An OS/2 application that does not have a PM window, and therefore cannot use a PM message queue for receiving notification messages, can use an OS/2 Control Program queue instead. The Control Program queue method of notification should also be considered for time-critical PM applications, because it is faster than using the PM message queue.
To receive notifications on a Control Program queue, the application must specify the MCI_DOS_QUEUE flag with the MCI_OPEN command message when using mciSendCommand (or the dosqueue keyword with the open command when using mciSendString). This flag indicates that the window handle specified for receiving notification messages is actually a handle to a Control Program queue, not a PM window.
The application issues DosReadQueue, which mimics the PM message queue function by blocking until there is something in the queue to process. To place a notification message in the queue, the system issues DosWriteQueue and specifies the queue handle given to it by the application.
The syntax for Control Program queues and PM message queues varies slightly. A typical PM message queue process function has the following four parameters:
HWND hwnd /* Window handle */ ULONG msg /* Notification type */ MPARAM mp1 /* Message parameter 1 */ MPARAM mp2 /* Message parameter 2 */
The DosReadQueue call has eight parameters. The system uses the first four parameters of DosReadQueue in the same manner as a PM message queue process function.
HQUEUE hq /* Queue handle */ PREQUESTDATA pRD /* Pointer to REQUESTDATA */ PULONG pmp1 /* Pointer to mp1 information */ PPVOID pmp2 /* Pointer to mp2 information */
The second parameter of DosReadQueue points to the REQUESTDATA structure, which contains a ulData field. This field corresponds to the msg field of PM message queues. The application can use the remaining parameters of DosReadQueue for its own purposes.
The following example code illustrates how an application can use Control Program queue functions to handle multimedia notification messages.
{
PID OwnerPID=0;
HQUEUE QHandle =0;
char ch, retstring[100], QueueName[100];
strcpy(QueueName, "\\QUEUES\\");
if (argc == 2) strcat(QueueName, argv[1]);
else strcat(QueueName, "DEFAULT");
if (DosCreateQueue(&QHandle, QUE_FIFO, QueueName)) return(1L);
if (DosOpenQueue(&OwnerPID, &QHandle, QueueName)) return(1L);
_beginthread( QMonitor, (PVOID)NULL, 65536L, (PVOID)QHandle);
SendString((LPSTR)"open d:\\mmos2\\sounds\\applause.wav shareable
dosqueue wait alias a",
(LPSTR)retstring, 100,
(HWND)QHandle, 0);
SendString((LPSTR)"setpositionadvise a on every 3000 wait",
(LPSTR)retstring, 100,
(HWND)QHandle, 0);
SendString((LPSTR)"play a notify", (LPSTR)retstring, 100, (HWND)QHandle, 0);
ch=(char)getch();
SendString((LPSTR)"close a wait", (LPSTR)retstring, 100, (HWND)QHandle, 0);
DosCloseQueue(QHandle);
return(0L);
}
VOID _Optlink QMonitor( PVOID qh)
{
APIRET rc=0;
BYTE Priority;
REQUESTDATA RD;
ULONG msg, mp1, mp2;
printf("QMonitor Started!\n");
while (1)
{
DosReadQueue((HQUEUE)qh, &RD, (PULONG)&mp1, (PPVOID)&mp2, 0L, (BOOL32)0,
&Priority, (HEV)0);
switch(RD.ulData)
{
case MM_MCINOTIFY:
printf(" msg=MM_MCINOTIFY:\n");
printf(" mp1=%d\n",mp1);
printf(" mp2=%d\n",mp2);
break;
case MM_MCIPASSDEVICE:
printf(" msg=MM_MCIPASSDEVICE:\n");
printf(" Device id=%d\n",mp1);
switch (mp2)
{
case MCI_LOSING_USE:
printf(" MCI_LOSING_USE:\n");
break;
case MCI_GAINING_USE:
printf(" MCI_GAINING_USE:\n");
break;
default:
printf(" mp2=%d\n",mp2);
break;
}
break;
case MM_MCIPOSITIONCHANGE:
printf(" msg=MM_MCIPOSITIONCHANGE:\n");
printf(" mp1=%d\n",mp1);
printf(" mp2=%d\n",mp2);
break;
case MM_MCICUEPOINT:
printf(" msg=MM_MCICUEPOINT:\n");
printf(" mp1=%d\n",mp1);
printf(" mp2=%d\n",mp2);
break;
case MM_MCIPLAYLISTMESSAGE:
printf(" msg=MM_MCIPLAYLISTMESSAGE:\n");
printf(" mp1=%d\n",mp1);
printf(" mp2=%d\n",mp2);
break;
case MM_MCIEVENT:
printf(" msg=MM_MCIEVENT:\n");
printf(" mp1=%d\n",mp1);
printf(" mp2=%d\n",mp2);
break;
default:
printf(" msg=%d\n",RD.ulData);
printf(" mp1=%d\n",mp1);
printf(" mp2=%d\n",mp2);
break;
}
} /* endwhile */
return;
}
VOID SendString( LPSTR string, LPSTR retstring, ULONG retsize, HWND Handle,
ULONG userparm)
{
ULONG rc;
rc=mciSendString(string, retstring, retsize, Handle, userparm);
if (rc) printf("Error: (%s) rc=%d\n",string,rc);
return;
}
/* QUEUE.H */
#define INCL_BASE
#define INCL_32
#include<os2.h>
#include<os2me.h>
#include<mmioos2.h>
#include<stdio.h>
#include<stdlib.h>
#include<conio.h>
int main(int argc, char *argv[], char *envp[]);
VOID SendString(LPSTR string,
LPSTR retstring,
ULONG retsize,
HWND Handle,
ULONG userparm);
VOID _Optlink QMonitor( PVOID qh);