Convert the title calculation into a template tag

Convert the calculate form title template into a template tag.
The result of the template tag is applied as the title property
of the <H3> HTML tag allowing users to view the full title on
mouse hover if the title was truncated.

Signed-off-by: Roberto Rosario <Roberto.Rosario@mayan-edms.com>

mayan/apps/common/classes.py

@@ -4,7 +4,6 @@ import hashlib
 
 from django.apps import apps
 from django.db import models
-from django.template import loader
 from django.template.response import TemplateResponse
 from django.urls import reverse
 from django.utils.encoding import force_text, python_2_unicode_compatible

mayan/apps/common/templatetags/common_tags.py

@@ -3,10 +3,13 @@ from __future__ import unicode_literals
 from json import dumps
 
 from django.template import Context, Library
+from django.template.defaultfilters import truncatechars
 from django.template.loader import get_template
 from django.utils.encoding import force_text
+from django.utils.translation import ugettext_lazy as _
 
 import mayan
+from mayan.apps.appearance.settings import setting_max_title_length
 
 from ..classes import Collection
 from ..literals import MESSAGE_SQLITE_WARNING
@@ -58,3 +61,28 @@ def render_subtemplate(context, template_name, template_context):
     new_context = Context(context.flatten())
     new_context.update(Context(template_context))
     return get_template(template_name).render(new_context.flatten())
+
+
+@register.simple_tag(takes_context=True)
+def common_calculate_title(context):
+    if context.get('title'):
+        return truncatechars(
+            value=context.get('title'), arg=setting_max_title_length.value
+        )
+    else:
+        if context.get('delete_view'):
+            return _('Confirm delete')
+        else:
+            if context.get('form'):
+                if context.get('object'):
+                    return _('Edit %s') % context.get('object')
+                else:
+                    return _('Confirm')
+            else:
+                if context.get('read_only'):
+                    return _('Details for: %s') % context.get('object')
+                else:
+                    if context.get('object'):
+                        return _('Edit: %s') % context.get('object')
+                    else:
+                        return _('Create')