[fix] recover headless capture and use WGC for usbmmidd displays

apps/desktop/src/platform/windows/virtual_display/usbmmidd_virtual_display.cpp

@@ -217,6 +217,22 @@ int CountUsbmmiddMonitors() {
   return count;
 }
 
+std::wstring FindUsbmmiddDisplayDeviceName() {
+  for (const auto& adapter : EnumerateUsbmmiddAdapters()) {
+    if (adapter.attached_to_desktop) return adapter.device_name;
+  }
+  return {};
+}
+
+bool IsUsbmmiddDisplayDevice(const std::wstring& device_name) {
+  for (const auto& adapter : EnumerateUsbmmiddAdapters()) {
+    if (adapter.attached_to_desktop &&
+        _wcsicmp(adapter.device_name.c_str(), device_name.c_str()) == 0)
+      return true;
+  }
+  return false;
+}
+
 bool IsUsbmmiddDriverInstalled() {
   const HDEVINFO device_info = SetupDiGetClassDevsW(
       &GUID_DEVCLASS_DISPLAY, nullptr, nullptr, DIGCF_PRESENT);

apps/desktop/src/platform/windows/virtual_display/usbmmidd_virtual_display.h

@@ -42,6 +42,9 @@ UsbmmiddStatus QueryUsbmmiddStatus();
 
 // Adapters attached to the desktop, i.e. monitors currently plugged in.
 int CountUsbmmiddMonitors();
+// GDI device name of an attached usbmmidd output, or empty while settling.
+std::wstring FindUsbmmiddDisplayDeviceName();
+bool IsUsbmmiddDisplayDevice(const std::wstring& device_name);
 // Root-enumerated device node present, plugged or not.
 bool IsUsbmmiddDriverInstalled();
 

apps/desktop/src/platform/windows/virtual_display/virtual_display_provisioner.cpp

@@ -190,7 +190,10 @@ bool VirtualDisplayProvisioner::Acquire(VirtualDisplayMode mode,
   std::string local_error;
   if (error == nullptr) error = &local_error;
   if (active_.load(std::memory_order_relaxed)) return true;
-  cancel_.store(false, std::memory_order_relaxed);
+  if (Cancelled()) {
+    *error = "cancelled";
+    return false;
+  }
 
   bool helper_reachable = false;
   const ULONGLONG started = GetTickCount64();

apps/desktop/src/platform/windows/virtual_display/virtual_display_provisioner.h

@@ -29,6 +29,9 @@ class VirtualDisplayProvisioner {
       delete;
 
   bool Acquire(VirtualDisplayMode mode, std::string* error);
+  // Owner calls this before launching an Acquire worker. Clearing cancellation
+  // inside the worker would lose a Stop() racing with thread startup.
+  void PrepareAcquire() { cancel_.store(false, std::memory_order_relaxed); }
   void Release();
   bool active() const { return active_.load(std::memory_order_relaxed); }
   // True when Release() has something to undo. Read on the owner's thread
@@ -37,7 +40,7 @@ class VirtualDisplayProvisioner {
     return active() || pending_helper_release_ || plugged_locally_ > 0;
   }
   // Makes a blocking Acquire() return early with "cancelled" at its next poll
-  // (helper install/plug can take up to two minutes). Cleared by Acquire().
+  // (helper install/plug can take up to two minutes).
   void RequestCancel() { cancel_.store(true, std::memory_order_relaxed); }
 
  private: