/ 
TUI-Vision-2.000_002
/ TUI::TextView::TextDevice

NAME

TUI::TextView::TextDevice - abstract base class for text output devices

HIERARCHY

TObject
  TView
    TScroller
      TTextDevice

DESCRIPTION

TTextDevice is an abstract base class for text-based output devices in Turbo Vision. It represents a scrollable, TTY-like text view and provides the common infrastructure required by terminal-style views.

The class itself does not implement a concrete device. Instead, it defines a minimal interface for reading and writing text buffers that must be implemented by derived classes such as TTerminal. In addition to the scrolling behavior inherited from TScroller, TTextDevice integrates with Perl's IO::Handle interface and supports standard output methods such as print, printf, and say.

Most input-related methods are implemented as stubs and return fixed values. Reading support must be provided explicitly by subclasses if required.

ATTRIBUTES

The following attributes are exposed as read-only accessors and are intended for internal use by the text device implementation.

opened

Indicates whether the device is considered open. This attribute defaults to true and is managed internally.

The following attributes are private and not part of the public API. They are documented here for completeness only.

egress

Internal output buffer used for staged writes.

esize

Size of the internal output buffer (default: 2048 bytes).

autoflush

Boolean flag controlling whether output is flushed automatically after each write operation.

METHODS

new_TTextDevice

my $device = new_TTextDevice($bounds, $aHScrollBar, $aVScrollBar);

Factory constructor for creating a new TTextDevice instance. This constructor delegates initialization to TScroller and prepares the object for use as a text output device.

autoflush

my $value = $self->autoflush();
$self->autoflush($value);

Gets or sets the autoflush flag. When enabled, output is flushed automatically after each write operation.

do_sputn

my $num = $self->do_sputn($string, $count);

Abstract output method used internally by syswrite. Derived classes must override this method to perform actual output operations.

print

my $success = $self->print(@list);

Appends data to the device using syswrite internally.

printf

my $success = $self->printf($format, @list);

Formats data and appends it to the device using syswrite internally.

say

my $success = $self->say(@list);

Appends data followed by a newline and writes it to the device.

printflush

my $success = $self->printflush(@list);

Appends data to the device and forces an immediate flush.

syswrite

my $num | undef = $self->syswrite($scalar, | $length, | $offset);

Writes raw data to the device. This method delegates the actual output operation to do_sputn and mirrors the behavior of the original Turbo Vision runtime.

flush

my $success | undef = $self->flush();

Flushes any buffered output. Returns "0 but true" on success.

name

my $name = $self->name();

Returns the class name ("TTextDevice").

eof

my $bool = $self->eof();

Indicates end-of-file. This implementation always returns true.

error

my $bool = $self->error();

Returns the error state. This implementation always returns false.

clearerr

my $value = $self->clearerr();

Clears the error state. This implementation performs no action.

read

my $num = $self->read($buf, $len, | $offset);

Stub method for reading data. Always returns an empty result in this class.

getline

my $line | undef = $self->getline();

Stub method for reading a line. Always returns an empty result.

getlines

my @lines = $self->getlines();

Stub method for reading all lines. Always returns an empty list.

getc

my $char = $self->getc();

Stub method for reading a single character.

ungetc

my $success = $self->ungetc($ord);

Stub method for pushing a character back into the input stream.

binmode

my $success = $self->binmode(| $layer);

Stub method for enabling binary mode. Always returns true.

blocking

my $bool | undef = $self->blocking(| $bool);

Stub method for controlling blocking mode.

fileno

my $fd = $self->fileno();

Returns the file descriptor number. Always returns -1.

seek

my $success = $self->seek($position, $whence);

Stub method for seeking.

tell

my $pos = $self->tell();

Stub method for retrieving the current position.

truncate

my $success = $self->truncate($length);

Stub method for truncating the device.

stat

my @list = $self->stat();

Stub method for retrieving device statistics.

ioctl

my $success = $self->ioctl($function, $scalar);

Stub method for device control operations.

fcntl

my $success = $self->fcntl($function, $scalar);

Stub method for file control operations.

fdopen

my $success = $self->fdopen($fd, $mode);

Stub method for opening a file descriptor.

new_from_fd

my $obj = $self->new_from_fd();

Stub method for creating a device from a file descriptor. Always returns undef.

SEE ALSO

TUI::TextView::Terminal, TUI::Views::Scroller

AUTHORS

Borland International (original Turbo Vision design)
J. Schneider <brickpool@cpan.org> (Perl implementation and maintenance)

COPYRIGHT AND LICENSE

Copyright (c) 1990-1994, 1997 by Borland International

Copyright (c) 2025-2026 the "AUTHORS" as listed above.

This software is licensed under the MIT license (see the LICENSE file, which is part of the distribution).