dmRealizeObjectThe brute functions is a set of graphics-support functions that a printer driver can use to carry out certain graphics operations. The brute functions permit a printer driver to use the resources of GDI rather than provide its own support to complete some graphics operations.
Brute functions primarily provide support for memory bitmaps. On each call to a printer-driver function, the driver checks the PDEVICE structure and determines if it represents a memory bitmap. If such cases, the driver calls a corresponding brute function, passing on all the parameters, to carry out the graphics operation.
For banding drivers, the driver calls the brute functions for the main output device as well as for the memory bitmaps.
The following brute functions take the same parameters and return values as the corresponding driver functions and actually call the display driver to manipulate monochrome memory bitmaps:
dmRealizeObject
dmEnumDFonts
dmEnumObject
dmColorInfo
For graphics, most raster drivers call the dmColorInfo function to map colors. Display drivers then add together the three color components (R, G, and B). If the weighted, average color value of these components is equal to or greater than 128, then the color maps to white. Otherwise, it maps to black.
The IBM Color Printer driver does the same thing in monochrome mode. However, in color mode, each color is compared individually to the 128 value. Hewlett-Packard printers that use the PCL driver are only adjustable for text.
Notice that the following colors all map to white on EGA, VGA, and 8514/a displays:
Light grey
Green
Yellow
Magenta
Cyan
Nonbanding drivers (such as PostScript or a plotter driver) use the brute functions to support memory bitmaps. Whenever a pointer to the driver's PDEVICE structure is passed to the driver, GDI may substitute a pointer to a BITMAP structure. The driver can differentiate between the two cases because the first member (bmType) of a BITMAP structure must be zero, whereas the first member (often called epType) of a PDEVICE structure must be nonzero. If this first member is zero, the driver simply passes the same arguments through to the corresponding brute function and returns its return value.
Banding drivers operate by using a memory bitmap to simulate the display surface. Therefore, a banding driver calls the brute function with a pointer to a BITMAP structure that defines the band bitmap. The driver also has to translate some coordinate parameters from device coordinates to bitmap coordinates since, in general, there will be many bands in different positions on a page of output. The brute functions, however, always use coordinates relative to the bitmap, that is, (0,0) to (bmWidth, bmHeight).
Therefore, many output functions may take the following form:
Function(LPPDEVICE lpDevice, ... )
{
if (!lpDevice-> epType)
{
/* output to memory bitmap */
return dmFunction(lpDevice, ... );
}
/* if this is a nonbanding driver, perform
* device-specific output. Otherwise, for a
* banding driver,
*/
/* transform coordinates according to band position
*/
somerandomxcoordinate -= lpDevice-> xBandPosition;
somerandomycoordinate -= lpDevice-> yBandPosition;
/* assume that a BITMAP structure is stored somewhere in
* the PDEVICE for the band bitmap
*/
lpDevice = (LPPDEVICE)&lpDevice-> epBandBmpHdr;
return dmFunction(lpDevice, ... );
}
The brute functions operate by calling the corresponding display driver function to manipulate a memory bitmap. Therefore, they have exactly the same parameters as the corresponding driver functions, with the exception that the lpDevice parameters are always assumed to point to BITMAP structures.
Since driver capabilities and bitmap formats vary from display to display, the printer driver should use the brute functions only for monochrome (not color) bitmaps. Also, since the scan line and polyline support is required for all display drivers, the printer driver can assume that this support is in the brute functions.
The following brute functions are available for output:
dmBitBlt
dmOutput
dmPixel
dmStrBlt
dmScanLR
There is currently no dmExtTextOut function; the driver calls the ExtTextOut function.
Although the dot-matrix (brute) library functions in GDI (such as dmBitBlt and dmOutput) only support monochrome printers, a color printer driver can call corresponding functions in the the color library which do implement color. The color library supports all the dot-matrix (dm) functions except dmTranspose. The dmTranspose function does not depend on color format. The arguments and return values of these functions are the same as those for the GDI monochrome versions of these functions.
The library implements color using a 3-plane RGB (Red, Green, Blue) banding bitmap, which is converted to CMYK (Cyan, Magenta, Yellow, Black) when the bitmap is sent to the printer. If a printer requires a different format, the color library must be modified.
Both dmBitBlt and dmOutput compile short, efficient functions into the stack segment and then call them to perform the actual operation. In protected mode, this requires creating a code segment alias for the stack segment. A selector must be allocated for these two functions to operate. It is stored in the global variable ScratchSelector, which is external to the library and which must be supplied by the driver. In the sample IBM Color Printer driver, the selector is allocated and freed in Enable and Disable, respectively.