[host] nvfbc: avoid recreating mouse hook and 1x1 window

The mouse hook code is very fragile, and we would like to avoid unhooking
and re-hooking as much as possible.

After this commit, this is done only once, and the hook and 1x1 window is
only destroyed upon exit. This, of course, comes with the downside of
the slight performance penalty if the guest machine is used directly while
the host is running and the client is not running.

host/platform/Windows/capture/NVFBC/src/nvfbc.c

@@ -61,6 +61,9 @@ struct iface
 
   int mouseX, mouseY, mouseHotX, mouseHotY;
   bool mouseVisible, hasMousePosition;
+
+  bool mouseHookCreated;
+  bool forceCompositionCreated;
 };
 
 static struct iface * this = NULL;
@@ -188,12 +191,21 @@ static bool nvfbc_init(void)
   }
 
   this->cursorEvents[0] = lgCreateEvent(true, 10);
-  mouseHook_install(on_mouseMove);
 
   if (this->seperateCursor)
     this->cursorEvents[1] = lgWrapEvent(event);
 
+  if (!this->mouseHookCreated)
+  {
+    mouseHook_install(on_mouseMove);
+    this->mouseHookCreated = true;
+  }
+
+  if (!this->forceCompositionCreated)
+  {
     dwmForceComposition();
+    this->forceCompositionCreated = true;
+  }
 
   DEBUG_INFO("Cursor mode      : %s", this->seperateCursor ? "decoupled" : "integrated");
 
@@ -226,9 +238,6 @@ static void nvfbc_stop(void)
 
 static bool nvfbc_deinit(void)
 {
-  mouseHook_remove();
-  dwmUnforceComposition();
-
   if (this->cursorEvents[0])
   {
     lgFreeEvent(this->cursorEvents[0]);
@@ -249,6 +258,12 @@ static void nvfbc_free(void)
   if (this->frameEvent)
     lgFreeEvent(this->frameEvent);
 
+  if (this->mouseHookCreated)
+    mouseHook_remove();
+
+  if (this->forceCompositionCreated)
+    dwmUnforceComposition();
+
   free(this);
   this = NULL;
   NvFBCFree();