Determining That Display Driver Supports Transparent Mode (77934)

SUMMARY

In some display drivers compatible with Microsoft Windows, the BitBlt and StretchBlt functions support transparent mode. Before using this feature, an application must determine whether the display driver supports this mode by calling the GetDeviceCaps function.

MORE INFORMATION

Two of the multimedia display drivers, MMV7VGA.DRV and MMWD480.DRV, support transparent mode. When using GetDeviceCaps to determine the capabilities of these drivers, it is common to use the RASTERCAPS index. However, to determine if transparent mode is supported, an application must use the CAPS1 index.

Use the bitwise AND operator with C1_TRANSPARENT mask to determine if the appropriate bit is set; if it is, the driver supports transparent mode. The following code fragment demonstrates this test:

   bTransSupport = (GetDeviceCaps(hDC, CAPS1) & C1_TRANSPARENT)
                    ? TRUE : FALSE;