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, 522 insertions, 0 deletions

diff --git a/tdemarkdown/md4c/test/coverage.txt b/tdemarkdown/md4c/test/coverage.txt
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+
+# Coverage
+
+This file is just a collection of unit tests not covered elsewhere.
+
+Most notably regression tests, tests improving code coverage and other useful
+things may drop here.
+
+(However any tests requiring any additional command line option, like enabling
+an extension, must be included in their respective files.)
+
+
+## GitHub Issues
+
+### [Issue 2](https://github.com/mity/md4c/issues/2)
+
+Raw HTML block:
+
+```````````````````````````````` example
+<gi att1=tok1 att2=tok2>
+.
+<gi att1=tok1 att2=tok2>
+````````````````````````````````
+
+Inline:
+
+```````````````````````````````` example
+foo <gi att1=tok1 att2=tok2> bar
+.
+<p>foo <gi att1=tok1 att2=tok2> bar</p>
+````````````````````````````````
+
+Inline with a line break:
+
+```````````````````````````````` example
+foo <gi att1=tok1
+att2=tok2> bar
+.
+<p>foo <gi att1=tok1
+att2=tok2> bar</p>
+````````````````````````````````
+
+
+### [Issue 4](https://github.com/mity/md4c/issues/4)
+
+```````````````````````````````` example
+![alt text with *entity* &copy;](img.png 'title')
+.
+<p><img src="img.png" alt="alt text with entity ©" title="title"></p>
+````````````````````````````````
+
+
+### [Issue 9](https://github.com/mity/md4c/issues/9)
+
+```````````````````````````````` example
+> [foo
+> bar]: /url
+>
+> [foo bar]
+.
+<blockquote>
+<p><a href="/url">foo
+bar</a></p>
+</blockquote>
+````````````````````````````````
+
+
+### [Issue 10](https://github.com/mity/md4c/issues/10)
+
+```````````````````````````````` example
+[x]:
+x
+- <?
+
+  x
+.
+<ul>
+<li><?
+
+x
+</li>
+</ul>
+````````````````````````````````
+
+
+### [Issue 11](https://github.com/mity/md4c/issues/11)
+
+```````````````````````````````` example
+x [link](/url "foo &ndash; bar") x
+.
+<p>x <a href="/url" title="foo – bar">link</a> x</p>
+````````````````````````````````
+
+
+### [Issue 14](https://github.com/mity/md4c/issues/14)
+
+```````````````````````````````` example
+a***b* c*
+.
+<p>a*<em><em>b</em> c</em></p>
+````````````````````````````````
+
+
+### [Issue 15](https://github.com/mity/md4c/issues/15)
+
+```````````````````````````````` example
+***b* c*
+.
+<p>*<em><em>b</em> c</em></p>
+````````````````````````````````
+
+
+### [Issue 21](https://github.com/mity/md4c/issues/21)
+
+```````````````````````````````` example
+a*b**c*
+.
+<p>a<em>b**c</em></p>
+````````````````````````````````
+
+
+### [Issue 33](https://github.com/mity/md4c/issues/33)
+
+```````````````````````````````` example
+```&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;
+.
+<pre><code class="language-&amp;&amp;&amp;&amp;&amp;&amp;&amp;&amp;"></code></pre>
+````````````````````````````````
+
+
+### [Issue 36](https://github.com/mity/md4c/issues/36)
+
+```````````````````````````````` example
+__x_ _x___
+.
+<p><em><em>x</em> <em>x</em></em>_</p>
+````````````````````````````````
+
+
+### [Issue 39](https://github.com/mity/md4c/issues/39)
+
+```````````````````````````````` example
+[\\]: x
+.
+````````````````````````````````
+
+
+### [Issue 40](https://github.com/mity/md4c/issues/40)
+
+```````````````````````````````` example
+[x](url
+'title'
+)x
+.
+<p><a href="url" title="title">x</a>x</p>
+````````````````````````````````
+
+
+### [Issue 65](https://github.com/mity/md4c/issues/65)
+
+```````````````````````````````` example
+`
+.
+<p>`</p>
+````````````````````````````````
+
+
+### [Issue 74](https://github.com/mity/md4c/issues/74)
+
+```````````````````````````````` example
+[f]:
+-
+    xx
+-
+.
+<pre><code>xx
+</code></pre>
+<ul>
+<li></li>
+</ul>
+````````````````````````````````
+
+
+### [Issue 78](https://github.com/mity/md4c/issues/78)
+
+```````````````````````````````` example
+[SS ẞ]: /url
+[ẞ SS]
+.
+<p><a href="/url">ẞ SS</a></p>
+````````````````````````````````
+
+
+### [Issue 83](https://github.com/mity/md4c/issues/83)
+
+```````````````````````````````` example
+foo
+>
+.
+<p>foo</p>
+<blockquote>
+</blockquote>
+
+````````````````````````````````
+
+
+### [Issue 95](https://github.com/mity/md4c/issues/95)
+
+```````````````````````````````` example
+. foo
+.
+<p>. foo</p>
+````````````````````````````````
+
+
+### [Issue 96](https://github.com/mity/md4c/issues/96)
+
+```````````````````````````````` example
+[ab]: /foo
+[a] [ab] [abc]
+.
+<p>[a] <a href="/foo">ab</a> [abc]</p>
+````````````````````````````````
+
+```````````````````````````````` example
+[a b]: /foo
+[a   b]
+.
+<p><a href="/foo">a   b</a></p>
+````````````````````````````````
+
+
+### [Issue 97](https://github.com/mity/md4c/issues/97)
+
+```````````````````````````````` example
+*a **b c* d**
+.
+<p><em>a <em><em>b c</em> d</em></em></p>
+
+````````````````````````````````
+
+
+### [Issue 100](https://github.com/mity/md4c/issues/100)
+
+```````````````````````````````` example
+<foo@123456789012345678901234567890123456789012345678901234567890123.123456789012345678901234567890123456789012345678901234567890123>
+.
+<p><a href="mailto:foo@123456789012345678901234567890123456789012345678901234567890123.123456789012345678901234567890123456789012345678901234567890123">foo@123456789012345678901234567890123456789012345678901234567890123.123456789012345678901234567890123456789012345678901234567890123</a></p>
+````````````````````````````````
+
+```````````````````````````````` example
+<foo@123456789012345678901234567890123456789012345678901234567890123x.123456789012345678901234567890123456789012345678901234567890123>
+.
+<p>&lt;foo@123456789012345678901234567890123456789012345678901234567890123x.123456789012345678901234567890123456789012345678901234567890123&gt;</p>
+````````````````````````````````
+(Note the `x` here which turns it over the max. allowed length limit.)
+
+
+### [Issue 107](https://github.com/mity/md4c/issues/107)
+
+```````````````````````````````` example
+***foo *bar baz***
+.
+<p>*<strong>foo <em>bar baz</em></strong></p>
+
+````````````````````````````````
+
+
+### [Issue 124](https://github.com/mity/md4c/issues/124)
+
+```````````````````````````````` example
+~~~
+                x
+~~~
+
+~~~
+                 x
+~~~
+.
+<pre><code>                x
+</code></pre>
+<pre><code>                 x
+</code></pre>
+````````````````````````````````
+
+
+### [Issue 131](https://github.com/mity/md4c/issues/131)
+
+```````````````````````````````` example
+[![alt][img]][link]
+
+[img]: img_url
+[link]: link_url
+.
+<p><a href="link_url"><img src="img_url" alt="alt"></a></p>
+````````````````````````````````
+
+
+### [Issue 142](https://github.com/mity/md4c/issues/142)
+
+```````````````````````````````` example
+[fooﬗ]: /url
+[fooﬕ]
+.
+<p>[fooﬕ]</p>
+````````````````````````````````
+
+
+### [Issue 149](https://github.com/mity/md4c/issues/149)
+
+```````````````````````````````` example
+- <script>
+- foo
+bar
+</script>
+.
+<ul>
+<li><script>
+</li>
+<li>foo
+bar
+</script></li>
+</ul>
+````````````````````````````````
+
+
+## Code coverage
+
+### `md_is_unicode_whitespace__()`
+
+Unicode whitespace (here U+2000) forms a word boundary so these cannot be
+resolved as emphasis span because there is no closer mark.
+
+```````````````````````````````` example
+*foo *bar
+.
+<p>*foo *bar</p>
+````````````````````````````````
+
+
+### `md_is_unicode_punct__()`
+
+Ditto for Unicode punctuation (here U+00A1).
+
+```````````````````````````````` example
+*foo¡*bar
+.
+<p>*foo¡*bar</p>
+````````````````````````````````
+
+
+### `md_get_unicode_fold_info()`
+
+```````````````````````````````` example
+[Příliš žluťoučký kůň úpěl ďábelské ódy.]
+
+[PŘÍLIŠ ŽLUŤOUČKÝ KŮŇ ÚPĚL ĎÁBELSKÉ ÓDY.]: /url
+.
+<p><a href="/url">Příliš žluťoučký kůň úpěl ďábelské ódy.</a></p>
+````````````````````````````````
+
+
+### `md_decode_utf8__()` and `md_decode_utf8_before__()`
+
+```````````````````````````````` example
+á*Á (U+00E1, i.e. two byte UTF-8 sequence)
+ *  (U+2000, i.e. three byte UTF-8 sequence)
+.
+<p>á*Á (U+00E1, i.e. two byte UTF-8 sequence)
+ *  (U+2000, i.e. three byte UTF-8 sequence)</p>
+````````````````````````````````
+
+
+### `md_is_link_destination_A()`
+
+```````````````````````````````` example
+[link](</url\.with\.escape>)
+.
+<p><a href="/url.with.escape">link</a></p>
+````````````````````````````````
+
+
+### `md_link_label_eq()`
+
+```````````````````````````````` example
+[foo bar]
+
+[foo bar]: /url
+.
+<p><a href="/url">foo bar</a></p>
+````````````````````````````````
+
+
+### `md_is_inline_link_spec()`
+
+```````````````````````````````` example
+> [link](/url 'foo
+> bar')
+.
+<blockquote>
+<p><a href="/url" title="foo
+bar">link</a></p>
+</blockquote>
+````````````````````````````````
+
+
+### `md_build_ref_def_hashtable()`
+
+All link labels in the following example all have the same FNV1a hash (after
+normalization of the label, which means after converting to a vector of Unicode
+codepoints and lowercase folding).
+
+So the example triggers quite complex code paths which are not otherwise easily
+tested.
+
+```````````````````````````````` example
+[foo]: /foo
+[qnptgbh]: /qnptgbh
+[abgbrwcv]: /abgbrwcv
+[abgbrwcv]: /abgbrwcv2
+[abgbrwcv]: /abgbrwcv3
+[abgbrwcv]: /abgbrwcv4
+[alqadfgn]: /alqadfgn
+
+[foo]
+[qnptgbh]
+[abgbrwcv]
+[alqadfgn]
+[axgydtdu]
+.
+<p><a href="/foo">foo</a>
+<a href="/qnptgbh">qnptgbh</a>
+<a href="/abgbrwcv">abgbrwcv</a>
+<a href="/alqadfgn">alqadfgn</a>
+[axgydtdu]</p>
+````````````````````````````````
+
+For the sake of completeness, the following C program was used to find the hash
+collisions by brute force:
+
+~~~
+
+#include <stdio.h>
+#include <string.h>
+
+
+static unsigned etalon;
+
+
+
+#define MD_FNV1A_BASE       2166136261
+#define MD_FNV1A_PRIME      16777619
+
+static inline unsigned
+fnv1a(unsigned base, const void* data, size_t n)
+{
+    const unsigned char* buf = (const unsigned char*) data;
+    unsigned hash = base;
+    size_t i;
+
+    for(i = 0; i < n; i++) {
+        hash ^= buf[i];
+        hash *= MD_FNV1A_PRIME;
+    }
+
+    return hash;
+}
+
+
+static unsigned
+unicode_hash(const char* data, size_t n)
+{
+    unsigned value;
+    unsigned hash = MD_FNV1A_BASE;
+    int i;
+
+    for(i = 0; i < n; i++) {
+        value = data[i];
+        hash = fnv1a(hash, &value, sizeof(unsigned));
+    }
+
+    return hash;
+}
+
+
+static void
+recurse(char* buffer, size_t off, size_t len)
+{
+    int ch;
+
+    if(off < len - 1) {
+        for(ch = 'a'; ch <= 'z'; ch++) {
+            buffer[off] = ch;
+            recurse(buffer, off+1, len);
+        }
+    } else {
+        for(ch = 'a'; ch <= 'z'; ch++) {
+            buffer[off] = ch;
+            if(unicode_hash(buffer, len) == etalon) {
+                printf("Dup: %.*s\n", (int)len, buffer);
+            }
+        }
+    }
+}
+
+int
+main(int argc, char** argv)
+{
+    char buffer[32];
+    int len;
+
+    if(argc < 2)
+        etalon = unicode_hash("foo", 3);
+    else
+        etalon = unicode_hash(argv[1], strlen(argv[1]));
+
+    for(len = 1; len <= sizeof(buffer); len++)
+        recurse(buffer, 0, len);
+
+    return 0;
+}
+~~~