ExtEscape function

The ExtEscape function enables an application to access device capabilities that are not available through GDI.

Syntax

int ExtEscape(
  HDC    hdc,
  int    iEscape,
  int    cjInput,
  LPCSTR lpInData,
  int    cjOutput,
  LPSTR  lpOutData
);

Parameters

hdc

A handle to the device context.

iEscape

The escape function to be performed. It can be one of the following or it can be an application-defined escape function.

Value Meaning
CHECKJPEGFORMAT
Checks whether the printer supports a JPEG image.
CHECKPNGFORMAT
Checks whether the printer supports a PNG image.
DRAWPATTERNRECT
Draws a white, gray-scale, or black rectangle.
GET_PS_FEATURESETTING
Gets information on a specified feature setting for a PostScript driver.
GETTECHNOLOGY
Reports on whether or not the driver is a Postscript driver.
PASSTHROUGH
Allows the application to send data directly to a printer. Supported in compatibility mode and GDI-centric mode.
POSTSCRIPT_DATA
Allows the application to send data directly to a printer. Supported only in compatibility mode.
POSTSCRIPT_IDENTIFY
Sets a PostScript driver to GDI-centric or PostScript-centric mode.
POSTSCRIPT_INJECTION
Inserts a block of raw data in a PostScript job stream.
POSTSCRIPT_PASSTHROUGH
Sends data directly to a PostScript printer driver. Supported in compatibility mode and PostScript-centric mode.
QUERYESCSUPPORT
Determines whether a particular escape is implemented by the device driver.
SPCLPASSTHROUGH2
Enables applications to include private procedures and other resources at the document level-save context.

cjInput

The number of bytes of data pointed to by the lpszInData parameter.

lpInData

A pointer to the input structure required for the specified escape. See also Remarks.

cjOutput

The number of bytes of data pointed to by the lpszOutData parameter.

lpOutData

A pointer to the structure that receives output from this escape. This parameter must not be NULL if ExtEscape is called as a query function. If no data is to be returned in this structure, set cbOutput to 0. See also Remarks.

Return Value

The return value specifies the outcome of the function. It is greater than zero if the function is successful, except for the QUERYESCSUPPORT printer escape, which checks for implementation only. The return value is zero if the escape is not implemented. A return value less than zero indicates an error.

Remarks

Note  This is a blocking or synchronous function and might not return immediately. How quickly this function returns depends on run-time factors such as network status, print server configuration, and printer driver implementation—factors that are difficult to predict when writing an application. Calling this function from a thread that manages interaction with the user interface could make the application appear to be unresponsive.
 
Use this function to pass a driver-defined escape value to a device.

Use the Escape function to pass one of the system-defined escape values to a device, unless the escape is one of the defined escapes in nEscape. ExtEscape might not work properly with the system-defined escapes. In particular, escapes in which lpszInData is a pointer to a structure that contains a member that is a pointer will fail.

Note, that the behavior described in this article is the expected behavior, but it is up to the driver to comply with this model.

The variables referenced by lpszInData and lpszOutData should not be the same or overlap. If the input and the output buffer size variables overlap, they may not contain the correct values after the call returns. For the best results, lpszInData and lpszOutData should refer to different variables.

The CHECKJPEGFORMAT printer escape function determines whether a printer supports printing a JPEG image.

Before using the CHECKJPEGFORMAT printer escape function, call the QUERYESCSUPPORT printer escape function to determine whether the driver supports CHECKJPEGFORMAT. For sample code that demonstrates the use of CHECKJPEGFORMAT, see Testing a Printer for JPEG or PNG Support.

The CHECKPNGFORMAT printer escape function determines whether a printer supports printing a PNG image.

Before using the CHECKJPEGFORMAT printer escape function, call the QUERYESCSUPPORT printer escape function to determine whether the driver supports CHECKJPEGFORMAT. For sample code, see Testing a Printer for JPEG or PNG Support.

The DRAWPATTERNRECT printer escape creates a white, gray scale, or solid black rectangle by using the pattern and rule capabilities of Page Control Language (PCL) on Hewlett-Packard LaserJet or LaserJet-compatible printers. A gray scale is a gray pattern that contains a specific mixture of black and white pixels.

An application should use the QUERYESCSUPPORT escape to determine whether the printer is capable of drawing patterns and rules before using the DRAWPATTERNRECT escape.

  • Rules drawn with DRAWPATTERNRECT are not subject to clipping regions in the device context.
  • Applications should not try to erase patterns and rules created with DRAWPATTERNRECT by placing opaque objects over them.

If the printer supports white rules, these can be used to erase patterns created by DRAWPATTERNRECT. If the printer does not support white rules, there is no method for erasing these patterns.

If an application cannot use the DRAWPATTERNRECT escape and the device is a printer, it should generally use the PatBlt function instead. Note that if PatBlt is used to print a black rectangle, the application should use the BLACKNESS raster operator. If the device is a plotter, however, the application should use the Rectangle function.

The GET_PS_FEATURESETTING printer escape function retrieves information about a specified feature setting for a PostScript driver.

This escape function is supported only if the PostScript driver is in PostScript-centric mode or in GDI-centric mode. To set the PostScript driver mode, call the POSTSCRIPT_IDENTIFY escape function.

To perform this operation, call the ExtEscape function with the following parameters.

The GET_PS_FEATURESETTING printer escape function is valid if called any time after calling the CreateDC function and before calling the DeleteDC function.

The GETTECHNOLOGY printer escape function identifies the type of printer driver.

For non-XPSDrv printers, this escape reports whether the driver is a Postscript driver.

For XPSDrv printers, this escape reports whether the driver is the Microsoft XPS Document Converter (MXDC). If it is, the escape returns the zero-terminated string "http://schemas.microsoft.com/xps/2005/06"

The PASSTHROUGH printer escape function sends data directly to a printer driver. To perform this operation, call the ExtEscape function with the following parameters.

The PASSTHROUGH printer escape function is supported by PostScript drivers in GDI-centric mode or compatibility mode, but not in PostScript-centric mode. Drivers in PostScript-centric mode can use the POSTSCRIPT_PASSTHROUGH escape function. To set a PostScript driver mode, call the POSTSCRIPT_IDENTIFY escape function.

For PASSTHROUGH data sent by EPSPRINTING or PostScript-centric applications, the PostScript driver will not make any modifications. For PASSTHROUGH data sent by other applications, if the PostScript driver is using BCP (Binary Communication Protocol) or TBCP (Tagged Binary Communication Protocol) output protocol, the driver does the appropriate BCP or TBCP quoting on special characters, as described in "Adobe Serial and Parallel Communications Protocols Specification." This means that the application should send either ASCII or pure binary PASSTHROUGH data.

The POSTSCRIPT_DATA printer escape function sends data directly to a printer driver. To perform this operation, call the ExtEscape function with the following parameters.

The POSTSCRIPT_DATA function is identical to the PASSTHROUGH escape function except that it is supported by PostScript drivers in compatibility mode only. It is not supported by PostScript drivers in PostScript-centric mode or in GDI-centric mode.

Drivers in PostScript-centric mode can use the POSTSCRIPT_PASSTHROUGH escape function, and drivers in GDI-centric mode can use the PASSTHROUGH escape function. To set a PostScript driver's mode, call the POSTSCRIPT_IDENTIFY escape function.

The POSTSCRIPT_IDENTIFY printer escape function sets a PostScript driver to GDI-centric mode or PostScript-centric mode.

To put the driver in GDI-centric or PostScript-centric modes, first call the QUERYESCSUPPORT printer escape function to determine whether the driver supports the POSTSCRIPT_IDENTIFY printer escape function. If so, you can assume the driver is PSCRIPT 5.0. Then, before you call any other printer escape function, you must call POSTSCRIPT_IDENTIFY and specify either PSIDENT_GDICENTRIC or PSIDENT_PSCENTRIC. You must call the QUERYESCSUPPORT and POSTSCRIPT_IDENTIFY printer escape functions before calling any other printer escape function.

Note  After the PostScript driver is set to GDI-centric mode or PostScript-centric mode, you will not be allowed to call the POSTSCRIPT_IDENTIFY printer escape function anymore.
 
If you do not use the POSTSCRIPT_IDENTIFY printer escape function, the PostScript driver is in compatibility mode and provides identical support for the PASSTHROUGH, POSTSCRIPT_PASSTHROUGH, and POSTSCRIPT_DATA printer escape functions.

For PostScript drivers that support the POSTSCRIPT_PASSTHROUGH, PASSTHROUGH, and POSTSCRIPT_PASSTHROUGH printer escape functions are identical.

In PostScript-centric mode, the application is responsible for all PostScript output that marks the paper using the POSTSCRIPT_PASSTHROUGH escape function. GDI functions are not allowed. The driver is responsible for the overall document structure and printer control settings. The application can use the POSTSCRIPT_INJECTION printer escape function to inject a block of raw data (including DSC comments) into the job stream at specific places.

The POSTSCRIPT_INJECTION printer escape function inserts a block of raw data at a specified point in a PostScript job stream.

A PostScript driver supports this escape function in GDI-centric mode or PostScript-centric mode support, but not in compatibility mode.

To set the PostScript driver's mode, call the POSTSCRIPT_IDENTIFY escape function.

To perform this operation, call the ExtEscape function with the following parameters.

The driver internally caches the injection data and emits it at appropriate points in the output. The cached information is flushed when it is no longer needed. At the latest, it is flushed after the EndDoc call.

In GDI-centric mode, the application can only inject valid DSC block data by using the POSTSCRIPT_INJECTION printer escape function. A valid DSC block must satisfy all of the following conditions:

  • It consists of an integral sequence of "lines."
  • Each "line" must begin with "%%".
  • Each "line" except the last line must end with <CR>, <LF>, or <CR><LF> except for the last line. If the last line does not end with <CR>, <LF>, or <CR><LF>, the driver appends <CR><LF> after the last byte of the injection data.
  • Each "line" must be 255 bytes or less including the "%%" but not counting the <CR>/<LF> line termination.
The POSTSCRIPT_PASSTHROUGH printer escape function sends data directly to a PostScript printer driver.

A PostScript driver supports this escape function when in PostScript-centric mode or in compatibility mode, but not in GDI-centric mode.

To set the PostScript driver's mode, call the POSTSCRIPT_IDENTIFY escape function.

The QUERYESCSUPPORT printer escape function checks the implementation of a printer escape function.

The SPCLPASSTHROUGH2 printer escape function allows applications that print to PostScript devices using EPSPRINTING to include private PostScript procedures and other resources at the document-level save context.

This escape is supported only for backward compatibility with Adobe Acrobat. Other applications should not use this obsolete escape.

The application must call this escape before calling StartDoc so that the driver will cache the data for insertion at the correct point in the PostScript stream. If this escape is supported, the driver will also allow escape DOWNLOADFACE calls prior to StartDoc. The driver internally caches the data to be inserted and the data required by any escape DOWNLOADFACE calls prior to StartDoc and emits them all immediately before %%EndProlog. The sequence of SPCLPASSTHROUGH2 and DOWNLOADFACE calls will be preserved in the order their data is passed in, that is, a later call results in data output after an earlier call's data. The driver will consider fonts downloaded by pre-StartDoc escape DOWNLOADFACE calls as unavailable for removal during the scope of the job.

This escape is not recorded in EMF files by the operating system, therefore applications must ensure that EMF recording is turned off for those jobs using the escape.

Examples

For an example, see Sizing a JPEG or PNG Image.

Requirements

   
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

See Also

Escape

GetDeviceCaps

Print Spooler API Functions

Printing