Updated: 11 December 1998

OpenVMS RTL Screen Management (SMG$) Manual

The output generated by this Fortran program is shown in Figure SMG-37.

Figure SMG-37 Output Generated by Fortran Program Calling SMG$READ_KEYSTROKE

1       OPTION TYPE=EXPLICIT 
 
        !+ 
        ! This VAX BASIC program demonstrates the use of 
        ! SMG$READ_KEYSTROKE to read a keystroke from the terminal. 
        ! 
 
        DECLARE LONG kb_id, ret_status, term_code, I, timer 
        EXTERNAL SUB LIB$SIGNAL( LONG BY VALUE ) 
        EXTERNAL SUB LIB$STOP( LONG BY VALUE ) 
        EXTERNAL LONG CONSTANT SS$_TIMEOUT 
 
 %INCLUDE "$SMGDEF" %FROM %LIBRARY "SYS$LIBRARY:BASIC$STARLET" 
 
        EXTERNAL LONG FUNCTION SMG$CREATE_VIRTUAL_KEYBOARD( LONG, STRING ) 
        EXTERNAL LONG FUNCTION SMG$DELETE_VIRTUAL_KEYBOARD( LONG ) 
        EXTERNAL LONG FUNCTION SMG$READ_KEYSTROKE( LONG, LONG, STRING, & 
            LONG, LONG ) 
 
 
        !+ 
        ! Prompt the user for the timer value.  A value of 0 will cause 
        ! the type ahead buffer to be read. 
        !- 
 
        INPUT "Enter timer value (0 to read typeahead buffer):  ";timer 
 
        !+ 
        ! Establish a SMG connection to SYS$INPUT.  Signal any unexpected 
        ! errors. 
        !- 
 
        ret_status = SMG$CREATE_VIRTUAL_KEYBOARD( kb_id, "SYS$INPUT:" ) 
        IF (ret_status AND 1%) = 0% THEN 
            CALL LIB$SIGNAL( ret_status ) 
        END IF 
 
        !+ 
        !   Read a keystoke, tell the user what we found. 
        !- 
 
        ret_status = SMG$READ_KEYSTROKE( kb_id, term_code, , timer, ) 
        IF (ret_status <> SS$_TIMEOUT) AND ((ret_status AND 1%) = 0%) THEN 
            CALL LIB$SIGNAL( ret_status ) 
        END IF 
 
        PRINT "term_code = ";term_code 
        SELECT term_code 
 
            CASE 0 TO 31 
                PRINT "You typed a control character" 
 
            CASE 32 TO 127 
                PRINT "You typed: ";CHR$(term_code) 
 
            CASE SMG$K_TRM_PF1 TO SMG$K_TRM_PERIOD 
                PRINT "You typed one of the keypad keys" 
 
            CASE SMG$K_TRM_UP TO SMG$K_TRM_RIGHT 
                PRINT "You typed one of the cursor positioning keys" 
 
            CASE SMG$K_TRM_F6 TO SMG$K_TRM_F20 
                PRINT "You typed one of the function keys" 
 
            CASE SMG$K_TRM_FIND TO SMG$K_TRM_NEXT_SCREEN 
                PRINT "You typed one of the editing keys" 
 
            CASE SMG$K_TRM_TIMEOUT 
                PRINT "You did not type a key fast enough" 
 
            CASE ELSE 
                PRINT "I'm not sure what key you typed" 
 
        END SELECT 
 
        !+ 
        ! Close the connection to SYS$INPUT, and signal any errors. 
        !- 
 
        ret_status = SMG$DELETE_VIRTUAL_KEYBOARD( kb_id ) 
        IF (ret_status AND 1%) = 0% THEN 
            CALL LIB$SIGNAL( ret_status ) 
        END IF 
 
        END 
 
 
      

This BASIC program reads a key and returns the word-terminator-code and the name of the keystroke entered. One sample of the commands entered and the output generated by this program is as follows:

$ RUN READ_KEY Enter the timer value (0 to read type-ahead buffer): ? 9 term_code = 100 You typed: d

Note that, in this example, the user entered the keystroke "d" following the first prompt. The keystroke entered was not echoed.

The Read Locator Information routine reads information from a DECwindows workstation terminal's locator device (such as a mouse or tablet).

Format

SMG$READ_LOCATOR keyboard-id ,row-number ,column-number ,word-terminator-code [,timeout] [,parse-routine]

RETURNS

OpenVMS usage:	cond_value
type:	longword (unsigned)
access:	write only
mechanism:	by value

Arguments

keyboard-id

OpenVMS usage:	identifier
type:	longword (unsigned)
access:	read only
mechanism:	by reference

Keyboard identifier. The keyboard-id argument is the address of an unsigned longword containing the identifier of the desired virtual keyboard.

You can create a virtual keyboard by calling the SMG$CREATE_VIRTUAL_KEYBOARD routine.

row-number

OpenVMS usage:	word_unsigned
type:	word (unsigned)
access:	read only
mechanism:	by reference

Row number to which the locator is pointing. The row-number argument is the address of an unsigned word that contains the row number of the virtual display at which the read is to be performed.

column-number

OpenVMS usage:	word_unsigned
type:	word (unsigned)
access:	read only
mechanism:	by reference

Column number to which the locator is pointing. The column-number argument is the address of an unsigned word that contains the column number of the virtual display at which the read is to be performed.

word-terminator-code

OpenVMS usage:	word_unsigned
type:	word (unsigned)
access:	write only
mechanism:	by reference

Locator terminator code. The word-terminator-code argument is the address of an unsigned word into which is written a code indicating what locator button terminated the read. Locator terminator codes are of the form SMG$K_TRM_keyname. The key names are listed in Table 3-1.

timeout

OpenVMS usage:	longword_signed
type:	longword (signed)
access:	read only
mechanism:	by reference

Timeout count. The optional timeout argument is the address of a signed longword that contains a number of seconds. If specified, any character typed before the timeout is returned in the buffer.

parse-routine

OpenVMS usage:	longword_unsigned
type:	longword (signed)
access:	read only
mechanism:	by reference

Address of a user-supplied parse routine that is called to parse the locator input. The optional parse-routine argument is the address of an unsigned longword that contains the parse routine. If this argument is not specified, ANSI locator input is assumed.

For more information on the parse routine, see Call Format for a Parse Routine in the Description section.

Description

SMG$READ_LOCATOR reads information from a DECwindows workstation terminal's locator device. (This routine does not read locator information from the VT300 series terminals.) A locator device is a mouse or a tablet. This routine returns the row and column specified by the locator, as well as the button pressed. This routine assumes the locator will respond with an ANSI response. If another format is used, you must specify the parse-routine argument with the address of a routine that is called to parse the locator response.

Call Format for a Parse Routine

The parse routine is called only if the parse-routine argument was specified in the SMG$READ_LOCATOR argument list.

The calling format of a parse routine is as follows:

parse-routine keyboard-id ,response ,row ,column ,button

Arguments

keyboard-id

OpenVMS usage:	identifier
type:	longword (unsigned)
access:	read only
mechanism:	by reference

Keyboard identifier. The keyboard-id argument is an unsigned longword containing the identifier of the desired virtual keyboard.

response

OpenVMS usage:	char_string
type:	character string
access:	read only
mechanism:	by descriptor

Locator response to be parsed. The response argument is the address of a descriptor pointing to the response string to be read.

row

OpenVMS usage:	word_unsigned
type:	word (unsigned)
access:	write only
mechanism:	by reference

Receives the row number to which the locator is pointing. The row argument is an unsigned word that contains the row number of the virtual display.

column

OpenVMS usage:	word_unsigned
type:	word (unsigned)
access:	write only
mechanism:	by reference

Receives the column number to which the locator is pointing. The column argument is an unsigned word that contains the column number of the virtual display.

button

OpenVMS usage:	word_unsigned
type:	word (unsigned)
access:	write only
mechanism:	by reference

Receives the button that was pressed. The button argument is an unsigned word that contains the button pressed. Returned value should be SMG$K_TRM_keyname.

Condition Values Returned

SS$_NORMAL	Normal successful completion.
SMG$_EOF	End of file.
SMG$_INVARG	Invalid argument.
SMG$_INVDIS_ID	Invalid display-id.
SMG$_WRONUMARG	Wrong number of arguments.

The Read String routine reads a string from a virtual keyboard.

Format

SMG$READ_STRING keyboard-id ,resultant-string [,prompt-string] [,maximum-length] [,modifiers] [,timeout] [,terminator-set] [,resultant-length] [,word-terminator-code] [,display-id] [,initial-string] [,rendition-set] [,rendition-complement] [,terminator-string]

RETURNS

OpenVMS usage:	cond_value
type:	longword (unsigned)
access:	write only
mechanism:	by value

Arguments

keyboard-id

OpenVMS usage:	identifier
type:	longword (unsigned)
access:	read only
mechanism:	by reference

Specifies the virtual keyboard from which input is to be read. The keyboard-id argument is the address of an unsigned longword that contains the keyboard identifier.

The keyboard identifier is returned by SMG$CREATE_VIRTUAL_KEYBOARD.

resultant-string

OpenVMS usage:	char_string
type:	character string
access:	write only
mechanism:	by descriptor

String into which the input line is written. The resultant-string argument is the address of a descriptor pointing to the string into which the text is written.

prompt-string

OpenVMS usage:	char_string
type:	character string
access:	read only
mechanism:	by descriptor

String used to prompt for the read operation. The prompt-string argument is the address of a descriptor pointing to the prompt string.

maximum-length

OpenVMS usage:	longword_signed
type:	longword (signed)
access:	read only
mechanism:	by reference

Specifies the maximum number of characters to be read. The maximum-length argument is the address of a signed longword that contains the maximum number of characters to be read. The maximum valid value for this argument is 512. If omitted, 512 is the default.

modifiers

OpenVMS usage:	mask_longword
type:	longword (unsigned)
access:	read only
mechanism:	by reference

Optional bit mask that specifies optional behavior. The modifiers argument is the address of an unsigned longword that contains the flag.

Valid values for modifiers are as follows:

TRM$M_TM_CVTLOW	Converts lowercase characters to uppercase characters.
TRM$M_TM_NOECHO	Characters entered are not echoed on the screen.
TRM$M_TM_NOEDIT	Advanced editing is disabled for this read operation.
TRM$M_TM_NORECALL	Line recall is disabled.
TRM$M_TM_PURGE	Type-ahead buffer is purged before read is begun.
TRM$M_TM_TRMNOECHO	Termination character, if any, is not displayed.

The TRM$ symbols are defined by the $TRMDEF macro/module in Digital-supplied system symbol libraries. See the terminal driver section of the OpenVMS I/O User's Reference Manual for more information on modifiers for read operations.

timeout

OpenVMS usage:	longword_signed
type:	longword (signed)
access:	read only
mechanism:	by reference

Specifies the number of seconds allowed between the time the prompt is issued and the completion of the input operation. The timeout argument is the address of a signed longword that contains the timeout value.

If timeout is specified, all characters typed before the expiration time or until a terminate key is entered are returned in resultant-string. If omitted, the input operation remains active until a terminator is typed.

terminator-set

OpenVMS usage:	unspecified
type:	unspecified
access:	read only
mechanism:	by descriptor, fixed length

Either a mask that specifies which characters are to be treated as terminators (short form) or a descriptor pointing to such a mask (long form). The terminator-set argument is the address of a descriptor pointing to the mask.

If you want to use terminators with ASCII values in the range 0 to 31, use the short form, which consists of two longwords. The first longword is zero, and the second longword is a terminator character bit mask. You create this mask by setting the bit that corresponds to the ASCII value of the desired terminator. For example, to specify that Ctrl/A (ASCII value 1) is a terminator, you set bit 1 in the terminator-set mask.

To use terminators with ASCII values outside the range 0 to 31, use the long form. First create a descriptor of this form:

The mask itself has the same format as that of the short form; however, the long form allows the use of a more comprehensive set of terminator characters. For example, a mask size of 16 bytes allows any 7-bit ASCII character to be set as a terminator, while a mask size of 32 bytes allows any 8-bit character to be set as a terminator. Any mask size between 1 and 32 bytes is acceptable.

If the terminator mask is all zeros, there are no specified terminators. In that case, the read terminates when the number of characters specified in maximum-length has been transferred or when timeout is reached.

If the terminator-set argument is omitted, the set of terminators is the OpenVMS default terminator set. For more information, see the OpenVMS I/O User's Reference Manual.

resultant-length

word-terminator-code

display-id

If you are using the Screen Management Facility input and output routines, this argument specifies the virtual display in which the input is to occur. The virtual display specified must be pasted to the same pasteboard as specified by keyboard-id and must not be occluded. You cannot accept input from an occluded area of the virtual display.

In the case of multiple virtual displays, each virtual display has an associated virtual cursor position. At the same time, there is a single physical cursor position corresponding to the current location of the physical cursor. If the display-id argument is specified, the read begins at the current virtual cursor position in the specified virtual display. If display-id is omitted, the read begins in the current physical cursor position. Note that the length of the prompt-string plus the key entered is limited to the number of visible columns in the display.

initial-string

rendition-set

Attribute specifier. The optional rendition-set argument is the address of a longword bit mask in which each attribute set causes the corresponding attribute to be set in the display. The following attributes can be specified using the rendition-set argument:

SMG$M_BLINK	Displays blinking characters.
SMG$M_BOLD	Displays characters in higher-than-normal intensity (bolded).
SMG$M_REVERSE	Displays characters in reverse video; that is, using the opposite default rendition of the virtual display.
SMG$M_UNDERLINE	Displays underlined characters.
SMG$M_INVISIBLE	Specifies invisible characters; that is, the characters exist in the virtual display but do not appear on the pasteboard.
SMG$M_USER1 through SMG$M_USER8	Displays user-defined attributes.

The display-id argument must be specified when you use the rendition-set argument.

rendition-complement

The optional arguments rendition-set and rendition-complement let the user control the attributes of the virtual display in which the read is done. The rendition-set argument sets certain virtual display attributes, while rendition-complement complements these attributes. If the same bit is specified in both the rendition-set and rendition-complement parameters, rendition-set is evaluated first, followed by rendition-complement. By using these two parameters together, the user can control each virtual display attribute in a single procedure call. On a single-attribute basis, the user can cause the following transformations:

Set	Complement	Action
0	0	Attribute set to default
1	0	Attribute on
0	1	Attribute set to complement of current setting
1	1	Attribute off

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