DrvBitBlt

DrvBitBlt

BOOL DrvBitBlt(

IN SURFOBJ *psoDst,
IN SURFOBJ *psoSrc,
IN SURFOBJ *psoMask,
IN CLIPOBJ *pco,
IN XLATEOBJ *pxlo,
IN RECTL *prclDst,
IN POINTL *pptlSrc,
IN POINTL *pptlMask,
IN BRUSHOBJ *pbo,
IN POINTL *pptlBrush,
IN ROP4 rop4
);

DrvBitBlt provides general bit-block transfer capabilities between device-managed surfaces, between GDI-managed standard-format bitmaps, or between a device-managed surface and a GDI-managed standard-format bitmap.

Parameters

psoDst

Points to the SURFOBJ structure that describes the surface on which to draw.

psoSrc

Points to a SURFOBJ structure that describes the source for the bit-block transfer operation, if required by the rop4 parameter.

psoMask

Points to a SURFOBJ structure that describes a surface to be used as a mask for the rop4 parameter. The mask is a bitmap with 1 bit per pixel. Typically, a mask is used to limit the area to be modified in the destination surface. Masking is selected by setting the rop4 parameter to the value 0xAACC. The destination surface is unaffected if the mask is 0x0000.

The mask will be large enough to cover the destination rectangle.

If this parameter is null and a mask is required by the rop4 parameter, the implicit mask in the brush is used.

pco

Points to a CLIPOBJ structure that limits the area to be modified. GDI services (CLIPOBJ_Xxx) that enumerate the clip region as a set of rectangles are provided. Whenever possible, GDI simplifies the clipping involved; for example, this function is never called with a single clipping rectangle. GDI clips the destination rectangle before calling this function, making additional clipping unnecessary.

pxlo

Points to a XLATEOBJ structure that specifies how color indices should be translated between the source and destination surfaces.

If the source surface is palette-managed, its colors are represented by indices into a lookup table of RGB values. The XLATEOBJ structure can be queried for a translate vector that will allow the device driver to translate any source index into a color index for the destination.

The situation is more complicated when, for example, the source is RGB, but the destination is palette-managed. In this case, the closest match to each source RGB value must be found in the destination palette. The driver can call the XLATEOBJ_iXlate service to perform this operation.

Optionally, the device driver can match colors when the target palette is the default device palette.

prclDst

Points to a RECTL structure that defines the area to be modified. This structure uses the coordinate system of the destination surface. The lower and right edges of this rectangle are not part of the bit-block transfer, meaning the rectangle is lower right exclusive.

DrvBitBlt is never called with an empty destination rectangle. The two points that define the rectangle are always well-ordered.

pptlSrc

Points to a POINTL structure that defines the upper left corner of the source rectangle, if a source exists. This parameter is ignored if there is no source.

pptlMask

Points to a POINTL structure that defines which pixel in the mask corresponds to the upper left corner of the source rectangle, if a source exists. This parameter is ignored if the psoMask parameter is null.

pbo

Points to the brush object that defines the pattern for the bit-block transfer. GDI’s BRUSHOBJ_pvGetRbrush service can be used to retrieve the device’s realization of the brush. This parameter is ignored if the rop4 parameter does not require a pattern.

pptlBrush

Points to a POINTL structure that defines the origin of the brush in the destination surface. The upper left pixel of the brush is aligned at this point, and the brush repeats according to its dimensions. This parameter is ignored if the rop4 parameter does not require a pattern.

rop4

Specifies a raster operation that defines how the mask, pattern, source, and destination pixels are combined to write to the destination surface.

This is a quaternary raster operation, which is an extension of the ternary Rop3 operation. A Rop4 has 16 relevant bits, which are similar to the 8 defining bits of a Rop3. The simplest way to implement a Rop4 is to consider its 2 bytes separately: The low byte specifies a Rop3 that should be calculated if the mask is one; the high byte specifies a Rop3 that can be calculated and applied if the mask is 0.

Return Value

The return value is TRUE if the bit-block transfer operation is successful. Otherwise, it is FALSE, and an error code is logged.

Comments

DrvBitBlt is optional if the device surface is a standard-format bitmap created using EngCreateBitmap. It is required if the device’s surface was created using EngCreateDeviceSurface. If a device’s surface is a standard-format bitmap, DrvBitBlt will not be called unless the driver hooks the call with DrvSynchronize. The driver then has the option to pass complicated transfers back to GDI by calling EngBitBlt. The EngBitBlt function divides the transfer into simpler calls for the driver.

A driver must implement DrvBitBlt if drawing is done on device-managed surfaces. At a minimum, DrvBitBlt must support the following:

·Bit-bit-block transfer between a standard format in the device’s preferred format and the device surface.

·The SRCCOPY (0xCCCC) ROP.

·Arbitrary clipping.

GDI’s CLIPOBJ_Xxx services allow the clipping to be reduced to a series of clipping rectangles. A translation vector assists in color index translation for palettes.

Note Do not dereference parameter pointers unless the ROP indicates they are needed. For example, never unnecessarily dereference pbo->iSolidColor because doing so for a ROP such as BLACKNESS can cause an access violation. (This rule also applies to any function that includes a MIX parameter.)

DrvBitBlt is a large and complex function that performs most of the work required to write a driver for a raster display device that does not have a standard format frame buffer. Sample code is provided for the Microsoft VGA driver that illustrates the basic functionality of a planar device.

For more information on raster operations, see the Win32 SDK.