Creating a Device Context

You can create a normal device context by calling DevOpenDC. This function requires that you specify one of the six normal types. It also requires that you pass certain device-initialization data, including a logical address, the device-driver name, device-driver data, a description of the device type, and information about the queue (if the device is a queued device). The device-initialization data is passed in a DEVOPENSTRUC structure.

The following figure is an example of this structure.

    typedef struct _DEVOPENSTRUC {   /* dop                          */
        PSZ      pszLogAddress       /* Logical-device address       */
        PSZ      pszDriverName       /* Device-driver name           */
        PDRIVDATA  pdriv             /* Pointer to extra driver data */
        PSZ      pszDataType         /* Type of queued data          */
        PSZ      pszComment          /* Optional spooler info        */
        PSZ      pszQueueProcName    /* Queue-processor name         */
        PSZ      pszQueueProcParams  /* Queue-processor arguments    */
        PSZ      pszSpoolerParams    /* Spooler arguments            */
        PSZ      pszNetworkParams    /* Network arguments            */
    } DEVOPENSTRUC;

The last four fields in this structure apply only to queued devices.

The following figure shows how to create a nondisplay device context for a printer.

    HDC hdcPrinter;                     /* Handle of printer device context    */
    HAB hab;                            /* Anchor-block handle                 */
    DEVOPENSTRUC dop;                   /* Device information                  */

    dop.pszLogAddress = "lpt1";         /* Logical-device address              */
    dop.pszDriverName = "EPSON";        /* Device-driver name                  */
    dop.pdriv = (PDRIVDATA) NULL;       /* Pointer to driver data              */
    dop.pszDataType = "PM_Q_STD";       /* Standard queued data                */

    hdcPrinter = DevOpenDC(hab,
                           OD_DIRECT,   /* Direct device type                  */
                           "*",         /* No data in OS2.INI                  */
                           4,           /* Use first 4 fields in dop structure */
                           (PDEVOPENDATA) &dop,
                           (HDC) NULL);

The following figure is an example of how to create a standard device context for a metafile.

    HDC hdcMeta;                                 /* Handles of metafile       */
                                                 /*    and window DCs         */
    HAB hab;                                     /* Anchor-block handle       */
    DEVOPENSTRUC dop;                            /* Device information        */

    dop.pszLogAddress = NULL;                    /* Logical-device address    */
    dop.pszDriverName = "DISPLAY";               /* Device-driver name        */

    hdcMeta = DevOpenDC(hab,
                        OD_METAFILE,             /* Metafile DC               */
                        "*",                     /* No data in OS2.INI        */
                        2,                       /* Use first 2 fields in dop */
                        (PDEVOPENDATA) &dop,     /* Structure for system info */
                        NULL)                    /* Compatible with screen    */