The GetDeviceCaps function retrieves device-specific information for the specified device.
int GetDeviceCaps(
__in HDC hdc,
__in int nIndex
);Parameters
hdc [in]
A handle to the DC.
nIndex [in]
The item to be returned. This parameter can be one of the following values.
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_NONEDevice 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, then GetDeviceCaps returns the capabilities of the primary monitor.
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 |
Examples
For an example, see Preparing to Print.
Preparing to Print
The following code sample calls the GetDeviceCaps function with the RASTERCAPS value to determine whether the selected printer is capable of printing bitmaps. If the GetDeviceCaps return value indicates that the printer does not support StretchDIBits, the sample displays a message box to inform the user. Note that when targeting a printer DC, you should use a DIB instead of a DDB.
// Examine the raster capabilities of the device identified by pd.hDC
// to verify that it supports the StretchDIBits function.
if (!(GetDeviceCaps(pd.hDC, RASTERCAPS)
& RC_STRETCHDIB))
{
DeleteDC(pd.hDC);
MessageBox(hWnd,
TEXT("Printer does not support StretchDIBits."),
TEXT("Device Error"),
MB_OK);
} After the sample application determines that the selected printer is capable of printing bitmaps, it follows these steps:
1.Sets a Boolean flag that the application can examine to determine whether to allow printing to continue.
2.Registers the application’s abort procedure, which is used to cancel a print job.
3.Displays a modeless Cancel dialog box.
4.Disables the application’s window while the dialog box is displayed.
These steps are illustrated in the following code sample.
// Set the flag used by the AbortPrintJob dialog procedure.
bPrint = TRUE;
// Register the application's AbortProc function with GDI.
SetAbortProc(pd.hDC, AbortProc);
// Display the modeless Cancel dialog box.
hdlgCancel = CreateDialog(hinst, TEXT("AbortDlg"),
hWnd, (DLGPROC) AbortPrintJob);
// Disable the application's window.
EnableWindow(hWnd, FALSE); After the application registers the AbortProc abort procedure, GDI calls the function periodically during the printing process to determine whether to cancel the job. If the user chooses to cancel the job, GDI notifies the spooler that it should delete the corresponding journal file from the print queue and reset the printer to its default state.