[host] add new D12 capture interface

Note, this capture interface is not yet feature complete but does seem
to be stable.

host/platform/Windows/include/com_ref.h

@@ -0,0 +1,98 @@
+/**
+ * Looking Glass
+ * Copyright © 2017-2023 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <stdbool.h>
+#include <windows.h>
+#include <malloc.h>
+
+#include "common/locking.h"
+
+/**
+ * These functions are to assist in tracking and releasing COM objects
+ */
+
+typedef struct ComScope ComScope;
+
+struct ComScope
+{
+  bool          threadSafe;
+  LG_Lock       lock;
+
+  unsigned      size;
+  unsigned      used;
+  struct
+  {
+    IUnknown *** ptr;
+    IUnknown   * ref;
+  }
+  * refs;
+
+  void (*free)(void * ptr);
+};
+
+void comRef_initScope(unsigned size, ComScope ** instance,
+  void *(allocFn)(size_t size), void (freeFn)(void * ptr), bool threadSafe);
+
+void comRef_freeScope(ComScope ** instance);
+
+IUnknown ** comRef_new(ComScope * scope, IUnknown *** dst);
+
+#define comRef_initGlobalScope(size, scope) \
+  comRef_initScope((size), &(scope), malloc, free, true)
+
+#define comRef_freeGlobalScope(scope) \
+  comRef_freeScope(&(scope))
+
+#define comRef_scopePush(size) \
+  ComScope * _comRef_localScope = alloca(sizeof(*_comRef_localScope) + \
+    sizeof(*(_comRef_localScope->refs)) * size); \
+  comRef_initScope(size, &_comRef_localScope, NULL, NULL, false);
+
+#define comRef_scopePop() \
+  comRef_freeScope(&_comRef_localScope)
+
+#define comRef_defineLocal(type, name) \
+  type ** name = NULL; \
+  comRef_new(_comRef_localScope, (IUnknown ***)&(name));
+
+#define _comRef_toGlobal(globalScope, dst, src) \
+{ \
+  IUnknown ** global = comRef_new((globalScope), (IUnknown ***)&(dst)); \
+  *global = (IUnknown *)*(src); \
+  *(src)  = NULL; \
+}
+
+/**
+ * Release a COM reference immediately
+ * This is just a helper, the ref is still tracked if used again
+ */
+inline static ULONG comRef_release(IUnknown ** ref)
+{
+  if (!ref)
+    return 0;
+
+  ULONG count = 0;
+  if (*ref)
+    count = IUnknown_Release(*ref);
+  *ref = NULL;
+  return count;
+}
+
+#define comRef_release(ref) comRef_release((IUnknown **)(ref))