GDIINFO

typedef struct tagGDIINFO {
    short int           dpVersion;
    short int           dpTechnology;
    short int           dpHorzSize;
    short int           dpVertSize;
    short int           dpHorzRes;
    short int           dpVertRes;
    short int           dpBitsPixel;
    short int           dpPlanes;
    short int           dpNumBrushes;
    short int           dpNumPens;
    short int           dpCapsFE;
    short int           dpNumFonts;
    short int           dpNumColors;
    short int           dpDEVICEsize;
    unsigned short int  dpCurves;
    unsigned short int  dpLines;
    unsigned short int  dpPolygonals
    unsigned short int  dpText;
    unsigned short int  dpClip;
    unsigned short int  dpRaster;
    short int           dpAspectX;
    short int           dpAspectY;
    short int           dpAspectXY;
    short int           dpStyleLen;
    POINT               dpMLoWin;
    POINT               dpMLoVpt;
    POINT               dpMHiWin;
    POINT               dpMHiVpt;
    POINT               dpELoWin;
    POINT               dpELoVpt;
    POINT               dpEHiWin;
    POINT               dpEHiVpt;
    POINT               dpTwpWin;
    POINT               dpTwpVpt;
    short int           dpLogPixelsX;
    short int           dpLogPixelsY;
    short int           dpDCManage;
    unsigned short int  dpCaps1;
    long                dpSpotSizeX;
    long                dpSpotSizeY;
    short int           dpNumPalReg;
    short int           dpPalReserved;
    short int           dpColorRes;
} GDIINFO;

Contains information about the graphics device supported by a device driver. GDI retrieves this structure when it loads the driver and uses the information in the structure to initialize the driver.

dpVersion

Version number. The high-order byte specifies the major version, the low-order byte the minor version. For example, in a device driver developed for Windows 3.1, this member should contain 0x030A.

dpTechnology

Device technology. Can be one of these values:

All other values are reserved.

dpHorzSize

Width, in millimeters, of the physical display surface.

dpVertSize

Height, in millimeters, of the physical display surface.

dpHorzRes

Width, in pixels, of the display surface. For nonraster devices, this width is equivalent to the number of vertical grid lines used by the device to plot points on the display surface. In such cases, a pixel is defined to be the smallest mark the device can draw.

dpVertRes

Height, in raster lines, of the display. For nonraster devices, this height is equivalent to the number of horizontal grid lines used by the device to plot points on the display surface. In such cases, a raster line is equivalent to a gridline.

dpBitsPixel

Number of adjacent bits on each plane required to define a single pixel.

dpPlanes

Number of planes required to define the pixels. For a typical raster device with red, green, and blue bit planes (such as a 3-plane EGA), this member is 3.

dpNumBrushes

Number of device-specific brushes supported by the device.

dpNumPens

Number of device-specific pens supported by the device.

dpCapsFE

Capability bits for Far East fonts. Can be a combination of these values:

dpNumFonts

Number of device-specific fonts supported by the device.

dpNumColors

Number of entries in the color table for the device or the number of reserved colors for a palette-capable device.

dpDEVICEsize

Size, in bytes, of the PDEVICE structure for this device. It must be at least two bytes.

dpCurves

Curve-drawing capabilities. This member specifies the types of curves a device can draw, whether the interior of those figures that can be handled can be brushed in, and whether the borders of those figures that can be handled can be drawn with wide lines, styled lines, or lines that are both wide and styled. Can be a combination of these values:

All other values are reserved.

dpLines

Polyline and line-drawing capabilities. This member also specifies the types of lines a device can draw, whether the interior of figures can be brushed in, and whether the borders of figures can be drawn with wide lines, styled lines, or lines that are both wide and styled. Can be a combination of these values:

All other values are reserved. The high-order byte must be zero.

dpPolygonals

Polygon-, rectangle-, and scan-line drawing capabilities. This member also specifies whether the interior of those figures that can be handled can be brushed in, and whether the borders of those figures that can be handled can be drawn with wide lines, styled lines, or lines that are both wide and styled. Can be a combination of these values:

All other values are reserved. The high byte must be zero.

dpText

Level of text support the device driver provides. Can be a combination of these values:

If one of these values is specified, the device must support that capability for all fonts, whether realized by the device or provided by GDI.

dpClip

Clipping capabilities. Can be one of these values:

dpRaster

Raster capabilities. Can be a combination of these values:

dpAspectX

Relative width of a device pixel. This value, in the range 1 through 1000, helps specify the device's aspect ratio.

dpAspectY

Relative height of a device pixel. This value, in the range 1 through 1000, helps specify the device's aspect ratio.

dpAspectXY

Relative diagonal width of a device pixel. This value, in the range 1 through 1000, helps specify the device's aspect ratio. It must be equal to the square root of the sum of the squares of dpAspectX and dpAspectY.

dpStyleLen

Minimum length of a dot generated by a styled pen. The length is relative to the width of a device pixel and should be given in the same units as dpAspectX. For example, if dpAspectX is 5 and the minimum length required is 3 pixels, dpStyleLen should be 15.

dpMLoWin

Width and height of the metric (low resolution) window. The width is dpHorzSize*10; the height is dpVertSize*10.

dpMLoVpt

Horizontal and vertical resolutions of the metric (low resolution) viewport. The horizontal resolution is dpHorzRes; the vertical resolution is –dpVertRes.

dpMHiWin

Width and height of the metric (high resolution) window. The width is dpHorzSize*100; the height is dpVertSize*100.

dpMHiVpt

Horizontal and vertical resolutions of the metric (high resolution) viewport. The horizontal resolution is dpHorzRes; the vertical resolution is –dpVertRes.

dpELoWin

Width and height of the English (low resolution) window. The width is dpHorzSize*1000; the height is dpVertSize*1000.

dpELoVpt

Horizontal and vertical resolutions of the English (low resolution) viewport. The horizontal resolution is dpHorzRes*254; the vertical resolution is –dpVertRes*254.

dpEHiWin

Width and height of the English (high resolution) window. The width is dpHorzSize*10,000; the height is dpVertSize*10,000.

dpEHiVpt

Horizontal and vertical resolutions of the English (high resolution) viewport. The horizontal resolution is dpHorzRes*254; the vertical resolution is –dpVertRes*254.

dpTwpWin

Width and height of the twip window. There are 20 twips per 1 printer's point and 72 printer's points per inch. The width is dpHorzSize*14400; the height is dpVertSize*14400.

dpTwpVpt

Horizontal and vertical resolutions of the twip viewport. The horizontal resolution is dpHorzRes*254; the vertical resolution is –dpVertRes*254.

dpLogPixelsX

Number of pixels per logical inch along a horizontal line on the display surface. This value is used to match fonts.

dpLogPixelsY

Number of pixels per logical inch along a vertical line on the display surface. This value is used to match fonts.

dpDCManage

Device-context management capabilities. Can be one of these values:

The values 0x0003, 0x0005, and 0x0007 are not valid and must not be used.

dpCaps1

Additional raster abilities. Can be one of these values:

All other values are reserved.

dpSpotSizeX

Horizontal spot size for TrueType fonts on this device.

dpSpotSizeY

Vertical spot size for TrueType fonts on this device.

dpNumPalReg

Number of entries in the device's palette. This is the total number of simultaneous colors available for palette-capable devices. Nonpalette-capable devices ignore this value.

dpPalReserved

Even number of reserved system colors available for palette-capable devices. Nonpalette-capable devices ignore this value.

dpColorRes

Palette resolution, which equals the number of bits going into video DACS. Nonpalette-capable devices ignore this value.

The dpText member requires that for each precision level the precision levels below are also set. For example, the TC_SA_INTEGER value requires that the TC_SA_DOUBLE value be set, and the TC_SA_CONTIN value requires that all three values be set. Because the lowest precision level of each capability be supported, no value is provided in dpText for the lowest level of each capability.

The dpAspectX, dpAspectY, and dpAspectXY members specify the relative width, height, and diagonal width of a device pixel and correspond directly to the device's aspect ratio. For devices whose pixels do not have integral diagonal widths, the member values can be multiplied by a convenient factor to preserve information. For example, pixels on a device with a 1 to 1 aspect ratio have a diagonal width of 1.414. For reasonable results, the aspect members should be set to 100, 100, and 141, respectively. For numerical stability, the member values should be kept under 1000.

The window/viewport pair members are the numerator and denominator of the scale fraction used to correct for the device aspect ratio, and to set to a fixed unit of measurement, either metric or English. These numbers should be integers in the range of -32768 through 32767. When calculating these constants, out-of-range values can be divided by some number to bring them back into range as long as the corresponding window or viewport constant is divided by the same number.

The dpRaster member is also used to specify scaling support. If the RC_SCALING value is set, the device does graphics scaling. Certain devices perform graphics at one resolution and text at another. Some applications require that character cells be an integral number of pixels. If a device reports that its graphics resolution is 75 dpi but its text resolution is 300 dpi, its character cells are not an integral number of pixels (because they are digitized at 300 dpi). To get around this problem, GDI uses scaling devices. The device driver registers itself as a 300 dpi device but all the graphics at 300 dpi are scaled to 75 dpi. Any device that scales must have the RC_SCALING value set. Scaling always reduces the resolution; it never increases it. GDI calls the Control function with GETSCALINGFACTOR escape before output to a device. The scaling factor is a shift count that is a power of two. Therefore, a scaling factor of 2 means "reduce by 4", and a scaling factor of 1 means "reduce by 2". Scaling devices are strongly discouraged because compatible bitmaps to scaling devices cannot image both graphics and text.

The number of reserved colors on the palette is always 20, with 16 corresponding to the VGA colors and 4 special colors. Half of the reserved palette colors are placed at the beginning and half at the end of the palette.

See also Enable, PDEVICE