proto/ft: don't make games think opentrack is running after it quits

Some background:

Our dll's for freetrack and npclient protocols don't support indication
whether opentrack is running or not. Worse yet, they're whitelisted on
Arma's anticheat system so we can't modify them at arbitrary times.

It's possible to run multiple opentrack instances at a time and we can't
have multiple instances stepping upon each other's toes. It's kind of
pointless to run multiple sessions but hey.

Implementation:

Guard with a mutex against multiple instances. Only the first instance
(that uses the freetrack protocol at all) gets to control whether the
dll's are accessible.

Remove the registry keys after either freetrack protocol exits or
software exits, but only if we're the first opentrack instance running
freetrack protocol at all.

Issue: #332

1 files changed, 64 insertions, 0 deletions

diff --git a/proto-ft/mutex.cpp b/proto-ft/mutex.cpp
new file mode 100755
index 00000000..0d50c9bd
--- /dev/null
+++ b/proto-ft/mutex.cpp
@@ -0,0 +1,64 @@
+#include "ftnoir_protocol_ft.h"
+#include <windows.h>
+
+class check_for_first_run : public runonce
+{
+    bool checked_for_first_run;
+    bool is_first_instance;
+
+public:
+    bool is_first_run() override
+    {
+        return checked_for_first_run && is_first_instance;
+    }
+
+    void try_runonce() override
+    {
+        constexpr const char* name = "opentrack-freetrack-runonce";
+
+        if (checked_for_first_run)
+            return;
+
+        // just leak it, no issue
+        HANDLE h = CreateMutexA(nullptr, false, name);
+
+        switch (WaitForSingleObject(h, 0))
+        {
+        case WAIT_OBJECT_0:
+            is_first_instance = true;
+            checked_for_first_run = true;
+            break;
+        case WAIT_TIMEOUT:
+            checked_for_first_run = true;
+            break;
+        default:
+            checked_for_first_run = false;
+            break;
+        }
+
+        if (checked_for_first_run && !is_first_instance)
+            CloseHandle(h);
+
+        qDebug() << "ft runonce:" << "first-run" << is_first_instance << "checked" << checked_for_first_run;
+    }
+
+    void try_exit() override
+    {
+        if (is_first_instance)
+        {
+            qDebug() << "ft runonce: removing registry keys";
+            FTNoIR_Protocol::set_protocols(false, false);
+        }
+    }
+
+public:
+    check_for_first_run() : checked_for_first_run(false), is_first_instance(false)
+    {
+    }
+    ~check_for_first_run()
+    {
+        try_exit();
+    }
+};
+
+std::unique_ptr<runonce> FTNoIR_Protocol::runonce_check = std::unique_ptr<runonce>(static_cast<runonce*>(new check_for_first_run()));