Truncate posts by lines

boards/templates/boards/post.html

@@ -63,7 +63,7 b''
 <div class="message">
     {% autoescape off %}
         {% if truncated %}
-            {{ post.get_text|truncatewords_html:50 }}
+            {{ post.get_text|truncatewords_html:50|truncate_lines:3 }}
         {% else %}
             {{ post.get_text }}
         {% endif %}

boards/templatetags/board.py

@@ -1,6 +1,12 b''
+import re
 from django.shortcuts import get_object_or_404
 from django import template
 
+ELLIPSIZER = '...'
+
+REGEX_LINES = re.compile(r'(<div class="br"></div>)', re.U | re.S)
+REGEX_TAG = re.compile(r'<(/)?([^ ]+?)(?:(\s*/)| .*?)?>', re.S)
+
 
 register = template.Library()
 
@@ -72,3 +78,68 b' def post_view(post, moderator=False, nee'
         'truncated': truncated,
         'opening_post_id': opening_post_id,
     }
+
+
[e-mail](is_safe=True)
+def truncate_lines(text, length):
+    if length <= 0:
+        return ''
+
+    html4_singlets = (
+        'br', 'col', 'link', 'base', 'img',
+        'param', 'area', 'hr', 'input'
+    )
+
+    # Count non-HTML chars/words and keep note of open tags
+    pos = 0
+    end_text_pos = 0
+    current_len = 0
+    open_tags = []
+
+    while current_len <= length:
+        m = REGEX_LINES.search(text, pos)
+        if not m:
+            # Checked through whole string
+            break
+        pos = m.end(0)
+        if m.group(1):
+            # It's an actual non-HTML word or char
+            current_len += 1
+            if current_len == length:
+                end_text_pos = pos
+            continue
+        # Check for tag
+        tag = REGEX_TAG.match(m.group(0))
+        if not tag or current_len >= length:
+            # Don't worry about non tags or tags after our truncate point
+            continue
+        closing_tag, tagname, self_closing = tag.groups()
+        # Element names are always case-insensitive
+        tagname = tagname.lower()
+        if self_closing or tagname in html4_singlets:
+            pass
+        elif closing_tag:
+            # Check for match in open tags list
+            try:
+                i = open_tags.index(tagname)
+            except ValueError:
+                pass
+            else:
+                # SGML: An end tag closes, back to the matching start tag,
+                # all unclosed intervening start tags with omitted end tags
+                open_tags = open_tags[i + 1:]
+        else:
+            # Add it to the start of the open tags list
+            open_tags.insert(0, tagname)
+
+    if current_len <= length:
+        return text
+    out = text[:end_text_pos]
+
+    if not out.endswith(ELLIPSIZER):
+        out += ELLIPSIZER
+    # Close any tags still open
+    for tag in open_tags:
+        out += '</%s>' % tag
+    # Return string
+    return out