GetDeviceCaps function (wingdi.h)

Článek
03/11/2023

The GetDeviceCaps function retrieves device-specific information for the specified device.

Syntax

int GetDeviceCaps(
  [in] HDC hdc,
  [in] int index
);

Parameters

[in] hdc

A handle to the DC.

[in] index

The item to be returned. This parameter can be one of the following values.

Index

Meaning

DRIVERVERSION

The device driver version.

TECHNOLOGY

Device technology. It can be any one of the following values.

DT_PLOTTER	Vector plotter
DT_RASDISPLAY	Raster display
DT_RASPRINTER	Raster printer
DT_RASCAMERA	Raster camera
DT_CHARSTREAM	Character stream
DT_METAFILE	Metafile
DT_DISPFILE	Display file

If the hdc parameter is a handle to the DC of an enhanced metafile, the device technology is that of the referenced device as specified to the CreateEnhMetaFile function. To determine whether it is an enhanced metafile DC, use the GetObjectType function.

HORZSIZE

Width, in millimeters, of the physical screen.

VERTSIZE

Height, in millimeters, of the physical screen.

HORZRES

Width, in pixels, of the screen; or for printers, the width, in pixels, of the printable area of the page.

VERTRES

Height, in raster lines, of the screen; or for printers, the height, in pixels, of the printable area of the page.

LOGPIXELSX

Number of pixels per logical inch along the screen width. In a system with multiple display monitors, this value is the same for all monitors.

LOGPIXELSY

Number of pixels per logical inch along the screen height. In a system with multiple display monitors, this value is the same for all monitors.

BITSPIXEL

Number of adjacent color bits for each pixel.

PLANES

Number of color planes.

NUMBRUSHES

Number of device-specific brushes.

NUMPENS

Number of device-specific pens.

NUMFONTS

Number of device-specific fonts.

NUMCOLORS

Number of entries in the device's color table, if the device has a color depth of no more than 8 bits per pixel. For devices with greater color depths, -1 is returned.

ASPECTX

Relative width of a device pixel used for line drawing.

ASPECTY

Relative height of a device pixel used for line drawing.

ASPECTXY

Diagonal width of the device pixel used for line drawing.

PDEVICESIZE

Reserved.

CLIPCAPS

Flag that indicates the clipping capabilities of the device. If the device can clip to a rectangle, it is 1. Otherwise, it is 0.

SIZEPALETTE

Number of entries in the system palette. This index is valid only if the device driver sets the RC_PALETTE bit in the RASTERCAPS index and is available only if the driver is compatible with 16-bit Windows.

NUMRESERVED

Number of reserved entries in the system palette. This index is valid only if the device driver sets the RC_PALETTE bit in the RASTERCAPS index and is available only if the driver is compatible with 16-bit Windows.

COLORRES

Actual color resolution of the device, in bits per pixel. This index is valid only if the device driver sets the RC_PALETTE bit in the RASTERCAPS index and is available only if the driver is compatible with 16-bit Windows.

PHYSICALWIDTH

For printing devices: the width of the physical page, in device units. For example, a printer set to print at 600 dpi on 8.5-x11-inch paper has a physical width value of 5100 device units. Note that the physical page is almost always greater than the printable area of the page, and never smaller.

PHYSICALHEIGHT

For printing devices: the height of the physical page, in device units. For example, a printer set to print at 600 dpi on 8.5-by-11-inch paper has a physical height value of 6600 device units. Note that the physical page is almost always greater than the printable area of the page, and never smaller.

PHYSICALOFFSETX

For printing devices: the distance from the left edge of the physical page to the left edge of the printable area, in device units. For example, a printer set to print at 600 dpi on 8.5-by-11-inch paper, that cannot print on the leftmost 0.25-inch of paper, has a horizontal physical offset of 150 device units.

PHYSICALOFFSETY

For printing devices: the distance from the top edge of the physical page to the top edge of the printable area, in device units. For example, a printer set to print at 600 dpi on 8.5-by-11-inch paper, that cannot print on the topmost 0.5-inch of paper, has a vertical physical offset of 300 device units.

VREFRESH

For display devices: the current vertical refresh rate of the device, in cycles per second (Hz).

A vertical refresh rate value of 0 or 1 represents the display hardware's default refresh rate. This default rate is typically set by switches on a display card or computer motherboard, or by a configuration program that does not use display functions such as ChangeDisplaySettings.

SCALINGFACTORX

Scaling factor for the x-axis of the printer.

SCALINGFACTORY

Scaling factor for the y-axis of the printer.

BLTALIGNMENT

Preferred horizontal drawing alignment, expressed as a multiple of pixels. For best drawing performance, windows should be horizontally aligned to a multiple of this value. A value of zero indicates that the device is accelerated, and any alignment may be used.

SHADEBLENDCAPS

Value that indicates the shading and blending capabilities of the device. See Remarks for further comments.

SB_CONST_ALPHA	Handles the SourceConstantAlpha member of the BLENDFUNCTION structure, which is referenced by the blendFunction parameter of the AlphaBlend function.
SB_GRAD_RECT	Capable of doing GradientFill rectangles.
SB_GRAD_TRI	Capable of doing GradientFill triangles.
SB_NONE	Device does not support any of these capabilities.
SB_PIXEL_ALPHA	Capable of handling per-pixel alpha in AlphaBlend.
SB_PREMULT_ALPHA	Capable of handling premultiplied alpha in AlphaBlend.

RASTERCAPS

Value that indicates the raster capabilities of the device, as shown in the following table.

RC_BANDING	Requires banding support.
RC_BITBLT	Capable of transferring bitmaps.
RC_BITMAP64	Capable of supporting bitmaps larger than 64 KB.
RC_DI_BITMAP	Capable of supporting the SetDIBits and GetDIBits functions.
RC_DIBTODEV	Capable of supporting the SetDIBitsToDevice function.
RC_FLOODFILL	Capable of performing flood fills.
RC_PALETTE	Specifies a palette-based device.
RC_SCALING	Capable of scaling.
RC_STRETCHBLT	Capable of performing the StretchBlt function.
RC_STRETCHDIB	Capable of performing the StretchDIBits function.

CURVECAPS

Value that indicates the curve capabilities of the device, as shown in the following table.

CC_NONE	Device does not support curves.
CC_CHORD	Device can draw chord arcs.
CC_CIRCLES	Device can draw circles.
CC_ELLIPSES	Device can draw ellipses.
CC_INTERIORS	Device can draw interiors.
CC_PIE	Device can draw pie wedges.
CC_ROUNDRECT	Device can draw rounded rectangles.
CC_STYLED	Device can draw styled borders.
CC_WIDE	Device can draw wide borders.
CC_WIDESTYLED	Device can draw borders that are wide and styled.

LINECAPS

Value that indicates the line capabilities of the device, as shown in the following table:

LC_NONE	Device does not support lines.
LC_INTERIORS	Device can draw interiors.
LC_MARKER	Device can draw a marker.
LC_POLYLINE	Device can draw a polyline.
LC_POLYMARKER	Device can draw multiple markers.
LC_STYLED	Device can draw styled lines.
LC_WIDE	Device can draw wide lines.
LC_WIDESTYLED	Device can draw lines that are wide and styled.

POLYGONALCAPS

Value that indicates the polygon capabilities of the device, as shown in the following table.

PC_NONE	Device does not support polygons.
PC_INTERIORS	Device can draw interiors.
PC_POLYGON	Device can draw alternate-fill polygons.
PC_RECTANGLE	Device can draw rectangles.
PC_SCANLINE	Device can draw a single scanline.
PC_STYLED	Device can draw styled borders.
PC_WIDE	Device can draw wide borders.
PC_WIDESTYLED	Device can draw borders that are wide and styled.
PC_WINDPOLYGON	Device can draw winding-fill polygons.

TEXTCAPS

Value that indicates the text capabilities of the device, as shown in the following table.

TC_OP_CHARACTER	Device is capable of character output precision.
TC_OP_STROKE	Device is capable of stroke output precision.
TC_CP_STROKE	Device is capable of stroke clip precision.
TC_CR_90	Device is capable of 90-degree character rotation.
TC_CR_ANY	Device is capable of any character rotation.
TC_SF_X_YINDEP	Device can scale independently in the x- and y-directions.
TC_SA_DOUBLE	Device is capable of doubled character for scaling.
TC_SA_INTEGER	Device uses integer multiples only for character scaling.
TC_SA_CONTIN	Device uses any multiples for exact character scaling.
TC_EA_DOUBLE	Device can draw double-weight characters.
TC_IA_ABLE	Device can italicize.
TC_UA_ABLE	Device can underline.
TC_SO_ABLE	Device can draw strikeouts.
TC_RA_ABLE	Device can draw raster fonts.
TC_VA_ABLE	Device can draw vector fonts.
TC_RESERVED	Reserved; must be zero.
TC_SCROLLBLT	Device cannot scroll using a bit-block transfer. Note that this meaning may be the opposite of what you expect.

COLORMGMTCAPS

Value that indicates the color management capabilities of the device.

CM_CMYK_COLOR	Device can accept CMYK color space ICC color profile.
CM_DEVICE_ICM	Device can perform ICM on either the device driver or the device itself.
CM_GAMMA_RAMP	Device supports GetDeviceGammaRamp and SetDeviceGammaRamp
CM_NONE	Device does not support ICM.

Return value

The return value specifies the value of the desired item.

When nIndex is BITSPIXEL and the device has 15bpp or 16bpp, the return value is 16.

Remarks

When nIndex is SHADEBLENDCAPS:

For a printer, GetDeviceCaps returns whatever the printer reports.
For a display device, all blending operations are available; besides SB_NONE, the only return values are SB_CONST_ALPHA and SB_PIXEL_ALPHA, which indicate whether these operations are accelerated.

On a multiple monitor system, if hdc is the desktop, GetDeviceCaps returns the capabilities of the primary monitor. If you want info for other monitors, you must use the multi-monitor APIs or CreateDC to get a HDC for the device context (DC) of a specific monitor.

Note Display1 is typically the primary monitor, but not always.

GetDeviceCaps provides the following six indexes in place of printer escapes.

Index	Printer escape replaced
PHYSICALWIDTH	GETPHYSPAGESIZE
PHYSICALHEIGHT	GETPHYSPAGESIZE
PHYSICALOFFSETX	GETPRINTINGOFFSET
PHYSICALOFFSETY	GETPHYSICALOFFSET
SCALINGFACTORX	GETSCALINGFACTOR
SCALINGFACTORY	GETSCALINGFACTOR

Note GetDeviceCaps reports info that the display driver provides. If the display driver declines to report any info, GetDeviceCaps calculates the info based on fixed calculations. If the display driver reports invalid info, GetDeviceCaps returns the invalid info. Also, if the display driver declines to report info, GetDeviceCaps might calculate incorrect info because it assumes either fixed DPI (96 DPI) or a fixed size (depending on the info that the display driver did and didn’t provide). Unfortunately, a display driver that is implemented to the Windows Display Driver Model (WDDM) (introduced in Windows Vista) causes GDI to not get the info, so GetDeviceCaps must always calculate the info.

Examples

For an example, see Preparing to Print.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	wingdi.h (include Windows.h)
Library	Gdi32.lib
DLL	Gdi32.dll

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