added support for Pandoc-style image attributes (#41)

CHANGELOG.md

@@ -3,6 +3,8 @@
 
 ## v0.6.0 (dev)
 
+* Added support for Pandoc-style attributes on images:
+  `![alt_text](image_file){#id .class1 .class2 width=10em height=5em}` (#41).
 * Executable code blocks now use PATH to locate executables under Windows, and
   thus now work with Python environments.  Previously PATH was ignored under
   Windows due to the implementation details of Python's `subprocess.Popen()`

README.md

@@ -504,6 +504,14 @@ operating systems.  All image paths not starting with `http://` or `https://`
 are assumed to refer to local image files (files on your machine), and will
 result in errors if these files are not found.
 
+[Pandoc-style attributes](https://pandoc.org/MANUAL.html#images) can be used
+with images:
+```
+![alt_text](image_file){#id .class1 .class2 width=10em height=5em}
+```
+This allows image id, classes, and dimensions to be specified without
+resorting to HTML.
+
 
 ### LaTeX
 

text2qti/markdown.py

@@ -32,6 +32,14 @@
 import markdown.extensions.footnotes
 import markdown.extensions.tables
 import markdown.extensions.md_in_html
+from markdown.inlinepatterns import ImageInlineProcessor, IMAGE_LINK_RE
+
+from .config import Config
+from .err import Text2qtiError
+from .version import __version__ as version
+from . import pymd_pandoc_attr
+
+
 md_extensions = [
     markdown.extensions.smarty.makeExtension(),
     markdown.extensions.sane_lists.makeExtension(),
@@ -40,12 +48,8 @@
     markdown.extensions.footnotes.makeExtension(),
     markdown.extensions.tables.makeExtension(),
     markdown.extensions.md_in_html.makeExtension(),
+    pymd_pandoc_attr.makeExtension(),
 ]
-from markdown.inlinepatterns import ImageInlineProcessor, IMAGE_LINK_RE
-
-from .config import Config
-from .err import Text2qtiError
-from .version import __version__ as version
 
 
 

text2qti/pymd_pandoc_attr.py

@@ -0,0 +1,105 @@
+# -*- coding: utf-8 -*-
+#
+# Copyright (c) 2021, Geoffrey M. Poore
+# All rights reserved.
+#
+# Licensed under the BSD 3-Clause License:
+# http://opensource.org/licenses/BSD-3-Clause
+#
+
+
+'''
+Pandoc-style attribute syntax for Python-Markdown.
+Attribute support is currently limited to images.
+See https://pandoc.org/MANUAL.html#images.
+
+Inspired by https://github.com/Python-Markdown/markdown/blob/master/markdown/extensions/attr_list.py.
+'''
+
+
+from markdown.extensions import Extension
+from markdown.treeprocessors import Treeprocessor
+from typing import List, Tuple
+import re
+
+
+IDENTIFIER_PATTERN = r'[A-Za-z][0-9A-Za-z_\-]+'
+ID_PATTERN = rf'#{IDENTIFIER_PATTERN}'
+CLASS_PATTERN = rf'\.{IDENTIFIER_PATTERN}'
+KV_PATTERN = rf'{IDENTIFIER_PATTERN}=[0-9A-Za-z_\-%]+'
+ATTR_PATTERN = (
+    r'\{[ ]*(?!\})('
+    rf'(?:{ID_PATTERN}(?=[ \}}]))?'
+    rf'(?:{CLASS_PATTERN}(?=[ \}}])|{KV_PATTERN}(?=[ \}}])|[ ]+(?=[^ \}}]))*'
+    r')[ ]*\}'
+)
+
+def _handle_id(scanner: re.Scanner, token: str) -> Tuple[str, str]:
+    return '#', token[1:]
+
+def _handle_class(scanner: re.Scanner, token: str) -> Tuple[str, str]:
+    return '.', token[1:]
+
+def _handle_key_value(scanner: re.Scanner, token: str) -> Tuple[str, str]:
+    return token.split('=', 1)
+
+_scanner = re.Scanner([
+    (ID_PATTERN, _handle_id),
+    (CLASS_PATTERN, _handle_class),
+    (KV_PATTERN, _handle_key_value),
+    (r'[ ]+', None),
+])
+
+def get_attrs(string: str) -> List[Tuple[str, str]]:
+    '''
+    Parse a string of attributes `<attrs>` that has already been extracted
+    from a string of the form `{<attrs>}`.  Return a list of attribute tuples
+    of the form `(<key>, <value>)`.
+    '''
+    results, remainder = _scanner.scan(string)
+    return results
+
+
+class PandocAttrTreeprocessor(Treeprocessor):
+    ATTR_RE = re.compile(ATTR_PATTERN)
+    def run(self, doc):
+        for elem in doc.iter():
+            if self.md.is_block_level(elem.tag):
+                pass
+            else:
+                # inline, only for images currently
+                if elem.tag == 'img' and elem.tail and elem.tail.startswith('{'):
+                    match = self.ATTR_RE.match(elem.tail)
+                    if match:
+                        self.assign_attrs(elem, match.group(1))
+                        elem.tail = elem.tail[match.end():]
+
+    def assign_attrs(self, elem, attrs):
+        '''
+        Assign attrs to element.
+        '''
+        for k, v in get_attrs(attrs):
+            if k == '#':
+                elem.set('id', v)
+            elif k == '.':
+                elem_class = elem.get('class')
+                if elem_class:
+                    elem.set('class', f'{elem_class} {v}')
+                else:
+                    elem.set('class', v)
+            else:
+                elem_style = elem.get('style')
+                if elem_style:
+                    elem.set('style', f'{elem_style} {k}:{v};')
+                else:
+                    elem.set('style', f'{k}:{v};')
+
+
+class PandocAttrExtension(Extension):
+    def extendMarkdown(self, md):
+        md.treeprocessors.register(PandocAttrTreeprocessor(md), 'pandoc_attr', 8)
+        md.registerExtension(self)
+
+
+def makeExtension(**kwargs):
+    return PandocAttrExtension(**kwargs)

text2qti/version.py

@@ -1,4 +1,4 @@
 # -*- coding: utf-8 -*-
 
 from .fmtversion import get_version_plus_info
-__version__, __version_info__ = get_version_plus_info(0, 6, 0, 'dev', 3)
+__version__, __version_info__ = get_version_plus_info(0, 6, 0, 'dev', 4)