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, 357 insertions, 0 deletions

diff --git a/tdemarkdown/md4c/test/tables.txt b/tdemarkdown/md4c/test/tables.txt
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+
+# Tables
+
+With the flag `MD_FLAG_TABLES`, MD4C enables extension for recognition of
+tables.
+
+Basic table example of a table with two columns and three lines (when not
+counting the header) is as follows:
+
+```````````````````````````````` example
+| Column 1 | Column 2 |
+|----------|----------|
+| foo      | bar      |
+| baz      | qux      |
+| quux     | quuz     |
+.
+<table>
+<thead>
+<tr><th>Column 1</th><th>Column 2</th></tr>
+</thead>
+<tbody>
+<tr><td>foo</td><td>bar</td></tr>
+<tr><td>baz</td><td>qux</td></tr>
+<tr><td>quux</td><td>quuz</td></tr>
+</tbody>
+</table>
+````````````````````````````````
+
+The leading and succeeding pipe characters (`|`) on each line are optional:
+
+```````````````````````````````` example
+Column 1 | Column 2 |
+---------|--------- |
+foo      | bar      |
+baz      | qux      |
+quux     | quuz     |
+.
+<table>
+<thead>
+<tr><th>Column 1</th><th>Column 2</th></tr>
+</thead>
+<tbody>
+<tr><td>foo</td><td>bar</td></tr>
+<tr><td>baz</td><td>qux</td></tr>
+<tr><td>quux</td><td>quuz</td></tr>
+</tbody>
+</table>
+````````````````````````````````
+
+```````````````````````````````` example
+| Column 1 | Column 2
+|----------|---------
+| foo      | bar
+| baz      | qux
+| quux     | quuz
+.
+<table>
+<thead>
+<tr><th>Column 1</th><th>Column 2</th></tr>
+</thead>
+<tbody>
+<tr><td>foo</td><td>bar</td></tr>
+<tr><td>baz</td><td>qux</td></tr>
+<tr><td>quux</td><td>quuz</td></tr>
+</tbody>
+</table>
+````````````````````````````````
+
+```````````````````````````````` example
+Column 1 | Column 2
+---------|---------
+foo      | bar
+baz      | qux
+quux     | quuz
+.
+<table>
+<thead>
+<tr><th>Column 1</th><th>Column 2</th></tr>
+</thead>
+<tbody>
+<tr><td>foo</td><td>bar</td></tr>
+<tr><td>baz</td><td>qux</td></tr>
+<tr><td>quux</td><td>quuz</td></tr>
+</tbody>
+</table>
+````````````````````````````````
+
+However for one-column table, at least one pipe has to be used in the table
+header underline, otherwise it would be parsed as a Setext title followed by
+a paragraph.
+
+```````````````````````````````` example
+Column 1
+--------
+foo
+baz
+quux
+.
+<h2>Column 1</h2>
+<p>foo
+baz
+quux</p>
+````````````````````````````````
+
+Leading and trailing whitespace in a table cell is ignored and the columns do
+not need to be aligned.
+
+```````````````````````````````` example
+Column 1 |Column 2
+---|---
+foo | bar
+baz| qux
+quux|quuz
+.
+<table>
+<thead>
+<tr><th>Column 1</th><th>Column 2</th></tr>
+</thead>
+<tbody>
+<tr><td>foo</td><td>bar</td></tr>
+<tr><td>baz</td><td>qux</td></tr>
+<tr><td>quux</td><td>quuz</td></tr>
+</tbody>
+</table>
+````````````````````````````````
+
+The table cannot interrupt a paragraph.
+
+```````````````````````````````` example
+Lorem ipsum dolor sit amet.
+| Column 1 | Column 2
+| ---------|---------
+| foo      | bar
+| baz      | qux
+| quux     | quuz
+.
+<p>Lorem ipsum dolor sit amet.
+| Column 1 | Column 2
+| ---------|---------
+| foo      | bar
+| baz      | qux
+| quux     | quuz</p>
+````````````````````````````````
+
+Similarly, paragraph cannot interrupt a table:
+
+```````````````````````````````` example
+Column 1 | Column 2
+---------|---------
+foo      | bar
+baz      | qux
+quux     | quuz
+Lorem ipsum dolor sit amet.
+.
+<table>
+<thead>
+<tr><th>Column 1</th><th>Column 2</th></tr>
+</thead>
+<tbody>
+<tr><td>foo</td><td>bar</td></tr>
+<tr><td>baz</td><td>qux</td></tr>
+<tr><td>quux</td><td>quuz</td></tr>
+<tr><td>Lorem ipsum dolor sit amet.</td><td></td></tr>
+</tbody>
+</table>
+````````````````````````````````
+
+The first, the last or both the first and the last dash in each column
+underline can be replaced with a colon (`:`) to request left, right or middle
+alignment of the respective column:
+
+```````````````````````````````` example
+| Column 1 | Column 2 | Column 3 | Column 4 |
+|----------|:---------|:--------:|---------:|
+| default  | left     | center   | right    |
+.
+<table>
+<thead>
+<tr><th>Column 1</th><th align="left">Column 2</th><th align="center">Column 3</th><th align="right">Column 4</th></tr>
+</thead>
+<tbody>
+<tr><td>default</td><td align="left">left</td><td align="center">center</td><td align="right">right</td></tr>
+</tbody>
+</table>
+````````````````````````````````
+
+To include a literal pipe character in any cell, it has to be escaped.
+
+```````````````````````````````` example
+Column 1 | Column 2
+---------|---------
+foo      | bar
+baz      | qux \| xyzzy
+quux     | quuz
+.
+<table>
+<thead>
+<tr><th>Column 1</th><th>Column 2</th></tr>
+</thead>
+<tbody>
+<tr><td>foo</td><td>bar</td></tr>
+<tr><td>baz</td><td>qux | xyzzy</td></tr>
+<tr><td>quux</td><td>quuz</td></tr>
+</tbody>
+</table>
+````````````````````````````````
+
+Contents of each cell is parsed as an inline text which may contents any
+inline Markdown spans like emphasis, strong emphasis, links etc.
+
+```````````````````````````````` example
+Column 1 | Column 2
+---------|---------
+*foo*    | bar
+**baz**  | [qux]
+quux     | [quuz](/url2)
+
+[qux]: /url
+.
+<table>
+<thead>
+<tr><th>Column 1</th><th>Column 2</th></tr>
+</thead>
+<tbody>
+<tr><td><em>foo</em></td><td>bar</td></tr>
+<tr><td><strong>baz</strong></td><td><a href="/url">qux</a></td></tr>
+<tr><td>quux</td><td><a href="/url2">quuz</a></td></tr>
+</tbody>
+</table>
+````````````````````````````````
+
+However pipes which are inside a code span are not recognized as cell
+boundaries.
+
+```````````````````````````````` example
+Column 1 | Column 2
+---------|---------
+`foo     | bar`
+baz      | qux
+quux     | quuz
+.
+<table>
+<thead>
+<tr><th>Column 1</th><th>Column 2</th></tr>
+</thead>
+<tbody>
+<tr><td><code>foo     | bar</code></td><td></td></tr>
+<tr><td>baz</td><td>qux</td></tr>
+<tr><td>quux</td><td>quuz</td></tr>
+</tbody>
+</table>
+````````````````````````````````
+
+
+## GitHub Issues
+
+### [Issue 41](https://github.com/mity/md4c/issues/41)
+```````````````````````````````` example
+* x|x
+---|---
+.
+<ul>
+<li>x|x
+---|---</li>
+</ul>
+````````````````````````````````
+(Not a table, because the underline has wrong indentation and is not part of the
+list item.)
+
+```````````````````````````````` example
+* x|x
+  ---|---
+x|x
+.
+<ul>
+<li><table>
+<thead>
+<tr>
+<th>x</th>
+<th>x</th>
+</tr>
+</thead>
+</table>
+</li>
+</ul>
+<p>x|x</p>
+````````````````````````````````
+(Here the underline has the right indentation so the table is detected.
+But the last line is not part of it due its indentation.)
+
+
+### [Issue 42](https://github.com/mity/md4c/issues/42)
+
+```````````````````````````````` example
+] http://x.x *x*
+
+|x|x|
+|---|---|
+|x|
+.
+<p>] http://x.x <em>x</em></p>
+<table>
+<thead>
+<tr>
+<th>x</th>
+<th>x</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>x</td>
+<td></td>
+</tr>
+</tbody>
+</table>
+````````````````````````````````
+
+
+### [Issue 104](https://github.com/mity/md4c/issues/104)
+
+```````````````````````````````` example
+A | B
+--- | ---
+[x](url)
+.
+<table>
+<thead>
+<tr>
+<th>A</th>
+<th>B</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td><a href="url">x</a></td>
+<td></td>
+</tr>
+</tbody>
+</table>
+````````````````````````````````
+
+
+### [Issue 138](https://github.com/mity/md4c/issues/138)
+
+```````````````````````````````` example
+| abc | def |
+| --- | --- |
+.
+<table>
+<thead>
+<tr>
+<th>abc</th>
+<th>def</th>
+</tr>
+</thead>
+</table>
+````````````````````````````````