WinMsgBox.cpp

/*******************************************************************************
 * WinMsgBox.cpp -- DLL component code to demonstrate displaying a Windows
 *   message box and getting a user's response.
 *
 * See https://github.com/robdunn4/QSpice/ for complete documentation & code.
 ******************************************************************************/
/*
 * Notes:
 *
 * (1) This code can be compiled with the DMC compiler included with QSpice.
 *
 * (2) The below GUI_HWND declaration is supported by the 2025.06.26 and
 *     later releases of QSpice.  It may or may not be generated by the
 *     QSpice C++ code template generator.  If not, you'll can manually
 *     add it to your code.
 *
 * (3) This example simply displays a message box to the user when the
 *     Vtrig input port goes high.  The user can choose to abort the
 *     simulation, continue until the next trigger event, or ignore
 *     future trigger events.  You can, of course, implement it in any
 *     fashion that is useful for your particular application.
 *
 * Possible use cases:
 *   * Log file exists.  Overwrite, append, or cancel?
 *   * Missing or corrupt configuration file.  Continue using defaults?
 *   * A large amount of data has been logged.  Continue logging?
 *   * Input port X value is out of expected range.  Continue?
 */

#include <Windows.h>
#include <stdio.h>

extern "C" __declspec(dllexport) int (*Display)(const char *format, ...) = 0;
extern "C" __declspec(dllexport) void *GUI_HWND = 0;   // <-- manually added

union uData {
  bool                   b;
  char                   c;
  unsigned char          uc;
  short                  s;
  unsigned short         us;
  int                    i;
  unsigned int           ui;
  float                  f;
  double                 d;
  long long int          i64;
  unsigned long long int ui64;
  char                  *str;
  unsigned char         *bytes;
};

// int DllMain() must exist and return 1 for a process to load the .DLL
// See https://docs.microsoft.com/en-us/windows/win32/dlls/dllmain for more
// information.
int __stdcall DllMain(void *module, unsigned int reason, void *reserved) {
  return 1;
}

/*
 * Per-instance data structure
 */
struct InstData {
  bool bTrigState;   // last Vtrig input state
  bool bIgnore;      // ignore subsequent trigger events
  bool bTerminate;   // terminate ASAP
};

// forward declarations
int doMsg(double t);

/*
 * QSpice evaluation function
 */
extern "C" __declspec(dllexport) void winmsgbox(
    InstData **ppInst, double t, uData *data) {
  double  Vin   = data[0].d;   // input
  bool    Vtrig = data[1].b;   // input
  double &Vout  = data[2].d;   // output

  /* initialization section */
  InstData *pInst = *ppInst;
  if (!pInst) {
    // allocate and clearper-instance data
    pInst = *ppInst = (InstData *)calloc(1, sizeof(InstData));

    // debug testing message...
    Display("GUI_HWND=0x%08x\n", static_cast<HWND>(GUI_HWND));

    // GUI_HWND is null if run from the command line; we'll suppress
    // messages but it is valid to allow them -- comment out to test
    // that behavior
    if (GUI_HWND == NULL) pInst->bIgnore = true;
  }

  /* implementation section */
  Vout = Vin;

  // if trigger unchanged, quick out
  if (pInst->bTrigState == Vtrig) return;

  // trigger changed, save the state
  pInst->bTrigState = Vtrig;

  // if ignoring triggers, quick out
  if (pInst->bIgnore) return;

  // if not rising edge, quick out
  if (!Vtrig) return;

  // for debugging...
  Display("Trigger event detected @t=%lf\n", t);

  // display msgbox, get user response
  int res = doMsg(t);
  switch (res) {
  case IDABORT:
    Display("User selected Abort...\n");
    pInst->bTerminate = true;
    break;
  case IDRETRY:
    Display("User selected Retry...\n");
    break;
  case IDIGNORE:
    pInst->bIgnore = true;
    Display("User selected Ignore...\n");
    break;
  }
}

/*
 * MaxExtStepSize() for terminating gracefully
 */
extern "C" __declspec(dllexport) double MaxExtStepSize(
    InstData *pInst, double t) {
  static double maxStep = 1e308;
  static double termSim = -1e308;

  if (pInst->bTerminate) {
    Display("Terminating simulation \"gracefully\" @ t=%lf...\n", t);
    return termSim;
  }

  return maxStep;
}

/*
 * release allocated per-instance data
 */
extern "C" __declspec(dllexport) void Destroy(InstData *pInst) { free(pInst); }

/*
 * display message box & get/return user response
 *
 * note:  search "WinAPI MessageBoxA()" for parameter details
 */
int doMsg(double t) {
  // we should use snprintf() here but DMC compiler implements C++98 and
  // snprintf() isn't a thing until C++11...
  char msg[512];
  sprintf(msg,
      "Trigger event detected @t=%lf\n\n"
      "Abort to terminate simulation,\nRetry to continue until next "
      "event,\nor Ignore to ignore subsequent events",
      t);

  // show the msgbox, return result
  int res = MessageBoxA(static_cast<HWND>(GUI_HWND), msg, "WinMsgBox",
      MB_ABORTRETRYIGNORE | MB_ICONERROR | MB_APPLMODAL);
  return res;
}