Grabbing all keyboards

src/linux/server/keyboard.cpp

@@ -91,33 +91,52 @@ int open_event_device(int index) {
   return -1;
 }
 
-int grab_first_keyboard() {
+std::vector<int> grab_keyboards() {
+  auto fds = std::vector<int>();
   for (auto i = 0; i < EVDEV_MINORS; ++i) {
     const auto fd = open_event_device(i);
     if (fd >= 0) {
       if (is_keyboard(fd) &&
           wait_until_keys_released(fd) &&
-          grab_keyboard(fd, true))
-        return fd;
-      ::close(fd);
+          grab_keyboard(fd, true)) {
+        fds.push_back(fd);
+      }
+      else {
+        ::close(fd);
+      }
     }
   }
-  return -1;
+  return fds;
 }
 
-void release_keyboard(int fd) {
-  if (fd >= 0) {
-    grab_keyboard(fd, false);
-    ::close(fd);
-  }
+void release_keyboards(const std::vector<int>& fds) {
+  for (auto fd : fds)
+    if (fd >= 0) {
+      grab_keyboard(fd, false);
+      ::close(fd);
+    }
 }
 
-bool read_event(int fd, int* type, int* code, int* value) {
-  auto ev = input_event{ };
-  if (!read_all(fd, reinterpret_cast<char*>(&ev), sizeof(input_event)))
-    return false;
-  *type = ev.type;
-  *code = ev.code;
-  *value = ev.value;
-  return true;
+bool read_event(const std::vector<int>& fds, int* type, int* code, int* value) {
+  auto rfds = fd_set{ };
+  FD_ZERO(&rfds);
+  auto max_fd = 0;
+  for (auto fd : fds) {
+    max_fd = std::max(max_fd, fd);
+    FD_SET(fd, &rfds);
+  }
+
+  if (::select(max_fd + 1, &rfds, nullptr, nullptr, nullptr) > 0)
+    for (auto fd : fds)
+      if (FD_ISSET(fd, &rfds)) {
+        auto ev = input_event{ };
+        if (!read_all(fd, reinterpret_cast<char*>(&ev), sizeof(input_event)))
+          return false;
+        *type = ev.type;
+        *code = ev.code;
+        *value = ev.value;
+        return true;
+      }
+
+  return false;
 }

src/linux/server/keyboard.h

@@ -1,5 +1,7 @@
 #pragma once
 
-int grab_first_keyboard();
-void release_keyboard(int fd);
-bool read_event(int fd, int* type, int* code, int* value);
+#include <vector>
+
+std::vector<int> grab_keyboards();
+void release_keyboards(const std::vector<int>& fds);
+bool read_event(const std::vector<int>& fds, int* type, int* code, int* value);

src/linux/server/main.cpp

@@ -18,8 +18,8 @@ int main() {
 
     const auto stage = read_config(ipc_fd);
     if (stage) {
-      const auto event_fd = grab_first_keyboard();
-      if (event_fd >= 0) {
+      const auto event_fds = grab_keyboards();
+      if (!event_fds.empty()) {
         const auto uinput_fd = create_uinput_keyboard(uinput_keyboard_name);
         if (uinput_fd >= 0) {
           // main loop
@@ -28,7 +28,7 @@ int main() {
             auto type = 0;
             auto code = 0;
             auto value = 0;
-            if (!read_event(event_fd, &type, &code, &value))
+            if (!read_event(event_fds, &type, &code, &value))
               break;
 
             // let client update configuration
@@ -54,7 +54,7 @@ int main() {
           }
           destroy_uinput_keyboard(uinput_fd);
         }
-        release_keyboard(event_fd);
+        release_keyboards(event_fds);
       }
     }
     shutdown_ipc(ipc_fd);