Version 0 of hl_tcl, Tcl/Tk syntax highlighter

Updated 2020-09-27 03:15:05 by apIsimple

The hl_tcl package is a syntax highlighter for Tcl/Tk code.

It can be applied to a Tk text widget or to a static html page.

The Tk text widget may be made read-only or editable. Also, the hl_tcl may take an argument, sort of command to watch the viewing / editing.

When applied to html pages, the hl_tcl highlights Tcl/Tk code snippets embedded between <code> </code> tags.

The hl_tcl has highlighted its own code in Reference .

Some of blah-blah

The Tcl being incredibly dynamic language sets a lot of problems before any Tcl syntax highlighter. Probably, a Tcl string spanning several lines is the main challenge at that.

Below is a line that brings most (not hl_tcl in Reference ) of Tcl highlighters in a stupor:

      if {[set i [string first {"} $line $i]]==-1} {return no}

... as well as this one:

      regsub -all {(([^[email protected]]|\\@)[.?!]("|'|'')?([])])?) } $fieldText {\1  } fieldText

Good luck for a highlighter when the second line (or similar) follows the first, giving it a matching quote and thus bringing it out of the stupor.

Those stand-alone quotes are widely used in regexp and regsub Tcl commands, so that when a honest Tcl highlighter (like Geany ) stumbles upon a quote, it tries its best to highlight the rest of code as a string, till the next occurence of unescaped quote.

Thus, we have

in Geany

... instead of

in hl_tcl

There are "tricky" highlighters (like Gedit that behave more wisely at the stumbling a quote: they permit only a one-line Tcl strings (if not continued with \\), so that the string highlighting would be most likely finished in the same line it started. No problems except for this silly line. And no delays due to the highlighting the rest of code...

... as seen in:

in Gedit/Pluma

Some of editors

Geany IDE . Probably, the best Tcl highlighter and the great programming tool at that. Still, it has few drawbacks:

  • doesn't highlight the above mentioned Tcl lines properly
  • doesn't highlight ${var} in contrast with $var
  • tries to highlight any (even hexidecimal) number it encounters, thus set a 1fix or set b #abxxx looks a bit peculiar
  • set c {#000000 #FFFFFF} is quite a legal Tcl command, not for Geany
  • no highlighting TclOO (method, mixin, my etc.)

Vim . Probably, the fastest Tcl highlighter. Great and awful. Nonetheless:

  • tricky with those above mentioned Tcl lines
  • doesn't highlight ttk commands (Tk only) and TclOO
  • tries to highlight every bit of Tcl, e.g. set set set is highlighted as three set commands ;)
  • as a result, much more florid than others

Kate . As nearly good as Geany, still doesn't highlight ttk and TclOO.

TKE . Written in Tcl/Tk, it might be the best of all to highlight the Tcl/Tk. In spite of its suspended state it still can. Has issues with highlighting strings and the performance.

Pluma and Gedit seem to use the same Tcl highlighting engine that gives rather good results. Still, the mentioned above drawbacks are here too. And no highlighting of tk, ttk, TclOO.

Notepad . Very fast Tcl highlighter. Still, the mentioned above drawbacks are here all the same. No highlighting of tk, ttk, TclOO. Plus an obsolete version of Tcl, i.e. no highlighting lset, lassign etc.

What can we do?

To develop a correct (and fast at that) Tcl highlighter, we would have to be familiar with Tcl core. Though, no hopes to achieve this ideal through repeating the core in Tcl/Tk or massively using the regular expressions.

That said, while implementing Tcl/Tk highlighter in pure Tcl/Tk, we might hope to achieve a reasonable compromise between the performance and the elimination of blunders.

It seems hl_tcl got close to this compromise. Specifically, it provides:

  • special highlighting for Tcl and TclOO commands
  • special highlighting for Tk and ttk commands
  • special highlighting for declarations (proc, method, oo::class etc.) and return
  • in-line comments being recognized and thus highlighted only after ;#
  • proper handling of most regexp and regsub expressions containing a quote
  • highlighting the multi-line strings, with possible switching this mode off (a-la Gedit) to improve the performance
  • customizing colors of the highlighting
  • highlighting viewable/editable Tk text widget and static html pages
  • good performance at editing 1000-4000 LOC and rather acceptable for 4000-9000 LOC
  • even monstrous 10000 LOC and more are handled fast at the "tricky" mode a-la Gedit

The hl_tcl doesn't provide the following:

  • highlighting numbers
  • highlighting -options
  • highlighting brackets except for in strings

These are in no way critical drawbacks. A bit less florid Tcl code might be even preferable.

The Tcl can arrange its pitfalls for hl_tcl (I know where). Also, tricky practices or tastes can make a fool of hl_tcl. Still hopefully these pranks are few and rare to encounter.

Use for text widget

The code below:

      package require hl_tcl
      proc ::stub {} {puts "stub: [$::txt index end]"}
      ::hl_tcl::hl_init $::txt
      #... inserting a text into the text widget
      ::hl_tcl::hl_text $::txt $readonly $multi ::stub

sets an example of hl_tcl usage. Here are the details:

  • ::stub is a procedure to watch the text editing; here it simply puts out the text's last index
  • hl_init is called before filling the text widget with a Tcl code
  • hl_text is called to highlight the Tcl code of the text widget and view/edit it

The hl_init takes arguments:

  • txt is the text widget's path
  • args is options of text widget (omittable)

The args may contain pairs option value where option may be:

  • -colors for a list of colors: clrCOM, clrCOMTK, clrSTR, clrVAR, clrCMN, clrPROC
  • -dark for a flag "dark background of text" (i.e. simplified -colors)
  • -font for a font attributes

The hl_text takes arguments:

  • text widget's path
  • readonly flag (may be omitted, by default "no")
  • multi-line strings flag (may be omitted, by default "yes")
  • procedure name to watch the editing (may be omitted, by default "")

Other hl_tcl procedures are:

  • hl_readonly gets/sets a read-only mode and/or a command to watch a text widget at viewing/editing it
  • hl_colors gets/sets colors of highlighting
  • hl_font gets/sets font attributes for text widget
  • hl_all updates ("rehighlights") all highlighted existing text widgets

See details in Reference .

Use for static html

In the , there is a Tcl script named tcl_html.tcl that highlights Tcl snippets of static html page(s).

It runs as follows:

      tclsh tcl_html.tcl "glob-pattern-of-html-files"

For example:

      tclsh ~/UTILS/hl_tcl/tcl_html.tcl "~/UTILS/mulster/tasks/ruff/src/*"

In this example, the html files are located in ~/UTILS/mulster/tasks/ruff/src/*.

Perhaps, you would want to modify the tcl_html.tcl, this way:

  • replace <code class="tcl"> with html tags starting the Tcl code in your html files
  • replace </code> with html tags finishing the Tcl code in your html files


Note that hl_tcl is still disposed to update. It's too raw for now.