TIP 510: Add Rbc and Tkpath widgets to Tk

EuroTcl/OpenACS 11 - 12 JULY 2024, VIENNA
Author:         RenĂ© Zaumseil <[email protected]>
State:          Deferred
Type:           Project
Vote:           Done
Created:        5-Jun-2018
Keywords:       Tk
Tcl-Version:    9.0
Tk-Branch:      tip-510
Vote-Summary:   Rejected 1/3/1
Votes-For:      DKF
Votes-Against:  KBK, JN, FV
Votes-Present:  BG
Vote-Comments:  code not yet ready, needs porting to macOS; alternate
                might be to just co-distribute, just as TDBC is with Tcl

This tip depends on TIP #556. It is deferred until TIP #556 is accepted.


Rbc aka "Refactored BLT Components" have graph widgets and Tk commands which are missing in Tk.

Tkpath is a 2D-canvas like widget modelled after SVG.

This TIP intends to add the following commands to Tk:

rbc::graph, rbc::stripchart and rbc::barchart as graph

To get the original functionality a -style option will be added. This option can only be set on creation time.

rbc::vector as graph::vector

The vector is currently only used inside the graph widget. The namespace hidden version leaves room for a first class command with the same name.

rbc::winop snap as tk snap

Only the snap functionality is needed here. The busy command already exists as "tk busy" :)

tkp::canvas as path

The new path widget will contain the SVG like items and an additional window item to include other windows. Support functions will be placed in the ::path namespace.

New oo::class like widgets tko::frame, tko::labelframe and tko::toplevel

The new widgets will contain the same functionalite like the original tk widgets. They are oo:class's and it is possible to add,change and delte methods and options dynamically. The widgets could also be used as oo superclass's.

New tko::widget oo base class for widgets.

The class provide the extended cget/configure tcl methods (see tkoWidget.n.md) and a C interface (see tkoWidget.3.md) to build new widgets.


Rbc commands

Tk has already adopted some of BLT/Rbc commands. Still missing are the above mentioned commands.

Rbc is available on sourceforge and github, but the development is stalled.

BLT, the orignal source, is at sourceforge. The author G. Howlett makes sporadic changes. Then there are large times without activity. It is not possible to estimate when a new version will be ready.

Modernizing Rbc and including it in Tk will give some great new widgets. There is also less risk because Rbc is already used in different projects.


The original developer of Tkpath passed away. There are some mirrors, but with no real development. More information could be found on https://wiki.tcl-lang.org/page/tkpath.

The intent of Tkpath was to substitute the Tk canvas. This leads to problems with advanced features (matrix transformations). Therefore the new path widget will only contain SVG like items. The only exception is the window item. This item is necessary to embed other widgets.

oo::class like widgets

Currently there is no megawidget support core package. These tip will go some steps in this direction. With widgets as oo::class's we can easyly extent existing widgets, just use it as a superclass. The provided cget/configure methods allow add, delete and changing of options. The implementation can be used in C and in Tcl.

The new widgets graph and path are also implemented as oo::class. This will make it easy to extent the functionality. As an example see the file .../library/graph.tcl in which the method binding of the graph widget is implemented.


A patch implementing these changes is available in the fossil repository in the tip-510 branch.


Documentation is available in md-Format in the .../doc/ directory.

C interface

C-source interface files are in .../generic/tko/. No functionality is currently exported.

C sources

C-source code files are in .../generic/tko/. The new files are added to the makefiles. The calls to the initialization functions are added in tkWindow.c

Tcl sources

Tcl-source code is in .../library/. The new files are added into tk.tcl.


Test files are available in the .../tests/tko/ directory.

Test binaries


See also discussion at the wiki.

A first voting was rejected, mostly because of the missing Mac implementation. See:


and with some analysis from Donal:


Open issues

Any help especially with the Mac implementation would be great!

And could please look someone with configure foo at the Makefile's



This document has been placed in the public domain.