hl_tcl, Tcl/Tk syntax highlighter

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, the usage of quotes and esp. the strings spanning several lines are the main challenges.

Below is a line that brings most (not hl_tcl, as seen 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 orphan quotes are often used in regexp and regsub Tcl commands, so that when a honest Tcl highlighter (like Geany ) stumbles upon an orphan quote, it tries its best to highlight the rest of code as a string, till the next unmatched quote.

Thus, we have

in Geany

... instead of

in hl_tcl

There are "tricky" highlighters (like Gedit ) that behave more wisely at the stumbling an orphan 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 most of others

Kate . As nearly good as Geany. As nearly florid as Vim (set set set). 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. And very basic. All the same drawbacks. 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 an ideal (correct and fast) Tcl/Tk highlighter, we would have to dive into Tcl core. Though, no hopes to achieve the 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. as well as return, yield
  • special highlighting for #comments, $variables, "strings", -options
  • 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 brackets, except for matched ones and inside the strings

These are in no way critical drawbacks. A little less florid Tcl code might be even preferable for other tastes.

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 -readonly yes -cmd ::stub

      #... 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; it sets the highlighting options and disables the highlighting till hl_text runs;
  • hl_text runs to highlight the Tcl code of the text widget and to view/edit it.

The hl_init takes arguments:

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

The args is a list of -option value where -option may be:

  • -colors - list of colors: clrCOM, clrCOMTK, clrSTR, clrVAR, clrCMN, clrPROC, clrOPT
  • -dark - flag "dark background of text", i.e. simplified -colors (default "no")
  • -font - attributes of text font
  • -readonly - flag "text is read-only" (default "no")
  • -multiline - flag "multi-line strings" (default "yes")
  • -cmd - command to watch editing/viewing (default "")
  • -seen - number of first lines seen at start (default 99999999)
  • -optRE - flag "use a regular expression to highlight options" (default "yes")

The rest of hl_tcl procedures are:

  • hl_all updates all highlighted existing text widgets, e.g. at changing a color scheme of application
  • hl_readonly gets/sets a read-only mode and/or a command to watch a text widget at viewing/editing it

See details in Reference .

Use for static html

In the hl_tcl.zip , 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, then try and go this way:

  • replace no with yes for dark html pages
  • 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

These are arguments of ::hl_tcl_html::highlight procedure. The tag pairs can be multiple if the html pages contain them, e.g.:

::hl_tcl_html::highlight $fhtml no \
    {<code class="tcl">} {</code>} \
    {<pre class="code">} {</pre>}


Note that hl_tcl is still disposed to be updated.