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 futureuse;
short int dpNumFonts;
short int dpNumColors;
unsigned 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;
short int dpCaps1;
long int dpSpotSizeX;
long int dpSpotSizeY;
short int dpPalColors;
short int dpPalReserved;
short int dpPalResolution;
} GDIINFO;
The GDIINFO structure contains information about graphics devices supported by the device driver. GDI retrieves this structure when it loads the driver and uses the information in the structure to initialize the driver.
dpVersion
Specifies the 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
Specifies the device technology. It can be one of the following values.
| Value | Meaning |
| DT_PLOTTER (0) | Vector plotter |
| DT_RASDISPLAY (1) | Raster display |
| DT_RASPRINTER (2) | Raster printer |
| DT_RASCAMERA (3) | Raster camera |
| DT_CHARSTREAM (4) | Character stream, PLP |
| DT_METAFILE (5) | Metafile, VDM |
| DT_DISPFILE (6) | Display file |
dpHorzSize
Specifies the width of the physical display surface in millimeters.
dpVertSize
Specifies the height of the physical display surface in millimeters.
dpHorzRes
Specifies the width of the display surface in pixels. 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
Specifies the height of the display in raster lines. 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
Specifies the number of adjacent bits on each plane required to define a single pixel.
dpPlanes
Specifies the 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
Specifies the number of device-specific brushes supported by this device.
dpNumPens
Specifies the number of device-specific pens supported by this device.
futureuse
Reserved; do not use.
dpNumFonts
Specifies the number of device-specific fonts supported by this device.
dpNumColors
Specifies the number of entries in the color table for this device or the number of reserved colors for palette-capable devices.
dpDEVICEsize
Specifies the size (in bytes) of the PDEVICE structure for this device. It must be at least two bytes.
dpCurves
Specifies whether the device driver can perform circles, pie wedges, chord arcs, and ellipses. The dpCurves 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. The dpCurves member can be a combination of the following values.
| Value | Meaning |
| CC_NONE (0x0000) | Curves not supported. |
| CC_CIRCLES (0x0001) | Can perform circles. |
| CC_PIE (0x0002) | Can perform pie wedges. |
| CC_CHORD (0x0004) | Can perform chord arcs. |
| CC_ELLIPSES (0x0008) | Can perform ellipses. |
| CC_WIDE (0x0010) | Can perform wide lines. |
| CC_STYLED (0x0020) | Can perform styled lines. |
| CC_WIDESTYLED (0x0040) | Can perform lines that are wide and styled. |
| CC_INTERIORS (0x0080) | Can perform interiors. |
| CC_ROUNDRECT (0x0100) | Can perform round rectangles. |
All other values are reserved.
dpLines
Specifies whether the device driver can perform polylines and lines. The dpLines 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. The dpLines member can be a combination of the following values.
| Value | Meaning |
| LC_NONE (0x0000) | Lines not supported. |
| LC_POLYLINE (0x0002) | Can perform polylines. |
| LC_WIDE (0x0010) | Can perform wide lines. |
| LC_STYLED (0x0020) | Can perform styled lines. |
| LC_WIDESTYLED (0x0040) | Can perform wide styled lines. |
| LC_INTERIORS (0x0080) | Can perform interiors. |
All other values are reserved. The high byte must be zero.
dpPolygonals
Specifies whether the device driver can perform polygons, rectangles, and scan lines. The dpPolygonals 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. The dpPolygonals member can be a combination of the following values.
| Value | Meaning |
| PC_NONE (0x0000) | Polygons not supported. |
| PC_ALTPOLYGON (0x0001) | Can perform alternate-fill polygons. |
| PC_RECTANGLE (0x0002) | Can perform rectangles. |
| PC_WINDPOLYGON (0x0004) | Can perform winding-number-fill polygons. |
| PC_SCANLINE (0x0008) | Can perform scan lines. |
| PC_WIDE (0x0010) | Can perform wide borders. |
| PC_STYLED (0x0020) | Can perform styled borders. |
| PC_WIDESTYLED (0x0040) | Can perform borders that are wide and styled. |
| PC_INTERIORS (0x0080) | Can perform interiors. |
All other values are reserved. The high byte must be zero.
dpText
Specifies the level of text support the device driver provides. The dpText member can be a combination of the following values.
| Value | Meaning |
| TC_OP_CHARACTER (0x0001) | Can generate character-precision text. If this value is not given (or implied by the TC_OP_STROKE value), the driver can generate string-precision text only. |
| TC_OP_STROKE (0x0002) | Can generate stroke-precision text. The value implies the TC_OP_CHARACTER value. |
| TC_CP_STROKE (0x0004) | Can draw partially clipped characters. If this value is not given, the character must be entirely within the clipping region to be drawn. |
| TC_CR_90 (0x0008) | Can rotate characters in 90-degree increments. If this value is not given (or implied by the TC_CR_ANY value), the driver can not rotate text. |
| TC_CR_ANY (0x0010) | Can rotate characters to any angle. This value implies the TC_CR_90 value. |
| TC_SF_X_YINDEP (0x0020) | Can scale characters independently along the x- and y-axes. If this value is not given, the driver may be able to scale characters but not independently along the axes. |
| TC_SA_DOUBLE (0x0040) | Can scale characters by doubling. If this value is not given (or implied by the TC_SA_INTEGER or TC_SA_CONTIN values), the driver cannot scale text. |
| TC_SA_INTEGER (0x0080) | Can scale characters by integral multiples. This value implies the TC_SA_DOUBLE value. |
| TC_SA_CONTIN (0x0100) | Can scale characters by any multiple. This value implies the TC_SA_DOUBLE and TC_SA_INTEGER values. |
| TC_EA_DOUBLE (0x0200) | Can generate bold characters by doubling the weight. If this value is not given, the driver cannot modify character weights. |
| TC_IA_ABLE (0x0400) | Can generate italic characters by skewing. |
| TC_UA_ABLE (0x0800) | Can generate underlined characters. |
| TC_SO_ABLE (0x1000) | Can generate struck-out characters. |
| TC_RA_ABLE (0x2000) | Can use raster fonts to generate text. |
| TC_VA_ABLE (0x4000) | Can use vector fonts to generate text. |
| TC_RESERVED (0x8000) | Reserved; must be zero. |
If a device claims to have an ability, it must have it for all fonts, whether realized by the device or provided by GDI.
dpClip
Specifies whether the device can clip output. This member can be one of the following values.
| Value | Meaning |
| CP_NONE (0) | Device cannot clip. |
| CP_RECTANGLE (1) | Device can output using a single rectangle. |
| CP_REGION (2) | Device can output using a region (which may be several rectangles). |
dpRaster
Specifies raster abilities. This member can be a combination of the following values.
| Value | Meaning |
| RC_NONE (0x0000) | Device has no raster capabilities. |
| RC_BITBLT (0x0001) | Can transfer bitmaps. The driver exports the BitBlt function. |
| RC_BANDING (0x0002) | Requires banding support. |
| RC_SCALING (0x0004) | Requires scaling support. |
| RC_BITMAP64 (0x0008) | Supports bitmaps that are larger than 64K bytes. |
| RC_GDI20_OUTPUT (0x0010) | Supports the Windows 2.x functions. The driver exports the ExtTextOut, GetCharWidth, and FastBorder functions. |
| RC_GDI20_STATE (0x0020) | Supports state blocks in device contexts. |
| RC_SAVEBITMAP (0x0040) | Saves bitmaps locally in “shadow” memory. Driver exports the SaveScreenBitmap function. |
| RC_DI_BITMAP (0x0080) | Can get and set device-independent bitmaps (DIBs). The Driver exports the DeviceBitmapBits function. |
| RC_PALETTE (0x0100) | Can do color-palette management. |
| RC_DIBTODEV (0x0200) | Can transfer device-independent bitmaps directly to device. The driver exports the SetDIBitsToDevice function. |
| RC_BIGFONT (0x0400) | Supports Windows 3.x fonts. If this value is not given, GDI ensures that the driver receives Windows 2.x fonts only. |
| RC_STRETCHBLT (0x0800) | Can stretch and compress bitmaps while transferring the bitmap. The driver exports the StretchBlt function. |
| RC_FLOODFILL (0x1000) | Can perform flood filling. The driver exports the FloodFill function. |
| RC_STRETCHDIB (0x2000) | Can stretch and compress device-independent bitmaps while transferring the bitmap. The driver exports the StretchDIBits function. |
| RC_OP_DX_OUTPUT (0x4000) | Can fill opaque rectangle and set character widths on calls to the ExtTextOut function. |
| RC_DEVBITS (0x8000) | Supports device bitmaps. Driver exports the BitmapBits and SelectBitmap function. |
dpAspectX
Specifies the relative width of a device pixel. This value, in the range 1 to 1000, helps specify the device's aspect ratio.
dpAspectY
Specifies the relative height of a device pixel. This value, in the range 1 to 1000, helps specify the device's aspect ratio.
dpAspectXY
Specifies the relative diagonal width of a device pixel. This value, in the range 1 to 1000, helps specify the device's aspect ratio. It must be equal to the square root of the sum of the squares of the dpAspectX and dpAspectY members.
dpStyleLen
Specifies the 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 the dpAspectX member. For example, if dpAspectX is 5 and the minimum length required is 3 pixels, the dpStyleLen member should be 15.
dpMLoWin
Specifies the width and height of the metric (low resolution) window. Width is dpHorzSize*10; height is dpVertSize*10.
dpMLoVpt
Specifies the horizontal and vertical resolutions of the metric (low resolution) viewport. Horizontal is dpHorzRes; vertical is –dpVertRes.
dpMHiWin
Specifies the width and height of the metric (high resolution) window. Width is dpHorzSize*100; height is dpVertSize*100.
dpMHiVpt
Specifies the horizontal and vertical resolutions of the metric (high resolution) viewport. Horizontal is dpHorzRes; vertical is –dpVertRes.
dpELoWin
Specifies the width and height of the English (low resolution) window. Width is dpHorzSize*1000; height is dpVertSize*1000.
dpELoVpt
Specifies the horizontal and vertical resolutions of the English (low resolution) viewport. Horizontal is dpHorzRes*254; vertical is –dpVertRes*254.
dpEHiWin
Specifies the width and height of the English (high resolution) window. Width is dpHorzSize*10,000; height is dpVertSize*10,000.
dpEHiVpt
Specifies the horizontal and vertical resolutions of the English (high resolution) viewport. Horizontal is dpHorzRes*254; vertical is –dpVertRes*254.
dpTwpWin
Specifies the width and height of the twip window. There are 20 twips per 1 printer's point and 72 printer's points per inch. Width is dpHorzSize*14400; height is dpVertSize*14400.
dpTwpVpt
Specifies the horizontal and vertical resolutions of the twip viewport. Horizontal is dpHorzRes*254; vertical is –dpVertRes*254.
dpLogPixelsX
Specifies the number of pixels per logical inch along a horizontal line on the display surface. This is used to match fonts.
dpLogPixelsY
Specifies the number of pixels per logical inch along a vertical line on the display surface. This is used to match fonts.
dpDCManage
Specifies whether the device driver can manage multiple device contexts (DC). This member can be one of the following values.
| Value | Meaning |
| 0x0000 | Driver allows multiple DCs. It creates a new PDEVICE for each DC that specifies a new device and filename pair, but uses the same PDEVICE for any subsequent DCs that specify the same device and filename pair. |
| DC_SPDEVICE (0x0001) | Driver allows multiple DCs but it creates a new PDEVICE for each DC regardless of whether the device and filename pairs are the same. |
| DC_1PDEVICE (0x0002) | Driver allows multiple DCs but only if all DCs have unique device and filename pairs. The driver creates a PDEVICE for each DC. The driver returns an error on any attempt to create a second DC with an existing device and filename pair. |
| DC_IGNOREDFNP (0x0004) | Driver allows multiple DCs but only creates one PDEVICE. All DCs share the same PDEVICE regardless of the device and filename pairs. |
| 0x0006 | Driver allows only one DC. The driver returns an error on any attempt to create a second DC. |
The values 0x0003, 0x0005, and 0x0007 are not valid and must not be used.
dpCaps1
Specifies additional raster abilities. The member can be one of the following values.
| Value | Meaning |
| C1_TRANSPARENT (0x0001) | Performs BitBlt and StretchBlt functions with a transparent background. |
| TC_TT_ABLE (0x0002) | Informs GDI that the driver is capable of producing TrueType as raster fonts. The driver must call the dmExtTextOut function to draw the raster font into the bitmap. The value is similar to TC_RA_ABLE. |
All other values are reserved.
dpSpotSizeX
Specifies the horizontal spot size for TrueType fonts on this device.
dpSpotSizeY
Specifies the vertical spot size for TrueType fonts on this device.
dpPalColors
Specifies the total number of simultaneous colors available in Windows 3.x for palette-capable devices. Nonpalette-capable devices ignore this value.
dpPalReserved
Specifies the even number of reserved system colors available in Windows 3.x for palette-capable devices. Nonpalette-capable devices ignore this value.
dpPalResolution
Specifies the 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 that the precision levels below it are also set. For example, the TC_SA_INTEGER value requires that the the TC_SA_DOUBLE value be set, and the TC_SA_CONTIN value requires that all three be set. Since it is required that the lowest precision level of each ability be supported, no value is provided in dpText for the lowest level of each ability.
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 good 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 to 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 indicate a scaling device. 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 reported that its graphics resolution was 75 dpi but its text resolution was 300 dpi, then its character cells would not be an integral number of pixels (since they were digitized at 300 dpi). To get around this problem, GDI uses scaling devices. The device driver registers itself as a 300 dpi device and 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 func-tion 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.
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.
Enable, Control, GETSCALINGFACTOR, PDEVICE