Source CrossFire MessageBox Engine — Internal Call Hooking

[byte_corvus]

Cleaning out my local storage and found this snippet for CrossFire. It's an internal MessageBox hook that bypasses the standard UI flow by hitting the engine's direct popup handler. Useful if you're reverse engineering the CShell module and need a quick debug output or a way to trigger custom client alerts without re-hooking the entire renderer.

void EngineMessageBox(const char* szMessage)
{
    typedef void(__fastcall* ChangePopupFlowFn)(uint32_t, uint32_t, uint32_t, const char*, uint32_t, uint64_t);
    ChangePopupFlowFn fn = (ChangePopupFlowFn)(CShell + 0xADDRESS);
    if (fn)
        fn(0xOFFSET, 0xOFFSET, 0, szMessage, 0, 0);
}

Implementation Notes:

1. You'll need to find your own CShell base address and relevant offsets for the ChangePopupFlow function. If you're currently reversing the client, search for strings related to existing game errors like "vertex lock failed".
2. The function expects the parameters as laid out above; make sure you're properly aligning the stack if you plan on hooking the entry point rather than just calling it.
3. It's a straightforward way to inject information into the game's native UI system without dealing with ImGui or external overlays.

Spoiler: Usage Example

static bool call_once = false;
if (call_once == false)
{
    EngineMessageBox("Debug Message Here");
    call_once = true;
}

It’s nothing revolutionary, but it beats writing your own UI for basic logging while you're grinding out offsets. Anyone currently digging into the latest CrossFire client's CShell exports?