[client] evdev: fix input capture and device handling

Classify configured devices by keyboard and pointer capability so
automatic keyboard capture leaves relative pointer devices with the
display server.

Run descriptor, grab, physical-state, and LED operations on one worker.
Marshal normalized events through each display server's event loop and
serialize ownership changes with per-lane barriers.

Fall back whole lanes to native input when an evdev cohort cannot be
owned, and retry missing or removed devices without disabling the rest.

Handle report framing, SYN_DROPPED, high-resolution wheels, queue
overflow, held-state cleanup, and guest-driven keyboard LEDs. Restore
host LEDs and kernel grabs during teardown.

Re-evaluate capture when the active input transport changes.

client/include/evdev.h

@@ -36,22 +36,31 @@ bool evdev_start(void);
 void evdev_stop(void);
 
 /**
- * restore the display server hooks and free the device state; only
+ * free the device state; only call once display server callbacks have stopped
- * call once display server callbacks have stopped
  */
 void evdev_free(void);
 
 /**
- * grab the keyboard for exclusive access
+ * update the keyboard and pointer capture requirements
  */
-void evdev_grabKeyboard(void);
+void evdev_setGrab(bool keyboard, bool pointer);
 
 /**
- * ungrab the keyboard
+ * return the event fd used to dispatch captured input
  */
-void evdev_ungrabKeyboard(void);
+int evdev_getEventFD(void);
 
 /**
- * returns true if input should only be processed by evdev
+ * dispatch captured input on the display server's event thread
+ */
+void evdev_dispatch(void * opaque);
+
+/**
+ * return true if keyboard input should only be processed by evdev
  */
 bool evdev_isExclusive(void);
+
+/**
+ * return true if pointer input should only be processed by evdev
+ */
+bool evdev_isPointerExclusive(void);

client/include/input.h

@@ -25,6 +25,7 @@
 
 typedef void (*LGInputKeyboardLEDsFn)(void * opaque,
     bool valid, uint8_t leds);
+typedef void (*LGInputAvailabilityFn)(void * opaque, bool available);
 
 void lgInput_init(void);
 void lgInput_free(void);
@@ -43,11 +44,20 @@ bool lgInput_supports(LG_InputSupport support);
  * call back into the input layer. */
 void lgInput_setKeyboardLEDsListener(
     LGInputKeyboardLEDsFn callback, void * opaque);
+/* The listener is called synchronously with the current input availability
+ * and later from transport threads whenever it changes. The callback must
+ * not call back into the input layer. */
+void lgInput_setAvailabilityListener(
+    LGInputAvailabilityFn callback, void * opaque);
 
 bool lgInput_keyDown(int key);
 bool lgInput_keyUp(int key);
 bool lgInput_keyboardLEDs(bool numLock, bool capsLock, bool scrollLock);
 void lgInput_releaseKeys(void);
+void lgInput_releaseButtons(void);
+/* Release all tracked keyboard and mouse button state under one active-input
+ * transaction. */
+void lgInput_releaseAll(void);
 
 bool lgInput_mouseMotion(int32_t x, int32_t y);
 bool lgInput_mousePosition(uint32_t x, uint32_t y, uint32_t width,

client/src/app.c

@@ -174,6 +174,9 @@ bool app_isOverlayMode(void)
 
 void app_updateCursorPos(double x, double y)
 {
+  if (evdev_isPointerExclusive())
+    return;
+
   const bool overlay = app_isOverlayMode();
   if (overlay)
   {
@@ -375,7 +378,7 @@ static int mapInputToImGuiButton(uint32_t button)
   return -1;
 }
 
-void app_handleButtonPress(int button)
+void app_handleButtonPressInternal(int button)
 {
   g_cursor.buttons |= (1U << button);
   app_updateMouseButtons();
@@ -399,7 +402,13 @@ void app_handleButtonPress(int button)
     DEBUG_ERROR("app_handleButtonPress: failed to send message");
 }
 
-void app_handleButtonRelease(int button)
+void app_handleButtonPress(int button)
+{
+  if (!evdev_isPointerExclusive())
+    app_handleButtonPressInternal(button);
+}
+
+void app_handleButtonReleaseInternal(int button)
 {
   g_cursor.buttons &= ~(1U << button);
   app_updateMouseButtons();
@@ -422,8 +431,17 @@ void app_handleButtonRelease(int button)
     DEBUG_ERROR("app_handleButtonRelease: failed to send message");
 }
 
+void app_handleButtonRelease(int button)
+{
+  if (!evdev_isPointerExclusive())
+    app_handleButtonReleaseInternal(button);
+}
+
 void app_handleWheelMotion(double motion)
 {
+  if (evdev_isPointerExclusive())
+    return;
+
   if (app_isOverlayMode())
     g_state.io->MouseWheel -= motion;
 }
@@ -570,11 +588,15 @@ void app_handleKeyRelease(int sc)
 
 void app_handleKeyboardTyped(const char * typed)
 {
+  if (evdev_isExclusive())
+    return;
+
   app_registerImGuiText(typed);
   ImGuiIO_AddInputCharactersUTF8(g_state.io, typed);
 }
 
-void app_handleKeyboardModifiers(bool ctrl, bool shift, bool alt, bool super)
+void app_handleKeyboardModifiersInternal(
+    bool ctrl, bool shift, bool alt, bool super)
 {
   g_state.modCtrl  = ctrl;
   g_state.modShift = shift;
@@ -582,8 +604,57 @@ void app_handleKeyboardModifiers(bool ctrl, bool shift, bool alt, bool super)
   g_state.modSuper = super;
 }
 
+void app_handleKeyboardModifiers(bool ctrl, bool shift, bool alt, bool super)
+{
+  if (!evdev_isExclusive())
+    app_handleKeyboardModifiersInternal(ctrl, shift, alt, super);
+}
+
+void app_handleInputResetInternal(bool keyboard, bool pointer)
+{
+  if (pointer)
+  {
+    g_cursor.buttons = 0;
+    app_updateMouseButtons();
+    g_state.io->MouseDown[ImGuiMouseButton_Left  ] = false;
+    g_state.io->MouseDown[ImGuiMouseButton_Right ] = false;
+    g_state.io->MouseDown[ImGuiMouseButton_Middle] = false;
+  }
+
+  if (keyboard)
+  {
+    for(int key = 0; key < KEY_MAX; ++key)
+      if (linux_to_imgui[key])
+        ImGuiIO_AddKeyEvent(g_state.io, linux_to_imgui[key], false);
+
+    g_state.modCtrl      = false;
+    g_state.modShift     = false;
+    g_state.modAlt       = false;
+    g_state.modSuper     = false;
+    g_state.escapeActive = false;
+    g_state.escapeTime   = 0;
+    g_state.escapeAction = -1;
+    memset(g_state.escapeKeys, 0, sizeof(g_state.escapeKeys));
+    memset(g_state.escapeShiftKeys, 0,
+        sizeof(g_state.escapeShiftKeys));
+    atomic_store_explicit(
+        &g_state.keyModifiers, 0, memory_order_release);
+  }
+
+  if (keyboard && pointer)
+    lgInput_releaseAll();
+  else if (keyboard)
+    lgInput_releaseKeys();
+  else if (pointer)
+    lgInput_releaseButtons();
+  app_invalidateWindow(false);
+}
+
 void app_handleKeyboardLEDs(bool numLock, bool capsLock, bool scrollLock)
 {
+  if (evdev_isExclusive())
+    return;
+
   if (!core_inputEnabled())
     return;
 
@@ -594,6 +665,9 @@ void app_handleKeyboardLEDs(bool numLock, bool capsLock, bool scrollLock)
 void app_handleMouseRelative(double normx, double normy,
     double rawx, double rawy)
 {
+  if (evdev_isPointerExclusive())
+    return;
+
   MTRACE("rel delta=%.3f,%.3f raw=%.3f,%.3f inWin=%d inView=%d "
       "grab=%d", normx, normy, rawx, rawy, g_cursor.inWindow,
       g_cursor.inView, g_cursor.grab);

client/src/app_internal.h

@@ -25,5 +25,10 @@
 
 void app_handleKeyPressInternal(int scancode);
 void app_handleKeyReleaseInternal(int scancode);
+void app_handleButtonPressInternal(int button);
+void app_handleButtonReleaseInternal(int button);
+void app_handleKeyboardModifiersInternal(
+    bool ctrl, bool shift, bool alt, bool super);
+void app_handleInputResetInternal(bool keyboard, bool pointer);
 
 #endif

client/src/core.c

@@ -25,6 +25,7 @@
 #include "kb.h"
 #include "message.h"
 #include "input.h"
+#include "evdev.h"
 
 #include "common/time.h"
 #include "common/debug.h"
@@ -140,6 +141,8 @@ bool core_inputEnabled(void)
 void core_updateKeyboardGrab(void)
 {
   const bool inputEnabled = core_inputEnabled();
+  const bool localActive  = g_state.focused && !app_isOverlayMode() &&
+    !g_state.ignoreInput;
   /* Explicit capture is local window state and must survive an input provider
    * becoming unavailable or changing during startup. */
   const bool capture      = g_cursor.grab && g_params.grabKeyboard &&
@@ -150,6 +153,7 @@ void core_updateKeyboardGrab(void)
   const bool active       = g_state.focused && !app_isOverlayMode() &&
     (capture || (inputEnabled && (view || automatic)));
 
+  evdev_setGrab(active, localActive && g_cursor.grab);
   if (active)
     g_state.ds->grabKeyboard();
   else

client/src/input.c

@@ -42,15 +42,19 @@ static struct
   LG_Lock   bindingLock;
   LG_RWLock activeLock;
   LG_Lock   keyboardLEDsDispatch;
+  LG_Lock   availabilityDispatch;
   uint32_t  nextBindingEpoch;
 
   LGInputKeyboardLEDsFn keyboardLEDsCallback;
   void                  * keyboardLEDsOpaque;
+  LGInputAvailabilityFn availabilityCallback;
+  void                  * availabilityOpaque;
 
   struct InputBinding fallback;
   struct InputBinding transport;
   struct InputBinding active;
   bool                useTransport;
+  bool                notifiedAvailable;
 
   _Atomic(bool)     keys[KEY_MAX];
   _Atomic(uint32_t) buttons;
@@ -126,6 +130,30 @@ static void dispatchKeyboardLEDs(void)
   LG_UNLOCK(l_input.keyboardLEDsDispatch);
 }
 
+static bool updateAvailabilityNL(void)
+{
+  const bool available = l_input.active.ops != NULL;
+  if (l_input.notifiedAvailable == available)
+    return false;
+
+  l_input.notifiedAvailable = available;
+  return true;
+}
+
+static void dispatchAvailability(void)
+{
+  LG_LOCK(l_input.availabilityDispatch);
+  LG_LOCK_SHARED(l_input.activeLock);
+  LGInputAvailabilityFn callback  = l_input.availabilityCallback;
+  void                * opaque    = l_input.availabilityOpaque;
+  const bool            available = l_input.active.ops != NULL;
+  LG_UNLOCK_SHARED(l_input.activeLock);
+
+  if (callback)
+    callback(opaque, available);
+  LG_UNLOCK(l_input.availabilityDispatch);
+}
+
 static void releaseKeysNL(void)
 {
   for (int key = 0; key < KEY_MAX; ++key)
@@ -234,9 +262,12 @@ static void fallbackStatusChanged(void * opaque,
   if (l_input.fallback.ops &&
       l_input.fallback.epoch == (uint32_t)(uintptr_t)opaque)
     keyboardLEDsChanged = updateStatusNL(&l_input.fallback, status);
+  const bool availabilityChanged = updateAvailabilityNL();
   LG_UNLOCK_EXCLUSIVE(l_input.activeLock);
   if (keyboardLEDsChanged)
     dispatchKeyboardLEDs();
+  if (availabilityChanged)
+    dispatchAvailability();
 }
 
 static void transportStatusChanged(void * opaque,
@@ -250,9 +281,12 @@ static void transportStatusChanged(void * opaque,
   if (l_input.transport.ops &&
       l_input.transport.epoch == (uint32_t)(uintptr_t)opaque)
     keyboardLEDsChanged = updateStatusNL(&l_input.transport, status);
+  const bool availabilityChanged = updateAvailabilityNL();
   LG_UNLOCK_EXCLUSIVE(l_input.activeLock);
   if (keyboardLEDsChanged)
     dispatchKeyboardLEDs();
+  if (availabilityChanged)
+    dispatchAvailability();
 }
 
 void lgInput_init(void)
@@ -261,6 +295,7 @@ void lgInput_init(void)
   l_input.transport         = (struct InputBinding) { 0 };
   l_input.active            = (struct InputBinding) { 0 };
   l_input.useTransport      = true;
+  l_input.notifiedAvailable = false;
 
   for (int key = 0; key < KEY_MAX; ++key)
     atomic_init(&l_input.keys[key], false);
@@ -269,6 +304,7 @@ void lgInput_init(void)
   LG_LOCK_INIT(l_input.bindingLock);
   LG_RWLOCK_INIT(l_input.activeLock);
   LG_LOCK_INIT(l_input.keyboardLEDsDispatch);
+  LG_LOCK_INIT(l_input.availabilityDispatch);
 }
 
 void lgInput_free(void)
@@ -278,6 +314,7 @@ void lgInput_free(void)
 
   LG_LOCK(l_input.bindingLock);
   LG_LOCK(l_input.keyboardLEDsDispatch);
+  LG_LOCK(l_input.availabilityDispatch);
   LG_LOCK_EXCLUSIVE(l_input.activeLock);
   resetActiveNL();
   fallback                       = l_input.fallback;
@@ -287,7 +324,10 @@ void lgInput_free(void)
   l_input.transport              = (struct InputBinding) { 0 };
   l_input.keyboardLEDsCallback   = NULL;
   l_input.keyboardLEDsOpaque     = NULL;
+  l_input.availabilityCallback   = NULL;
+  l_input.availabilityOpaque     = NULL;
   LG_UNLOCK_EXCLUSIVE(l_input.activeLock);
+  LG_UNLOCK(l_input.availabilityDispatch);
   LG_UNLOCK(l_input.keyboardLEDsDispatch);
 
   if (fallback.ops && fallback.ops->setStatusListener)
@@ -297,6 +337,7 @@ void lgInput_free(void)
 
   LG_UNLOCK(l_input.bindingLock);
   LG_RWLOCK_FREE(l_input.activeLock);
+  LG_LOCK_FREE(l_input.availabilityDispatch);
   LG_LOCK_FREE(l_input.keyboardLEDsDispatch);
   LG_LOCK_FREE(l_input.bindingLock);
 }
@@ -325,10 +366,13 @@ static void setBinding(struct InputBinding * target,
   LG_LOCK_EXCLUSIVE(l_input.activeLock);
   *target = next;
   const bool keyboardLEDsChanged = updateActiveNL(false);
+  const bool availabilityChanged = updateAvailabilityNL();
   LG_UNLOCK_EXCLUSIVE(l_input.activeLock);
 
   if (keyboardLEDsChanged)
     dispatchKeyboardLEDs();
+  if (availabilityChanged)
+    dispatchAvailability();
 
   if (next.ops && next.ops->setStatusListener)
     next.ops->setStatusListener(next.opaque, statusFn,
@@ -343,9 +387,12 @@ static void dropBinding(struct InputBinding * target)
   const bool wasActive = bindingEqual(&l_input.active, target);
   *target = (struct InputBinding) { 0 };
   const bool keyboardLEDsChanged = updateActiveNL(wasActive);
+  const bool availabilityChanged = updateAvailabilityNL();
   LG_UNLOCK_EXCLUSIVE(l_input.activeLock);
   if (keyboardLEDsChanged)
     dispatchKeyboardLEDs();
+  if (availabilityChanged)
+    dispatchAvailability();
   LG_UNLOCK(l_input.bindingLock);
 }
 
@@ -374,9 +421,12 @@ void lgInput_useTransport(bool enable)
   LG_LOCK_EXCLUSIVE(l_input.activeLock);
   l_input.useTransport = enable;
   const bool keyboardLEDsChanged = updateActiveNL(false);
+  const bool availabilityChanged = updateAvailabilityNL();
   LG_UNLOCK_EXCLUSIVE(l_input.activeLock);
   if (keyboardLEDsChanged)
     dispatchKeyboardLEDs();
+  if (availabilityChanged)
+    dispatchAvailability();
 }
 
 bool lgInput_available(void)
@@ -423,6 +473,21 @@ void lgInput_setKeyboardLEDsListener(
   LG_UNLOCK(l_input.keyboardLEDsDispatch);
 }
 
+void lgInput_setAvailabilityListener(
+    LGInputAvailabilityFn callback, void * opaque)
+{
+  LG_LOCK(l_input.availabilityDispatch);
+  LG_LOCK_SHARED(l_input.activeLock);
+  l_input.availabilityCallback = callback;
+  l_input.availabilityOpaque   = opaque;
+  const bool available = l_input.active.ops != NULL;
+  LG_UNLOCK_SHARED(l_input.activeLock);
+
+  if (callback)
+    callback(opaque, available);
+  LG_UNLOCK(l_input.availabilityDispatch);
+}
+
 bool lgInput_keyDown(int key)
 {
   if (key < 0 || key >= KEY_MAX)
@@ -483,6 +548,21 @@ void lgInput_releaseKeys(void)
   LG_UNLOCK_EXCLUSIVE(l_input.activeLock);
 }
 
+void lgInput_releaseButtons(void)
+{
+  LG_LOCK_EXCLUSIVE(l_input.activeLock);
+  releaseButtonsNL();
+  LG_UNLOCK_EXCLUSIVE(l_input.activeLock);
+}
+
+void lgInput_releaseAll(void)
+{
+  LG_LOCK_EXCLUSIVE(l_input.activeLock);
+  releaseKeysNL();
+  releaseButtonsNL();
+  LG_UNLOCK_EXCLUSIVE(l_input.activeLock);
+}
+
 bool lgInput_mouseMotion(int32_t x, int32_t y)
 {
   LG_LOCK_SHARED(l_input.activeLock);

client/src/main.c

@@ -3603,7 +3603,7 @@ static int lg_run(void)
   }
 
   if (evdev_start())
-    DEBUG_INFO("Using evdev for keyboard capture");
+    DEBUG_INFO("Using evdev for input capture");
 
   // override the SIGINIT handler so that we can tell the difference between
   // SIGINT and the user sending a close event, such as ALT+F4
@@ -3739,7 +3739,13 @@ static int lg_run(void)
     .largeCursorDot      = g_params.largeCursorDot,
     .allowNoInput        = strcmp(g_params.transport, "test") == 0,
     .opengl              = needsOpenGL,
-    .jitRender           = g_params.jitRender
+    .jitRender           = g_params.jitRender,
+    .eventSource         =
+    {
+      .fd       = evdev_getEventFD(),
+      .callback = evdev_dispatch,
+      .opaque   = NULL,
+    },
   };
 
   g_state.dsInitialized = g_state.ds->init(params);

client/tests/app_keybind_test.c

@@ -163,6 +163,10 @@ bool core_inputEnabled(void)
   return t.input;
 }
 
+void core_updateKeyboardGrab(void)
+{
+}
+
 void core_setGrab(bool enable)
 {
   ++t.grabN;

client/tests/keybind_test.c

@@ -224,6 +224,10 @@ void core_updatePositionInfo(void)
   ++t.posN;
 }
 
+void core_updateKeyboardGrab(void)
+{
+}
+
 void core_setCursorInView(bool enable)
 {
   ++t.cursorN;

client/tests/mouse_test.c

@@ -282,6 +282,12 @@ void app_mouseTrace(const char * file, unsigned int line,
   (void)format;
 }
 
+void evdev_setGrab(bool keyboard, bool pointer)
+{
+  (void)keyboard;
+  (void)pointer;
+}
+
 static bool inputSupports(void * opaque, LG_InputSupport support)
 {
   return support == LG_INPUT_SUPPORT_MOUSE_ABSOLUTE &&

doc/input.rst

@@ -95,7 +95,10 @@ Evdev capture
 -------------
 
 Advanced users may list Linux evdev devices in ``input:evdev``. They become
-active whenever Looking Glass grabs the keyboard, including capture mode and
+active when Looking Glass captures their keyboard or relative-pointer role.
-automatic keyboard capture. The client user must be allowed to read those
+Automatic capture takes keyboard-only devices without taking mouse input from
-devices. Keep ``input:evdevExclusive=yes`` unless duplicate input from the
+the window system, while full capture takes both roles. Guest keyboard lock
-window system is specifically required.
+LEDs are mirrored while a writable keyboard is captured. The client user must
+be allowed to read the configured devices and write them for LED mirroring.
+Keep ``input:evdevExclusive=yes`` unless input from other window-system
+devices is also required.