QTextMarkdownWriter: Avoid omitting or misplacing ending indicators

If we need to word-wrap a paragraph after a long formatted span,
write any ending markers before the newline (amends
280d679c556ab8ead4748a627d7cd4c1950027fb ).

Break before a fragment if the whole thing is past the column limit;
in that case, write out any ending format markers before the newline.

And now we have test coverage: prepend characters one-at-a-time to a
line that already has a two-word formatted span at the end, and watch
it successively break after the span, in the middle, and then before,
while never putting a newline before the ending markers or failing to
write them.

Fixes: QTBUG-116927
Change-Id: I140e10d19a491cb599bf7ecf8514af866b5383f3
Pick-to: 6.5 6.6 6.7
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

1 files changed, 21 insertions, 2 deletions

diff --git a/src/gui/text/qtextmarkdownwriter.cpp b/src/gui/text/qtextmarkdownwriter.cpp
index 5d6c673179..8cce9df0dd 100644
--- a/src/gui/text/qtextmarkdownwriter.cpp
+++ b/src/gui/text/qtextmarkdownwriter.cpp
@@ -495,6 +495,7 @@ int QTextMarkdownWriter::writeBlock(const QTextBlock &block, bool wrap, bool ign
     bool italic = false;
     bool underline = false;
     bool strikeOut = false;
+    bool endingMarkers = false;
     QString backticks(qtmw_Backtick);
     for (QTextBlock::Iterator frag = block.begin(); !frag.atEnd(); ++frag) {
         missedBlankCodeBlockLine = false;
@@ -562,19 +563,27 @@ int QTextMarkdownWriter::writeBlock(const QTextBlock &block, bool wrap, bool ign
                     if (startsOrEndsWithBacktick)
                         markers += qtmw_Space;
                     mono = monoFrag;
+                    if (!mono)
+                        endingMarkers = true;
                 }
                 if (!blockFmt.headingLevel() && !mono) {
                     if (fontInfo.bold() != bold) {
                         markers += "**"_L1;
                         bold = fontInfo.bold();
+                        if (!bold)
+                            endingMarkers = true;
                     }
                     if (fontInfo.italic() != italic) {
                         markers += u'*';
                         italic = fontInfo.italic();
+                        if (!italic)
+                            endingMarkers = true;
                     }
                     if (fontInfo.strikeOut() != strikeOut) {
                         markers += "~~"_L1;
                         strikeOut = fontInfo.strikeOut();
+                        if (!strikeOut)
+                            endingMarkers = true;
                     }
                     if (fontInfo.underline() != underline) {
                         // Markdown doesn't support underline, but the parser will treat a single underline
@@ -582,6 +591,8 @@ int QTextMarkdownWriter::writeBlock(const QTextBlock &block, bool wrap, bool ign
                         // That will have to do.
                         markers += u'_';
                         underline = fontInfo.underline();
+                        if (!underline)
+                            endingMarkers = true;
                     }
                 }
             }
@@ -591,7 +602,8 @@ int QTextMarkdownWriter::writeBlock(const QTextBlock &block, bool wrap, bool ign
                 bool breakingLine = false;
                 while (i < fragLen) {
                     if (col >= ColumnLimit) {
-                        m_stream << qtmw_Newline << wrapIndentString;
+                        m_stream << markers << qtmw_Newline << wrapIndentString;
+                        markers.clear();
                         col = m_wrappedLineIndent;
                         while (i < fragLen && fragmentText[i].isSpace())
                             ++i;
@@ -601,6 +613,13 @@ int QTextMarkdownWriter::writeBlock(const QTextBlock &block, bool wrap, bool ign
                         int wi = nearestWordWrapIndex(fragmentText, j);
                         if (wi < 0) {
                             j = fragLen;
+                            // can't break within the fragment: we need to break already _before_ it
+                            if (endingMarkers) {
+                                m_stream << markers;
+                                markers.clear();
+                            }
+                            m_stream << qtmw_Newline << wrapIndentString;
+                            col = m_wrappedLineIndent;
                         } else if (wi >= i) {
                             j = wi;
                             breakingLine = true;
@@ -624,7 +643,7 @@ int QTextMarkdownWriter::writeBlock(const QTextBlock &block, bool wrap, bool ign
                         col += subfrag.size();
                     }
                     i = j + 1;
-                }
+                } // loop over fragment characters (we know we need to break somewhere)
             } else {
                 if (!m_linePrefixWritten && col == wrapIndentString.size()) {
                     m_stream << m_linePrefix;