host/linux/x11_keyboard.h"
+
+namespace {
+
+constexpr base::TimeDelta kMappingExpireDuration =
+    base::TimeDelta::FromMilliseconds(200);
+
+}  // namespace
+
+namespace remoting {
+
+struct X11KeyMapper::KeyInfo {
+  uint32_t keycode;
+  base::TimeTicks expire_at;
+
+  bool operator<(const KeyInfo& other) const {
+    // When expire time are the same, prefer larger keycode for higher test
+    // predictability and less impact on more important layout.
+    return expire_at != other.expire_at ? expire_at < other.expire_at
+                                        : keycode > other.keycode;
+  }
+};
+
+X11KeyMapper::X11KeyMapper(X11Keyboard* keyboard)
+    : keyboard_(keyboard), clock_(new base::DefaultTickClock()) {
+  std::vector<uint32_t> keycodes = keyboard_->GetUnusedKeycodes();
+  for (int keycode : keycodes) {
+    available_keycodes_.push_back({keycode, base::TimeTicks()});
+  }
+  std::sort(available_keycodes_.begin(), available_keycodes_.end());
+}
+
+X11KeyMapper::~X11KeyMapper() {
+  // Clear all used key mappings.
+  for (const KeyInfo& info : available_keycodes_) {
+    if (!info.expire_at.is_null()) {
+      keyboard_->ChangeKeyMapping(info.keycode, 0);
+    }
+  }
+  keyboard_->Sync();
+}
+
+X11KeyMapper::MapResult X11KeyMapper::MapCharacter(uint32_t code_point) {
+  MapResult result{false, 0, 0, base::TimeDelta()};
+  if (keyboard_->FindKeycode(code_point, &result.keycode, &result.modifiers)) {
+    uint32_t keycode = result.keycode;
+    auto position = std::find_if(
+        available_keycodes_.begin(), available_keycodes_.end(),
+        [keycode](const KeyInfo& info) { return info.keycode == keycode; });
+    if (position != available_keycodes_.end()) {
+      ResetKeyInfoExpirationTime(position);
+    }
+    result.success = true;
+    return result;
+  }
+
+  if (available_keycodes_.empty()) {
+    return result;
+  }
+
+  KeyInfo& info = available_keycodes_.front();
+
+  if (info.expire_at > clock_->NowTicks()) {
+    result.retry_after = info.expire_at - clock_->NowTicks();
+    return result;
+  }
+
+  if (!keyboard_->ChangeKeyMapping(info.keycode, code_point)) {
+    return result;
+  }
+
+  result.success = true;
+  result.keycode = info.keycode;
+
+  // Modifiers can always be 0 since |code_point| is mapped to both upper and
+  // lower case.
+
+  ResetKeyInfoExpirationTime(available_keycodes_.begin());
+
+  keyboard_->Sync();
+  return result;
+}
+
+void X11KeyMapper::SetClockForTesting(std::unique_ptr<base::TickClock> clock) {
+  clock_ = std::move(clock);
+}
+
+void X11KeyMapper::ResetKeyInfoExpirationTime(
+    std::vector<KeyInfo>::iterator position) {
+  position->expire_at = clock_->NowTicks() + kMappingExpireDuration;
+  while (position + 1 < available_keycodes_.end() &&
+         *(position + 1) < *position) {
+    std::swap(*position, *(position + 1));
+    position++;
+  }
+}
+
+}  // namespace remoting