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

remoting/host/linux/x_server_keyboard_interface.cc

+// 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/x_server_keyboard_interface.h"
+
+#include <X11/extensions/XInput.h>
+#include <X11/extensions/XTest.h>
+#include <X11/XKBlib.h>
+
+#include "base/strings/stringprintf.h"
+#include "remoting/host/linux/unicode_to_keysym.h"
+#include "ui/gfx/x/x11_types.h"
+
+namespace {
+
+bool FindKeycodeForKeySym(Display* display,
+                          KeySym key_sym,
+                          uint32_t* keycode,
+                          uint32_t* modifiers) {
+  *keycode = XKeysymToKeycode(display, key_sym);
+
+  const uint32_t kModifiersToTry[] = {
+      0,
+      ShiftMask,
+      Mod2Mask,
+      Mod3Mask,
+      Mod4Mask,
+      ShiftMask | Mod2Mask,
+      ShiftMask | Mod3Mask,
+      ShiftMask | Mod4Mask,
+  };
+
+  // TODO(sergeyu): Is there a better way to find modifiers state?
+  for (size_t i = 0; i < arraysize(kModifiersToTry); ++i) {
+    unsigned long key_sym_with_mods;
+    if (XkbLookupKeySym(display, *keycode, kModifiersToTry[i], nullptr,
+                        &key_sym_with_mods) &&
+        key_sym_with_mods == key_sym) {
+      *modifiers = kModifiersToTry[i];
+      return true;
+    }
+  }
+  return false;
+}
+
+KeySym CodePointToKeySym(uint32_t code_point) {
+  if (code_point == 0) {
+    return NoSymbol;
+  }
+  std::string sym_hex = base::StringPrintf("U%x", code_point);
+  return XStringToKeysym(sym_hex.c_str());
+}
+
+}  // namespace
+
+namespace remoting {
+
+XServerKeyboardInterface::XServerKeyboardInterface(Display* display) :
+    display_(display) {}
+
+XServerKeyboardInterface::~XServerKeyboardInterface() {}
+
+std::vector<uint32_t> XServerKeyboardInterface::GetUnusedKeycodes() {
+  std::vector<uint32_t> unused_keycodes_;
+  int min_keycode;
+  int max_keycode;
+  XDisplayKeycodes(display_, &min_keycode, &max_keycode);
+  uint32_t keycode_count = max_keycode - min_keycode + 1;
+
+  int sym_per_key;
+  gfx::XScopedPtr<KeySym> mapping(XGetKeyboardMapping(
+      display_, min_keycode, keycode_count, &sym_per_key));
+  for (int keycode = max_keycode; keycode >= min_keycode; keycode--) {
+    bool used = false;
+    int offset = (keycode - min_keycode) * sym_per_key;
+    for (int level = 0; level < sym_per_key; level++) {
+      if (mapping.get()[offset + level]) {
+        used = true;
+        break;
+      }
+    }
+    if (!used) {
+      unused_keycodes_.push_back(keycode);
+    }
+  }
+  return unused_keycodes_;
+}
+
+void XServerKeyboardInterface::PressKey(uint32_t keycode, uint32_t modifiers) {
+  XkbLockModifiers(display_, XkbUseCoreKbd, modifiers, modifiers);
+
+  XTestFakeKeyEvent(display_, keycode, True, CurrentTime);
+  XTestFakeKeyEvent(display_, keycode, False, CurrentTime);
+
+  XkbLockModifiers(display_, XkbUseCoreKbd, modifiers, 0);
+}
+
+bool XServerKeyboardInterface::FindKeycode(uint32_t code_point,
+                                           uint32_t* keycode,
+                                           uint32_t* modifiers) {
+  std::vector<uint32_t> keysyms;
+  GetKeySymsForUnicode(code_point, &keysyms);
+
+  for (std::vector<uint32_t>::iterator it = keysyms.begin();

[Sergey Ulanov, 2016/09/21 19:59:23]

Use range loop please:
  for (auto& keysym : keysyms)

You could also change GetKeySymsForUnicode() to return std::vector<> instead of
taking it in the arguments. With copy elision the compiler may generate more
efficient code and this line would be simpler:
  for (auto& keysym : GetKeySymsForUnicode(code_point))

[Yuwei, 2016/09/23 01:40:38]

Done.

+       it != keysyms.end(); ++it) {
+    if (FindKeycodeForKeySym(display_, *it, keycode, modifiers)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool XServerKeyboardInterface::ChangeKeyMapping(
+    uint32_t keycode,

[Sergey Ulanov, 2016/09/21 19:59:23]

int instead of uint32_t.

[Yuwei, 2016/09/23 01:40:37]

Is there any reason we prefer int? Looks like keycode is defined as unsigned...

+    uint32_t lower_case_code_point,
+    uint32_t upper_case_code_point) {

[Sergey Ulanov, 2016/09/21 19:59:23]

Maybe use KeySym for these two parameters?

[Sergey Ulanov, 2016/09/21 19:59:24]

Do we need it here? It doesn't appear to be useful XServerKeyMapper passes same
value for these two parameters.

[Yuwei, 2016/09/23 01:40:37]

Removed.

I just thought it could be useful if we allow setting lower and upper case
separately. It's currently not used.

[Yuwei, 2016/09/23 01:40:37]

KeySym is tyepdef'ed as unsigned int. I tried to avoid using KeySym in function
signature so that the header doesn't need to include Xlib

+  KeySym lower_case_keysym = CodePointToKeySym(lower_case_code_point);
+  KeySym upper_case_keysum = (lower_case_code_point == upper_case_code_point) ?
+      lower_case_keysym : CodePointToKeySym(upper_case_code_point);
+  if ((lower_case_code_point && !lower_case_keysym) ||
+      (upper_case_code_point && !upper_case_keysum)) {
+    // Non-null code point translated to NoSymbol. The server may not support
+    // Unicode-to-KeySym translation.
+    return false;
+  }
+  KeySym syms[2];

[Sergey Ulanov, 2016/09/21 19:59:24]

 = {lower_case_keysym, upper_case_keysum};

[Yuwei, 2016/09/23 01:40:37]

Done.

+  syms[0] = lower_case_keysym;
+  syms[1] = upper_case_keysum;
+  XChangeKeyboardMapping(display_, keycode, 2, syms, 1);
+  return true;
+}
+
+void XServerKeyboardInterface::Flush() {
+  XFlush(display_);
+}
+
+void XServerKeyboardInterface::Sync() {
+  XSync(display_, false);
+}
+
+}  // namespace remoting