Add tdemarkdown part - embeddable lightweight markdown viewing component.

TDEMarkdown is based on the md4c library and using TDEHTML for rendering
its output. For enhanced safety, on HTML widget is turned off everything
we don't need for viewing. It integrates nicely into Konqueror and
supports both Commonmark and GitHub markdown syntaxes.

Signed-off-by: Mavridis Philippe <mavridisf@gmail.com>

Prepare to merge tdemarkdown into tdelibs.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>

1 files changed, 442 insertions, 0 deletions

diff --git a/tdemarkdown/md4c/CHANGELOG.md b/tdemarkdown/md4c/CHANGELOG.md
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+
+# MD4C Change Log
+
+
+## Next Version (Work in Progress)
+
+Changes:
+
+ * Changes mandated by CommonMark specification 0.30.
+
+   Actually there are only very minor changes to recognition of HTML blocks:
+
+   - The tag `<textarea>` now triggers HTML block (of type 1 as per the
+     specification).
+
+   - HTML declaration (HTML block type 4) is not required to begin with an
+     upper-case ASCII character after the `<!`. Any ASCII character is now
+     allowed.
+
+   Other than that, the newest specification mainly improves test coverage and
+   clarifies its wording in some cases, without affecting the implementation.
+
+   Refer to [CommonMark
+   0.30 notes](https://github.com/commonmark/commonmark-spec/releases/tag/0.30)
+   for more info.
+
+Fixes:
+
+ * [#163](https://github.com/mity/md4c/issues/163):
+   Make HTML renderer to emit `'\n'` after the root tag when in the XHTML mode.
+
+ * [#165](https://github.com/mity/md4c/issues/165):
+   Make HTML renderer not to percent-encode `'~'` in URLs. Although it does
+   work, it's not needed, and it can actually be confusing with URLs such as
+   `http://www.example.com/~johndoe/`.
+
+ * [#167](https://github.com/mity/md4c/issues/167),
+   [#168](https://github.com/mity/md4c/issues/168):
+   Fix multiple instances of various buffer overflow bugs, found mostly using
+   a fuzz testing. Contributed by [dtldarek](https://github.com/dtldarek) and
+   [Thierry Coppey](https://github.com/TCKnet).
+
+ * [#169](https://github.com/mity/md4c/issues/169):
+   Table underline now does not require 3 characters per table column anymore.
+   One dash (optionally with a leading or tailing `:` appended or prepended)
+   is now sufficient. This improves compatibility with the GFM.
+
+ * [#172](https://github.com/mity/md4c/issues/172):
+   Fix quadratic time behavior caused by unnecessary lookup for link reference
+   definition even if the potential label contains nested brackets.
+
+ * [#173](https://github.com/mity/md4c/issues/173),
+   [#174](https://github.com/mity/md4c/issues/174):
+   Multiple bugs identified with [OSS-Fuzz](https://github.com/google/oss-fuzz)
+   were fixed.
+
+
+## Version 0.4.8
+
+Fixes:
+
+ * [#149](https://github.com/mity/md4c/issues/149):
+   A HTML block started in a container block (and not explicitly finished in
+   the block) could eat 1 line of actual contents.
+
+ * [#150](https://github.com/mity/md4c/issues/150):
+   Fix md2html utility to output proper DOCTYPE and HTML tags when `--full-html`
+   command line options is used, accordingly to the expected output format
+   (HTML or XHTML).
+
+ * [#152](https://github.com/mity/md4c/issues/152):
+   Suppress recognition of a permissive autolink if it would otherwise form a
+   complete body of an outer inline link.
+
+ * [#153](https://github.com/mity/md4c/issues/153),
+   [#154](https://github.com/mity/md4c/issues/154):
+   Set `MD_BLOCK_UL_DETAIL::mark` and `MD_BLOCK_OL_DETAIL::mark_delimiter`
+   correctly, even when the blocks are nested at the same line in a complicated
+   ways.
+
+ * [#155](https://github.com/mity/md4c/issues/155):
+   Avoid reading 1 character beyond the input size in some complex cases.
+
+
+## Version 0.4.7
+
+Changes:
+
+ * Add `MD_TABLE_DETAIL` structure into the API. The structure describes column
+   count and row count of the table, and pointer to it is passed into the
+   application-provided block callback with the `MD_BLOCK_TABLE` block type.
+
+Fixes:
+
+ * [#131](https://github.com/mity/md4c/issues/131):
+   Fix handling of a reference image nested in a reference link.
+
+ * [#135](https://github.com/mity/md4c/issues/135):
+   Handle unmatched parenthesis pairs inside a permissive URL and WWW auto-links
+   in a way more compatible with the GFM.
+
+ * [#138](https://github.com/mity/md4c/issues/138):
+   The tag `<tbody></tbody>` is now suppressed whenever the table has zero body
+   rows.
+
+ * [#139](https://github.com/mity/md4c/issues/139):
+   Recognize a list item mark even when EOF follows it.
+
+ * [#142](https://github.com/mity/md4c/issues/142):
+   Fix reference link definition label matching in a case when the label ends
+   with a Unicode character with non-trivial case folding mapping.
+
+
+## Version 0.4.6
+
+Fixes:
+
+ * [#130](https://github.com/mity/md4c/issues/130):
+   Fix `ISANYOF` macro, which could provide unexpected results when encountering
+   zero byte in the input text; in some cases leading to broken internal state
+   of the parser.
+
+   The bug could result in denial of service and possibly also to other security
+   implications. Applications are advised to update to 0.4.6.
+
+
+## Version 0.4.5
+
+Fixes:
+
+ * [#118](https://github.com/mity/md4c/issues/118):
+   Fix HTML renderer's `MD_HTML_FLAG_VERBATIM_ENTITIES` flag, exposed in the
+   `md2html` utility via `--fverbatim-entities`.
+
+ * [#124](https://github.com/mity/md4c/issues/124):
+   Fix handling of indentation of 16 or more spaces in the fenced code blocks.
+
+
+## Version 0.4.4
+
+Changes:
+
+ * Make Unicode-specific code compliant to Unicode 13.0.
+
+New features:
+
+ * The HTML renderer, developed originally as the heart of the `md2html`
+   utility, is now built as a standalone library, in order to simplify its
+   reuse in applications.
+
+ * With `MD_HTML_FLAG_SKIP_UTF8_BOM`, the HTML renderer now skips UTF-8 byte
+   order mark (BOM) if the input begins with it, before passing to the Markdown
+   parser.
+
+   `md2html` utility automatically enables the flag (unless it is custom-built
+   with `-DMD4C_USE_ASCII`).
+
+ * With `MD_HTML_FLAG_XHTML`, The HTML renderer generates XHTML instead of
+   HTML.
+
+   This effectively means `<br />` instead of `<br>`, `<hr />` instead of
+   `<hr>`, and `<img ... />` instead of `<img ...>`.
+
+   `md2html` utility now understands the command line option `-x` or `--xhtml`
+   enabling the XHTML mode.
+
+Fixes:
+
+ * [#113](https://github.com/mity/md4c/issues/113):
+   Add missing folding info data for the following Unicode characters:
+   `U+0184`, `U+018a`, `U+01b2`, `U+01b5`, `U+01f4`, `U+0372`, `U+038f`,
+   `U+1c84`, `U+1fb9`, `U+1fbb`, `U+1fd9`, `U+1fdb`, `U+1fe9`, `U+1feb`,
+   `U+1ff9`, `U+1ffb`, `U+2c7f`, `U+2ced`, `U+a77b`, `U+a792`, `U+a7c9`.
+
+   Due the bug, the link definition label matching did not work in the case
+   insensitive way for these characters.
+
+
+## Version 0.4.3
+
+New features:
+
+ * With `MD_FLAG_UNDERLINE`, spans enclosed in underscore (`_foo_`) are seen
+   as underline (`MD_SPAN_UNDERLINE`) rather than an ordinary emphasis or
+   strong emphasis.
+
+Changes:
+
+ * The implementation of wiki-links extension (with `MD_FLAG_WIKILINKS`) has
+   been simplified.
+
+    - A noticeable increase of MD4C's memory footprint introduced by the
+      extension implementation in 0.4.0 has been removed.
+    - The priority handling towards other inline elements have been unified.
+      (This affects an obscure case where syntax of an image was in place of
+      wiki-link destination made the wiki-link invalid. Now *all* inline spans
+      in the wiki-link destination, including the images, is suppressed.)
+    - The length limitation of 100 characters now always applies to wiki-link
+      destination.
+
+ * Recognition of strike-through spans (with the flag `MD_FLAG_STRIKETHROUGH`)
+   has become much stricter and, arguably, reasonable.
+
+    - Only single tildes (`~`) and double tildes (`~~`) are recognized as
+      strike-through marks. Longer ones are not anymore.
+    - The length of the opener and closer marks have to be the same.
+    - The tildes cannot open a strike-through span if a whitespace follows.
+    - The tildes cannot close a strike-through span if a whitespace precedes.
+
+   This change follows the changes of behavior in cmark-gfm some time ago, so
+   it is also beneficial from compatibility point of view.
+
+ * When building MD4C by hand instead of using its CMake-based build, the UTF-8
+   support was by default disabled, unless explicitly asked for by defining
+   a preprocessor macro `MD4C_USE_UTF8`.
+
+   This has been changed and the UTF-8 mode now becomes the default, no matter
+   how `md4c.c` is compiled. If you need to disable it and use the ASCII-only
+   mode, you have explicitly define macro `MD4C_USE_ASCII` when compiling it.
+
+   (The CMake-based build as provided in our repository explicitly asked for
+   the UTF-8 support with `-DMD4C_USE_UTF8`. I.e. if you are using MD4C library
+   built with our vanilla `CMakeLists.txt` files, this change should not affect
+   you.)
+
+Fixes:
+
+ * Fixed some string length handling in the special `MD4C_USE_UTF16` build.
+
+   (This does not affect you unless you are on Windows and explicitly define
+   the macro when building MD4C.)
+
+ * [#100](https://github.com/mity/md4c/issues/100):
+   Fixed an off-by-one error in the maximal length limit of some segments
+   of e-mail addresses used in autolinks.
+
+ * [#107](https://github.com/mity/md4c/issues/107):
+   Fix mis-detection of asterisk-encoded emphasis in some corner cases when
+   length of the opener and closer differs, as in `***foo *bar baz***`.
+
+
+## Version 0.4.2
+
+Fixes:
+
+ * [#98](https://github.com/mity/md4c/issues/98):
+   Fix mis-detection of asterisk-encoded emphasis in some corner cases when
+   length of the opener and closer differs, as in `**a *b c** d*`.
+
+
+## Version 0.4.1
+
+Unfortunately, 0.4.0 has been released with badly updated ChangeLog. Fixing
+this is the only change on 0.4.1.
+
+
+## Version 0.4.0
+
+New features:
+
+ * With `MD_FLAG_LATEXMATHSPANS`, LaTeX math spans (`$...$`) and LaTeX display
+   math spans (`$$...$$`) are now recognized. (Note though that the HTML
+   renderer outputs them verbatim in a custom `<x-equation>` tag.)
+
+   Contributed by [Tilman Roeder](https://github.com/dyedgreen).
+
+ * With `MD_FLAG_WIKILINKS`, Wiki-style links (`[[...]]`) are now recognized.
+   (Note though that the HTML renderer renders them as a custom `<x-wikilink>`
+   tag.)
+
+   Contributed by [Nils Blomqvist](https://github.com/niblo).
+
+Changes:
+
+ * Parsing of tables (with `MD_FLAG_TABLES`) is now closer to the way how
+   cmark-gfm parses tables as we do not require every row of the table to
+   contain a pipe `|` anymore.
+
+   As a consequence, paragraphs now cannot interrupt tables. A paragraph which
+   follows the table has to be delimited with a blank line.
+
+Fixes:
+
+ * [#94](https://github.com/mity/md4c/issues/94):
+   `md_build_ref_def_hashtable()`: Do not allocate more memory than strictly
+   needed.
+
+ * [#95](https://github.com/mity/md4c/issues/95):
+   `md_is_container_mark()`: Ordered list mark requires at least one digit.
+
+ * [#96](https://github.com/mity/md4c/issues/96):
+   Some fixes for link label comparison.
+
+
+## Version 0.3.4
+
+Changes:
+
+ * Make Unicode-specific code compliant to Unicode 12.1.
+
+ * Structure `MD_BLOCK_CODE_DETAIL` got new member `fenced_char`. Application
+   can use it to detect character used to form the block fences (`` ` `` or
+   `~`). In the case of indented code block, it is set to zero.
+
+Fixes:
+
+ * [#77](https://github.com/mity/md4c/issues/77):
+   Fix maximal count of digits for numerical character references, as requested
+   by CommonMark specification 0.29.
+
+ * [#78](https://github.com/mity/md4c/issues/78):
+   Fix link reference definition label matching for Unicode characters where
+   the folding mapping leads to multiple codepoints, as e.g. in `ẞ` -> `SS`.
+
+ * [#83](https://github.com/mity/md4c/issues/83):
+   Fix recognition of an empty blockquote which interrupts a paragraph.
+
+
+## Version 0.3.3
+
+Changes:
+
+ * Make permissive URL autolink and permissive WWW autolink extensions stricter.
+
+   This brings the behavior closer to GFM and mitigates risk of false positives.
+   In particular, the domain has to contain at least one dot and parenthesis
+   can be part of the link destination only if `(` and `)` are balanced.
+
+Fixes:
+
+ * [#73](https://github.com/mity/md4c/issues/73):
+   Some raw HTML inputs could lead to quadratic parsing times.
+
+ * [#74](https://github.com/mity/md4c/issues/74):
+   Fix input leading to a crash. Found by fuzzing.
+
+ * [#76](https://github.com/mity/md4c/issues/76):
+   Fix handling of parenthesis in some corner cases of permissive URL autolink
+   and permissive WWW autolink extensions.
+
+
+## Version 0.3.2
+
+Changes:
+
+ * Changes mandated by CommonMark specification 0.29.
+
+   Most importantly, the white-space trimming rules for code spans have changed.
+   At most one space/newline is trimmed from beginning/end of the code span
+   (if the code span contains some non-space contents, and if it begins and
+   ends with space at the same time). In all other cases the spaces in the code
+   span are now left intact.
+
+   Other changes in behavior are in corner cases only. Refer to [CommonMark
+   0.29 notes](https://github.com/commonmark/commonmark-spec/releases/tag/0.29)
+   for more info.
+
+Fixes:
+
+ * [#68](https://github.com/mity/md4c/issues/68):
+   Some specific HTML blocks were not recognized when EOF follows without any
+   end-of-line character.
+
+ * [#69](https://github.com/mity/md4c/issues/69):
+   Strike-through span not working correctly when its opener mark is directly
+   followed by other opener mark; or when other closer mark directly precedes
+   its closer mark.
+
+
+## Version 0.3.1
+
+Fixes:
+
+ * [#58](https://github.com/mity/md4c/issues/58),
+   [#59](https://github.com/mity/md4c/issues/59),
+   [#60](https://github.com/mity/md4c/issues/60),
+   [#63](https://github.com/mity/md4c/issues/63),
+   [#66](https://github.com/mity/md4c/issues/66):
+   Some inputs could lead to quadratic parsing times. Thanks to Anders Kaseorg
+   for finding all those issues.
+
+ * [#61](https://github.com/mity/md4c/issues/59):
+   Flag `MD_FLAG_NOHTMLSPANS` erroneously affected also recognition of
+   CommonMark autolinks.
+
+
+## Version 0.3.0
+
+New features:
+
+ * Add extension for GitHub-style task lists:
+
+   ```
+    * [x] foo
+    * [x] bar
+    * [ ] baz
+   ```
+
+   (It has to be explicitly enabled with `MD_FLAG_TASKLISTS`.)
+
+ * Added support for building as a shared library. On non-Windows platforms,
+   this is now default behavior; on Windows static library is still the default.
+   The CMake option `BUILD_SHARED_LIBS` can be used to request one or the other
+   explicitly.
+
+   Contributed by Lisandro Damián Nicanor Pérez Meyer.
+
+ * Renamed structure `MD_RENDERER` to `MD_PARSER` and refactorize its contents
+   a little bit. Note this is source-level incompatible and initialization code
+   in apps may need to be updated.
+
+   The aim of the change is to be more friendly for long-term ABI compatibility
+   we shall maintain, starting with this release.
+
+ * Added `CHANGELOG.md` (this file).
+
+ * Make sure `md_process_table_row()` reports the same count of table cells for
+   all table rows, no matter how broken the input is. The cell count is derived
+   from table underline line. Bogus cells in other rows are silently ignored.
+   Missing cells in other rows are reported as empty ones.
+
+Fixes:
+
+ * CID 1475544:
+   Calling `md_free_attribute()` on uninitialized data.
+
+ * [#47](https://github.com/mity/md4c/issues/47):
+   Using bad offsets in `md_is_entity_str()`, in some cases leading to buffer
+   overflow.
+
+ * [#51](https://github.com/mity/md4c/issues/51):
+   Segfault in `md_process_table_cell()`.
+
+ * [#53](https://github.com/mity/md4c/issues/53):
+   With `MD_FLAG_PERMISSIVEURLAUTOLINKS` or `MD_FLAG_PERMISSIVEWWWAUTOLINKS`
+   we could generate bad output for ordinary Markdown links, if a non-space
+   character immediately follows like e.g. in `[link](http://github.com)X`.
+
+
+## Version 0.2.7
+
+This was the last version before the changelog has been added.