Add QTextMarkdownWriter::writeTable(QAbstractTableModel)

This provides the ability to write live data from a table to Markdown,
which can be useful to load it into a text document or a wiki.
But so far QTextMarkdownWriter is still a private class, intended to be
used experimentally from QtQuick and perhaps later exposed in other ways.

Change-Id: I0de4673987e4172178604e49b5a024a05d4486ba
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

src/gui/text/qtextmarkdownwriter.cpp

@@ -64,6 +64,37 @@ bool QTextMarkdownWriter::writeAll(const QTextDocument &document)
     return true;
 }
 
+void QTextMarkdownWriter::writeTable(const QAbstractTableModel &table)
+{
+    QVector<int> tableColumnWidths(table.columnCount());
+    for (int col = 0; col < table.columnCount(); ++col) {
+        tableColumnWidths[col] = table.headerData(col, Qt::Horizontal).toString().length();
+        for (int row = 0; row < table.rowCount(); ++row) {
+            tableColumnWidths[col] = qMax(tableColumnWidths[col],
+                table.data(table.index(row, col)).toString().length());
+        }
+    }
+
+    // write the header and separator
+    for (int col = 0; col < table.columnCount(); ++col) {
+        QString s = table.headerData(col, Qt::Horizontal).toString();
+        m_stream << "|" << s << QString(tableColumnWidths[col] - s.length(), Space);
+    }
+    m_stream << "|" << endl;
+    for (int col = 0; col < tableColumnWidths.length(); ++col)
+        m_stream << '|' << QString(tableColumnWidths[col], QLatin1Char('-'));
+    m_stream << '|'<< endl;
+
+    // write the body
+    for (int row = 0; row < table.rowCount(); ++row) {
+        for (int col = 0; col < table.columnCount(); ++col) {
+            QString s = table.data(table.index(row, col)).toString();
+            m_stream << "|" << s << QString(tableColumnWidths[col] - s.length(), Space);
+        }
+        m_stream << '|'<< endl;
+    }
+}
+
 void QTextMarkdownWriter::writeFrame(const QTextFrame *frame)
 {
     Q_ASSERT(frame);

src/gui/text/qtextmarkdownwriter_p.h

@@ -56,6 +56,7 @@
 
 #include "qtextdocument_p.h"
 #include "qtextdocumentwriter.h"
+#include "QAbstractTableModel"
 
 QT_BEGIN_NAMESPACE
 
@@ -64,6 +65,7 @@ class Q_GUI_EXPORT QTextMarkdownWriter
 public:
     QTextMarkdownWriter(QTextStream &stream, QTextDocument::MarkdownFeatures features);
     bool writeAll(const QTextDocument &document);
+    void writeTable(const QAbstractTableModel &table);
 
     int writeBlock(const QTextBlock &block, bool table, bool ignoreFormat);
     void writeFrame(const QTextFrame *frame);

tests/auto/widgets/itemviews/qtableview/tst_qtableview.cpp

@@ -32,6 +32,9 @@
 #include <private/qtablewidget_p.h>
 #include <QtTest/QtTest>
 #include "private/qapplication_p.h"
+#if QT_CONFIG(textmarkdownwriter)
+#include "private/qtextmarkdownwriter_p.h"
+#endif
 
 #include <algorithm>
 
@@ -196,6 +199,10 @@ private slots:
     void viewOptions();
 
     void taskQTBUG_7232_AllowUserToControlSingleStep();
+
+#if QT_CONFIG(textmarkdownwriter)
+    void markdownWriter();
+#endif
 };
 
 // Testing get/set functions
@@ -4560,5 +4567,33 @@ void tst_QTableView::taskQTBUG_50171_selectRowAfterSwapColumns()
     }
 }
 
+// This has nothing to do with QTableView, but it's convenient to reuse the QtTestTableModel
+#if QT_CONFIG(textmarkdownwriter)
+
+// #define DEBUG_WRITE_OUTPUT
+
+void tst_QTableView::markdownWriter()
+{
+    QtTestTableModel model(2, 3);
+    QString md;
+    {
+        QTextStream stream(&md);
+        QTextMarkdownWriter writer(stream, QTextDocument::MarkdownDialectGitHub);
+        writer.writeTable(model);
+    }
+
+#ifdef DEBUG_WRITE_OUTPUT
+    {
+        QFile out("/tmp/table.md");
+        out.open(QFile::WriteOnly);
+        out.write(md.toUtf8());
+        out.close();
+    }
+#endif
+
+    QCOMPARE(md, QString::fromLatin1("|1      |2      |3      |\n|-------|-------|-------|\n|[0,0,0]|[0,1,0]|[0,2,0]|\n|[1,0,0]|[1,1,0]|[1,2,0]|\n"));
+}
+#endif
+
 QTEST_MAIN(tst_QTableView)
 #include "tst_qtableview.moc"