The Read Text from Display routine reads a line of text from a
    virtual display.

    Format

      SMG$READ_FROM_DISPLAY  display-id ,resultant-string

                             [,terminator-string] [,start-row]

                             [,rendition-string]

1  –  Returns

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

2  –  Arguments

 display-id

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

    Specifies the virtual display from which text is read. The
    display-id argument is the address of an unsigned longword that
    contains the display identifier.

    The display identifier is returned by SMG$CREATE_VIRTUAL_DISPLAY.

 resultant-string

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

    String into which SMG$READ_FROM_DISPLAY writes the information
    read from the virtual display. The resultant-string argument is
    the address of a descriptor pointing to the string into which the
    string is written.

 terminator-string

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

    String containing a terminator or terminators that end the
    backward search, thus determining the starting position of
    the returned string. The terminator-string argument is the
    address of a descriptor pointing to the string of terminators.
    If terminator-string is omitted, no back searching is performed;
    the returned string starts with the character at the current
    cursor position.

 start-row

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

    The start-row argument is the address of a signed longword that
    contains the row of the virtual display to read from. This is an
    optional argument.

 rendition-string

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

    Optional bit mask string that controls the video attributes.
    The rendition-string argument is the address of a descriptor
    pointing to the bit mask string. Each attribute set causes the
    corresponding attribute to be set for the corresponding byte in
    the text string in the display. The following attributes can be
    specified for each byte using the rendition-string argument:

    SMG$M_BLINK     Displays blinking characters.
    SMG$M_BOLD      Displays characters in higher-than-normal
                    intensity.
    SMG$M_REVERSE   Displays characters in reverse video; that is,
                    using the opposite of the default rendition of
                    the virtual display.
    SMG$M_          Displays underlined characters.
    UNDERLINE
    SMG$M_          Specifies invisible characters; that is, the
    INVISIBLE       characters exist in the virtual display but do
                    not appear on the pasteboard.