NAME
TUI::Drivers::Screen - global screen and video mode management
SYNOPSIS
use TUI::Drivers::Screen;
use TUI::Drivers::Const qw( smCO80 smFont8x8 );
# Initialize driver-side screen state.
TScreen->resume();
# Select an 80x50 style text mode (platform-adjusted by fixCrtMode).
TScreen->setVideoMode( smCO80 | smFont8x8 );
# Optional explicit clear.
TScreen->clearScreen();
# Restore startup mode/cursor on shutdown.
TScreen->suspend();DESCRIPTION
TScreen provides global screen and video mode management facilities used by the Turbo Vision driver layer.
The module maintains global state describing the current screen configuration and provides class-level routines to suspend, resume, and reinitialize the video subsystem.
TScreen is not an object-oriented class. It is not instantiated and does not represent a view. All interaction is performed through class method calls of the form TScreen->method.
Commonly Used Features
In normal application flow, TScreen is primarily used to coordinate screen lifecycle transitions (resume() and suspend()) and to switch video mode via setVideoMode().
When a mode change occurs, the module refreshes shared screen state such as $screenWidth, $screenHeight, and $hiResScreen, and updates mouse range through TMouse when mouse support is available.
VARIABLES
$startupMode
Stores the screen mode that was active before Turbo Vision initialized the video system.
This value is used to restore the original screen mode when Turbo Vision suspends or terminates.
$startupCursor
Stores the initial cursor shape before Turbo Vision modifies the cursor.
$screenMode
Holds the current screen mode requested by the application.
$screenWidth
Contains the current screen width in character columns.
Typical values are 80 or similar.
$screenHeight
Contains the current screen height in text rows.
Typical values are 25, 43, or 50 depending on the selected video mode.
$hiResScreen
Indicates whether a high-resolution text mode is active.
$checkSnow
Controls CGA snow checking behavior.
If true, Turbo Vision performs additional checks to avoid display artifacts on older CGA adapters. This variable should not be modified before application initialization has completed.
$screenBuffer
Reference to the internal screen buffer.
This variable is initialized during screen setup and tracks the location of the video memory buffer.
$cursorLines
Encodes the current cursor shape.
The high nibble represents the top scan line, and the low nibble represents the bottom scan line of the cursor.
$clearOnSuspend
Controls whether the screen is cleared when the video subsystem is suspended.
METHODS
clearScreen
TScreen->clearScreen();Clears the screen after the video subsystem has been resumed.
Most applications do not need to call this method explicitly.
fixCrtMode
my $mode = TScreen->fixCrtMode($mode);Adjusts the supplied screen mode value to match hardware constraints.
setVideoMode
TScreen->setVideoMode($mode);Selects a new screen mode.
This method changes the screen color mode and optionally the screen height. Typically, applications should call TProgram->setScreenMode instead, which performs additional updates such as palette and mouse repositioning.
suspend
TScreen->suspend();Suspends Turbo Vision video support and restores the original screen state.
This method is called automatically during application shutdown.
resume
TScreen->resume();Initializes the Turbo Vision video subsystem and switches the display to the mode specified by $screenMode.
This method initializes $screenWidth, $screenHeight, $hiResScreen, $checkSnow, $screenBuffer, and $cursorLines.
SEE ALSO
TUI::App::Program, TUI::Drivers::Display, TUI::Drivers::HardwareInfo
AUTHORS
- Borland International (original Turbo Vision design)
- J. Schneider <brickpool@cpan.org> (Perl implementation and maintenance)
CONTRIBUTORS
Contributors are documented in the POD of the respective framework modules.
COPYRIGHT AND LICENSE
Copyright (c) 1990-1994, 1997 by Borland International
Copyright (c) 2021-2026 the "AUTHORS" as listed above.
This software is licensed under the MIT license (see the LICENSE file, which is part of the distribution).