When receiving a key event on Linux, set host lock state to match client's

remoting/host/input_injector_x11.cc

Index: remoting/host/input_injector_x11.cc
diff --git a/remoting/host/input_injector_x11.cc b/remoting/host/input_injector_x11.cc
index 2e4bdc6880e74f2795edbed05a7ab8e5cf8d0fe5..df871ca6cc711f5cde7cc6a2571dbabd8da11977 100644
--- a/remoting/host/input_injector_x11.cc
+++ b/remoting/host/input_injector_x11.cc
@@ -10,6 +10,7 @@
 #include <X11/extensions/XTest.h>
 #include <X11/Xlib.h>
 #include <X11/XKBlib.h>
+#include <X11/keysym.h>
 #undef Status  // Xlib.h #defines this, which breaks protobuf headers.
 
 #include <set>
@@ -121,6 +122,9 @@ class InputInjectorX11 : public InputInjector {
     // Enables or disables keyboard auto-repeat globally.
     void SetAutoRepeatEnabled(bool enabled);
 
+    // Sets the keyboard lock states to those provided.
+    void SetLockStates(uint32_t states);
+
     void InjectScrollWheelClicks(int button, int count);
     // Compensates for global button mappings and resets the XTest device
     // mapping.
@@ -276,6 +280,10 @@ void InputInjectorX11::Core::InjectKeyEvent(const KeyEvent& event) {
       XTestFakeKeyEvent(display_, keycode, False, CurrentTime);
     }
 
+    if (event.has_lock_states()) {
+      SetLockStates(event.lock_states());
+    }
+
     if (pressed_keys_.empty()) {
       // Disable auto-repeat, if necessary, to avoid triggering auto-repeat
       // if network congestion delays the key-up event from the client.
@@ -347,6 +355,20 @@ void InputInjectorX11::Core::SetAutoRepeatEnabled(bool mode) {
   XChangeKeyboardControl(display_, KBAutoRepeatMode, &control);
 }
 
+void InputInjectorX11::Core::SetLockStates(uint32_t states) {
+  unsigned int caps_lock_mask = XkbKeysymToModifiers(display_, XK_Caps_Lock);
+  unsigned int num_lock_mask = XkbKeysymToModifiers(display_, XK_Num_Lock);
+  unsigned int lock_values = 0;
+  if (states & protocol::KeyEvent::LOCK_STATES_CAPSLOCK) {
+    lock_values |= caps_lock_mask;
+  }
+  if (states & protocol::KeyEvent::LOCK_STATES_NUMLOCK) {
+    lock_values |= num_lock_mask;
+  }
+  XkbLockModifiers(display_, XkbUseCoreKbd, caps_lock_mask | num_lock_mask,
+                   lock_values);

[rkjnsn, 2017/04/25 19:25:03]

We could check the existing states first instead of indiscriminately setting
them, but I'm not sure that would offer any advantages. Certainly, it would
result in an extra server round trip in the out-of-sync case.

XkbLockModifiers could fail, which would leave things no worse than today.
However, would it makes sense to log a warning in that case? It could
potentially be triggered every key press, so I currently just ignore any errors.

[Jamie, 2017/04/25 20:15:57]

I think this is fine. The documentation suggests that it can fail if the request
wasn't sent, but gives no indication as to why that might be.

+}
+
 void InputInjectorX11::Core::InjectScrollWheelClicks(int button, int count) {
   if (button < 0) {
     LOG(WARNING) << "Ignoring unmapped scroll wheel button";