TIP 561: Console Command for Linux/Unix

This repository contains the working console.tcl implementation for TIP 561, which proposes adding official support for the console command on Linux and other Unix platforms.

Overview

Currently, the console command works "out of the box" on Windows and macOS, but requires additional code on Linux/Unix. This TIP proposes making console support a standard feature across all Tk-enabled platforms.

About This File

This console.tcl file is the core implementation that provides the console functionality once activated.

Important: The full TIP 561 proposal includes additional wrapper code that delays initialization of this console until a user explicitly issues a console command (like console show). This ensures backward compatibility - Unix/Linux users who don't want the console will see no behavior change, with stdout/stderr continuing to go to the terminal as before.

See the TIP 561 documentfor the complete wrapper implementation that provides this lazy initialization behavior.

Key Improvements in This Implementation

1. Working Channel Transform Support (Tcl 8.6+)

The primary enhancement is a properly functioning channel transform implementation that correctly handles Unicode output.

The Problem: Previous channel transform attempts failed to display Unicode characters correctly. For example:

puts "hello \u21a9 there"
# Would display: hello â© there  (incorrect)
# Should display: hello ↩ there  (correct)

The Solution: Channel transforms receive UTF-8 encoded bytes from stdout/stderr, but the Tk console widget expects Unicode strings. The fix decodes the bytes before passing them to the console:

proc write {what x data} {
    set data [encoding convertfrom utf-8 $data]
    set data [string map {\r ""} $data]
    $consoleInterp eval [list ::tk::ConsoleOutput $what $data]
    return ""
}

This approach eliminates the need for the pre-8.6 puts wrapper method, which required renaming and redefining the puts command.

2. Proper Console Cleanup and Output Restoration

When the console window is closed, output is now correctly restored to the terminal:

• Uses wm protocol . WM_DELETE_WINDOW instead of bind <Destroy> to catch the close event early
• Properly pops channel transforms and restores terminal encoding
• Deletes the console interpreter cleanly

3. Improved Keyboard Shortcuts

Added platform-consistent font size controls:

• Control+= (unshifted) in addition to Control++
• Keypad Control+KP_Add and Control+KP_Subtract

These work automatically on Windows but require explicit bindings on Linux/X11.

Backward Compatibility

The pre-8.6 puts wrapper implementation remains in the code for systems running Tcl versions prior to 8.6. The version check at line 99 automatically selects the appropriate method:

if {[package vcompare [package present Tcl] 8.6] >= 0} {
    # Use modern channel transforms (this implementation)
} else {
    # Fall back to puts wrapper for Tcl < 8.6
}

Usage

For testing purposes, you can source this file directly:

source console.tcl
console show

In the final TIP 561 implementation, the wrapper code ensures the console is only initialized when explicitly requested by the user.

Benefits

1. Platform Consistency: Eliminates the incompatibility between Windows/macOS and Linux/Unix
2. Clean Implementation: Uses official channel transform API instead of command renaming hacks
3. Unicode Support: Properly handles international characters and symbols
4. Future-Proof: Uses documented APIs that won't break in future Tcl releases
5. Backward Compatible: Existing Unix/Linux behavior unchanged unless console is explicitly invoked

Related Links

• TIP 561 Proposal (if available)
• Original Tcl'ers Wiki Code

Testing

Tested on:

• Pop!_OS Linux (Ubuntu-based)
• Tcl/Tk 8.6+

The implementation should work on any Unix-like system with Tcl/Tk 8.6 or later.