[client] recovery: add force keybind

Add a configured escape key plus Shift+R command that requests display
recovery from the LGMP transport and switches video to SPICE.

Track the request on the main thread, report its asynchronous result,
and return its producer instance with the request serial for exact
correlation.

Preserve normal escape+R rotation behavior, including custom Shift
escape keys.

client/src/app.c

@@ -47,6 +47,12 @@
 
 #define SHADER_MOUSE_VALID (UINT32_C(1) << 31)
 
+enum
+{
+  KEY_MODIFIER_LEFT_SHIFT  = 0x1,
+  KEY_MODIFIER_RIGHT_SHIFT = 0x2,
+};
+
 #define MTRACE(fmt, ...) \
   do \
   { \
@@ -273,6 +279,9 @@ void app_handleFocusEvent(bool focused)
 
   if (!focused)
   {
+    atomic_store_explicit(
+        &g_state.keyModifiers, 0, memory_order_release);
+    g_state.escapeActive = false;
     core_setGrabQuiet(false);
     core_setCursorInView(false);
   }
@@ -289,8 +298,6 @@ void app_handleFocusEvent(bool focused)
     if (g_params.releaseKeysOnFocusLoss)
       lgInput_releaseKeys();
 
-    g_state.escapeActive = false;
-
     if (!g_params.showCursorDot)
       g_state.ds->setPointer(LG_POINTER_NONE);
 
@@ -418,10 +425,20 @@ void app_handleWheelMotion(double motion)
 
 void app_handleKeyPressInternal(int sc)
 {
+  if (sc == KEY_LEFTSHIFT)
+    atomic_fetch_or_explicit(&g_state.keyModifiers,
+        KEY_MODIFIER_LEFT_SHIFT, memory_order_acq_rel);
+  else if (sc == KEY_RIGHTSHIFT)
+    atomic_fetch_or_explicit(&g_state.keyModifiers,
+        KEY_MODIFIER_RIGHT_SHIFT, memory_order_acq_rel);
+
   if (!app_isOverlayMode() || !g_state.io->WantCaptureKeyboard)
   {
     if (sc == g_params.escapeKey && !g_state.escapeActive)
     {
+      memset(g_state.escapeKeys, 0, sizeof(g_state.escapeKeys));
+      memset(g_state.escapeShiftKeys, 0,
+          sizeof(g_state.escapeShiftKeys));
       g_state.escapeActive   = true;
       g_state.escapeTime     = microtime();
       g_state.escapeAction   = -1;
@@ -431,6 +448,7 @@ void app_handleKeyPressInternal(int sc)
 
     if (g_state.escapeActive)
     {
+      const bool repeat = g_state.escapeKeys[sc];
       g_state.escapeAction   = sc;
       g_state.escapeKeys[sc] = true;
       KeybindHandle handle;
@@ -438,7 +456,24 @@ void app_handleKeyPressInternal(int sc)
       {
         if (handle->sc == sc)
         {
-          handle->callback(sc, handle->opaque);
+          unsigned modifiers = atomic_load_explicit(
+              &g_state.keyModifiers, memory_order_acquire);
+          if (g_params.escapeKey == KEY_LEFTSHIFT)
+            modifiers &= ~(unsigned)KEY_MODIFIER_LEFT_SHIFT;
+          else if (g_params.escapeKey == KEY_RIGHTSHIFT)
+            modifiers &= ~(unsigned)KEY_MODIFIER_RIGHT_SHIFT;
+          const bool shift = modifiers != 0;
+          if (!repeat)
+            g_state.escapeShiftKeys[sc] =
+              shift && handle->shiftCallback;
+
+          if (g_state.escapeShiftKeys[sc])
+          {
+            if (!repeat)
+              handle->shiftCallback(sc, handle->shiftOpaque);
+          }
+          else
+            handle->callback(sc, handle->opaque);
           break;
         }
       }
@@ -472,6 +507,13 @@ void app_handleKeyPressInternal(int sc)
 
 void app_handleKeyReleaseInternal(int sc)
 {
+  if (sc == KEY_LEFTSHIFT)
+    atomic_fetch_and_explicit(&g_state.keyModifiers,
+        ~(unsigned)KEY_MODIFIER_LEFT_SHIFT, memory_order_acq_rel);
+  else if (sc == KEY_RIGHTSHIFT)
+    atomic_fetch_and_explicit(&g_state.keyModifiers,
+        ~(unsigned)KEY_MODIFIER_RIGHT_SHIFT, memory_order_acq_rel);
+
   if (g_state.escapeActive && sc == g_params.escapeKey)
   {
     if (g_state.escapeAction == -1)
@@ -486,7 +528,8 @@ void app_handleKeyReleaseInternal(int sc)
 
   if (g_state.escapeKeys[sc])
   {
-    g_state.escapeKeys[sc] = false;
+    g_state.escapeKeys[sc]      = false;
+    g_state.escapeShiftKeys[sc] = false;
     return;
   }
 
@@ -814,10 +857,13 @@ KeybindHandle app_registerKeybind(int sc, KeybindFn callback, void * opaque,
     return NULL;
   }
 
-  handle->sc          = sc;
-  handle->callback    = callback;
-  handle->description = description;
-  handle->opaque      = opaque;
+  handle->sc               = sc;
+  handle->callback         = callback;
+  handle->shiftCallback    = NULL;
+  handle->description      = description;
+  handle->shiftDescription = NULL;
+  handle->opaque           = opaque;
+  handle->shiftOpaque      = NULL;
 
   ll_push(g_state.bindings, handle);
   return handle;