Initial implementation of text folding

README.md

@@ -6,7 +6,8 @@ everything needed to efficiently develop TLV code in Vim:
 
  * File type detection
  * Syntax highlighting (including an optional color scheme)
- * Smart indentation
+ * Automatic (smart) indentation
+ * Automatic text folding
  * Checking for syntax errors (work in progress)
 
 Each of the features outlined above is discussed in more detail below.
@@ -74,11 +75,21 @@ Of course you are free to decide whether to use this color scheme or not, the
 choice is up to you. The syntax highlighting mode is intended to work well with
 other Vim color schemes as well.
 
-### Smart indentation
+### Automatic (smart) indentation
 
 The *vim-tlv-mode* plug-in uses Vim's ['indentexpr'] [indentexpr] option to
-implement smart indentation that understands TLV scope rules and automatically
-increases the indentation level as needed.
+implement smart indentation (that understands TLV scope rules and knows to
+ignore line type characters) and automatically increases the indentation level
+as needed.
+
+### Automatic text folding
+
+The *vim-tlv-mode* plug-in uses Vim's ['foldexpr'] [foldexpr] option to
+implement automatic text folding (that understands TLV scope rules and knows to
+ignore line type characters). This method of text folding is already a big
+improvement over indentation based folding (because that falls apart as soon as
+line type characters are introduced) but it's not perfect yet; I'd like to
+improve it further.
 
 ### Checking for syntax errors
 
@@ -110,6 +121,7 @@ This software is licensed under the [MIT license] [mit].
 
 
 [download-tlv-mode]: http://peterodding.com/code/vim/downloads/tlv-mode.zip
+[foldexpr]: http://vimdoc.sourceforge.net/htmldoc/options.html#'foldexpr'
 [github-tlv-mode]: https://github.com/xolox/vim-tlv-mode
 [homepage]: http://peterodding.com/code/vim/tlv-mode/
 [indentexpr]: http://vimdoc.sourceforge.net/htmldoc/options.html#'indentexpr'

TODO.md

@@ -4,7 +4,6 @@ This document lists work to be done on the *vim-tlv-mode* plug-in. The
 following points are in rough order of priority (in descending order):
 
  * Get integrated syntax checking working (out of the box).
- * Implement useful text folding for TLV files.
 
 Each point is discussed in more detail below.
 
@@ -41,11 +40,3 @@ plug-in. Impediments for the integration between *vim-tlv-mode* and the
 
 My goal is to have these issues resolved (in one way or another :-) as quickly
 as possible.
-
-## Implement useful text folding for TLV files
-
-It should be possible to hide code under a given scope. I believe that Vim's
-text folding feature is the best way to implement this. I'm not yet sure
-whether indentation based folding is good enough or if I should implement a
-smart text folding expression function that actually understands scoping rules
-instead of just looking at the indentation.

autoload/tlv.vim

@@ -1,10 +1,10 @@
 " Vim auto-load script
 " Language: TLV (Transaction-Level Verilog)
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: March 13, 2015
+" Last Change: March 30, 2015
 " URL: https://github.com/xolox/vim-tlv-mode
 
-let g:tlv#version = '0.1'
+let g:tlv#version = '0.2'
 
 function! tlv#compiler_is_installed() " {{{1
   " Check if the TLV compiler is installed. Returns true (1) when the compiler
@@ -64,15 +64,19 @@ function! tlv#auto_check_syntax() " {{{1
   endif
 endfunction
 
+function! tlv#foldexpr() " {{{1
+  " Support for automatic (smart) text folding. The result of this folding
+  " expression isn't exactly ideal yet, but it's one step up from indentation
+  " based text folding (that falls apart as soon as line type characters are
+  " used :-). I'd like to improve this further, but I'm not yet sure how...
+  return s:calculate_indent(getline(v:lnum)) / &tabstop
+endfunction
+
 function! tlv#indentexpr() " {{{1
   " Support for automatic (smart) indentation.
   let previous_lnum = prevnonblank(v:lnum - 1)
   let previous_line = getline(previous_lnum)
-  " Line type characters (any character in the first column other than a space
-  " or backslash) are to be considered indentation so we have to include them
-  " (manually) in the calculation of indentation. This explains why we can't
-  " use Vim's otherwise very handy indent() function :-).
-  let previous_indent = len(matchstr(previous_line, '^[^\\] *'))
+  let previous_indent = s:calculate_indent(previous_line)
   if previous_line =~ '^\s*[>|?@\\-]'
     " When the previous non blank line starts with one of the characters in
     " the [character class] above, the scope (and thus indentation) is
@@ -84,4 +88,18 @@ function! tlv#indentexpr() " {{{1
   endif
 endfunction
 
+function! s:calculate_indent(line) " {{{1
+  " Calculate the indentation level of a line (as the number of spaces). This
+  " is complicated by line type characters (any character in the first column
+  " other than a space or backslash) because they are to be considered
+  " indentation so we have to include them (manually) in the calculation of
+  " indentation. This explains why we can't use Vim's otherwise very handy
+  " indent() function :-).
+  if a:line =~ '^[^\\ ] '
+    return matchend(a:line, '^[^\\] \+')
+  else
+    return matchend(a:line, '^ *')
+  endif
+endfunction
+
 " vim: ts=2 sw=2 et

ftplugin/tlv.vim

@@ -1,7 +1,7 @@
 " Vim file type plug-in
 " Language: TLV (Transaction-Level Verilog)
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: March 13, 2015
+" Last Change: March 30, 2015
 " URL: https://github.com/xolox/vim-tlv-mode
 
 if exists('b:did_ftplugin')
@@ -21,10 +21,14 @@ call add(s:undo_ftplugin, 'setlocal expandtab<')
 setlocal tabstop=3 shiftwidth=3
 call add(s:undo_ftplugin, 'setlocal tabstop< shiftwidth<')
 
-" Enable automatic indentation support. {{{1
+" Enable support for automatic indentation. {{{1
 setlocal indentexpr=tlv#indentexpr()
 call add(s:undo_ftplugin, 'setlocal indentexpr<')
 
+" Enable support for automatic text folding. {{{1
+setlocal foldmethod=expr foldexpr=tlv#foldexpr()
+call add(s:undo_ftplugin, 'setlocal foldmethod< foldexpr<')
+
 " }}}1
 
 " Let Vim know how to disable the plug-in.