QTextMarkdownWriter: fix some bad cases with word wrap

If any non-breakable content (such as a link) already went past
80 columns, or if a word ended on column 80, it didn't wrap the rest of
the paragraph following.

Change-Id: I27dc0474f18892c34ee2514ea6d5070dae29424f
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>

src/gui/text/qtextmarkdownwriter.cpp

@@ -212,10 +212,19 @@ QTextMarkdownWriter::ListInfo QTextMarkdownWriter::listInfo(QTextList *list)
 static int nearestWordWrapIndex(const QString &s, int before)
 {
     before = qMin(before, s.length());
-    for (int i = before - 1; i >= 0; --i) {
-        if (s.at(i).isSpace())
-            return i;
+    int fragBegin = qMax(before - 15, 0);
+    if (lcMDW().isDebugEnabled()) {
+        QString frag = s.mid(fragBegin, 30);
+        qCDebug(lcMDW) << frag << before;
+        qCDebug(lcMDW) << QString(before - fragBegin, Period) + QLatin1Char('<');
     }
+    for (int i = before - 1; i >= 0; --i) {
+        if (s.at(i).isSpace()) {
+            qCDebug(lcMDW) << QString(i - fragBegin, Period) + QLatin1Char('^') << i;
+            return i;
+        }
+    }
+    qCDebug(lcMDW, "not possible");
     return -1;
 }
 
@@ -251,7 +260,7 @@ static void maybeEscapeFirstChar(QString &s)
 
 int QTextMarkdownWriter::writeBlock(const QTextBlock &block, bool wrap, bool ignoreFormat)
 {
-    int ColumnLimit = 80;
+    const int ColumnLimit = 80;
     QTextBlockFormat blockFmt = block.blockFormat();
     bool indentedCodeBlock = false;
     if (block.textList()) { // it's a list-item
@@ -419,12 +428,18 @@ int QTextMarkdownWriter::writeBlock(const QTextBlock &block, bool wrap, bool ign
                 int fragLen = fragmentText.length();
                 bool breakingLine = false;
                 while (i < fragLen) {
+                    if (col >= ColumnLimit) {
+                        m_stream << Newline << wrapIndentString;
+                        col = m_wrappedLineIndent;
+                        while (fragmentText[i].isSpace())
+                            ++i;
+                    }
                     int j = i + ColumnLimit - col;
                     if (j < fragLen) {
                         int wi = nearestWordWrapIndex(fragmentText, j);
                         if (wi < 0) {
                             j = fragLen;
-                        } else {
+                        } else if (wi >= i) {
                             j = wi;
                             breakingLine = true;
                         }

tests/auto/gui/text/qtextmarkdownwriter/data/blockquotes.md

@@ -13,7 +13,8 @@ MacFarlane writes:
 > > as readable as possible. The idea is that a Markdown-formatted document should
 > > be publishable as-is, as plain text, without looking like it's been marked up
 > > with tags or formatting instructions. ( 
-> > [http://daringfireball.net/projects/markdown/](http://daringfireball.net/projects/markdown/))
+> > [http://daringfireball.net/projects/markdown/](http://daringfireball.net/projects/markdown/)
+> > )
 
 > The point can be illustrated by comparing a sample of AsciiDoc with an
 > equivalent sample of Markdown. Here is a sample of AsciiDoc from the AsciiDoc

tests/auto/gui/text/qtextmarkdownwriter/data/wordWrap.md

@@ -0,0 +1,13 @@
+[The CommonMark Specification](https://spec.commonmark.org/0.29/) is the
+conservative formal specification of the Markdown format, while 
+[GitHub Flavored Markdown](https://guides.github.com/features/mastering-markdown/#GitHub-flavored-markdown)
+adds extra features such as task lists and tables.
+
+Qt owes thanks to the authors of the [MD4C parser](https://github.com/mity/md4c)
+for making markdown import possible. The QTextMarkdownWriter class does not
+have such dependencies, and also has not yet been tested as extensively, so we
+do not yet guarantee that we are able to rewrite every Markdown document that
+you are able to read and display with Text or QTextEdit. But you are free to
+write [bugs](https://bugreports.qt.io) about any troublesome cases that you
+encounter.
+

tests/auto/gui/text/qtextmarkdownwriter/tst_qtextmarkdownwriter.cpp

@@ -358,6 +358,7 @@ void tst_QTextMarkdownWriter::rewriteDocument_data()
     QTest::newRow("block quotes") << "blockquotes.md";
     QTest::newRow("example") << "example.md";
     QTest::newRow("list items after headings") << "headingsAndLists.md";
+    QTest::newRow("word wrap") << "wordWrap.md";
 }
 
 void tst_QTextMarkdownWriter::rewriteDocument()