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The 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.
 
Brute-Information Functions
 
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
 
Brute-Output Functions
 
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.
 
Color-Library Functions
 
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.
 
 
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